National Research Centre “Kurchatov Institute”

FEDERAL STATE BUDGETARY INSTITUTION “STATE SCIENTIFIC CENTER OF THE RUS-SIAN FEDERATION - INSTITUTE FOR THEORETICAL AND EXPERIMENTAL PHYSICS”

(NRC “KURCHATOV INSTITUTE” FSBI “SSC RF ITEP”)

APPROVED by Deputy director for scienceFSBI “SSC RF ITEP” of NRC “KI”

_________________A.A. Golubev “____” ______ 2015

REPORTON THE SCIENTIFIC AND RESEARCH WORK IN THE SCOPE OF THE CONTEST AMONG

YOUNG FAIR GROUPS’ LEADERS

“THE SYSTEM OF INJECTION AND EXTRACTION OF BEAMS FOR THE ALTERNATIVE OPTION OF THE CR STORAGE RING”

(final)

Compiled by Shatunov P.Yu.

Moscow 2015

Short summary of the results for the whole year During the year of 2015 a lot of work dedicated to research and design of Collector Ring (CR) Injec-tion/Extraction system has been done. In close cooperation with the other CR subsystems designers, our group has performed the next tasks:

The system of beam injection is designed in details. Matching with other subsystems is checked.

Parameters of the fast dipole kicker magnets are determined. The technical specification for this subsystem is published.

The modeling of power source for fast kickers is provided. The technical specification for subsystem of scintillators is published. First stage of the magnet field simulation for the injection septum-magnet is done. The research of optimal betatron tune for all operational regymes of the CR storage ring is

done. The influence of nonlinear magnetic elements on the beam losses in the storage ring during the

first turns is investigated. The technical specification for the subsystem of the beam scrapers is published. The research work on the influence of betatron tune resonances on the beam losses using the

FMA method is provided. The beam extraction scheme is developed in details. The first stage of magnetic field calculations for the extraction septum magnet is done. The technical specification for the fast pick-up subsystem is published. The influence of the realistic magnetic field harmonics of high order on the beam dynamics in

the storage ring is calculated. The technical specification for the residual gas profile monitor (RGM) is published.

Also during the 2015 our research took part in many technical workshops and conferences covering the subject of the CR storage ring. During the intensive cooperation work in Novosibirsk and Darmstadt it has become obvious that ammount of submitted improvements during last one and a half year is so big that an addendum to the TDR should be published. In this addendum all the research work of BINP developers on the CR project should be published. This work is started.

Detailed results

1. Beam dynamics at Collector Ring

1.1. CR linear optics finalization

As a result of the CR design progress, after mutual matching of all accelerator components arrangement several changes in focusing system were made. For example, quadrupoles in straight sections were moved significantly. These changes lead to revision of the linear lattice design as well as nonlinear effects control. At present the arrangement of all magnet system components, beam diagnostic elements and experimental devices is finally fixed and approved by all working groups. The lattice functions of all three CR regimes are presented in Figs. 1.1.1-3.

Fig. 1. Lattice functions and beam sizes along half ring, Pbar mode.

Fig. 2. Lattice functions and beam sizes along half ring, RIB mode.

Fig. 3. Lattice functions and beam sizes along half ring, ISO mode.

Main aperture limitations are given by RF-resonators acceptance, SC pickups and profile of vacuum chamber in arcs’ dipoles and quadrupoles. In Fig.1.1.4 the cross sections of injected hot beam are presented for different modes and in all magnetic elements. With black the vacuum chamber profile is depicted.

Fig. 4. Transverse injected beam profile for three modes inscribed into vacuum chambers of magnetic elements.

1.2. Nonlinear dynamics of injected particles and study of lattice chromatic aberrations

Since the momentum spread is very large in injected beam (±3% for antiprotons) the natural betatron tunes chromaticity must be compensated. Six families of sextupole magnets are foreseen for this aim. The distribution of sextupole field between families can be done in a different way. For example, the total integral of sextupole gradient can be minimized in order to reduce limitations on dynamic aperture (DA). The contribution to the tunes chromaticity from the sextupoles with strength S i can be written as:

,

Where βi and Di are the beta- and dispersion function at the sextupole position, Bρ is rigidity. The same expression written in matrix form is the following:

.

Finally the vector of sextupoles strength with respect to it’s minimization can be expressed via pseudoinverse matrix:

.

At the same time, the study of the second order chromatic effects, i.e. second-order dispersion function

D1 and chromatic beta beating in the revised version of antiproton lattice, uncovered their

importance with respect to beam dynamics. In Fig. 1.2.1 the beta-functions for the on- and off-energy particles are shown.

Fig. 5. Beta-functions for on-momentum and off-momentum (±3%) particles. Pbar mode.

In the next Fig. 1.2.2 the transverse beam sizes are presented with beta-function chromaticity and second order dispersion taken into account. It is quite clear that the beam size chromatic variation is strong, especially in the straight sections where the aperture is limited by RF-system and SC pickups. Obviously, these chromatic effects depends strongly on the sextupole scheme. To avoid antiprotons losses during injection the sextupole gradient distribution should be chosen not only with respect to nonlinear dynamics optimization but also taking into account beam sizes chromatic variation.

Fig. 6. Transverse beam sizes with chromatic effects included. Thin dashed lines corresponds to linear optics.

Although the chromatic sextupoles are the main source of nonlinearities affecting particle dynamics the weak high order harmonics of main elements’ magnetic field must be studied. In Figs. 1.2.3-4 the inhomogeneity of the dipole and “wide”quadrupole magnetic field is shown.

Fig. 7. Dipole field inhomogeneity in the range of ±5·10-4. Black line shows the vacuum chamber.

Fig. 8. Deviation of wide quad’s magnetic field from linear dependence in the range of ±5·10-4. Black line shows vacuum chamber, red line shows pole profile.

For the Pbar and RIB modes nonlinear dynamics study is important in the sense of stability and capture efficiency. (For the ISO mode nonlinear fields optimized to fulfill isochronicity condition.) The influence of different nonlinearities sources on DA is presented in Fig. 1.2.5 for the antiproton regime (on-energy tracking). Colour shows the number of turns before particle with given initial

transverse coordinates hits the vacuum chamber in case of instable motion. Blue is used for maximal 300 turns, red is for 1 turn.

Fig. 9. DA affected by different sources of nonlinearities: linear (up-left), sextupoles (up-right), quads imperfections (down-left), dipoles imperfections (down-right). Initial transverse coordinates x,y are in

centimeters. Black rectangle shows injected beam.

It is clearly seen that the main restrictions on DA comes from chromatic sextupoles. In Fig. 1.2.6 the DA for on- and off-energy particles with largest momentum deviation in Pbar mode is presented. All the predicted nonlinearities are included.

Fig. 10. DA for particles with momentum deviations: Δp/p = -3% (up), Δp/p = 0 (middle), Δp/p = +3% (down). Pbar mode.

It is well known that DA is very sensitive to the choice of the working point at the tune diagram due to dense resonance net furrowing it. The tune scans were done and the results for Pbar regime are shown in Fig. 1.2.7.

Fig. 11. DA scans: Δp/p = -3% (left), Δp/p = 0 (center), Δp/p = +3% (right). Pbar regime. Red colour corresponds to DA ratio to injected beam size DA/σ = 1.5, blue corresponds to DA/ σ = 0.

One can see that the chosen tunes (magenta point) are close to optimal position. Probably the point can be moved slightly right in horizontal direction to increase DA for the particles with negative momentum deviation, which is affected by 5νx=22 resonance. At the same time DA is not very large in all square. The same scan is done for RIB mode (see Fig. 1.2.8).

Fig. 12. DA scans in RIB mode, Δp/p = -1.5% (left), Δp/p= 0 (center), Δp/p = +1.5% (right). Red shows DA/ σ = 5.5, blue for DA/ σ = 0.

Here no problems with DA foreseen due to twice smaller momentum spread with respect to Pbar regime. However the strong sextupole resonances are clearly seen in diagram. May be the sextupole scheme should be optimized to suppress individual resonances via redistribution of corresponding azimuthal harmonics. The need of large stability region on tune diagrams depends on the beam footprint – tune spread, provided by both tune nonlinear chromaticity and tune-amplitude dependence. In Fig 1.2.9 the footprints of antiproton beam and ion beam are presented. Latter is very compact.

Fig. 13. Beam footprint for antiprotons (left) and ions (right). Red point shows design working point.

Even more sensitive method to mark out the dangerous resonances is so called Frequency Map Analysis (FMA). The principle of method is the following. From simulated (or measured) turn-by-turn coordinates the part is cut out (see Fig. 1.2.10) and used to determine betatron tune with very high precision using NAFF analysis. Then with “running window” the tune dependence on time is obtained. The tune straying is the indication of unstable chaotic motion and it can be detected during first hundreds of turns. While scanning with working point across tune diagram one can clearly see the most dangerous resonances and choose the point far away.

Fig. 14. To FMA principle.

