Post on 14-Feb-2021
M. Biagini, INFN-LNF
For the Tau/charm Study Group
XCIX Congresso SIF, Trieste 25 /09/13
Overview A t/charm Factory, an e+e- collider with very high luminosity at
the 2-4.5 GeV center of mass energy, to be built on the Rome University at Tor Vergata campus, was studied by the Consorzio N. Cabibbo Laboratory and the INFN Frascati Laboratories
This project is the natural evolution of the flagship Italian project SuperB Factory, funded by the Italian Government in 2010 with a budget that turned out to be insufficient to cover the total costs of the project, and then cancelled in Dec. 2012
The study of rare events at the t/charm energy was already planned as a Phase-II of SuperB. This design keeps all the unique features of SuperB, including the polarization of the electron beam, with the possibility to take data in a larger energy range, with reduced accelerator dimensions and construction and operation costs
Accelerator study group LNF team CabibboLab team M. Biagini M. Boscolo A. Chiarucci A. Clozza A. Drago S. Guiducci C. Ligi G. Mazzitelli R. Ricci C. Sanelli M. Serio S. Tomassini
S. Bini
F. Cioeta
D. Cittadino
M. D’Agostino
M. Del Franco
A. Delle Piane
E. Di Pasquale
G. Frascadore
S. Gazzana
R. Gargana
S. Incremona
A. Michelotti
L. Sabbatini
LNS team
ESRF & Pisa team
G. Schillaci
M. Sedita
P. Raimondi
S. Liuzzo
E. Paoloni
t/charm Factory main features Energy tunable in the range Ecm = 1-4.8 GeV
1035 cm-2 s-1 peak luminosity at the t/charm threshold and upper
Symmetric beam energies
Longitudinal polarization in the electron beam (60-70%)
Possibility of e-e- collisions (to be studied)
Beam parameters for reasonable lifetimes and beam currents
Low power consumption lower running costs
Injection system scaled from the SuperB one
Possible applications: SASE-FEL @2.4 6 GeV
Beam Test Facility line
Beam parameters Beam parameters to reach a baseline luminosity of 1035
cm-2 s-1 @ 2 GeV/beam have been chosen
An upgrade to 2x1035 cm-2 s-1 can be possible by increasing
the beam current
Design features are the same as for the SuperB design: “Large Piwinski angle & crab waist sextupoles” collision
scheme
Low H-emittance lattice
Small H-V coupling ultra low V-emittance
Small IP b functions and beam sizes
Beam-beam tune shifts < 0.1
Same RF frequency as PEP-II (re-use of cavities)
Low beam power
Table of parameters @ 2 GeV/beam
Baseline design L=1035, with possibility to increase currents for 2x1035 cm-2 s-1
Intra Beam Scattering and hourglass factors included
Beam power about 15 times less than the SuperB baseline one (4 MW (HER) and 2MW (LER) of RF power)
Luminosity vs Energy
At low energy (last column) insertion of 8 wigglers is foreseen to keep same damping times Polarization will be maximum around 4 GeV c.m
Tau-Charm Layout @ Tor Vergata
t-charm complex view
LINAC
Damping Ring
Storage Rings (preliminary)
IP
TLs
Main Rings lattice: Arc
Y Sexts mux=3pi muy=pi
X Sexts mux=3pi muy=pi
X Octupoles
The sextupoles arrangement allows for a very good correction of non-linearities and provides a very large dynamic aperture without the Final Focus
Main Rings lattice: Final Focus
X Sexts mux=muy=pi Y Off Phase Sexts
X Off Phase Sexts
Crab Sext
Y Sexts mux=muy=pi
The Final Focus sextupoles need to compensate for the huge chromaticity coming from the final doublets. Their effect on the dynamic aperture is important but has been minimized as much as possible
Final Chosen tolerated Values
S.M.Liuzzo, ESRF, Università Tor Vergata 15
Lifetimes and backgrounds Backgrounds and lifetime are two issues strictly
connected one to the other, even if they have different implications for the accelerator design and operation, being determined by the same physical process that may induce particle losses
Backgrounds can be cured with detectors shielding, masking and collimator systems, while a short lifetime can be handled with continuous top-up injections
A Monte Carlo simulation is used to determine the beam lifetimes and the beam-stay-clear needed for acceptable beam loss rates
Beam lifetimes estimate
Final Focus collimation system
20
Final Focus collimation system (similarly to SuperB)
20
COL1 COL2 COL3
SFX0
COL4
SFX4
PRIMARY SECONDARY
Collimators are located where bx and Dx are large
M. Boscolo, Tau-Charm at High Luminosity, May 29th 2013
H-collimators
SDY0 SDY4
V-collimators
Main Rings magnets
Dipole
Gradient dipole
Quadrupole
Sextupole
!CHAOS Control System
CUs are the drivers attached to devices
DOC is the RAM
KVDB is the HardDisk
UI,EU are the CPUs running user applications
Chaos can be view as a distributed computer
BSON is the BUS
!CHAOS (Control System based on Highly Abstracted Operating Structure) is the proposed software infrastructure to realize the Control System
Damping Ring mechanical layout
Damping Ring
Main Rings
Main Rings side by side
The present maximum separation between main rings is about 3.5m 3.5m
Feedbacks
Primary Network
Secondary Network
t-charm alignment case study
Only the outer reference points of the secondary network are visible.
