1. Accelerators in a new light
Overview of VELA and CLARA Test Facilities at Daresbury Laboratory Deepa Angal-Kalinin, STFC
VHEE17: Very High Energy Electron Radiotherapy, Medical & Accelerator Physics Cockcroft Institute, 24 – 26 Jul 2017

2. Versatile Electron Linear Accelerator (VELA)
A high performance, modular S-band RF photoinjector facility capable of delivering a high quality electron beam to two beam areas.
Two large, flexible, fully shielded experimental areas (BA1 and BA2).
Easy access for industry and academia.
High performance capability of VELA used to develop state-of-the art photoinjector for future Free Electron Laser facilities (CLARA and UK XFEL).
Beam Parameters
Beam Energy
4 – 6 MeV
Bunch Charge
0.04 – 250 pC
Bunch length (σt,rms)
0.5 – 10 ps
Normalised emittance
1 – 4 µm
Beam size (σx,y,rms)
0.5 – 5 mm
Energy spread (σe,rms)
1 – 5 %
Bunch repetition rate
1 – 10 Hz
(400 Hz with HRRG)
Not all parameters achievable simultaneously. Beam parameters vary along the beam line. 2

3. 10 Hz Repetition Rate Gun VELA photocathode gun
2.5 cell S-band ALPHA-X Gun – on loan from Strathclyde Univ.
Maximum gradient of 100 Hz.
Maximum RF pulsed power 10 MW, RF pulse duration 3 sec.
Ti:Sapphire drive laser system (266nm, ~1mJ)
RF and laser systems specified at max. repetition rate up to 400 Hz.
Planned upgrade for vacuum load lock system for easy replacement of cathode.
Extensive photocathode R&D programme with vacuum and surface science
Copper photocathode integrated into the gun as back wall of the cavity, with QE of measured. 3

4. VELA Injector and Diagnostics Line
Dedicated diagnostics suite includes diagnostics devices for charge, position and transverse profile measurements.
The Transverse Deflecting Cavity (TDC) allows to measure the bunch length as well as to map 6D phase space of electron bunches. 4

5. Bunch Length measurement with TDC
VELA Commissioning
Bunch charges from 40 fC to 250 pC with peak beam energy of ~5 MeV are reliably achieved.
Dark current, measured with two different cathodes, has shown continual improvement.
Longitudinal and Transverse beam qualities characterised through, slit, quadrupole scans, spectrometer line and TDC measurements.
Micron level beam emittance
Trans. emittance measurement
First cathode
Second cathode
Measured dark current with different cathodes
Bunch Length measurement with TDC 5

6. VELA Academic and Industrial Engagement
Electron Diffraction System on VELA allows single shot ED patterns to be obtained with sub-pC bunches from a variety of simple metals and semiconductors. (UCL/Swansea/York/STFC)
Single gold crystal ED pattern
using single 40 fC VELA electron bunch
Scintillator
Detector
Sample
Compton Photon
X-ray
Feasibility of using Time of Flight information to create 3D X-ray Compton Scatter imaging for cargo scanning. (UCL/RapiScan/STFC) 6

7. VELA Academic and Industrial Engagement
Cavity Beam Position Monitor Development: Single cavity tests performed, planned 3 cavity tests with CLARA FE in (RHUL/FMB)
Novel acceleration concepts and diagnostics R&D : Flexible end station installed in Beam Area1 to allow rapid reconfiguration of experiments on optical breadboard inside large vacuum vessel.
Additional beam line to tailor/characterise the beam. 7

8. Compact Linear Accelerator for Research and Applications (CLARA)
An upgrade of the existing VELA Photoinjector Facility to a 250 MeV Free-Electron Laser Test Facility.
Proof-of-principle demonstration and new FEL capabilities.
Will address many scientific and technology challenges for future large scale UK-FEL facility
Shorter Pulses
Improved Temporal Coherence
Tailored Pulse Structures
Stability & Power
Key technologies
New photo-injector technologies
Novel undulators (short period, superconducting….)
New accelerating structures: X-Band etc ...
Advanced single bunch diagnostics. 8

9. CLARA High Repetition Rate Gun
1.5 cell S-band gun with RF probe
Maximum gradient of 120 Hz, or 100 Hz
10kW cooling capacity
Vacuum load lock system for easy replacement of cathode
CLARA stability requires:
0.1% rms amplitude
0.1o rms phase
Necessitates <0.01oC rms temperature regulation!
Now installed for beam characterisation
Designed in collaboration with:
Lancaster University, UK
Institute of Nuclear Research, Moscow
Cooling Channel Pressure
Temperature Profile
Photocathode system development support from:
INFN-LASA (Milano), DESY (Hamburg and Zeuthen) & LBNL 9

10. VELA and CLARA Located inside same accelerator hall,
3 x 4 m S-Band Linacs provided by PSI
2 m S-Band Linac manufactured by
Research Instruments
Located inside same accelerator hall,
Share RF and PI laser for both VELA and CLARA guns. Simultaneous operation not possible. 10

11. VELA with CLARA FE Possible operating modes with CLARA Front End
Spectrometer for CLARA and VELA gun characterisation

12. VELA with CLARA FE Possible operating modes with CLARA Front End
To BA1
~50 MeV
~15 MeV in VB mode
To BA2
~25 MeV

13. VELA with CLARA FE Possible operating modes with CLARA Front End
~50 MeV
~15 MeV in VB mode

14. VELA with CLARA FE Possible operating modes with CLARA Front End
~50 MeV
~15 MeV in VB mode
To BA1
~50 MeV
~15 MeV in VB mode
~5MeV on VELA as will still be available for some experiments (e.g. Electron Diffraction)
Spectrometer for CLARA and VELA gun characterisation
To BA2
~25 MeV

15. VHEE with CLARA FE Two main scenarios considered in simulations:
A large round beam with minimal divergence
A focal point inside the VHEE experiment
Both scenarios assume a constant beam momentum of 46 MeV/c and a bunch charge of 250 pC.
1. A large round beam with minimal divergence

16. VHEE with CLARA FE
2. A focal point inside the VHEE experiment 1 2

17. CLARA Schematic & Project Phases
CLARA assumes S-band acceleration and deflecting cavities and X-band linearization. Simulations show that Linac 4 could be swapped for X-band - would be excellent demonstration for FEL community.
Phase 1, 50 MeV
Phase 2, 250 MeV
Phase 3, 100nm FEL

18. Commissioning started March 2017.
CLARA build Phase-1
2015/16
Commissioning started March 2017.
Variable Bunch Compressor (VBC)
Laser Heater Stage
Accelerating Linac2 S-Band 70MeV
VELA
Dump
Collimator & YAG diagnostics
Accelerating Linac1 S-Band 35MeV
High Rep Rate Gun
CLARA
Photocathode loadlock 18

19. CLARA build Phase-2 2017/19 CLARA VELA 19 High Rep Rate Gun
Accelerating Linac1 S-Band 35MeV
Collimator & YAG diagnostics
Accelerating Linac2 S-Band 70MeV
Variable Bunch Compressor (VBC)
Laser Heater Stage
Photocathode loadlock
High Rep Rate Gun
CLARA
VELA 19

20. The Electron Hall December 2016 February 2016
CLARA is installed in the Electron Hall
To provide a very stable FEL, the temperature of the facility needs to be very stable.
Electron Hall has been refurbished in 2016 to maintain the temperature within the building to ±1 °C and ±0.05 °C within the shielded enclosure.
December 2016
February 2016

21. VELA & CLARA Future Plans
CLARA-FE installation complete, first electrons from 10 Hz photoinjector on CLARA line on 9th May 2017.
Linac1 RF conditioning is currently being carried out.
HRRG ready for commissioning on VELA line.
Once commissioned, possible to provide VELA with:
Low energy (4 – 5 MeV) HRRG beam (up to 400 Hz repetition rate),
High energy (~50 MeV) CLARA-FE beam (10 Hz repetition rate).
Beam characterisation and R&D to establish the design parameters for CLARA will continue alongside some dedicated allocation time for exploitation programme.
CLARA Phase 2 modules ready for commissioning in late Hz/HRRG guns will be swapped at the same time to meet CLARA specifications of 100 Hz repetition rate and to provide higher beam power to the VELA beam areas.
First FEL lasing on CLARA by end of 2021. 21

22. VELA/CLARA Tours Today @15:50hrs After Coffee Break
Thank you for your attention