2. Injection-extraction scheme

2.1. Basic requirements for the inlet septum magnet

During the development of the inlet septum magnet, were found several weaknesses in the proposed version of the magnet in the TDR. First, because of the required pulse duration and high inductance value of the losses on the winding resistance is up 60kDzh almost the entire charge initial charge (see Fig. 2.1.1). Secondly, it is doubtful durability "knife" magnet made of a few turns of a water-cooled bus 9х12мм2, since pulse knife feels a strong impact. A third disadvantage is the material of the vacuum chamber. The evaluation shows that in a vacuum chamber made of stainless steel with a thickness of 5 mm will be allocated kilowatts of power because of the induced currents. The design of a water-cooled vacuum chamber is extremely complex and requires increasing the aperture of the magnet.

Table 1. Basic parameters of the inlet septum magnet described in TDR.

Bending angle α 0.125 rMagnetic field B 0.85 TBending radius r 15.3 mEffective length l 2.2 m

Width and height of the gap w, h 170 , 150 mmMagnetic field power WB 19 kJ

The number of windings n 16Inductance L 0.95 mH

Cable and windings resistance R, Rcable 9.8 , 5.6 mOhmCurrent I 6400 A

Pulse duration, period T 400 msCapacity voltages U0 190 (103 in

TDR )V

Capacity C 3.37 FStored energy W 60.9 kJEnergy loss ΔW 60.8 kJ

Vacuum chamber thickness δ 5 mmSeptum magnet thickness Δ < 25 mm

Fig. 1. Current decay in the septum magnet.

It was proposed to divide a long septum magnet into three parts (see Fig. 2.1.2.) to solve these problems. Each part ot the septum magnet turns beam by the angle of the angle 43.8 mrad. The length of the magnet ≈ 113.96 cm. The pulse length must be reduced to 3 msec, which together with reduced inductance, provides a significantly smaller energy losses (see Fig. 2.1.3). Unfortunately, the currents in the vacuum chamber induced by 5 kGs magnetic field are too large. For solving this problem is was proposed to use ceramic vacuum chamber. Although the cost of this camera is much more expensive than the cost of the stainless steel chamber, in fact it is the only possible solution.

Fig. 2. The injection region. The pulsed septum magnets, quadrupole magnets of the channel and the storage ring, the CR bending magnet and the so called septum-quad are shown.

Fig. 2.1.4 shows a diagram of the inlet septum magnet with incoming and accumulated beam for all four modes of operation. The magnet is pulsed and has two coils. The first coil has 16 turns and is bounded on the yoke so it is mechanically protected from the deformations during the pulse. The second coil has one turn and forms the magnetic field in the gap. The septum is a part of the second coil. It is specially shaped from the outer side to decrease the gap between the injected beam and the orbit of CR preserving the mechanical strength. Simulation of the ring structure and preliminary design shows that the minimum possible deviations if the incoming beam orbit is 121 mm for RIB, 127mm and 128mm for two pbar modes and 148.12 mm for the isochronous mode of operation .

The vacuum chamber of the magnet is chosen from one of serial chambers firm Friatec, with a length of 105 cm, a radius of 170 mm and a wall thickness of 10 mm.

Fig. 3. Current pulse in the septum magnet.

Fig. 4. Scheme of short septum magnet with beams for 4 modes of operation.

Presently the design of the septum magnet is in good stage, 3d magnetic calculations are provided, the design of specialized vacuum chamber has been started. It is consider that the whole design of the injection region can be done up to the end of the year.In the 2.1.2 the main parameters of the short septum magnet developed in BINP for the CR project are presented. At Fig. 2.1.4-Fig. 2.1.6, the blueprints of the design and the 3D model of the magnet are shown.

Table 2. Basic parameters of the inlet septum magnet.

Width and height of the gap w, h 200, 175 mm

Magnetic field B 0.5 TThe number of windings n 16Effective length l 1.1396 mAngle α 0.0438 rBending radius r 26 mInductance L 0.371 mHCapacity C 0.615 mFVoltage U 3341.19 VCurrent I 4250 APulse duration, period T 3 msVacuum chamber thickness δ 10 mmSeptum thickness Δ >15 mm

Fig. 5. 2D magnetic calculations for the ISM.

Fig. 6. The 3D model of the inlet septum-magnet.

To get the required position and angle of the inlet septum one should estimate the minimum possible deviation of injected beam orbit and to find the right settings of fast kickers. According to the present development stage the kickers are formed of three sections which consist of three plates each 60 cm long. Kicker creates beam orbit effective magnetic field up to 0.54 kGs, with a maximum charge for up to 55kV. The strength of kickers were adopted to hame maximum freedom for every type of the incoming beam in any mode of operations. The limits here are the vacuum chamber size in the CR01QS01 quadrupole and CR04QS02 quadrupole. The vacuum chamber of the septums also limits possible beam deviation. On the following pictures Fig. 2.1.7-Fig. 2.1.10 the beam trajectories together with the beam sizes are shown.

Fig. 7. PBAR1 option. Incoming beam with minimum deviation (orange lines, Hkickers=0.486kGs, dxseptum=12.71cm) and maximum deviation limited by QS1 quad aperture (magenta lines,

Hkickers=0.535kGs, dxseptum=13.98cm)

Fig. 8. PBAR2 option. Incoming beam with minimum deviation (orange lines, Hkickers=0.428kGs, dxseptum=12.8cm) and maximum deviation limited by septum aperture (magenta lines,

Hkickers=0.468kGs, dxseptum=14.00cm)

Fig. 9. RIB option. Incoming beam with minimum deviation (orange lines, Hkickers=0.488kGs, dxseptum=12.1cm) and maximum deviation limited by septum aperture (magenta lines,

Hkickers=0.535kGs, dxseptum=13.33cm)

Fig. 10. ISO option. Hkickers=0.476kGs (half of sections), dxseptum=14.8cm.2.2. Beam extraction

The extraction of the beam from the CR storage ring is proposed for the three regimes of operation — the accumulation of rare ions and two modes for accumulation of rare p-bars. For extraction the beam is kicked by the dipole kicker at the end of the straight section. Then it propogates through the the arc of the ring and enters the extraction septum magnet. This magnet bends the extracted beam for additional angle and guides it to the transfer channel.

Fig. 11. Horizontal and vertical beam sizes in the extraction straight section given for four modes of operation — two modes for accumulation of antiprotons, one mode for accumulation of rare isotopes

and one for experiments with isochronous mode. The position of the extraction septum magnet is shown with green rectangle. All sizes in cm.

The position of the extraction septum magnet is defined by several factors — the magnetic field in the dipole kickers, the transversal size of the extracted beam, the aperture limitations in the magnetic elements of the ring arc. The shift of the septum magnet from the storage ring's orbit is defined by the size of the circulating beam. For the Collector Ring maximum beam size is reached during the first turns of the beam before the switching on of the stochastic cooling. As it is easily seen from the Fig. 2.2.1, where the beam sizes are shown for all modes of operation, the size of the beam in isochronous mode defined the position of the septum magnet. Beam sizes

for just injected and cooled (emittance 20 mm·mrad) beam at the point of minimal distance between the septum magnet and the CR orbit are presented in the .

Table 3. Beam half-sizes at the point of extraction

Horizontal size (mm)1 turn

Vertical size (mm)1 turn.

Horizontal size (mm)Cooled beam

Vertical size (mm)Cooled beam

RIB 44.0 55.1 13.9 17.4

P-bar 1 39.8 66.2 11.5 19.1

P-bar 2 52.4 63.5 15.1 18.3

Isochronous 88.7 34.1 - -

From the other side the maximum beam deviation and angle of the extracted beam is defined by the aperture limitation in the magnetic elements between the kickers and septum magnet. At the Fig. 2.2.2 main limitations for the rare ion beam extraction are shown. The simulation has shown that for CR the main limitation is the aperture of the quadrupole magnet CR02QR04 — the last quad before the septum magnet. The good field region for this quad is limited by the circle of 95mm (see. Fig. 2.2.3). The beam goes through the quad with big deviationof the orbit only once during the extraction so we can consider the maximum beam deviation to be 120 mm. Then the beam position at the entrance of the extraction septum magnet is 137 mm, and the angle to the orbit of CR is 1.03 degree.

Fig. 12. Aperture limitations for the extracted beam. RIB mode of operaton.

Fig. 13. The cross-section of the CR02QR04 quadrupole magnet.

It is proposed to use the straight ceramic vacuum chamber with round cross-section for the septum magnet. The internal diameter is 70 mm, the thickness of the vacuum chamber is 5 mm. The angle between the extracted beam and the transfer channel is 7.1 degree. As soon as vacuum chamber straight the magnet should be also straight. The magnetic field in the dipole septum and the angle of the dipole to the orbit of CR is chosen to optimize the propagation of the beam through the vacuum chamber and to maximize free space for the circulating beam (see. Fig. 2.2.4). As a result of this reasearch the following parameters are chosen — magnetic field 1.0 Т and radius of the beam orbit 13 m.

Fig. 14. The optimization of the position and angle of the extraction septum magnet.

Fig. 15. The scheme of the transversal cross-section of the extraction septum magnet and the beam profiles of the extracted and circulating beam for several modes of operation.

