J. Pozimski

Understanding extraction and beam transport in the ISIS H− Penning surface plasma ion sourcea)

The ISIS H(-) Penning surface plasma source has been developed to produce beam currents up to 70 mA and pulse lengths up to 1.5 ms at 50 Hz. This paper details the investigation into beam extraction and beam transport in an attempt to understand the beam emittance and to try to improve the emittance. A scintillator profile measurement technique has been developed to assess the performance of different plasma electrode apertures, extraction electrode geometries, and postextraction acceleration configurations. This work shows that the present extraction, beam transport, and postacceleration system are suboptimal and further work is required to improve it.

PAMELA - a model for an FFAG based hadron therapy machine

Approximately one third of the worlds 15000 accelerators are used for tumour therapy and other medical applications [1]. The characteristics of FFAGs make them ideally suited to such applications, as the much smaller magnet size and greater compactness offers considerable cost and operational benefits. In the first stage the work on PAMELA will focus on the optimization of the FFAG design to deliver the specific machine parameters demanded by therapy applications. In this phase of the PAMELA project the effort will concentrate on the design of a semi-scaling type FFAGs to deliver a 450 MeV/u carbon ion beam, including detailed lattice and tracking studies. The second stage will use the existing expertise in the BASROC consortium [2] to undertake a design of the magnets and RF system for PAMELA. An outline of the overall concept of PAMELA will be discussed and the actual status of the work will be presented.

RFQ cold model RF measurements and waveguide-to-coaxial line transition design for the front-end test stand at RAL

A 324 MHz four vane RFQ cold model has been built, as part of the development of a proton driver front end test stand at the Rutherford Appleton Laboratory (RAL) in the UK. This paper will present the results of RF measurements performed on the cold model, which include analysis of resonant modes, Q-value measurements and electric field profile measurements using a bead-pull perturbation method. These measurements were done before and after brazing of the four vanes and the results were compared to Microwave Studio simulations. Additionally, a tuner has been designed, built and tested and the results will be presented together with the preliminary results of the electromagnetic design of waveguide-to-coaxial line transition structures for the four vane RFQ.

Demonstration of a laserwire emittance scanner for hydrogen ion beams at CERN

A non-invasive, compact laserwire system has been developed to measure the transverse emittance of an H- beam and has been demonstrated at the new LINAC4 injector for the LHC at CERN. Light from a low power, pulsed laser source is conveyed via fibre to collide with the H- beam, a fraction of which is neutralized and then intercepted by a downstream diamond detector. Scanning the focused laser across the H- beam and measuring the distribution of the photo-neutralized particles enables the transverse emittance to be reconstructed. The vertical phase-space distribution of a 3 MeV beam during LINAC4 commissioning has been measured by the laserwire and verified with a conventional slit and grid method.

The ISIS Penning H- SPS and Diagnostic Developments at RAL

This paper covers the recent work carried out at the Rutherford Appleton Laboratory (RAL) on the ISIS Ion Source Development Rig (ISDR). The development of a retarding potential energy analyzer is described and a measured energy spread of 17.6 eV ± 1.5 eV from the ion source is reported. Variation in energy spread versus discharge current is shown. The development of a pepperpot emittance scanner to study emittance variation along the beam axis is discussed.