Advanced Accelerator Research - INFN · 2001. 10. 20. · ARDAARDA Advanced Accelerator Research...
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ARDA ARDA Advanced Accelerator Research STANFORD LINEAR ACCELERATOR CENTER Presented at Lepton Photon 2001, Rome, Italy The accelerator research program at SLAC performs research on accelerator technology and particle beam physics pushing both energy and luminosity in high-energy electron colliders. Research ranges from development of existing facilities, to work toward next generation linear colliders, as well as the design of new techniques and devices for high- gradient acceleration and focusing for electron linear colliders up to 5 TeV. Work involves collaborations with physicists from several universities, other laboratories and the private sector. http://www.slac.stanford.edu/grp/ara/ 0 10 –10 –20 0 20 0 10 –10 –20 0 20 0 10 –10 –20 0 20 0 10 –10 –20 0 20 0 10 –10 –20 0 20 0 10 –10 –20 0 20 0 10 –10 –20 0 20 0 10 –10 –20 0 20 P x(µrad) P x(µrad) X (µm) X (µm) X (µm) X (µm) Coherent Dipole Motion 0 50 100 150 200 250 0. 5 1 1. 5 2 2. 2.5 3 Luminosity(10 33 cm 2 s 1 ) Minute measurement simulation A highly accurate self-consistent particle code to simulate the beam- beam collision in e + e — storage rings has been developed. It adopts a method of solving the Poisson equation with an open boundary. The method consists of two steps: assigning the potential on a finite boundary using the Green’s function, and then solving the potential inside the boundary with a fast Poisson solver. The method allows us to select much smaller region of mesh and therefore increase the resolution of the solver. The luminosity simulated with this method agrees quantitatively with the measurement for the PEP-II B factory ring in the linear and nonlinear beam current regimes, demonstrating its predictive capability in detail. To make a direct comparison between simulation and experimental observation, we have recorded the luminosity during a period of four hours on October 1, 2000. The plot shows the measured and simulated luminosities at the same beam current. Poincare map of coherent dipole oscillation at N + =(1,5,9,13)x10 10 in horizontal plane. The resonances are 3ν x + =116 and 7ν x — =172. Combiner Rings IP Drive Beam Linac 350 MeV Decelerator Loop Decelerator Loop 3π/2 Arc 3π/2 Arc Injection Transport Drive Beam Recirculation Loop e – Main Linac 3π/2 Arc 2 GeV 2 GeV 4 GeV Damping Ring Injector Linac Scavenger Loop e + e – Layout of a Two Beam System Using Recirculation NLC Upgrade from 1 to 1.7 TeV drive linac Two-Beam Upgrade 3 dB 3 dB 3 dB klystron rf klystron rf transfer waveguides 3 dB 3 dB 4.8 dB 4.8 dB 3 dB Initial Configuration 87 MW 261 MW 524 MW 524 MW 1.048 GW (total) 261MW 0.9m structure Decelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator In a two-beam linear collider the energy is first stored in a low energy high current drive beam. This beam is decelerated to provide the energy for high gradient acceleration of the high-energy electron and positron beams. On the top you see a configuration that uses recirculation to accelerate the drive beam. On the bottom you see a method for increasing the energy of the NLC with an additional two-beam power source from 1 TeV to 1.7 TeV. TWO—BEAM LINEAR COLLIDER TWO—BEAM LINEAR COLLIDER In collaboration with KEK and FNAL we are working on the design of X-band accelerator structures for the Next Linear Collider. The primary thrust of this work is the suppression of the effects of long range dipole wakefields by a factor of 100 or more through detuning and damping of the dipole modes in the structure. Other important goals include achieving stable operation for accelerating gradients of up to 100 MeV/m, optimizing the RF efficiency, integral beam position monitors within the structure, and developing the fabrication technology. We are now studying short low group velocity traveling wave structures and even shorter standing wave structures because they run more reliably at high gradients than the 1.8 m long structures we have built in the past. HIGH GRADIENT, LOW WAKEFIELD ACCELERATOR STRUCTURE 1 4 9 16 25 36 49 64 81 s (m) 0.001 0.01 0. 