The yoke of the septum magnet is made by c-type scheme. The size of the vartical and horizontal gap in the dipole is optimized to preserve the same inductance as for the injection septum-magnet. It allows the usage of the same type power source. The septum-magnet has two coils. The primary coil has 16 turns and is made of watercooled copper wire of 16х16 mm cross-section. The pulse of the electric current is applied to this coil. The secondary coil is inductively coupled with the primary coil. The secondary coil is combined with the septum (see. Fig. 2.2.5).

Fig. 16. The magnetic field simulation for the extraction septum magnet.

The thickness of the septum-magnet is selected to be enough for shielding of the orbit of the storage ring from the magnetic field in the septum magnet. Magnetic field simulations have shown that with the pulse length of the 1.5 ms and the septum thickness of 20 mm the residual magnetic field on the orbit of the storage ring does not exceed the value of 10Gs. (see. Fig. 2.2.6). The septum itself can be profiled in the same style as it was done with the injection septum magnet to allow the minimal shift of the septum magnet from the orbit of the ring but preserving the demanded solidity. As it is seen from Fig. 2.2.5, taking into consideration the deviation of extracted beam, the thickness of the vacuum chamber in the septum magnet, the thickness of the septum, the thickness of the vacuum chamber of the storage ring, we come to conclusion the beam in the isochronous mode contradicts with the extraction septum magnet. This can be solved by the applying the tiny facet to the septum of the magnet. The 5 mm facet on the end of the septum should not make the situation with the residual magnetic field on the orbit worse. This will be checked soon. On Fig. 2.2.7 the 3d model of the septum magnet together with the vaccum chambers is shown. This model is prepared for 3D magnetic simulations. At 2.2.2 the main parameters of the extraction septum magnet are presented.

Table 4. The main parameters of the extraction septum magnet.

Width and height of the gap w, h 86.5, 86.5 mmMagnetic field B 1.0 TThe number of windings n 16Effective length l 1.473 mAngle α 3.04 degBending radius r 13 mCurrent I 4250 APulse duration, period T 3 msVacuum chamber thickness δ 5 mmSeptum thickness Δ >20 mm

Fig. 17. 3D model of the extraction septum magnet.

3. Fast kickers system. 3.1 System overview

The magnets described in this document are classified as dipole kickers. The dipole kickersproduce a homogeneous field on the plane transversely to the direction of propagation of the beam.There are two types of dipole kickers. The Dipole Injection/Extraction kickers deflect the injected beam into the acceptance of the storage ring.

Fig. 18: Collector ring.Designed for the CR kicker (Fig. 3.1.1) will be used both for injection and for extraction of the beam in various antiproton and ion-optical modes. Coming from the separators area via the common injection line one bunch of 50 ns length shall be injected into the CR. After cooling in the CR a much longer bunch must be extracted using the same kicker. Pulsed magnetic field is used to fulfill this task. To provide it, the necessary maximum integrated magnetic field shall be 1944 mT×m.

Fig. 19: Sketch of the kicker tank including magnets.

Three kicker magnet units are installed in one vacuum tank as shown in Fig. 3.1.2 Therefore, two vacuum tanks are necessary. The pulsed power unit is connected by six cables to each kicker magnet module. Within the two vacuum chambers six magnet units are placed. The supplier is required to provide all materials, equipment, tools, facilities and labor to perform the detailed engineering design, manufacturing and testing of turnkey Kicker Magnet Systems as per this specification.

3.2 Kicker Magnet System

Table 5. Parameters of the kicker magnets.

Parameter ValueNumber of kicker units 6 Magnet type window frame Deflection horizontal Integrated field 194,4 mT×mMaximum B-field for deflection the beam

54 mT

B-field direction Vertical ( up or down)Field quality in the good region field ΔB / B max

<±10-2

Good region field X/Y, mm ±75/±60Unit length on ferrite 470 mm Horizontal Aperture of magnet unit 180 mm Vertical Aperture of magnet unit 130 mm Number of coils 1 Number of turns per coil 1 Current for maximum B-field 5.6 kA (6.1 kA maintenance) Loading voltage for maximum B-field 64 kV (70 kV maintenance) Inductivity of unit (calc.) 1 μH Thickness of ferrite 40 mm B-Field in ferrite (calc.) 130 mT Ferrite material 8C11 (Ferroxcube), CMD5005 (Ceramic Magnetics)Ferrite mass per module (calc.) 74 kg Rise/fall time response of magnet to real current pulse

< 318 ns

Flat top length 0.05 μs – 1.5 μs Jitter of the flat top length < +/- 5 ns Faulty shot rate < 10-3

As can be seen from Fig. 3.2.1, there are small gaps in the middle of the top and bottom part of the ferrite core. These gaps shall be filled with a thin (1-2 mm) copper plate. Ferrite material may be selected from 8C11 (Ferroxcube), CMD5005 (Ceramic Magnetics) or similar and must be appropriate for use under ultra-high vacuum conditions.

Fig. 20. Cross section of the kicker magnet

Glue is forbidden inside the vacuum chamber. To improve the vacuum quality, the magnet modules shall be built using a minimum possible number of parts.The horizontal and vertical offset between the separate kicker modules (perpendicular to beam axis) shall be below ±0,5 mm. The modules shall be parallel to each other. Deviations from this parallelism must be below ±0.5 degrees. The alignment of the magnets in the longitudinal and cross direction must be possible.

3.3 Magnetic field calculations.

Fig. 21. Magnetic field cross section distribution.

Fig. 22. Magnetic field distribution along

beam axis

3.4 Vacuum chamber

The system consists of six magnet modules. They are placed in two vacuum chambers.As the requirements on storage time are comparatively moderate for the rare isotope beams, it is sufficient to keep the CR vacuum in the range of 10 -9 mbar. The vacuum chamber itself shall provide obtainment of 5*10-10

mbar before the kicker magnets are installed. The outgassing rate of all installed materials should be very low to ensure the required vacuum quality. Each vacuum tank is equipped with two vacuum pumps. Totally, 2×3 high-voltage cables are connected to each kicker magnet unit. Each kicker magnet unit requires two cable feed boxes. These boxes are placed above the magnet on the vacuum tank. Transformer oil is used as an insulating material.

The main parameters of this system are summarized in 3.4.1 below.

Table 6. Some key parameters of the injection kicker module.

Parameter Values Total length of one vacuum tank 1840 mm without bellows Number of vacuum tanks 2Number of kicker modules in each vacuum tank 3Unit length on ferrite 470 mm Distance between units 130 mm Inner diameter of vacuum tank ~ 500 mm Outer diameter of vacuum chamber main flanges 605 mm Wall thickness of vacuum tank >8 mm Side wall thickness of vacuum tank 20 mmDistance of middle axis of vacuum tank to cable plugs ~ 400 mmVacuum quality <1*10-9

mbar Electrical insulation of HV connectors >70 kV Total weight of vacuum tank with kicker units 630 kgMain flanges (connection to beam pipe) CF200 according to vacuum

spec.

Fig. 24. Vacuum chamber cross section

The flanges and a vacuum pump are placed under the vacuum chamber. Two pumps are connected to the vacuum chamber through CF100 flanges (according to the vacuum specification). The beam height (i.e. also the height of the central axis of the vacuum chamber) shall be 1400 mm above ground. The stand, delivered by the manufacturer, guarantees a stable and correct position of the vacuum chamber and allows adjustment using the adjustment feet delivered by the company. Technical guideline F-TG-S-3.51e describes the basic requirements of the stand. The kicker modules shall be installed in the chamber using a guide system. This system shall provide movement of the kicker magnet perpendicular to the beam axis during adjustment of the magnet system. The position of the modules shall be well defined and must not be changed.The whole system must withstand voltages of up to 70 kV / DC without electrical breakdown. The voltage will be applied for a sustained period. A vacuum pressure gauge shall be integrated to check and monitor the pressure in the chamber. The flange is milled in a side wall of the vacuum chamber. Bellows must be installed on each side of the vacuum tank to provide flexibility in radial direction to allow adjustment of the chamber.Fiducials shall be fixed on the chamber to allow alignment of the magnets. Lifting eyes allow transportation of the chamber with one crane. Transportation by forklift shall also be possible. Detailed information about the injection / extraction vacuum details is described in the common specification F-CS-VC-02e.

3.5 Pulse quality

3.5.1 shows the pulse parameters based on TDR-CR-V15 as shown in Fig. 3.5.1 and Fig. 3.5.2.

Table 7. Requirements of the magnet current pulse

The flat top of pulse up to 1.5 μs (adjustable) Max. repetition rate for the loading of the energy storage devices

1 Hz

Minimum time delay between pulses <200 ms Flat top error with current 3.5-6.1 kA < 2.0 %Current Rise/Fall time (0 to 100 %) < 318 ns Reproducibility (ΔIP/IP) < 0.5 % Overshoot < 2%

Fig. 25. The cycle of the kicker magnets in the antiproton mode.

Fig. 26. The cycle of the kicker magnets in the RIB mode.

Fig. 3.5.3. shows an acceptable deviation of the actual magnet current from the nominal current during the flat top time. This deviation, including droops, ripples and reflections, must be lower than 2%.The pulse quality must be independent of the current level. The reproducibility of the pulse amplitude error must be lower than 0.5 %.After reaching the maximum current, a slight overshoot occurs. This overshoot is less than 2% of the rated current and, therefore, is within the required quality. To obtain 2% overshoot, the capacity is installed parallel to the kicker magnet and the overshoot is dependent on the capacity value.

