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FETS Project Overview
High power short-pulse proton drivers are required for a wide range of applications including neutron spallation sources, neutrino factories, muon colliders, ADSRs and nuclear waste transmutation. In order to generate high power beams, proton drivers typically require multi-turn charge-exchange injection of H− ions into an accumulator ring. The overall deliverable power and quality of the beam is largely determined by the initial accelerating stage of the machine: the 'Front End'. Creating a front end to meet the demands of modern proton drivers is an ongoing challenge in accelerator technology.
For hands-on maintenance of high power proton drivers, the beam-loss-induced radio-activation of components must be kept to a minimum. One of the major sources of beam loss is the trapping of particles in the ring RF buckets. By pre-chopping the H− beam in the linac, trapping losses are considerably reduced. Chopping should be performed at low energy, in the front end, to ease the dumping of up to 40% of the beam. Chopping should also be as quick as possible so there are no partially chopped bunches leaving the linac. A sufficiently quick 'perfect' chopper has yet to be demonstrated world-wide.
The Front End Test Stand (FETS) is an experiment based in building R8 at the Rutherford Appleton Laboratory (RAL). It is a collaboration between ISIS, ASTeC, Imperial College, University of Warwick, University College London and Royal Holloway. This project will design, build and test the first stages necessary to produce a very high quality, perfectly chopped H− ion beam as required for high power proton drivers. The beam parameters are 3 MeV energy and 60 mA beam current at 50 Hz repetition rate and up to 2ms pulse duration. The major components and contact details are detailed below.
- Caesium-enhanced Penning surface plasma H− ion source
- 60 mA pulsed beam current at 50 Hz repetition rate and up to 2 ms pulse length
- 0.25 π mm mrad transverse emittance
|Dan Faircloth||Scott Lawrie|
|STFC ISIS facility||STFC ISIS facility|
- Three-solenoid magnetic low energy beam transport
- Space-charge neutralised
- 95% transmission
|University of Warwick|
- 324 MHz, 4 metre, 3 MeV radio frequency quadrupole
- Vane-type resonating cavity
- Bolted construction
|Alan Letchford||Jürgen Pozimski||Pete Savage|
|STFC ISIS facility||Joint STFC and Imperial College London||Imperial College London|
- Electromagnetic quadrupole and re-bunching cavity medium energy beam transport
- Transport beam through chopper to diagnostics line or rest of accelerator
- Low beam loss and emittance growth
|Ciprian Plostinar||Morteza Aslaninejad|
|STFC ASTec||Imperial College London|
- Novel separated 'fast-slow' electrostatic deflectors
- Fast chopper rise time <3 ns (between RFQ microbunches): no partially chopped bunches
- Slow chopper pulse rises in gap made by fast chopper
|STFC ISIS facility|
- Beam current transformers & beam position monitors
- Laser photo-detachment emittance scanning
|Christoph Gabor||Stephen Gibson||Simon Jolly|
|STFC ASTeC||Royal Holloway University of London||University College London|
- Labview PXI-based
- EPICS distribution
- Fast sampling and calculation
|Royal Holloway University of London|