Tau-Charm Injection System The preliminary layout of the injection system is based on
the design of the SuperB injection system
The same design for the linac and damping ring lattice is used
The main difference with respect to the SuperB design is the fact that only positrons are stored in the Damping Ring (DR)
As for the SuperB case, the linac can be used to accelerate electron pulses for an FEL synchrotron light source
Tau-Charm Injection System
0.6 GeV 1.0 GeV 1.3 GeV
Bypass
Positron Positron
Source DR
e-
e+ FEL Line
e+
e-
To MRs
FEL photoinjecto
r
Linac L1 Linac L3 Linac L2 e-
Bunch
Bunch
Compressor
Total electron linac energy 2.9 GeV Total positron linac energy 2.3 GeV
Linac L1 Linac L2 Linac L3
N. of klystrons 3 6 7
N. of cavities 9 18 21
Max. Energy (GeV) 0.62 1.24 1.45
The number of klystrons and cavities allows to reach the maximum The number of klystrons and cavities allows to reach the maximum positron energy of 2.3 GeV also with one klystron off
Positron Damping Ring • The preliminary magnetic layout of the damping ring is
completed
• The mechanical design of magnets and supports is in progress
• The mechanical layout is ready for next step: vacuum, diagnostic, radio frequency, survey and alignment
DR magnets design
Dipoles
Sextupoles
Long And short Quadrupoles
Tau/charm as a SASE-FEL
Conventional Facilities
133
The beam for the SASE FEL would be produced by a dedicated high brightness photo-injector
similar to that used at SPARC-LAB at LNF. A 50 Hz pulsed magnet will be used to combine the FEL
beam with the Tau/Charm injection beams. The maximum linac energy for the electron beam is
2.9 GeV, a long space is available for the FEL extension: Linac extension, transfer lines,
undulators and experimental halls.
The FEL injection system (S-band, 2.856 GHz) is composed by one 1.6 cell RF photo-injector
followed by 2 TW structures embedded in a solenoid magnetic field as required to operate in the
Velocity Bunching mode. It is a copy of the SPARC-LAB photo-injector, 8 m long.
The linac can be operated for the FEL in single or multi-bunch mode with a pulse length lower
than 800 ns, to be compatible with SLED system, and with a repetition rate of 50 Hz. The charge
per bunch can be chosen to better match the emittance and peak current requirements for the
FEL operation.
After the photo-injector the beam is accelerated up to 2.9 GeV in Linac L1, L2 and L3. Two pulsed
magnets are needed to separate the FEL bunches from the Tau/Charm bunches in the region of
the positron converter and other two can be used in the region of Damping Ring injection and
extraction, between linac L2 and L3. In this regions two magnetic bunch compressor systems can
be installed, suitably designed to increase the peak current.
A layout of the Tau/Charm complex with the FEL facility is shown in Figure 7.1.
Figure 7.1 - Tau/Charm complex with the SASE-FEL option.
To estimate the photons wavelength we consider an electron beam that traverses an
undulator, emitting electromagnetic radiation at the resonant wavelength:
r= u2 2
1=au2( ) (7.1)
1. Linac tunnel
2. Modulator and klystron
building
3. Damping Ring
4. Main Rings
5. Collider hall
6. Assembly hall
7. Vacuum Lab
8. Cryo Lab
9. Magnetic measurement
10. HVAC building
11. Electric station
12. Electric substation
13. Linac banda C tunnel
14. Undulators unnel
15. Experimental hall
• Possibility to drive a SASE X-ray FEL using the 2.4 GeV Tau/Charm Linac • To achieve an energy of 6 GeV (1.5 and 3 Angstrom photon wavelength)
additional Linac sections can be installed at the end of the last Linac, using the C-band (f = 5712 MHz) technology, which is being developed at LNF in the framework of the EU-TIARA project, and will be soon mounted at SPARC-LAB
• Assuming an accelerating gradient of 40 MV/m, additional 80 m of Linac sections (about 40) should be added (total Linac length 300 m)
Accelerator Report
Distributed mid-July, INFN-LNF publication September
Accelerator Report ToC 1. Introduction
2. Collider Main Rings
- Luminosity and Beam parameters
- Main Rings lattice
- Interaction Region design
- Dynamic Aperture and tolerance to errors
- Backgrounds and lifetimes
- Intra Beam Scattering
- E-cloud instability
3. Injection Complex
- General layout
- Positron Source
- Damping Ring
- Linac specifications
- Transfer Lines
- Injection into the Main Rings
4. Accelerator Systems – Diagnostics – Feedbacks – Controls – Vacuum Sysstem – Radio Frequency – Magnets (DR, MR) – Mechanical engineering – Survey and alignment – Power electronics
5. Conventional Facilities - Site - Mechanical layout - Infrastructures and civil engineering - Fluids - Cryogenics - Electrical engineering - Health Safety and Environment
6. Costs and schedule 7. Tau/charm as a SASE-FEL facility 8. Tau/charm as a beam Test
Facility
Conclusions A new infrastructure for a low energy Flavour Factory, with
possible applications in other fields such as FEL and BTF has been designed
A Report on the accelerator design (150 pp.) has been published and can be the base for a fast TDR phase
The N. Cabibbo Laboratory is in place to construct and run such a facility
The estimated cost of the facility would be entirely covered by the promised “SuperB” funding
However a decision on the future of the Flagship projects has not been taken yet, and the PNR (Piano Nazionale Ricerca) for the next 3 years is still in progress
INFN will have to take a final decision before the end of this year