Fig. 27. Close up view of the flat top of the magnet current.

3.6 Power supply system

Field Direction: The pulsed magnets shall deflect the ion/antiproton beams in the opposite directions.The pulse of magnet current should have a flat top with a variable length. The maximal required length of pulse is 1.5 µsec. The rise and fall time is not part of the pulse duration. The maximum current during the flat top is 5.6 kA with nominal charging voltage equal to 64 kV. A sketch of the electrical circuit is shown in Fig. 3.6.1.

Fig. 28. Schematic electrical circuit of the injection kicker module.

Each magnet will be powered by an individual power supply system. Fig. 3.6.1 shows the basic structure of the pulse generator, which produces rectangular pulses with different field polarities. The polarity of the magnetic field changes with the direction of the discharge current. The pulse generator consists of two energy storage devices with high-voltage transformer, Pulse Forming Networks (long

cables with a length of 150 m) and two high-voltage switches (thyratrons). The bending magnet (Kicker) itself is placed electrically between the energy storage devices, which are used to produce a nearly rectangular current pulse. All cables are charged with a high voltage before triggering.

The calculations take into account the cable losses. The rise time of the magnet field is 318 ns. The maximum pulse length depends on the cable length. The maximum pulse length of the kicker is 1.5 µs. The pulse length can be controlled by the timing of the high-voltage-switches. To achieve the required kick strength a PFN low characteristic impedance of 5.7 Ohm is chosen.The system is matched with a termination resistor (R=Z0) at both ends of the circuit to avoid unintended reflections.

3.7 Charging process of the energy storage device

Fig. 29. Electrical circuit for the charging process of the energy storage device.

Fig. 3.7.1 shows the schematic electrical circuit for the resonant charging process of the energy storage device. After charging of the capacitor bank (C-Bank) with a low level voltage (max 400 V) DC, the thyristor is switched and the energy stored in the capacitor transfers to the energy storage device and the voltage transforms up to 64 kV. This effective load process can be finished within 200 ms.The load time is dependent on the resonant frequency of the C-L circuit, which is determined by the values of the capacitor bank and the leaking inductance of the transformer.

3.8 High voltage switches and accessories

Two high voltage switches are required in order to control the pulse length. The switches shall operate without misfire and with a good jitter values (± 5 ns) in the voltage range of ~ 40 kV up to 64 kV. Current and voltage information of the cathode and reservoir heating of the thyratrons shall be displayed on the thyratron supply unit. Tube supply voltages (230 V / AC) must be stabilized to ± 2 V to avoid drifts of the working point. The heating currents of the switch tubes are monitored and, if they are outside the defined range of values, the interlock is triggered. A trigger pulse generator with the appropriate interface is also a part of the delivery for each pulser. The design of the housing in which the switches operate in oil is safe to touch and easy to maintain. Specifically, in this case it is important to ensure that a change of the thyratrons can be performed in a short time.

3.9 Energy storage device and transmission cable

A high voltage cable is used as an energy storage device. All calculations and estimations in this specification are based on the DRAKA pulse cable CPP20. The cable impedance is 17 Ohm. To provide a 5.7 Ohm impedance, three cables shall be connected in parallel. This is necessary for obtainment of 5.6 kA current amplitude. To achieve the required pulse length three cables with a length of 150 m for each PFN are required. Energy storage cable is used as a transmission cable. It

connects the pulser with the matching resistor located in the service room with the magnet in the accelerator building. Both sides of the cables should be equipped with removable connectors.

3.10 Terminating resistor

After each pulse, the total stored energy in the storage device is transferred into the termination resistors. These resistors shall be placed in oil with a sufficient flow to cool the setup. The peak power at the resistor stack at normal operation (5.6 kA) is ~268 MW (for one shot with duration 1.5 μs) and 536W average power per one cycle. The resistance value shall not exceed more than 2 % during operation. The temperature control must be done accordingly.The design of the resistor including housing is finished but improvements or / and modifications can be done. The disk resistor material itself consists of ceramic carbon. This design is based on an oil forced cooling. For optimized cooling sintered metal disks are mounted between the resistor disks. Therefore, the oil is able to flow between the disks. A compensating reservoir will be used to compensate temperature changes, etc. A desiccator prevents penetration of humidity into the oil. Changing Interval of the oil must be 3 years or (preferably) more.

Fig. 30. Terminating resistor

3.11 Voltage divider

The injection kicker will operate with high voltage. For the observation of the loading process, a HV-voltage divider is required. It must be able to measure the maximum HV-voltage and the time dependent loading process. The scaling factor of the divider must be 70 kV / 10 V. The requirement of the measurement accuracy is ± 0.5 % of the maximum voltage. The second voltage divider is required for the measurement of the capacitor bank voltage. The accuracy must be ± 0.5 % of the maximum load voltage (400 V). The scaling factor of the divider must be 400 V / 10 V. Furthermore, it must be able to observe the time dependent loading process of the capacitor bank.

3.12 Current transformers

To measure the time dependent magnet current a fast current transformer shall be installed. A fast current transformer is required to measure the time dependent magnet current, the signal shall become visible in the control room by connecting a 50 Ohm cable. The bandwidth requirement must be sufficient to measure the rising, leading edge and flatness of the magnet current. The scaling factor must be 6 kA / 10 V. The transformer shall be placed outside of the vacuum chamber and connected to the ground of the termination resistor. The second current transformer is required to measure the dump switch current. It must be of the same type as defined for the magnet current measurement.

3.13 Power supply

The main part of the kicker pulser is a DC power supply. It is required for the resonant charging process of the energy storage device. It must be able to fulfil the pulse accuracy and repetition rate of the pulser. The power supply must provide the maximum output power for the permanent mode. It must be short circuit proof. This power supply is remote controlled with the defined interface. All input and output signals must be potential free against ground potential. This applies to all digital and analog signals.The power supply must provide a local mode with the possibility of adjustment of the output voltage and current limitation controlled by a potentiometer (10-turns) active only in local state. Furthermore, the maximum output voltage must be adjustable by a potentiometer. The output voltage and output current must be available as analog signal with BNC connectors. These signals should have a voltage range of 0 – 10 V.

3.14 Control Interface

As an interface to the machine control system, the Scalable Control Unit (SCU) developed at FAIR shall be used. It is connected with the control system via copper-based Ethernet and the timing system via fiber optic cable. One 19” frame with a height of three rack units (3U) in one cabinet for each pulser must be reserved for installation of the SCU and additional control hardware. For cooling reasons, a space of 2U must be reserved below this 19” frame for installation of a fan. The necessary data (status, interlock and triggers) must be supplied potential free. For other signals (timing and analogue data) coaxial 50 Ω connectors shall be used. Galvanic decoupling is mandatory. Further information on SCU can be found in the technical guideline F-TG-C-02e. Detailed information about the power supply Interfaces is described in the technical note F-TN-C-0007e control interface for kicker power supplies. This is only a general description of the principle and includes only basic requirements.The following properties must be provided: Each PS must have inputs for:

Trigger pulse for energy storage charging – 2 pcs Trigger pulses for firing of the HV-switches – 2 pcs Signal enable/inhibit Signal power on/off Set amplitude (digital) – 2 pcs Reset (local reset also available)

The pulser must provide: Status and interlock with error memory Analogue current signal from the magnet current Analogue voltage signals from the thyratron outputs Analogue voltage signal from the energy storage device Local / remote power on / off

Local / remote reset faultStatus word must contain the list of interlocks:

PS error reset PS switch On PS switch Off Standby: PFN HV is prohibited PS is ready (no interlocks) Oil temperature of the pulser ok < 45°C Loading power supply ok Loading state of the energy storage: ok if voltage corresponds to the required amplitude±0.35% Charger is switched ON (contactor is ON) Heating voltage and current for each thyratron within the limits (to be determined by working

point of thyratron) storage is overcurrent (charging current) Storage is overvoltage PFN is overcurrent (charging current) PFN is overvoltage 1-st thyratron is overcurrent (discharging current) 2-st thyratron is overcurrent (discharging current) Power Supply doors open Remote/Local control Power Converter emergency button is pressed External interlock fault

The status power on, off, interlocks and internal errors are displayed with LEDs on the front panel. The power supply can be turned on/off with a key switch located on the front panel. The power supply has a local / remote switch on the front side. Local operation for maintenance purposes must be possible. A push button switch can reset internal errors, which is located on the front panel. 3.15 Engineering design

The design shall include the following items: A 3D model of the magnets, vacuum chamber supports and connection boxes shall be made. As a first step, the conceptual 3D model will be checked by BINP. During this process, only the solution and interface will be checked. After this CDR (conceptual design review) approval 2D manufacturing design and drawings shall be made. All drawings must be approved by BINP in the frame of the FDR (final design review). This release process does not absolve the supplier from design responsibility. The time schedule must be agreed with BINP, and a report on the status of the design, manufacturing and testing process must be provided. Deviations from the planned time schedule must be reported as soon as they are discovered. Each deviation from the specification must be reported and requires an agreement with the company.

