Richard D'Arcy

Abstract:

A series of Beam Position Monitors (BPMs) will be installed at the Front End Test Stand (FETS) at RAL as part of the 3 MeV Medium Energy Beam Transport (MEBT). The BPMs analyse 2 ms long, 60 mA beam pulses delivered to the MEBT by a 324 MHz Radio Frequency Quadrupole (RFQ). Initial linearity and resolution measurements from the prototype button BPMs are shown. The development of the algorithm for the processing of the BPM signals using a commercial PXI-based FPGA card is discussed and initial measurements of the electronics and signal processing are presented. The test-rig used to characterise each BPM and further develop the processing algorithm is described. The position and phase are measured several times throughout the duration of each pulse, and the measurements are made available via an EPICS server.

Abstract:

A CW-compatible, pulsed H- superconducting RF linac (a.k.a. PIP-II) is envisaged as a possible path for upgrading Fermilab's injection complex [1]. To validate the concept of the front-end of such machine, a test accelerator (a.k.a. PXIE) [2] is under construction. The warm part of this accelerator comprises a 10 mA DC, 30 keV H- ion source, a 2m-long LEBT, a 2.1 MeV CW RFQ, and a MEBT that feeds the first cryomodule. In addition to operating in the nominal CW mode, the LEBT should be able to produce a pulsed beam for both PXIE commissioning and modelling of the front-end nominal operation in the pulsed mode. Concurrently, it needs to provide effective means of inhibiting beam as part of the overall machine protection system. A peculiar feature of the present LEBT design is the capability of using the ∼1m-long section immediately preceding the RFQ in two regimes of beam transport dynamics: neutralized and space charge dominated. This paper introduces the PXIE LEBT, reports on the status of the ion source and LEBT installation, and presents the first beam measurements.

Abstract:

A 4 m-long, 324MHz four-vane RFQ, consisting of four coupled sections, has been designed for the Front End Test Stand (FETS) at RAL in the UK. A novel design method, integrating the CAD and electromagnetic design of the RFQ with beam dynamics simulations, was used to optimise the design of the RFQ. With the design of the RFQ fixed, the focus has been on optimising the transmission of the RFQ at 3MeV and matching the output of the FETS Low Energy Beam Transport (LEBT) to the RFQ acceptance. Extensive simulations have been carried out using General Particle Tracer (GPT) to map out the acceptance of the FETS RFQ for a 65 keV H- input beam. Particular attention has focussed on optimising the simulations to match the optimised output of the FETS Penning-type H- ion source. Results are presented of the transverse phase space limits on the RFQ input acceptance in both the zero current and full space charge regimes.

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. Understanding the pion production yield and transport properties of the beam line is an important part of the experiment. The beam line is a continuous solenoid channel, so it is only possible to place a beam diagnostic device at the end of the beam line. Building COMET in two phases provides the opportunity to investigate the pion production yield and to measure the transport properties of the beam line in Phase-I. This paper will demonstrate how this will be done using the experimental set up for COMET Phase-I. Copyright © 2013 by JACoW- cc Creative Commons Attribution 3.0 (CC-BY-3.0).

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.