ALICE Energy Recovery Linac Prototype: Current Status and Commissioning Successes

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ALICE Energy Recovery Linac PrototypeCurrent
Status andCommissioning Successes

• Lee Jones
• Accelerator Physics Group
• ASTeC
• STFC Daresbury Laboratory

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ALICE ERL Prototype status update Content

• Introduction
• Project status
• Ongoing work
• Photon science on the ALICE (formerly known as
  ERLP)
• The EMMA NS-FFAG project
• Injector commissioning results
• Future plans

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ALICE ERL Prototype Technical priorities

• Primary Goals
• Foremost Demonstrate energy recovery
• Produce and maintain bright electron bunches from
  a photoinjector
• Operate a superconducting Linac
• Produce short electron bunches from a compressor
  
• Further Development Goals
• Demonstrate energy recovery during FEL operation
  (with an insertion device that significantly
  disrupts the electron beam)
• Develop a FEL activity programme which is
  suitable to investigate the expected
  synchronisation challenges and demands of
  4GLS/NLS
• Produce simultaneous photon pulses from a laser
  and an ERL photon source which are synchronised
  at or below the 1 ps level

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ALICE ERL Prototype Location
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ALICE ERL Prototype Layout

• Nominal gun energy 350 keV
• Injector energy 8.35 MeV
• Circulating beam energy 35 MeV
• Linac RF frequency 1.3 GHz
• Bunch repetition rate 81.25 MHz
• Max bunch charge 80 pC
• Bunch train 100 ms
• Maximum average current 13 µA

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Construction status
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Construction status

• Photoinjector laser system operating since
  April 2006
• Gun installed and commissioned into a dedicated
  diagnostic beamline over a period of several
  months during three commissioning phases
• Accel superconducting modules undergoing
  commissioning
• Cryogenic system installed by Linde and DeMaco,
  and used to cool accelerating modules down to
  1.8 K
• All of the electron beam transport system has
  been installed and is under vacuum
• Installation work proceeding for various
  photon beam transport systems

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Drive laser Summary

• Diode-pumped NdYVO4
• Wavelength 1064 nm, doubled to 532 nm
• Pulse repetition rate 81.25 MHz
• Pulse duration 7, 13, 28 ps FWHM
• Pulse energy up to 45 nJ (at cathode)
• Macrobunch duration 100 ms _at_ 20 Hz

• Duty cycle 0.2 (maximum)
• Timing jitter lt 1 ps (specified) lt 650 fs
  (measured)
• Spatial profile Circular top-hat on photocathode
• Laser system commissioned at Rutherford Lab in
  2005, then moved to Daresbury in 2006

L.B. Jones, Status of the ERLP Photoinjector
driver laser, ERL 07 proceedings
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Gun Assembly

• JLab design CsGaAs cathode
• 500 kV DC supply
• Single bulk-doped ceramic, manufactured by
  WESGO

Cathode ball
Ceramic
Cathode
SF6 Vessel removed
Electrons
Laser
XHV
Support Stem

• Power supply commissioned 2005
• Ceramic delivery March 2006
• Spare ceramic delivered Nov 2006

Anode Plate
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Gun Commissioning Status

• Electron gun operated Jul-Aug 06, Jan-Apr 07
  Oct-Nov 07
• Problems experienced with cathode activation.
  Q.E. poor
• First beam from the gun recorded at 0108 on
  Wednesday 16th August 2006, with the gun
  operating at 250 kV
• Operating at 350 kV soon afterwards
• Routinely conditioning gun to 450 kV
• Steady improvement in both Q.E. lifetime
• Problems encountered with beam halo, field
  emission and high voltage breakdown
• Improved bakeout º Better vacuum
• Repeated failure of ceramic, now using
  Stanford spare

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Design criteria demonstrated so far

• Beam energy 350 keV ü
• Bunch charge gt 80 pC ü
• Quantum Efficiency (Q.E.) 3.7 with 1/e
  lifetime of 100 hours ü
• Bunch train length Single 7 ps pulse to 100 µs
  ü
• Train repetition rate Operated up to 20 Hz ü

