Electron Beam Test Facility (EBTF) & Photocathode R&D programme at Daresbury Laboratory Deepa Angal-Kalinin ASTeC, Daresbury Laboratory 27 th January’12, Frascati

EBTF Layout

EBTF layout: beam characterisation

Beam parameters in EBTF (CLARA - first few meters) (Please note that minimum and maximum numbers for EBTF are over all operating regimes) EBTF (required Minimum values) EBTF (required Maximum values) CLARA (single spike) Minimum/ Maximum CLARA (seeding) Minimum/ Maximum Comments Beam Energy4 MeV6.5 MeV6 /25 MeV Magnets in EBTF can go up to 25 MeV later for CLARA and some diag devices will be used at this higher energy. Bunch Charge10 pC250 pC10 pC250 pCExperimental modes Bunch length (σ t,rms ) 80 fs3 ps 35 fs /3ps MeV) 50 fs /3ps MeV) Bunch length changes along the line. CLARA in bunch compression mode. Experimental modes. Normalised emittance 0.1  m2.0  m 0.1/1 µm0.6/3.0 µm CLARA in bunch compression mode. Experimental modes Beam size (σ x,y,rms ) 0.1 mm3.5 mm0.1/2.0 mm0.1/4 mmVaries along the beam line Energy spread (σ e,rms ) 0.1%5%~ 0.1/1 %~ 0.1/5%Varies along the beam line Bunch repetition rate 1 Hz400 HzTBD Klystron Modulator & Laser 400 Hz

Technology Application Areas Application AreaEnergy (MeV)Repetition Rate (Hz)Beam Power (kW) Security Cargo Scanning  0.1 Medical X-Ray Radiotherapy  500 22 Isotope Production  10 Sterilisation Food 11 Medical   10

EBTF Synergies Application AreaEnergy (MeV)Repetition Rate (Hz)Beam Power (kW) Security Cargo Scanning  0.1 Medical X-Ray Radiotherapy  500 22 Isotope Production  10 Sterilisation Food 11 Medical   10 Accelerating Structures & RF Power Sources Beam Diagnostics & Control Systems

EBTF Construction Modules Module 1 Module 2 Module 3 Module 5 Module 6 Module 4 Module 7 Module 8 Module 9

Module 1 Transverse Deflecting Cavity RF Gun Light box Laser YAG Strathclyde Gun Vacuum Bake

Photocathode Gun Lightbox Beam diagnostic station Stripline BPM WCM Laser In EBTF Photoinjector section RF coupler

Location of EBTF at DL ALICE/ EMMA CI EBTF

Outer Hall : Floor Plan

EBTF Accelerator Implementation

EBTF photoinjector based on the ALPHA-X 2.5-cell S-band gun

Photocathode gun cavity ParameterValueUnits Frequency2998.5MHz Bandwidth< 5MHz Maximum beam energy6MeV Maximum accelerating field100MV/m Peak RF Input Power10MW Maximum repetition rate10Hz Maximum bunch charge250pC Operational Temperature °C Input couplingWR284

RF Requirements to the gun ParameterValueUnits Frequency MHz Bandwidth (1 dB points)<10 MHz Total peak output power> 8 MW MW Pulse Repetition Rate Range1 – 400 (10) Hz RF Pulse Duration<3.5 µs RF Flat Top Pulse Width>2.5 µs Amplitude stability Phase Stability0.1 ° Noise Power Within the Bandwidth< -60 dB Spurious Noise Power Outside the Bandwidth< -35 dB dB

Tuning studs Input coupler Dummy Load/Vacuum port CF70 entrance flange CF70 exit flange 9 cell Transverse Deflecting Cavity Collaboration with CI/Lancaster University

H-field E-field On-axis fields of the Transverse Deflecting Cavity Estimated peak transverse voltage 5 MV (limited by available RF power) Estimated resolution at 25 MeV beam energy ~30fs

Beam transport through Transverse Deflecting Cavity. Transverse kick amplitude 3.5 MV Vertical trajectories Particle energies Correctors before and after TDC - on Dipole & post TDC quads off.

EBTF beam dynamics simulations Bunch charge1pC, RMS laser pulse length 40fs

EBTF beam dynamics simulation. Bunch charge250 pC, RMS laser pulse length 40fs

Simulation of the transport of 250 pC bunch to the user area

Outer Hall Preparation Work Outer Hall/Inner Hall partition removed. Floor repairs completed. Structural check on floor in progress (area above NINA tunnel in Outer Hall). Survey network implemented, shield wall build initiated. New steelwork support design for roof beams complete. Radial crane steelwork modification completed. Sept 2011 Nov 2011

Key Milestone Dates MilestoneDate

Photocathode Research Programme GaAs (III-V) photocathode technology has been established at ASTeC (in collaboration with ISP, Novosibirsk), initially with a primary goal to develop high average current high quantum efficiency photocathodes for 4GLS ERL branch. After cancellation of 4GLS project the programme has been steered to photoinjector upgrade of energy recovery linac prototype ALICE with the aim to increase its operational performance. The load-lock photocathode preparation system developed for the purpose allows also to study the physics and technology of these cathodes. Dedicated R&D programme to investigate emission properties of GaAs cathodes is in advanced stage. With EBTF/CLARA, new programme of metal photo cathodes has been initiated at ASTeC.

ALICE DC photocathode gun upgrade Photocathode gun 500 kV power supply Photocathode preparation facility Upgrade of the gun allows  Reduce the down time required for activation of the photocathode and allows ALICE for operation with higher bunch charge.  Remove activation/caesiation procedure out of the gun  Improve vacuum in the gun  Reduce contamination of the high voltage electrodes with Cs and other products of photocathode preparation  Make photocathode activation more controllable  Allows for experiments with different types of photocathodes Due to ASTeC priorities on projects, PPF will not be implemented on ALICE. The developed technology and facilities will be used for wide range of R&D experiments to understand physics and performance of photocathodes.

Photocathode R&D at ASTeC Schematic of planned experimental system to measure transverse energy spread of electrons, emitted from GaAs photocathodes as a function of their electron affinity (and, finally QE), incident laser wavelength and photocathode temperature.

Photocathode R&D at ASTeC Planned photocathode test facility with a diagnostics beamline to characterise the emission performance of GaAs photocathodes at room and cryogenic temperatures. The measurements will focus on complete 6D beam characterisation including emittance, photocathode response time and energy spread. This work is intended to deliver progress towards a high–current, short–pulse photoinjector electron source based on GaAs technology.

Initial Programme on Metal Photocathodes Establish reliable and reproducible sample preparation procedure to minimise the final surface contamination (done at SLAC) Prepare atomic flat surfaces for single crystal and poly-crystalline copper Investigation of impact of surface roughness on photocathode performance Determine QE for different method of surface regeneration (Ar, H and Ozone cleaning) Determination of surface roughness after each procedure Identify the effect of each individual residual gas species(H 2, CO, CO 2, H 2 O and CH 3 ) on photocahode degradation Investigation of wide band gap coating (CsBr) on copper on photocathode performance Design of the photocathode transport system (vacuum suitcase) to deliver photocathode into the gun

Acknowledgements to colleagues from ASTeC & Technology Department (STFC) for their contributions to this talk.