4. Beam Observation System 4.1 Overview

The Collector Ring (CR) is a dedicated storage ring in the FAIR project, where the main emphasis is laid on the effective stochastic precooling of intense beams of stable ions, rare isotopes or antiprotons.The CR shall fulfil three tasks:

Stochastic precooling of antiprotons coming from the antiproton separator (AS) at a fixed kinetic energy of 3 GeV, to be then delivered to the HESR storage ring. After the installation of the RESR, the antiproton beam will be delivered to this ring for accumulation.

Stochastic precooling of secondary rare isotope beams coming from the fragment separator (Super-FRS) at a fixed kinetic energy of 740 MeV/u, which will then be delivered to the RESR storage ring.

Mass measurements of short-lived secondary rare isotope beams from the Super-FRS in the isochronous mode. To allow for a large area of the mass surface to be covered and for different atomic charge states of the secondary ions, it shall be possible to tune the isochronous mode of the CR in a range of transition energies from gt=1.43 to gt =1.84.

There are several types of operational cycles with beams in CR starting from injection and finishing with extraction, and beam parameters change significantly during the cycles. The momentum spread is largest at injection, when very short bunches of several hundred ns from the production targets (either rare isotopes or antiprotons) are injected. At this instant, the horizontal aperture of the ring is filled. After a 1.5 ms bunch rotation and a 150 ms adiabatic debunching, the momentum spread is decreased, whereas this process leaves the transverse emittance unchanged in both directions. After these procedures the bunch fills all the perimeter of the CR. The reduced momentum spread is a necessary prerequisite for stochastic cooling. The cooling time for the antiprotons is 10 s and is estimated as 5 s after further CR upgrade. The cooling time for highly charged rare isotope beams is much shorter (1.5 s). After the procedure of stochastic cooling, all phase subspaces are strongly reduced. The cooling is followed by the re-bunching procedure in 130 ms and further extraction of the beam. During all these times periods the particle beam may be observed with different parts of Beam Diagnostics (BD) system.Parameters of high intensity as well as low intensity beams shall be properly measured at the different stages of CR operation cycle. Highest sensitivity of devices is required to measure properties of a low-intensity antiproton beam as well as a high-intensity ion beam. Furthermore, different process like bunch rotation, injection efficiency, closed orbit distortion are a critical process and must be monitored precisely. Therefore, the beam diagnostic system must be highly-sensitive and must have a large dynamic range. 4.2 Beam Diagnostics Layout

The Beam Diagnostics system for Collector Ring consists of different subsystems, its layout is shown in Fig. 4.2.1. The optical function of the ring in different operational modes is presented in Fig. 4.2.2.

Beam Residual Gas Monitors (shown as yellow dots) Beam Position Monitors (shown as green dots) Beam Scintillating Screens (shown as red dots) Beam Scrappers (shown as blue dots) Beam Intensity Measurements (FCT, DCCT, Cryogenic Current Comparator, not shown) Beam Tune Measurements (BTF Exciter, Broadband Schottky Pickup, not shown) Beam Stopper with Intensity Measurement (not shown) Beam Schottky Resonators (not shown)

Fig. 31: Collector Ring layout

Fig. 32: Optical functions and the beam sizes for the CR (half the ring) for operations with antiprotons (left) and rare ions (right)

4.3 Residual Gas Profile Monitor

Purpose:A Residual Gas Monitor (RGM) is a non-intercepting diagnostic device for the precise determination of the transverse beam profile in a circulating beam in synchrotrons and storage rings.The measurement of the transverse beam profile is an important tool to determine the emittance and its evolution during the acceleration and cooling process. The Ionization Profile Monitor in the CR will be

used for this purpose. Additionally fast changes of the transverse profile caused by any beam manipulation in principle can be monitored in a turn-by-turn mode.The monitor will be designed for high-current operation at FAIR where conventional intercepting diagnostics will not withstand the high intensity ion beams.

1.1.1 Location:RGM is marked in the CR drawings as CR03DG1RH and CR03DG1RV – it is correspond to 2 devices, which measure horizontal, and vertical beam profile respectively. The RGMs will be installed between RF cavities and Stochastic Cooling Pickup at the middle of the extraction straight section of CR just after the quadrupole lens CR03QS02.

1.1.2 Operational principle:The basic physical process exploited here is the ionization of the rest gas. The residual gas particles are extracted by an electrical field from the beam path area and multiplied while the projected particle position is preserved. Finally they create light spots on a phosphor screen. The emitted light during the impact on the phosphor screen is measured by light detectors and partly evaluated online. Resource consuming evaluation is done via post processing.The standard measurement technique is a measurement of light spot on a phosphor screen as schematically depicted in Figure 3.

An electrical field of good uniformity is applied transverse to the beam axis (EFB, electrical field box). The electrical field accelerates the residual gas ionization products (residual gas ions or electrons) toward a position-sensitive-particle-to-light converter (OPD, optical particle detector). The emitted light is then detected by an image acquisition system. Due to the electrical field, the beam profile is a 2 dimensional projection of the 3 dimensional ionized residual gas cloud. Therefore two electrical field boxes are placed in series close together and turned by 90 degrees to produce a horizontal and a vertical beam profile. Due to intense beams the ionized residual gas cloud density distribution is changed by the beams space charge effect. In some RGMs a magnetic field is applied in parallel to each of the electrical fields to detain the residual gas particles from transverse moving. The residual gas particles spiral along the magnetic field lines toward the OPD. Because of the large residual gas ion cyclotron radius it is needed to detect the residual gas electrons when a magnetic field is used. Of course, additional magnets are needed to correct the affected beam path.In accelerators without dominant space charge effect RGMs without magnetic field can be used. During the ionization process the residual gas ions have an attitude to hold their transverse position after ionization contrary to residual gas electrons. Also in the space charge dominated accelerators it must be possible to measure without magnetic field. Therefore it is mandatory to layout the RGM in a way that it can detect residual gas ions and residual gas electrons with the same device. This affects at least the high voltage layout.Measured Quantity:The primary measurand is the charged particle – residual gas ions or residual gas electrons measured by the instrument during the passage of the entire bunch or its fraction. The circulating beam in the circular accelerators ionizes the residual gas thus produce the distribution residual particles (residual

Fig. 33: Schematic representation of RGM principle

gas ions or residual gas electrons). The residual gas distribution is measured with a RGM. This proportional to the transverse density of the particles in the circulating beam and their charge state.Measured parameters: The RGM instrument yields an average projected position of the residual gas particles as a function of time.Evaluated Parameters online: The beam parameters related to the measured / located ionized residual gas particles are the beam profile and the beam position. This quantities has to be calculated onlineMeasurement Challenges:Advantages: The beam profile measurement technology – is non-intercepting – and this is the biggest advantage compared to other methods for accelerator rings. Because the beam passes the device many times, an intercepting method would destroy the beam. The other advantage is the large number of profiles that are recorded even in high resolution mode. Moderate beam profile changes are visible. Finally, the high spacial resolution that is achieved by digital cameras as signal readout is an advantage.Limitations: The limiting factor is the framerate of the digital cameras. With newer and faster cameras, the bottleneck will be shifted to the data acquisition software to handle the large amount of generated data.The uniformity and the quality of the real electric and magnetic fields is the basis for meaningful and trustworthy results. The real mechanical realization has to be considered at the design and simulation phase of the fields also the high voltage supply lines inside the vacuum tank.Disadvantages: The disadvantages are the camera sensitivity to radiation caused by the beam and the need for sensitive handling of the OPD device and the cameras noise. RGMs and especially optical RGMs are complex devices, which have several components that affect mutually.Mechanical Setup:The mechanical parts of the RGM is presented in Fig. 4.3.2. They are the EFB, the OPD, the vacuum tank, the rack, the camera holder, the HV lamp holder and the HV adapterbox. Mainly stainless steel and ceramics as isolators are used. Special are the feed-throughs for high voltages of up to 10 kV. The central device is the electric field box. The OPD (optical particle detector) is visible from outside the vacuum tank through a viewport (CF100 or CF250). The UV light (MCP calibration) shines through a smaller viewport (CF35) from the opposite through the electric field box onto the MCP surface.All high voltage electrodes are isolated by ceramics for vacuum reason. It is important to reduce the surface area of isolators inside the vacuum to a minimum. This is an important task for the mechanical design process. The RGM is mounted on a CF200 flange.

Fig. 34: RGM measurement system components

The RGM (for example in horizontal direction) system consists of the following parts:1. Electric Field Box (EFB)2. Position Sensitive Optical Particle Detector (OPD)3. Image Acquisition System (IMAGE) with CCD camera4. High Voltage Supply (HV)5. Vacuum flange with electrical feed-through for 10kV6. Vacuum flange with view-ports7. UV lamp (UV) for calibration of the OPD8. Data Acquisition System (DAQ)

General Parameters:To fulfill the requirements for the CR beam cooling observation RGM system shall have parameters as listed in 4.3.1 and 4.3.2.