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Cryosystem accelerating modules
2006
Apr 1st Accelerating module delivered May -
4 K cryo commissioning carried out Jul
2nd Accelerating module delivered Oct
- Linac cooled to 2 K Nov
Booster cooled to 2 K Dec -
Modules cooled together

• Simulated a dynamic resistive heat load of
  112 W in both modules
• Achieved a pressure stability of 0.03 mbar
  at full (simulated) dynamic load in both of the
  modules at 2 K
• Achieved 0.10 mbar at 1.8 K

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ScRF Accelerating modules

• 2 Stanford/Rossendorf cryomodules, one
  configured as the Booster and the other as the
  Main Linac, also using the JLab HOM coupler
• 2 9 - Cell 1.3 GHz cavities per module
• Booster module
• 4 MV/m gradient
• 52 kW RF power

• Main Linac module
• 13.5 MV/m gradient
• 16 kW RF power
• Quality factor, Q0 5 109
• Total cryogenic load
• 180 W at 2 K

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ScRF Accelerating modules

• 2 Stanford/Rossendorf cryomodules, one
  configured as the Booster and the other as the
  Main Linac, also using the JLab HOM coupler
• 2 9 - Cell 1.3 GHz cavities per module
• Booster module
• 4 MV/m gradient
• 52 kW RF power

• Main Linac module
• 13.5 MV/m gradient
• 16 kW RF power
• Quality factor, Q0 5 109
• Total cryogenic load
• 180 W at 2 K

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Electron beam transport system
DipoleMagnet
Quadrupole Magnet
OTR
Girder
All modules now installed andunder vacuum.
Ready for beam !
Corrector Coil and EBPM Assembly
IonPump
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Current / ongoing work

• Preparing for 4th phase of gun commissioning
• 1st phase of beam comissioning
• RF Conditioning of accelerating modules
• Optimising of the cryogenic system with RF
  present
• Commissioning of high-power RF PLC control
  systems
• Commissioning of electron BTS sub-systems
• Controls / Diagnostics
• Beam Loss Monitor
• Machine Protection System
• Installation of the photon BTS for THz, FEL, EO
  CBS

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ALICE ERLp Photon science
North West Science Fund award of 3m over 3 years
X-rays Time resolved X-ray diffraction studies
probing shock compression of matter on
sub-picosecond timescales.
90º focus mirror
X-rays
Probe
Pump
IR
180º focus mirror
CBSInteractionPoint
THz
THz Ultrahigh intensity, broadband THz radiation
to be utilised for the study of live tissues.
25TWLaser
Laser-SR synergy Pump-probe expts with
table-top laser and SR
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Accelerator Hall
Laser Room
2.2 mJ, 35 fs at 1 kHz for EO
800 mJ, 100 fs at 10 Hz for CBS
Diagnostics Room
Courtesy G. Priebe, DL
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Compton Back-Scattering Þ X-rays
Courtesy J. Boyce, JLab
Courtesy DL Engineering Office
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High Harmonic Generation Þ UV
Courtesy G. Priebe, DL
Current A
energy eV
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Longitudinal diagnostics
Electro-Optic concept
encoding (bunch profile into optical pulse)
probe laser
bunch
to laser diagnostic
decoding(optical pulse into profile measurement)
Courtesy S. Jamison, DL
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Tunable Free-Electron Laser
Encoders
JLabWiggler (on loan)

• FEL Tunability by varying
• electron energy (24-35 MeV range)
• undulator gap (12-20 mm range)

l 4 - 12 mm
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The EMMA Project
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BASROC
British Accelerator Science and Radiation
Oncology Consortium