1 1 10 100 Wake (V/pC/mm/m) Transverse wake for RDDS1 structure. Points indicate the location of the bunches. RDDS1 structure on strongback. Cutaway view of the first standing wave structure. 0 10 20 30 40 50 60 70 80 0.4 0.3 0.2 0.1 0 0.1 0.2 0.3 0.4 Sample Amplitude Impulse response DAΦNE electron ring controller 0 10 20 30 40 50 60 70 80 90 100 60 50 40 30 20 10 0 10 20 kHz dB Magnitude response 0 10 20 30 40 50 60 70 80 90 100 200 150 100 50 0 50 100 150 200 Degrees kHz Phase response The programmable digital signal processing allows fine specification of the magnitude and phase response of the feedback control filter. This example shows a narrowband controller for the DAFNE electron ring. Implemented as an infinite impulse response (IIR) filter (impulse response is shown in the top figure) the controller has gain only within the 28 to 34 kHz band and provides significant rejection of the out-of-band noise. These IIR control techniques have been developed in conjunction with the installation of third harmonic RF cavities in the ALS and BESSY-II. A digital bunch-by-bunch longitudinal feedback system has been developed for use at PEP-II (SLAC), ALS (LBL), DAFNE (LNF-INFN) and 5 other European, US and Asian laboratories. The system utilizes the power of the programmable signal processing for numerous diagnostic and accelerator measurement purposes in conjunction with the feedback control task. DIGITAL FEEDBACK AND ANALYSIS FOR BEAM STABILITY DIGITAL FEEDBACK AND ANALYSIS FOR BEAM STABILITY HIGH GRADIENT, LOW WAKEFIELD ACCELERATOR STRUCTURE TE 10 : TE 10 TE 11 TE 20 TE 01 TE 20 : O O to accelerator feed cross—potent superhybrid combine/launcher rectangular circular mode transducer/taper mode-selective extractor to continuing delay line Toward a four—mode system Ceramic ring for DC isolation Active PIN/NIP diode window Metal spring for DC contact between RF structure and the active window 25u Metal line (on the PIN diode structure) Silicon Surface Aluminum line Silicon surface Magnified pictures of arcing traces on the aluminum lines Multimoded components and systems have been invented at SLAC. These components handle two to four modes simultaneously. The systems that could be built with these components are compact and efficient. We use planer geometry to take advantage of the planer symmetry in the third dimensions. This dimension could be increased to any desired value to reduce the field and increase the high power handling capabilitites. To connect these components to circular waveguides a special circular to rectangular multimoded tapers have been designed. Because of the requirements of the Next Linear Collider high-power rf systems, passive microwave components have been developed during the last few years. The power handling capabilities of these components have increased considerably. This has been achieved by increasing the size of these components with respect to the operating wavelength, i.e., by overmoding these components. Similar attempts have been made to increase the power handling capabilities of active semiconductor components. A switch made from a PIN diode array has been developed to operate in an overmoded waveguide carrying the TE01 mode. The system has operated at power levels up to 13 MW. RESEARCH IN HIGH POWER RF PULSE COMPRESSION AND CONTROL RESEARCH IN HIGH POWER RF PULSE COMPRESSION AND CONTROL WAKEFIELDS AND INSTABILITIES WAKEFIELDS AND INSTABILITIES Arbitrary Units 0 1 2 100 200 300 400 t Simulated oscilloscope trace forN = 3 10 10 , in arbitrary units. The time unit is one synchrotron period. 