First Results from the ERL Prototype

(ALICE) at DaresburyDavid Holder, on behalf of the ALICE team.

LINAC'08 Victoria, BC

2

Contents

• Introduction

• Overview of Gun Commissioning

• Cryogenics, Superconducting Modules & RF System Status

• Next Steps

• Summary

• Credits

3

• Introduction:– New Name– ALICE & EMMA Layout

• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF

System Status• Next Steps• Summary• Credits

4

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…

5

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)

6

• 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

7

Photoinjector

Gun ceramic – major source of delay – at Daresbury (~1 year late)

Copper brazed joint

(First electrons August 2006)

8

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.

9

Gun Diagnostic Layout

Injector commissioned with dedicated diagnostic line (now removed):

BUNCHERC

DE

A

BSOLENOID 1 SOLENOID 2

LASERTRANSVERSEKICKER

DIPOLE

FARADAYCUPS

10

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

11

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

12

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

13

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

15

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.

16

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

17

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

22

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

26

EMMA

Applications :

• medical

(oncology)

• muon

acceleration

• Accelerator-

Driven Sub-critical

Reactor (ADSR)

27

• Introduction• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF

System Status• Superconducting Module Status• Next Steps• Summary• Credits

28

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.

29

• Introduction• Overview of Gun Commissioning• Cryogenics, Superconducting Modules & RF

System Status• Superconducting Module Status• Next Steps• Summary• Credits

30

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