Table 8: Specification of RGM system

Parameter Antiprotons Rare IonsNumber of particles > 108 106 (TDR 109)

Particle charge (Z) 1 10-90

Particle kinetic energy 3 GeV 740 MeV/u

Revolution frequency 1.35 MHz 1.16 MHz

Beam size ϭx/ϭy (after injection) 4/6 cm 4/6 cm

Beam size ϭx/ϭy (after cooling) 0.6/0.9 cm 0.2/0.3 cm

Cooling time 10 sec 1.5 sec

Vacuum pressure 10-9 mbar 10-9 mbar

Maximum beam size (diameter) 14 cm 14 cm

Maximum integration time 100÷200 msec 100÷200 msec

Profile monitor length (both directions)

110 cm 110 cm

Horizontal aperture 16 cm 16 cm

Vertical aperture 16 cm 16 cm

Spatial resolution 1-2 mm 1-2 mm

Transverse detector size ≈14 cm ≈14 cm

Table 9: Specifications of RGM subsystems

Device Parameter Value UnitEFB field 10000 V/m

field uniformity 0.5 within working region

working region MCP active areaOPD (MCP) Stages 2 (chevron)

channel diameter 4-5 µmactive area length (in beam direction, minimal)

70 mm

active area length (transverse to beam direction, minimal)

150 mm

OPD (Phosphor) decay time 1000 us

Digital Camera frame rate 32 fpsresolution 1280 × 960

OpticsCalibration of OPD type UV lamp

wave length < 120 nmDAQ

Image Acquisition:The system in principle can operate with different OPD where electrons, which appears at the exit of MCP, goes directly to resistive plate thus locally charging it (see Fig. 4.3.3). Measuring the charge flows from both ends of the plate, you can determine where electronic avalanche hits the plate. The advantage of this approach is a total elimination of the transformation of particle flux to light, which, due to the reflections can lead to spurious peaks in the measured profile. This effect is observed in the case of ionization synchrotron COSY profile monitor (Germany). The disadvantage is the need to develop a special electronic unit and, since its count rate is limited, one need to control flow intensity.

Principle scheme of the registering part of profile monitor is shown in Fig. 4.3.4. Here the charge of electrons avalanche, generated by MCP from single ion, moves to a long resistive element R. Signals from two ends of this element move at the input of current-responsive amplifiers A1 and A2 through the separating capacities C1 and C2. Amplifier integrates short input pulses in feedback capacities C3, C4. Resistors R1 and R2 provide a flow of constant component of current, deposited on resistive plate. Resistors R3 and R4 provide maintenance of zero average on integrating capacities.Signals from amplifiers outputs come to the inputs of dual-channel ADC. Digital data from the output are preprocessed in programmable logic chip (FPGA) and transmitted via Ethernet channel in the computer of the registration system for the main processing of statistics.

ions

MCP

Resistive plate

e-

Fig. 35: Scheme of detector with resistive plate

Fig. 36: Principal scheme of registration DAQ for resistive stripline

The x-coordinate of the event is determined by the relation of difference of voltage increments U1 and U2 in the outputs of the amplifiers to the sum of these increments:

,where L – is the length of the resistive element.To substantially improve the resolution in the central part of the detector additional similar system, but with a shorter (L ~ 2-3 cm) resistive element can be used. In addition, the resistive plate should be split in longitudinal (relative to the beam) direction to increase count rate of the detector.The solution that transfer the “pictures” from the MCP to the image acquisition devices is not yet fixed because of the different requirements. 4.4 Beam Position Monitor

Purpose:The CR BPM system is a non-intercepting diagnostic device to measure the center of charge of a bunched particle distribution in the x-y plane. Measuring the center of charge position allows for beam alignment during commissioning and machine setup. It also allows for monitoring the closed orbit, and thus orbit correction in the storage ring for a save operation.Location:The CR BPMs will be installed inside the vertical dipole correctors due to limited space for diagnostic installations. Not the the same type will be used at all locations. Beam Position Monitors is marked in the CR drawings as CR01DX1, CR01DX2, CR01DX3, CR01DX4, CR02DX1, CR02DX2, CR02DX3, CR02DX4, CR02DX5, CR03DX1, CR03DX2, CR03DX3, CR03DX4, CR04DX1, CR04DX2, CR04DX3, CR04DX4, CR04DX5 – it is correspond to 18 devices, which measure horizontal, and vertical beam positions simultaneously.Operational principle:The non-destructive determination of the beam position (center of mass) relies on the measurement of charges induced by the electric field of the beam particles on an insulated metal plate. Because the electric field of a bunched beam is time dependent, an alternating current signal is seen. In a standard BPM setup four pickup plates are installed at the beam pipe wall. In general, pickups couple to the electromagnetic field as generated by the charged particle beams. The amplitude of the induced signal is inverse proportional to the beam distance to the electrode which yields the beam's center of mass for both transverse planes.At the present stage the CR BPM is considered to be based on the diagonal type pick-up. In this case, the displacement of the beam center with respect to the center of the vacuum chamber can be calculated from voltages on the orthogonal BPM plates. The difference voltage or

is sensitive to the beam displacement. Normalizing to the sum signals (for horizontal direction this sum is equal to ) the horizontal displacement x can be obtained via simple formulas:

,

.This formulas stands for horizontal and vertical direction respectively. The variables Kx and Ky are the horizontal and vertical position sensitivity, respectively. They are expressed in units of [K]=mm. Position sensitivity is the most fundamental pick-up parameter that was maximized during BPM design optimization. The offsets δx and δy represent the misalignment of the electric center of the pick-up with respect to the geometrical one.Other quantities featuring BPM are: Accuracy: defined as the ability of absolute position reading with respect to any absolutely known axis e.g., to the symmetry axis of a quadrupole magnet. The accuracy is mainly influenced by the pick-up

mechanical tolerances and the long term stability of the mechanical alignment. The accuracy of the beam position determination is a convolution of the mechanical adjustment of the BPM, displacement sensitivity and overall resolution of the readout (including e.g. amplification noise, digitalization resolution, etc.). The required position accuracy for the CR is 5 mm for a first turn measurement and 1 mm for a closed orbit measurement.Resolution: This is the ability for measuring small displacement variations. In contrast to the accuracy, relative values are compared here. The resolution usually is much better than the accuracy. The averaging procedure, typically over 1000 subsequent turns, increases the accuracy by a factor of 100. The required position resolution for the CR is 0.1 mm at 100 Hz read out rate.Dynamic range: means the range of beam current to which the system has to respond. In the case CR BPM, the signal adoption will be done by an amplifier, with switchable amplifier stages at the input stage of the electronics processing chain. Within the dynamic range, the position reading should have a negligible dependence with respect to the input level (beam current).Measured Quantity:Amplitudes of the time dependent signals induced in the four pickup electrodes, with the capability of a first (single) turn measurement of a 50 ns beam pulse. For the nominal case of 108 antiprotons, bunched in FWHM 50 ns pulse length a peak potential of about 10 µV was calculated using HFSS. For a factor of 100 lower currents during the start phase and increased bunch lengths during bunch rotation, the expected SNR drops to ~ 1 and lower. Highest peak potentials in the order of hundreds of mV are expected for machine runs with multiply charged ions 109 (50+) and during commissioning with protons. During the first revolution in p-bar runs 1010 pions will be detected with about 10 mV peak potential, for all following revolutions the signal will be reduced to just a percent of that value. As implication for the electronics, individual BPM plate signals need to be amplified with a bipolar broadband linear amplifier with fast switching option to detect pions and the 100 times weaker signal for p-bar only within the same cycle.Evaluated Parameters online: Beam position measurement on a bunch by bunch basis (single turn, one bunch per turn) for all BPM locations. The closed orbit is the beam position at all BPM locations for a given point in time. Typically the position data is evaluated over ~1000 subsequent turns which allows much higher position accuracy. In a later stage this information may be used in an automatic closed orbit correction mechanism like the closed-orbit feedback. In addition, position data will be used for base-band tune determination. This will be done in purely digital manner by applying a Fourier transformation to digitized position data.Evaluated Parameters via post-processing: Calibration parameters will be determined to correct the zero line offset. This will be realized with stabilized calibration signals that are applied to the input of the low noise preamplifiers. Correction parameters have to be determined with the help of test signals for compensation of mismatches between two channels in one beam-plane.BPM Geometry Optimization:In order to comply with the measurement task as described in the previous sections one should optimize the BPM geometry i.e. electrodes sizes and shapes, lengths and so on. During development of BPM for CR simulation was done with HFSS code where particles beam was modeled by 2 mm diameter wire and signal electrodes was modeled by power output ports with characteristic impedance 50 Ohm. As a result of simulation transfer function of electrodes was obtained in frequency range up to 100 MHz and higher, 2-dimensional transformation from electrodes signal to beam position was constructed using S-parameter. After that all geometry was changed in different manner to achieve the following goals:

- maximization of linearity and scale factor parameters- maximization of beam signal- minimization of capacity of signal electrodes down to 50-60 pF- minimization of electrical center offset down to 1-5 mm- minimization of cross talk between different pairs of electrodes down to -20 dB

During optimization about 15 different geometries was tested. You can see the most interest result which can be used as a final solution in the figures below.In Fig. 4.4.1 you can see “variant 5” in which special grounding electrodes was introduced for removing resonance behavior in range up to 150 MHz (see “variant 9” for example) and forming the needed capacity. The shape of signal electrodes is super-elliptical with power 3.5, and half-axes equal to 210 mm and 90 mm in horizontal and vertical direction respectively.