0 1 2 3 4 5 6 7 8 9 10 time, ms Amplitude, arb. units 3.5×10 10 3.3×10 10 3.1×10 10 2.6×10 10 2.0×10 10 1.6×10 10 Experimental oscilloscope traces for various currents. The third curve from the top is for N = 3.1 10 10 . A general numerical method has been developed to follow the probability distribution in phase space as a function of time. The technique, based on discretization of the local Perron-Frobenius operator, is simple in concept, easy to implement, and numerically stable in examples studied to date. Applied to the SLC damping rings, the method gives the observed current threshold for bunch lengthening, and several aspects of observed behavior above threshold, including the presence of a bursting or sawtooth mode. Collimators are often used in storage rings and accelerators to remove large- amplitude particles from the transverse profile of the beam. To suppress the wakefield, a tapered collimator jaws are preferable, as shown in Figure. An analytical theory of wakefields has been developed for both round and rectangular geometries of small-angle tapers. Theoretical predictions agree well with recent measurements of collimator wakes at the SLC linac. NEW SIMULATION CODE NEW SIMULATION CODE Beam Position (µm) –80 –60 –40 –20 0 Wire Scanner Detector Signal (ADC) 100 300 500 700 100 300 500 700 No Plasma s=10.1 ± 0.3 µm Laser Ionized Plasma s=5.3 ± 0.1 µm Carbon Wire Scanner eFFamCAT Roots Pump Laser Out Pulsed Gas Jet Turbo Pump O Beam In Laser In E150 Plasma Chamber 3D drawing of the plasma chamber FNAL, Hiroshima, KEK, LLNL, SLAC, Tennessee, UCLA Plasma Lens Experiment ADVANCED BEAM CONCEPTS ADVANCED BEAM CONCEPTS Laser Ionization Plasma Focusing 29 GeV Positron Beams Transverse positron beam profile with and without plasma lens. The beam size is reduced by about a factor two, corresponding to a focusing field ~MTesla/m.
Transcript of Advanced Accelerator Research - INFN · 2001. 10. 20. · ARDAARDA Advanced Accelerator Research...
ARDAARDAAdvanced Accelerator Research
S TA N F O R D L I N E A R A C C E L E R ATO R C E N T E R Presented at Lepton Photon 2001, Rome, Italy
The accelerator research program at SLAC performs research on accelerator technology and particle beam physics pushing both energy and luminosity in high-energy electron colliders. Research ranges from development of existing facilities, to work toward next generation linear colliders, as well as the design of new techniques and devices for high-gradient acceleration and focusing for electron linear colliders up to 5 TeV. Work involves collaborations with physicists from several universities, other laboratories and the private sector.
http://www.slac.stanford.edu/grp/ara/
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P x
(µra
d)P
x(µ
rad)
X (µm) X (µm) X (µm) X (µm)
Coherent Dipole Motion
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1.5
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Lum
inos
ity(1
033cm
2 s
1)
Minute
measurement
simulation
A highly accurate self-consistent particle code to simulate the beam-beam collision in e+ e— storage rings has been developed. It adopts a method of solving the Poisson equation with an open boundary. The method consists of two steps: assigning the potential on a finite boundary using the Green’s function, and then solving the potential inside the boundary with a fast Poisson solver. The method allows us to select much smaller region of mesh and therefore increase the resolution of the solver. The luminosity simulated with this method agrees quantitatively with the measurement for the PEP-II B factory ring in the linear and nonlinear beam current regimes, demonstrating its predictive capability in detail.
To make a direct comparison between simulation and experimental observation, we have recorded the luminosity during a period of four hours on October 1, 2000. The plot shows the measured and simulated luminosities at the same beam current.
Poincare map of coherent dipole oscillation at N+=(1,5,9,13)x1010 inhorizontal plane. The resonances are 3νx
+=116 and 7νx— =172.