• The long-term aim of BASROC is to build a
  complete hadron therapy facility using
  Non-Scaling Fixed-Field Alternating Gradient
  accelerator technology (NS-FFAG), combining the
  best features of cyclotron and synchrotron
  accelerators
• An FFAG combines the intensity and ease-of-use of
  cyclotrons ....... coupled with the benefits of
  synchrotrons, specifically beam control and the
  ability to accelerate proton and heavy ion beams
  to various energies
• EMMA The Electron Model of Many Applications
  will use ALICE as an injector at 10 MeV,
  accelerating electrons to 20 MeV. The goal is to
  learn how to design NS-FFAGs for various
  applications, including hadron therapy
• PAMELA The Particle Accelerator for MEdicaL
  Applications will be a 70-100 MeV proton NS-FFAG,
  itself a prototype to demonstrate the potential
  use of NS-FFAGs in hadron therapy, thus
  strengthening the case for hadron therapy
• Leading to a complete facility for the treatment
  of patients using hadron beams

Awarded 6.9m over 3½ years to design and build
EMMA
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EMMA on the ALICE ERL
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ALICE Gun diagnostic beamline

• transverse RMS emittance measured by double-slit
  scans at positions A and B
• bunch length with slit A and kicker cavity

Courtesy Y. Saveliev, DL
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RMS Geometric emittance (function of bunch charge)
RMS geometric emittance as a function of bunch
charge - Horizontal ( ) - Vertical ( ) ALICE
ERLp target was specified as 1p mm-mrad by ASTRA
for Q 80 pC Some factors are missing from the
ASTRA model 1,2
1 I.V. Bazarov et al., Proceedings of PAC07,
Albuquerque, 2007, pp. 1221-1223.
2 F. Zhou et al., Phys. Rev. ST - AB 5, 094203,
2003.
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Bunch length (function of bunch charge, at 10
level)
Bunch length at 10 of the peak value used due to
non-uniformity of the longitudinal profile. Data
were obtained with the RF transverse kicker (full
circles), energy mapping method (square) and
zero-crossing method (triangle). Open circles
are the results from the ASTRA model.
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Total and tilt-compensated energy spread
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FWHM Beam size for Q 54 pC
B1 , G
B2 , G
First solenoid
Second solenoid
Comparison of predicted and measured beam sizes
mmas a function of solenoid field strength
guass for Q 54 pC
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PI Gun driven by differing laser pulse durations
ASTRA Longitudinal phase space predictions
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PI Gun driven by differing laser pulse durations
Longitudinal drive laser profile
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PI Gun driven by differing laser pulse durations
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PI Gun driven by differing laser pulse durations
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PI Gun driven by differing laser pulse durations
Conclusion Longer laser pulses do not confer
significant benefits below 20 pC when compared
to short pulses in terms of bunch length energy
spectra.
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Immediate / future plans

• Immediate
• Beam through the booster, main linac and arcs
• Demonstrate energy recovery
• Followed by
• Fine tuning of the machine tune injector for
  minimum emittance, optimisation of energy
  recovery at nominal beam parameters, extensive
  beam measurements
• Short pulse commissioning longitudinal dynamics,
  EO diagnostics
• Energy recovery with FEL and first IR light from
  the FEL
• Simultaneously
• THz IR-FEL research programmes will start, as
  will CBS X-ray production using head-on
  electron-photon collisions
• Future
• Load-lock gun upgrade and possible re-design for
  vertical ceramic
• Re-installation of gun diagnostic line
• Installation of an improved high-current
  cryomodule

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Thank you for listening
EPAC 08 Proceedings Y.M. Saveliev et al.,
Results from ALICE (ERLP) DC photoinjector gun
commissioning, MOPC062, pages 208-210 Y.M.
Saveliev et al., Characterisation of electron
bunches from ALICE (ERLP) DC photoinjector gun at
two different laser pulse lengths, MOPC063, pages
211-213 Linac 08 proceedings D.J. Holder on
behalf of the ALICE team, First results from the
ERL prototype (ALICE) at Daresbury
Acknowledgements K.J. MiddlemanY.M.
SavelievD.J. HolderS.P. JamisonS.L. Smith
B.L. MilitsynB.D. MuratoriG. PriebeN.R.
ThompsonJ.W. McKenzie
Questions ?