first results from the erl prototype (alice) at daresbury david holder, on behalf of the alice team....
TRANSCRIPT
![Page 1: First Results from the ERL Prototype (ALICE) at Daresbury David Holder, on behalf of the ALICE team. LINAC'08 Victoria, BC](https://reader036.vdocuments.site/reader036/viewer/2022062417/551b33ea550346d41a8b5005/html5/thumbnails/1.jpg)
First Results from the ERL Prototype
(ALICE) at DaresburyDavid Holder, on behalf of the ALICE team.
LINAC'08 Victoria, BC
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Contents
• Introduction
• Overview of Gun Commissioning
• Cryogenics, Superconducting Modules & RF System Status
• Next Steps
• Summary
• Credits
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• Introduction:– New Name– ALICE & EMMA Layout
• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF
System Status• Next Steps• Summary• Credits
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ERLP (Energy Recovery Linac Prototype) – conceived as a prototype of an energy recovery-based 4th
generation light source...now called...
ALICE (Accelerators and Lasers In Combined Experiments)– An R&D facility dedicated to accelerator science and
technology development;– Offering a unique combination of accelerator, laser and free-
electron laser sources;– Enables studies of photon beam combination techniques;– Provides a suite of photon sources for scientific exploitation.
New Name
No, not THAT ALICE…
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ALICE & EMMA Layout
• Nominal Gun Energy 350 keV
• Injector Energy 8.35 MeV
• Beam Energy 35 MeV
• RF Frequency 1.3 GHz
• Bunch Rep Rate 81.25 MHz
• Nom Bunch Charge 80 pC
• Average Current 6.5 mA(over the 100 µs bunch train)
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• Introduction• Overview of Gun Commissioning
– Photoinjector– Gun Problems– Gun Diagnostic Layout– Gun Commissioning Results– Gun Commissioning Summary
• Cryogenics, Superconducting Modules & RF System Status
• Next Steps• Summary• Credits
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Photoinjector
Gun ceramic – major source of delay – at Daresbury (~1 year late)
Copper brazed joint
(First electrons August 2006)
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Gun Problems
• High voltage breakdown problems after cathode caesiation and from braze disintegration;
• Vacuum failures during bake-out of large diameter flange seals, feedthrough, valve and braze (again!);
• Contamination (caesium again?) and hydrocarbons;– impaired XHV conditions, field emission, halo, poor
cathode lifetime.
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Gun Diagnostic Layout
Injector commissioned with dedicated diagnostic line (now removed):
BUNCHERC
DE
A
BSOLENOID 1 SOLENOID 2
LASERTRANSVERSEKICKER
DIPOLE
FARADAYCUPS
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Gun Commissioning Results (1 of 3)R
MS
em
itta
nce
(pi-
mm
-m
rad)
RMS emittance vs. bunch charge
Horizontal Vertical
0
1
2
3
4
5
0
10 20 30 40 50 60 70 80Bunch Charge, pC
Bunch
length
@ 0
.1 (
mic
rom
etr
es)
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80
ASTRA
Bunch Charge, pC
ASTRA
Bunch length (at 10% of
peak value) vs.bunch charge
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Gun Commissioning Results (2 of 3)
0
5
10
15
20
25
30
35
40
0 10 20 30 40 50 60 70 80
EN
ER
GY
SP
RE
AD
@ 0
.1 ,
ke
V
BUNCH CHARGE, pC
TOTAL
COMPENSATED
MODEL
MODEL
Energy spread (at 10% of peak value) vs. bunch charge
Compensated = buncher ON
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Gun Commissioning Results (3 of 3)
0
5
10
15
20
300 320 340 360 380 400
SQRT (XY)FWHM (Astra)
SQ
RT
(X
Y),
mm
B1, G
SOL-01 scanBeam size (FWHM) on YAG "A"Q = 54pC (#712)
0
1
2
3
4
5
6
7
200 220 240 260 280 300 320
SQRT (XY)FWHM (Astra)
SQ
RT
(X
Y),
mm
B2, G
SOL-02 scanBeam size (FWHM) on YAG "B"Q = 54pC (#712) B1 = -348G
Beam size vs. solenoid 1 & 2 current, at Q=54 pC,
compared to ASTRA model
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Gun Commissioning Summary• Results:
– The gun can now be routinely HV conditioned to 450kV; – QE above ~3% is normally achieved after cathode
activations (bunch charges of well above 100pC have been achieved);
– The beam was fully characterised (emittance, bunch length, etc.) for bunch charges between 1 to 80pC;
– A good agreement between the ASTRA simulations and the experimental data was found for the bunch length and the energy spread but not for the emittance;
– Bunch characteristics were investigated at two different laser pulses of 7ps and 28ps:• At low Q<20pC, no significant difference was
observed;– The importance of a smooth longitudinal laser profile for
minimisation of the beam emittance was demonstrated. • Remaining gun-related issues:
– Ensure the absence of FE spots on the cathode;– Increase the cathode lifetime with QE >1.5%;– Resolve transverse emittance discrepancy (FE? QE non-
uniformity?).