In Fig. 4.4.2 you can see the pictures of cross influence of different pairs of signal electrodes. In such type of simulation one of electrodes was an “emitter” and the other three electrodes were “receiver” of the RF signal. Electrodes for horizontal position measurements – 1 and 2, for vertical position – 3 and 4. One can see that cross reference betweens 1,2 and 3,4 electrode pairs is suppressed to the level of 30-40 dB, and the transfer function behavior (exact shape) is the same for different electrodes. This means that the shape of the beam signal on the different electrodes will be the same. Dashed lines shows the case of transfer function then the wire is placed in the center of the BPM. The capacity of the BPM obtained from the slope of transfer function is equal to 60-65 pF.In Fig. 4.4.3 you can see the reconstructed map between electrodes signals and real beam position and linearity of the BPM itself. The blue dots is the real position of the wire and red dots is the reconstructed one. Upper pictures Fig. 4.4.3 shows the beam reconstructed position as a function of the wire position. For this case the scale factors and electrical center displacement equal to Kx = +427.6 mm, Kz = +181.2 mm, dx = -5.1 mm, dz = 1.7 mm, and the reconstruction error not more the 1.2 % and 1.3 % for horizontal and vertical direction respectively.

Fig. 37: Different geometries and their transfer functions in range [10, 300] MHz

In Fig. 4.4.4 the table with different parameters for most interesting BPM geometries is presented. The same procedure and algorithm of optimization was done for smaller type of BPM which will be installed in straight sections of the CR, while BPM presented on the Fig. 4.4.1 (as “variant 9”) will be installed in the arcs of the CR.

Fig. 38: S-parameter for different electrodes range [10, 300] MHz

Fig. 39: Transformation map between electrode signals and real beam position

Mechanical Setup:The mechanical parts of the BPM is presented in Fig. 4.4.5. Color scheme is the following: gray – vacuum chamber and flanges, gold – mechanical supports for electrodes, red – signal electrodes, magenta – grounding electrodes.

The BPM system consists of the following parts: Detector with four pickup electrodes, mechanical mount, electrical interconnections Vacuum chamber integrated in the quadrupole magnets Preamplifier close to the vacuum feed-through, radiation tolerant design Variable gain amplifier with switchable attenuator chain Clock splitter DAQ system with calibration output, FESA compliant, 10 GB Ethernet components or other

suitable for data concentration Power supplies for all electronic components in the beam line

Fig. 40: Optimization results for different geometries

Fig. 41: 3D model of the BPM

Schematic realization of signal chain and the distribution of components in areas of different radiation level: Starting with LNAs directly at the pickup, the first coaxial cable to the VGA, followed by second cable and DAQ-system in electronics room shown on Fig. 4.4.6.General Parameters:To fulfill the requirements for the CR beam position measurements, BPM system shall have parameters as listed in 4.3.1.

Table 10: Specification of BPM system

BPM Type «Big» «Small»Vacuum Chamber Round Round

Flange type Weldable 500 CF200

Length (flange to flange) 630 mm 630 mm

Diameter (inner) 450 mm 200 mm

Aperture (within electrodes) 420 х 180 mm 160 х 160 mm

Electrode length (signal) 250 mm 250 mm

Electrode length (grounding) 20 mm 20 mm

Electrode gap (between all) 5 mm 5 mm 4.5 Scintillating Screen

Purpose:Scintillating Screens are intercepting devices to measure a 2-dimensionalintensity distribution of the antiproton or ion beam in the transversal plane. In contrast to the methods implying direct projections (such as SEM-Grids, BIF-monitors and IPMs), screens deliver a true 2-dimensional image of the impinging intensity distribution. Beam-profile projections along the vertical and horizontal axes can be derived later from the 2D image, as well as center of mass or higher statistical moments of the distribution. Driven by the differential energy loss of the ion beam, scintillating screens are excited up to fluorescence levels. Important parameters like the light yield Y, the decay time τand the radiation hardness are characteristic material properties of the scintillator and depend on the actual beam parameters. Scintillating Screens are typically used for low to medium current applications in transport sections or as a first turn diagnostics in synchrotrons or storage rings and whenever a two-dimensional intensity distribution is important for machine operation.

Fig. 42: Schematic realization of signal chain and the distribution of components

Location:Scintillating Screens is marked in the CR drawings as CR04DF2S, CR01DF1S, CR02DF1S, CR02DF2S, CR04DF1S – it is correspond to 5 devices, which measure horizontal, and vertical beam profile simultaneously. Not the the same type will be used at all locations.Operational principle:Ions that impinge on the scintillator lose energy in the material according to their specific energy loss which is a function of the particle type, its energy, its charge, and the chosen type of scintillating material. In a scintillator some of the energy loss is converted to a number of isotropically emitted photons, typically in the optical wavelength range. Via an appropriate optical lens system the photons are transported to a digital camera and yield the beam profile in pixel space. Applying a calibration factor (to convert pixel separation into coordinate space), the physical size of the beam spot can be determined, and hence an image of the real beam distribution. The image calibration depends on the specific optical system. Reference marks on the screen holder allow an in-situ calibration.Measured Quantity:The measured quantity is the position-dependent (in transverse coordinates) light yield (emitted by the scintillator under ion impact) from which the intensity distribution of the particle beam is extracted. This beam diagnostics device should deliver the following information:

complete 2 dimensional beam distribution (raw data) light intensity histogram background corrected horizontal and vertical beam distribution (beam profiles) statistical moments (e.g. beam position, beam width, correlation coefficients, etc.)

Measurement Challenges:The light yield of a scintillator depends on several parameters such as the specific energy loss or the particle flux (number of particles per unit area).Material ageing, quenching effects and damage mechanisms differ between scintillator types, and, therefore, there is no multi-purpose material that can cope with the variety of beam types and intensities of the FAIR facility. A careful choice should be made according to signal estimates derived from the simulated beam spot sizes, beam parameters and detector design parameters. For typical screen at SC sizes of about 150 – 200 mm, the scintillating screens are mounted at an angle of 90° with respect to the beam axis and 45° to the camera. Here, the path length from the screen to the camera differs, depending on the impact position of the particle on the screen. This setup requires a large depth of field. This problem is not crucial because the magnification coefficient of the lens should be as small as 1:5060. It is necessary for the agreement between the SC and CCD matrix dimensions. It requires high-ratio of optical intervals of the lens, thus, a large optical depth is achievable. Figure 13 shows the proposed optical scheme of the SC. The typical dimensions of optical intervals are about a = 1800 mm, b = 36 mm for focal length of lens F = 35 mm, where a is the distance between lens and screen, b is a distance between lens and CCD matrix. Another option is a screen inserted into vacuum chamber at 45° angle to the beam. The disadvantage of this design is an increased amount of scintillating material and increased volume which is necessary for screen parking. The large dimensions of the screen reveal a problem of uniformity and durability of a scintillating powder.

Mechanical Setup:A schematic drawing of a typical scintillating screen setup with its major components is shown in Fig. 4.5.2 (screen is placed in 45° with respect to the beam and the camera):

Typical solution for such system system consists of the following parts: Scintillating screen on holder with reference marks for geometric calibration and alignment Mechanical drive to move the screen in and out of the beam Vacuum chamber to house and mount all the required components Optical viewport with appropriate spectral transmission and optical quality Lens system with matched reproduction scale Digital camera with external trigger property and adjustable parameters (e.g. gain, integration

time) Target illumination e.g. LED for calibration issues Electronics and DAQ for image acquisition

The model of the SC is presented in Fig. 4.5.3 andFig. 4.5.4. The mirror (see Fig. 4.5.1) can be aligned with four pins supporting the valve at the bottom of SC chamber. Application of the mirror allows us to place the lens and CCD camera in a horizontal plane on the stable support. The working stroke of the pneumatic actuator driving the screen is estimated as 40 mm.

Fig. 43: The optical scheme of Scintillating Screen

Fig. 44: Scheme of an intercepting scintillating screen setup

Optical system:We propose to use P43 phosphor as a scintillating material. It is widely used for similar purposes and meets the requirements of operational use. The optical constituents of one Scintillating Screen are the following parts:

Turning mirror Optical viewport fitting on a dedicated flange Lens system Digital camera system with external trigger and adjustable integration times Optical shielding for the camera-system to avoid incidence of ambient light

Fig. 45: Model of the SC. The CCD camera and optics are not shown

Fig. 46: SC layout with optical devices. LEDs for back-light are not shown

A fine alignment with a theodolite will guarantee the screen to be centered to the diagnostic chamber. The diagnostic chamber shall be aligned relative to the beam axis determined by the centers of entrance and exit flanges of the chamber.The application of lens with remote-controlled iris diaphragm is possible, but it seems that photon flux emitted by the screen at all CR beams parameters will not saturate the CCD camera. We propose to use a simple objective lens Tamron M118FM25 (Fig. 4.5.5 and 4.3.2).

