Richard D'Arcy

Abstract:

EMMA (Electron Machine with Many Applications) is a prototype non-scaling Fixed-Field Alternating Gradient (ns-FFAG) accelerator whose construction at Daresbury Laboratory, UK, was completed in the autumn of 2010. The energy recovery linac ALICE [1] serves as an injector for the EMMA ring, within an effective energy range of 10 to 20 MeV. The ring is composed of 42 cells, each containing one focusing and one defocusing quadrupole. Acceleration over many turns of the EMMA machine has recently been confirmed. In some cases the bunch will traverse upwards of 100 turns, at which point the effects of space-charge may be significant. It is therefore necessary to model the electron beam transport in the ring using a code capable of both calculating the effect of and compensating for space-charge. Therefore the General Particle Tracer (GPT) code [2] code has been used. A range of injection beam parameters have been modelled for comparison with experimental results and those of other codes. The simulated effects of space-charge on the tune shift of the machine are also compared with those expected from theory. Copyright © 2013 by JACoW.

Abstract:

The COMET experiment will search for very rare muon processes that will give us an insight into particle physics beyond the Standard Model. COMET requires an intense beam of muonswith amomentumless than 70MeV/c. This is achieved using an 8 GeV proton beam; a heavy metal target to primarily produce pions; a solenoid capture system; and a curved solenoid to perform charge and momentum selection. It was recently proposed to build COMET in two phases with physics measurements being made in both phases. This requires re-optimising the beam line for a shorter curved solenoid. This will affect the pion and muon yield; the momentum distributions at the detector; and the collimator scheme required. This paper will present the beam line design for COMET Phase-I, which aims to maximise the yield for low momentum muons suppressing sources of backgrounds in the beam. Copyright © 2013 by JACoW- cc Creative Commons Attribution 3.0 (CC-BY-3.0).

Abstract:

EMMA is the worlds first non-scaling FFAG, based at Daresbury Laboratory. EMMA has a very large acceptance and has demonstrated acceleration in the serpentine channel. PRISM (Phase Rotated Intense Slow Muon source) is a next generation muon to electron conversion experiment aiming to obtain intense quasi-monochromatic low energy muon beams by performing RF phase rotation in an FFAG ring. Current baseline design for PRISM applies the scaling FFAG ring, but an alternative machine could be based on a ns-FFAG principle. As the transverse-longitudinal coupling is present in ns-FFAGs due to a natural chromaticity, its effect on the final energy spread and beam quality needs to be tested. In order to gauge the expected results, an experiment was designed to be performed on EMMA. We report here the details of this experiment and the results gathered from EMMA operation. Copyright © 2013 by JACoW.

Abstract:

The Front End Test Stand (FETS) under construction at RAL is a demonstrator for the front end systems of a future high power proton linac. Possible applications include a linac upgrade for the ISIS spallation neutron source, new future neutron sources, accelerator driven sub-critical systems, a neutrino factory etc. Designed to deliver a 60mA H-minus beam at 3MeV with a 10% duty factor, FETS consists of a high brightness ion source, magnetic low energy beam transport (LEBT), 4-vane 324MHz radio frequency quadrupole, medium energy beam transport (MEBT) containing a high speed beam chopper and non-destructive photo-detachment diagnostics. This paper describes the current status of the project and future plans.

Abstract:

The H- ion source and beam-line at FETS will require the beam current and beam position to be continually monitored. Current transformer toroids will measure the beam current and beam position monitors (BPMs) will determine the beam position. The ion source delivers pulses at a rate of 50 Hz with a current up to 60 mA, each pulse is 2 ms long, and a 324 MHz micro-bunch structure imposed by the radio frequency quadrupole (RFQ) accelerating structure. The toroid outputs will be acquired on a fast oscilloscope. Two BPM designs are under consideration (shorted strip-line or button type) but the processing for both types is similar and has been designed, with simulated measurements made. Each BPM uses four pickups, at a frequency of 324 MHz, which are mixed using RF electronics to an intermediate frequency of 10.125 MHz. The resulting signals are then digitized at 40.500 MHz and processed in an FPGA to produce the position and phase of the beam at each BPM location, with a precision of better than 100 μm and 0.05 rad. The measurements from the toroids and BPMs will be available via EPICS servers at every pulse.