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• Introduction• Overview of Gun Commissioning• Cryogenics, Superconducting Modules &
RF System Status:– Cryosystem Commissioning– Booster Module & RF Layout– Module Commissioning Results– Field Emission Radiation Issue– Mitigating Strategies
• Next Steps• Summary• Credits
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Cryosystem Commissioning
• Partial system procured from Linde;• 4 K commissioning completed May 06;• SRF Module delivery April and July 06;• Problems with excessive system heat leaks (lack of
capacity) and heater failure;• Cryosystem output:
– Specification 118 W at 2 K with 1 mbar stability;– Measured 118 W at 2 K with ± 0.03 mbar
stability in May 07;• Static load:
– Specification < 15 W per module;– Measured 5 W for both modules (i.e. ~2.5 W
each);• System has operated successfully at 1.8 K – needs
further optimisation.
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Directional Coupler
E2V 116LS 16 kW CW IOT
Circulator (incl. Load)
E2V 116LS16 kW CW IOT
CPI CHK51320W30 kW CW IOT
3dB Hybrid
Load
Booster (8 MeV)
Cavity 2 @ 2.9 MV/m Cavity 1 @ 4.8 MV/m350 keV
In8.35 MeVOut
Directional Coupler
E2V 116LS 16 kW CW IOT
Circulator (incl. Load)
E2V 116LS16 kW CW IOT
CPI CHK51320W30 kW CW IOT
3dB Hybrid
Load
8 MeV
350 keVIn
8.35 MeVOut
Cavity 1, 4.8 MV/m
Booster Module & RF Layout
Cavity 2, 2.9 MV/m
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Module Commissioning Results
7.0 x 109 @ 9.8 MV/m
1.9 x 109 @ 14.8 MV/m
1.3 x 109 @ 11 MV/m
3.5 x 109 @ 8.2 MV/m
Qo
12.816.413.510.8Max Eacc (MV/m)
FE QuenchRF PowerFE QuenchFE QuenchLimitation
5 x 109
20.8
Cavity 2
5 x 109
18.9
Cavity 1
Booster
5 x 1095 x 109Qo
20.417.1Eacc (MV/m)
Cavity 2Cavity 1
Linac
Vertical Tests at DESY (Jul – Dec 2005)
Module Acceptance Tests at Daresbury (May – Sept 2007)
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Field Emission Radiation Issue
• At 9 MV/m (c.f. required value of 13.5), radiation monitor in linac LLRF rack goes into saturation.
• Predicted electronics lifetime only around 1000 hrs.
0
10
20
30
40
50
60
70
80
90
100
0.0 2.0 4.0 6.0 8.0 10.0 12.0
Gradient (MV/m)
Rad
iatio
n D
ose
(mS
v/hr
)
Linac Cavity 1
Linac Cavity 2
Power (Linac Cavity 1)
Power (Linac Cavity 2)
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Mitigating Strategies
• Lead shielding installed around linac;• New linac module (collaborative
design);• Further aggressive processing:
– Over longer conditioning periods;
– Varying frequency, pulse width and pulse repetition rate;– CW conditioning (only possible at lower power levels);
– Possibly condition the cavity when warm;
– Introduce helium into the vacuum (risky!)
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SC Module Commissioning Summary
• All 5 IOTs are successfully commissioned;• All 4 cavities show unexpected limitations due to field
emission;• ALICE operation at 35 MeV is still possible;• Measurements of cryogenic losses at intermediate
gradients show significant reduction compared with vertical test results;
• High levels of FE radiation measured and mitigating strategies implemented.
Maximum measured
Required
Cavity 1 10.8 4.8 MV/m Booster
Cavity 2 13.5 2.9 MV/m
Cavity 1 16.4 13.5 MV/m Linac
Cavity 2 12.8 13.5 MV/m
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• Introduction• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF
System Status• Next Steps:
– Accelerator (short term)– Science Programme– Accelerator Developments– EMMA
• Summary• Credits
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Accelerator (short term)
• First energy recovery (Fall 2008):– Without FEL, installation planned Spring 2009;
• Fine tuning: – Injector tuning for minimum emittance;– Optimisation of energy recovery at nominal beam
parameters;– Beam diagnostics;
• Short pulse commissioning stage:– Longitudinal dynamics, electro-optical diagnostic
studies;• Energy recovery with FEL (Spring 2009):
– First light!– Energy recovery of a disrupted beam.
• Then the fun really starts…
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Science Programme
IR FEL, CBS x-ray source and terahertz radiation research programme, including pump–probe research programme with all ALICE light sources:
– Terawatt laser (~10TW, 100 / 35 fs, 10Hz);– Infrared FEL (~4µm, ~15MW peak, ~1ps, ~10mJ);– Femptosecond tunable laser;– Terahertz radiation (broadband);– CBS x-ray source (15-30keV, 107 – 108
photons/pulse, <1ps);– Tissue Culture Laboratory (TCL).
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LINAC
BOO
STER
GU
N
SOL-01
H&V-01
H&V-06BPM-01
BUNCHERYAG-01
SOL-02
H&V-02 BPM-02
Q-01
YAG-02 Q-02
BPM-03
H&V-03 Q-03
Q-04
YAG-03
DIP-01
Q-05
DIP-02
YAG-??
FCUP-01
BPM-04H&V-04
Q-06Q-07
Q-08Q-09
DIP-3
Q-10
YAG-04
Q-11 BPM-05H&V-05
Q-12
INJECTOR
OTR-01BPM-01H&V-01
ST1
OTR-02 DIP-01DIP-02
DIP-03Q-01
OTR-03
BPM-02H&V-02
Q-02 Q-03 Q-04
OTR-04
BPM-01DIP-01
BPM-02SEXT-01
OTR-01
ST1 ARC1
ARC1
Q-01
V-01
Q-02
BPM-03
DIP-02
BPM-04
Q-03
V-02
Q-04
OTR-02SEXT-02
BPM-05DIP-03
BPM-06
OTR-01
Q-01Q-02
BPM-01H&V-01
OTR-02
Q-03Q-04
BPM-02H&V-02DIP-01
DIP-02BPM-03V-03
OTR-03
DIP-03
DIP-04Q-05
ST 2ST 2
ARC 2 PLM-01TCM-01
BPM-04H&V-04
BPM-05H&V-05
BPM-01H&V-01
Q-06Q-07
WIGGLER
ST 3ST 3
Q-01Q-02
Q-03Q-04
OTR-01
BPM-02H&V-02
BPM-01DIP-01
BPM-02SEXT-01
OTR-01
Q-01
V-01
Q-02
BPM-03DIP-02
BPM-03Q-03
V-02
Q-04
OTR-02SEXT-02BPM-05
DIP-03BPM-06
ARC 2
ST4
OTR-01Q-01 Q-02
BPM-01H&V-01
Q-03
DUMP-01
Q-04 Q-05
BPM-02H&V-02
OTR-02DIP-01 DIP-02 DIP-03
BPM-01Q-01
Q-02Q-03
OTR-01
DMP
1 m
Note: scale is for guidance only
ERLP SCHEMATIC DIAGRAM
v.0.2 (15/06/2006)extracted from AO-180/10078/E
Mobile laser
CBS
TW Laser
Phase I
Phase II
Wiggler
E-BEAM
EO d
iagn
ostic
IR FEL4-6µm THz
IR FEL4-6um
CBS X-ray
532 nm
Photogun laser
Science Programme
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• Accelerator physics research:– Photocathode research and testing (upgraded
load-lock system for cathode exchange & activation);
– New linac module;– Re-establishment of gun diagnostic line.
• EMMA - Electron Machine with Many Applications:– Non-scaling fixed field alternating gradient
accelerator;
Accelerator Developments
Why FFAG ?• fast acceleration (e.g. muons)• high power beam acceleration• variable electron energy
Why Non-Scaling ?• compact beamline vacuum chamber• hence, compact magnets
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EMMA
Applications :
• medical
(oncology)
• muon
acceleration
• Accelerator-
Driven Sub-critical
Reactor (ADSR)
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• Introduction• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF
System Status• Superconducting Module Status• Next Steps• Summary• Credits
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Summary
• Accelerator commissioning has now reached a critical stage;
• ALICE has provided the UK with an opportunity to develop generic technologies and skills important for the delivery of advanced accelerator-driven facilities, including:– Photoinjector, SCRF, cryogenics, diagnostics,
synchronisation etc.• ALICE will provide a unique R&D facility in Europe,
dedicated to accelerator science & technology development:– Offering a unique combination of accelerator, laser
and free-electron laser sources; – Enabling essential studies of beam combination
techniques;– Providing a suite of photon sources for scientific
exploitation.
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• Introduction• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF
System Status• Superconducting Module Status• Next Steps• Summary• Credits
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Credits• The ALICE technical team:
– Controls: Brian Martlew et al.– Vacuum: Tom Weston & Keith Middleman et al.– Installation engineering: Phil Atkinson et al.– Mechanical engineering: Neil Bliss et al.– Electrical engineering: Steve Griffiths et al.– Diagnostics: Rob Smith et al.– FEL: Jim Clarke et al.– Compton Back Scatter: Gerd Preibe et al. – THz Science: Mark Surman et al.– Running, Safety: Stephen Hill et al.– Photoinjector laser: Steve Jamison & Graeme Hirst et al.– Elaine Seddon, Mike Poole and Paul Quinn
• Our international collaborators including:– J Lab (George Neil, Fay Hannon, Kevin Jordon, Carlos Hernandez-Garcia,
Tom Powers et al.– FZD Rossendorf (Peter Michel, Frank Gabriel et al.) – Cornell (Bruce Dunham)– Stanford University (Todd Smith)– Institute of Semiconductor Physics, Novosibirsk (Alex Terekhov)
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Thanks for listening