Combiner Rings
IP
Drive Beam Linac
350 MeV Decelerator LoopDecelerator Loop
3π/2 Arc3π/2 Arc
Injection Transport
Drive Beam Recirculation Loop
e– Main Linac
3π/2 Arc
2 GeV 2 GeV
4 GeV
Damping Ring
Injector Linac
Scavenger Loop
e+
e–
Layout of a Two Beam System Using Recirculation
NLC Upgrade from 1 to 1.7 TeV
drive linac
Two-Beam Upgrade
3 dB
3 dB
3 dB
klystron rf
klystron rf
transfer waveguides
3 dB 3 dB4.8 dB4.8 dB
3 dB
Initial Configuration87 MW
261 MW
524 MW
524 MW
1.048 GW (total)
261MW
0.9m structure
Decelerator
Accelerator Accelerator Accelerator Accelerator Accelerator
Accelerator Accelerator Accelerator Accelerator Accelerator Accelerator
Accelerator
In a two-beam linear collider the energy is first stored in a low energy high current drive beam. This beam is decelerated to provide the energy for high gradient acceleration of the high-energy electron and positron beams. On the top you see a configuration that uses recirculation to accelerate the drive beam. On the bottom you see a method for increasing the energy of the NLC with an additional two-beam power source from 1 TeV to 1.7 TeV.
TWO—BEAM LINEAR COLLIDERTWO—BEAM LINEAR COLLIDER
In collaboration with KEK and FNAL we are working on the design of X-band accelerator structures for the Next Linear Collider. The primary thrust of this work is the suppression of the effects of long range dipole wakefields by a factor of 100 or more through detuning and damping of the dipole modes in the structure. Other important goals include achieving stable operation for accelerating gradients of up to 100 MeV/m, optimizing the RF efficiency, integral beam position monitors within the structure, and developing the fabrication technology. We are now studying short low group velocity traveling wave structures and even shorter standing wave structures because they run more reliably at high gradients than the 1.8 m long structures we have built in the past.
HIGH GRADIENT, LOW WAKEFIELD ACCELERATOR STRUCTURE
1 4 9 16 25 36 49 64 81
s (m)
0.001
0.01
0. 1
1
10
100
Wak
e (
V/p
C/m
m/m
)
Transverse wake for RDDS1 structure. Points indicate the location of the bunches.
RDDS1 structure on strongback.
Cutaway view of the first standing wave structure.
0 10 20 30 40 50 60 70 800.4
0.3
0.2
0.1
0
0.1
0.2
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Sample
Am
plitu
de
Impulse response
DAΦNE electron ring controller
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dB
Magnitude response
0 10 20 30 40 50 60 70 80 90 100200
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150
200
Deg
rees
kHz
Phase response
The programmable digital signal processing allows fine specification of the magnitude and phase response of the feedback control filter. This example shows a narrowband controller for the DAFNE electron ring. Implemented as an infinite impulse response (IIR) filter (impulse response is shown in the top figure) the controller has gain only within the 28 to 34 kHz band and provides significant rejection of the out-of-band noise. These IIR control techniques have been developed in conjunction with theinstallation of third harmonic RF cavities in the ALS and BESSY-II.
Kicker Structure
CombGenerator
Timing & Control
Beam Bunches
BPM
ExternalDriveInput
BunchError
Farm of DigitalSignal
Processors
QPSKModulator
Kicker Oscillator1.125 GHz
Phase-lockedto Ring
Master OscillatorPhase-locked
at 6*RF of Cavity
Poweramp
Hold-Buffer
D/A
A/D
Downsampler
DSP
XLow-
pass Filter +
A digital bunch-by-bunch longitudinal feedback system has been developed for use at PEP-II (SLAC), ALS (LBL), DAFNE (LNF-INFN) and 5 other European, US and Asian laboratories. The system utilizes the power of the programmable signal processing for numerous diagnostic and accelerator measurement purposes in conjunction with the feedback control task.
DIGITAL FEEDBACK AND ANALYSIS FOR BEAM STABILITY
DIGITAL FEEDBACK AND ANALYSIS FOR BEAM STABILITY
HIGH GRADIENT, LOW WAKEFIELD ACCELERATOR STRUCTURE
TE10:
TE10 TE11
TE20 TE01
TE20:
O
O
to accelerator feed
cross—potent superhybridcombine/launcher
rectangular circularmode transducer/taper
mode-selective extractor
to continuingdelay line
Toward a four—mode system
Ceramic ring for DC isolation
Active PIN/NIP diode window
Metal spring for DCcontact between RFstructure and the active window
25u
Metal line (on the PINdiode structure)
Silicon Surface
Aluminum line
Silicon surface
Magnified pictures of arcing traces on the aluminum lines
Multimoded components and systems have been invented at SLAC. These components handle two to four modes simultaneously. The systems that could be built with these components are compact and efficient. We use planer geometry to take advantage of the planer symmetry in the third dimensions. This dimension could be increased to any desired value to reduce the field and increase the high power handling capabilitites. To connect these components to circular waveguides a special circular to rectangular multimoded tapers have been designed.
Because of the requirements of the Next Linear Collider high-power rf systems, passive microwave components have been developed during the last few years. The power handling capabilities of these
components have increased considerably. This has been achieved by increasing the size of these components with respect to the operating wavelength, i.e., by overmoding these components. Similar attempts have been
made to increase the power handling capabilities of active semiconductor components. A switch made from a PIN diode array has been developed to operate in an overmoded waveguide carrying the TE01 mode. The system has operated at power levels up to 13 MW.
RESEARCH IN HIGH POWER RF PULSECOMPRESSION AND CONTROL
RESEARCH IN HIGH POWER RF PULSECOMPRESSION AND CONTROL
RDA
WAKEFIELDS AND INSTABILITIESWAKEFIELDS AND INSTABILITIES
Arb
itrar
y U
nits
0
1
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100 200 300 400t
Simulated oscilloscope trace forN = 3 1010, in arbitrary units. The time unit is one synchrotron period.
0 1 2 3 4 5 6 7 8 9 10time, ms
Am
plitu
de, a
rb. u
nits
3.5×1010
3.3×1010
3.1×1010
2.6×1010
2.0×1010
1.6×1010
Experimental oscilloscope traces for various currents. The third curve from the top is for N = 3.1 1010.
A general numerical method has been developed to follow the probability distribution in phase space as a function of time. The technique, based on discretization of the local Perron-Frobenius operator, is simple in concept, easy to implement, and numerically stable in examples studied to date. Applied to the SLC damping rings, the method gives the observed current threshold for bunch lengthening, and several aspects of observed behavior above threshold, including the presence of a bursting or sawtooth mode.
Collimators are often used in storage rings and accelerators to remove large-amplitude particles from the transverse profile of the beam. To suppress the wakefield, a tapered collimator jaws are preferable, as shown in Figure. An analytical theory of wakefields has been developed for both round and rectangular geometries of small-angle tapers. Theoretical predictions agree well with recent measurements of collimator wakes at the SLC linac.
NEW SIMULATION CODENEW SIMULATION CODE
Beam Position (µm)–80 –60 –40 –20 0
Wire
Sca
nner
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ecto
r S
igna
l (A
DC
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Laser Ionized Plasmas=5.3 ± 0.1 µm
Carbon Wire Scanner
eFFamCAT
Roots Pump
Laser Out
Pulsed Gas JetTurbo Pump
O Beam InLaser In
E150 Plasma Chamber
3D drawing of the plasma chamber
FNAL, Hiroshima, KEK, LLNL, SLAC, Tennessee, UCLA
Plasma Lens Experiment
ADVANCED BEAM CONCEPTSADVANCED BEAM CONCEPTSLaser Ionization Plasma Focusing
29 GeV Positron Beams
Transverse positron beam profile with and without plasma lens. The beam size is reduced by about a factor two, corresponding to a focusing field ~MTesla/m.
