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[edit] 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.

[edit] Ion Source

Penning ion source

• 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

Contacts:

[edit] LEBT

LEBT

• Three-solenoid magnetic low energy beam transport
• Space-charge neutralised
• 95% transmission

Contacts:

[edit] RFQ

RFQ machining

• 324 MHz, 4 metre, 3 MeV radio frequency quadrupole
• Vane-type resonating cavity
• Bolted construction

Contacts:

[edit] MEBT

MEBT

• 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

Contacts:

[edit] Chopper

Electrostatic chopper

• 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

Contacts:

[edit] Diagnostics

Principle of laser photodetachment emittance measurement

• Non-interceptive
• Beam current transformers & beam position monitors
• Laser photo-detachment emittance scanning

Contacts:

[edit] Controls/DAQ

Block diagram of BPM DAQ

• Labview PXI-based
• EPICS distribution
• Fast sampling and calculation

Contacts: