Commissioning ERLP & Simulations

1. Commissioning ERLP & Simulations David Holder ASTeC, Daresbury Laboratory Cockcroft "All Hands" Meeting

2. Technical Priorities for the ERL Prototype Demonstrate energy recovery Operate a superconducting linac Produce and maintain bright electron bunches from a photoinjector Produce short electron bunches from a compressor Demonstrate energy recovery with an insertion device that significantly disrupts the electron beam Have an FEL activity that is suitable for the synchronisation needs Produce simultaneous photon pulses from a laser and a photon source of the ERLP that are synchronised at or below the 1ps level Cockcroft "All Hands" Meeting

3. Parameters • Nominal Gun Energy 350keV • 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 • Max Average Current 13 µA Cockcroft "All Hands" Meeting

4. Accelerator Layout Cockcroft "All Hands" Meeting

5. Construction Status • Photoinjector laser operating since April ’06; • Gun operating since July 2006 into a dedicated gun diagnostic beamline; • Cryosystem installed and used to cool accelerating module to 2K – now undergoing modification; • Both superconducting accelerator modules awaiting final test with RF power and then beam; • All the beam transport modules present and most installed and pumping. Cockcroft "All Hands" Meeting

6. Construction Status Cockcroft "All Hands" Meeting

7. Construction Status Cockcroft "All Hands" Meeting

8. Photoinjector Laser - Collaboration with Central Laser Facility (Rutherford Appleton Lab) Cockcroft "All Hands" Meeting

9. Photoinjector Laser System Cockcroft "All Hands" Meeting

10. Gun Assembly Cathode ball Ceramic SF6 Vessel removed Cathode Electrons laser XHV Stem Anode Plate Cockcroft "All Hands" Meeting

11. Gun Diagnostic Beamline Cockcroft "All Hands" Meeting

12. Why Have a Gun Diagnostic Beamline? Dedicated diagnostic beamline to fully characterise the gun and benchmark the codes used for design; e.g. predicted effect of spacecharge: Cockcroft "All Hands" Meeting

13. booster buncher solenoid Injector Code Benchmarking Comparison of beam dynamics codes for injectors – for example ASTRA and GPT Cockcroft "All Hands" Meeting

14. Quantum Efficiency Scan over Cathode Surface Cockcroft "All Hands" Meeting

15. First Beam! Cockcroft "All Hands" Meeting

16. Gun Measurements Already Made HV conditioning of PSU and gun and investigations of abnormal gun behaviour at high voltage. So far we have measured: Quantum efficiency, bunch charge, cathode lifetime Dipole calibration Correctors calibration Transverse emittance And finally: YAGs images calibrated wrt their physical sizes Technical reports can be found in : \\apsv4\Astec\Projects\4gls\ERLP\Analysis Cockcroft "All Hands" Meeting

17. Performance Achieved So Far • Beam energy 350 kV (spec value); • Bunch charge 10 pC(ultimate target 80 pC); • Quantum efficiency measured in the gun 1.5%, measured in the lab 3.5%(ultimate target ~few percent); • Bunch train length 100 µs (spec value); • Train repetition rate 20 Hz (spec value). Cockcroft "All Hands" Meeting

18. Gun Commissioning Status • First beam from the gun recorded at 01:08 on Wednesday 16th August with the gun operating at 250 kV; • Encouraging results obtained initially; • Commissioning issues: • field emission; • HV breakdown; • short cathode lifetime; • Currently under investigation: • XHV conditions within the gun (leak/contamination?); • Effect of caesiation/activation on HV breakdown; • Optimisation of caesiation/activation process. Cockcroft "All Hands" Meeting

19. Beam Measurements Still Outstanding Beam steering: - how to achieve minimal angles wrt the axis; - magnet settings at variable bunch charge; Transverse emittance and bunch length measurements: - wrt bunch charge; Optimisation of laser spot size: - in terms of minimal emittance; Energy spread: - correlated and uncorrelated wrt bunch charge; Determination of “optimal” settings for 350keV and 80pC. Cockcroft "All Hands" Meeting

20. Cryosystem Commissioning Status • Cryogenic systems designed and installed by LINDE • Cooled linac and booster modules to 2 K (Dec 07); • Serious heat load problems found in commissioning; • New 4K to 2K transfer line due 16th April; • New exhaust gas heater installed yesterday. • Faster cool down is required to avoid “Q disease”: • Modifications underway to linac and booster transfer lines; • Plan to have the system fully commissioned by June 07. Cockcroft "All Hands" Meeting

21. 2007 Objective: Energy Recovery October 2007! Cockcroft "All Hands" Meeting

22. Future Exploitation of ERLP • Test accelerator for studies of: • Simulation codes for 4GLS; • Advanced accelerator operation; • Diagnostics (e.g. electro optic); • Photocathode guns; • Superconducting RF; • e-beam/laser synchronisation; • Narrow gap undulator test; • EMMA Injector! • Short pulse photon source: • IR FEL radiation; • Compton BS (x-rays); • Intense THz source; Cockcroft "All Hands" Meeting

23. Arc Design for 4GLS Confirming suitability of TBA arc design chosen for 4GLS: Cockcroft "All Hands" Meeting

24. LD LB q 4-dipole chicane Dipole Chicane Bunch Compression Studies Confirming 4 dipole chicane bunch compression scheme: Cockcroft "All Hands" Meeting

25. FEL Interaction Modelling • Modeling of FEL interaction using in Genesis 1.3; • Major tool used for design of 4GLS sources; • Commissioning measurements will confirm validity of code and other calculations. before FEL after FEL Cockcroft "All Hands" Meeting

26. Verify Start-to-End Modelling Results 1 4 3 2 First case of complete S2E modelling of an ERL with a FEL and energy recovery Cockcroft "All Hands" Meeting

27. The end Cockcroft "All Hands" Meeting