Table 11: Parameters of Tamron M118FM25

Imager Size 1/1.8Mount Type 1200 NFocal Length 800 NAperture Range 100 mmAngle of View (hor×ver) 16.6°×12.5°TV Distortion less than 0.2%Focusing Range 0.1 m – ∞Operation Manual with lockFilter Size M25.5 P=0.5 mmBack Focus(in air) 12.92 mmWeight 39 gOperating Temperature –10°C – +60°C

The CCD camera Prosilica GC1290 (Allied Vision Technology, USA) will be used for the beam image registration. It is a 1280×960 resolution CCD camera with Gigabit Ethernet interface. A high-quality Sony Exview HAD CCD sensor with 3.75×3.75 m pixel size is implemented. The CCD camera runs more than 30 frames per second at full resolution; it works with standard gigabit Ethernet hardware and cables, the cable lengths can be up to 100 meters. General view of the GC1290 camera with dimensions is presented in Figure 18, parameters are given in 4.5.2.

Fig. 47: Tamron M118FM25 Objective lens

Table 12: Parameters of GC1290

Resolution 1280 × 960Max frame rate at full resolution 32 fpsType CCD ProgressiveInterface IEEE 802.3 1000baseTA/D 12 bitOutput 8/12 bitSensor Size Type 1/3Sensor Sony ICX445Cell size 3.75 µmOn-board FIFO 16 MBBody Dimensions (L×W×H in mm) 33×46×59 including connectors,

w/o tripod and lens 4.6 Scrapper

Purpose:Scrapers and collimators are devices in particle accelerators which share a common architecture, but are used for two different purposes. They both typically have blocks of heavy metal such as tungsten or stainless steel which are moved in and out of the beam pipe to collide with particles circulating in the accelerator.Scrapers tend to be beam diagnostic devices. Their blades are relatively thin in the direction of the beam and they are used in conjunction with beam loss monitors to determine where the beam is inside the beam pipe. Scrapers (and collimators) have position read-back on the location of the blade in the beam. If a scraper blade is moved across the beam aperture and at a certain point a signal comes from beam loss monitors downstream of the scraper, then the operator knows that the beam's edge must be at the location of the blade in the beam pipe.

Fig. 48: CCD camera GC1290

Collimators are typically used to select a portion of the beam coming down a beam transfer line and reject the rest. Their blades tend to be longer in the direction of the beam so that multiple scattering between particles in the beam and the collimator block will ensure that unwanted particles are deflected out of the beam pipe. Collimation narrows the range of particle angles or momentum in the beam pipe to those that "fit" into the accelerator. Location:Scrappers is marked in the CR drawings as CR01DS1, CR02DS1, CR02DS2, CR03DS1, CR04DS1 – it is correspond to 5 devices, which blades can intercept beam orbit from different sides: inner/outer horizontal and up/down vertical independently. The the same type will be used at all locations.Operational principle:This type of scraper is used to scrape the beam in a region of the accelerator where the particles have been spread out into a thin wide beam, hence the rectangular beam pipe. This region in an accelerator is called a "high dispersion" region, which means that particles in the beam pipe separate with higher momentum particles moving outward to larger radius in the machine, lower momentum particles migrating to the inside. It is a four jaw scraper, so it can do either task: determine the outer boundaries of the beam, or create a momentum slit in horisontal or vertical beam direction.Measured Quantity:The scrapers consist of 4 one-sided copper jaws, one for each of the transversal planes. Scraping is always conducted by sweeping one or both jaws through the beam. The scraper's jaws move up and down, ind and out independently. Vertical and horizontal scrapers are used to separately determine the upper, lower, and side to side extents of the beam inside the pipe.Operational challenges:In principle some mechanism like the “counterweight” for the upper jaw is needed. The stepper motors for these devices are driven by amplifier drivers located far away in service buildings above ground, tending to reduce their output torque. The upper blade is being pulled down into the vessel by gravity and air pressure. These forces combined together are too much for the stepper motor, so the gravity component is eliminated with the “counterweight” mechanism. The lower jaw sees gravity and air pressure operating in opposite directions, almost canceling out, so its motor doesn't need any help.Two jawed scrapers need limit switches for each of their individual strokes, but they also need another set of limit switches that prevent the blocks from colliding together. This is accomplished by mounting a set of switches on the moving carriage of one block and a trip rod of the right length on the other carriage.Mechanical Setup:The model of the combined horizontal/vertical scrapper in Fig. 4.6.1 and parameters in 4.6.1. Both types has the same design.

Table 13: Parameters of Scrapper

Type «Big» «Small»Aperture (diameter) 450 мм 200 mm

Length (flange to flange) 512.5 mm 365 mm

Blade thickness 70 mm 70 mm

Blade width (vertical) 200 mm 150 mm

Blade width (horizontal) 400 mm 150 mm

Flange type Weldable500 CF200

Vacuum Chamber Round Round

4.7 Conclusion

During the year of 2015 a lot of work dedicated to research and design of Collector Ring Beam Diagnostics system has been done in close cooperation with the other CR subsystems. Current status of Beam Position Measurement subsystem, First Turn Diagnostics subsystem (Scintillating Screen and Beam Scrapper component), Beam Profile Measurement subsystem is presented in this document.

Fig. 49: Model (3D view) of the “Big” type Scrapper

Publications:

№ Authors, name of published work

Name of the issue, year, volume, page number, «from…

till…»

Impact factorof the

magazine

Database,Specify

Web of Science,Scopus,RINZ

Web-link Electronic ar-chive, pre-print

1

STATUS OF ION-OPTI-CAL DESIGN OF THE COLLECTOR RING O. Gorda, A. Dolinskii, S. Litvinov, GSI, Darmstadt, GermanyD. Berkaev, I. Koop, P. Shatunov, D. Shwartz, BINP, Novosibirsk, Russia

Proceedings of IPAC2014, Dresden, Germany

http://accel-conf.we-b.cern.ch/Ac-celConf/IPAC2014/papers/tupro041.pdf

2

I. Koop, D. Berkaev et al. Activity on CR Project at BINP

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/Session1_Koop-Activity_on_CR_project_at_BINP.pdf

3

D. Shwartz. Beam Dynamics @ Collector Ring

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/Session2_dshwartz_slides.ppt

4

I. Koop, D. Shwartz, Yu. Rogovsky. CR Layout

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/Session_Koop-CR_layout.pdf

5

D. Berkaev. CR Specification status

https://edms.cern.ch/file/1507846/1/Session3_Berkaev_Specs_Status_28_04_2014.pptx

6A. Krasnov. CR Vacuum System

Proceedings of the 7th BINP-FAIR-GSI

https://edms.cern.ch/

workshop file/1507846/1/Session5_Krasnov_CR_vacuum_v1.ppt

7

P. Shatunov. Injection layout in the CR. Requirements for kickers and septums.

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/15 07846/1/ Sessi on6_PSh atunov_inj_ext.pdf

8

A. Kasaev. CR Injection/Extraction Kicker

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/Session6_Kasaev_Injection_Extraction_in_the_CR_05_2015.ppt

9

S. Litvinov. Antiproton-separatorPresent Status

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/Session6_Litvinov_pbar_present_status_Novosib_may2015.ppt

10

Yu. Rogovsky. Beam Diagnostics developmentfor CR @ BINP

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/Session7_Rogovsky_21.05.2015_7th_BD_BINP.pptx

11

P.Shatunov, A. Kasaev, THE SYSTEM OF INJECTION OF BEAMS FOR CR.Preliminary Conceptual Design Report

Proceedings of the 7th BINP-FAIR-GSI workshop

https://edms.cern.ch/file/1507846/1/F_CDR_CR_Injection_Extraction.docx

12 Petr Shatunov “BINP-FAIR Collaboration”

Procedings of the International Workshop on Antiproton Physics and Technology at FAIR, Novosibirsk,

http://indico.inp.nsk.su/event/2/session/1/contribution/20/material/

November, 2015. slides/0.pdf

13

Dmitriy BERKAEV “Collector Ring at FAIR”

Procedings of the International Workshop on Antiproton Physics and Technology at FAIR, Novosibirsk, November, 2015.

http://indico.inp.nsk.su/event/2/session/4/contribution/24/material/slides/0.pptx

14

Dmitry SHWARTZ, “Beam dynamics at CR ”

Procedings of the International Workshop on Antiproton Physics and Technology at FAIR, Novosibirsk, November, 2015.

http://indico.inp.nsk.su/event/2/session/4/contribution/25/material/slides/0.ppt

15

Yury ROGOVSKY, “Beam diagnostics Overview for CR ”

Procedings of the International Workshop on Antiproton Physics and Technology at FAIR, Novosibirsk, November, 2015.

http://indico.inp.nsk.su/event/2/session/4/contribution/27/material/slides/0.pptx

16

A Dolinskii, D Berkaev, U Blell, C Dimopoulou, O Gorda, H Leibrock, S Litvinov, U Laier, I Koop, I Schurig

Physica Scripta, Volume 2015, Published 26 November 2015

http://iopscience.iop.org/article/10.1088/0031-8949/2015/T166/014040/pdf

Talks:

The work is carried out with the financial support of FAIR-Russia Research Center