DETERMINING PHASE-SPACE PROPERTIES OF THE LEDA RFQ OUTPUT BEAM
Quadruple scans were used to characterize the LEDA RFQ beam. Experimental data were fit to computer simulation models for the rms beam size. The codes were found to be inadequate in accurately reproducing details of the wire scanner data. When this discrepancy is resolved, we plan to fit using all the data in wire scanner profiles, not just the rms value.
High energy beam transport beamline for LEDA
Here the authors describe the High Energy Beam Transport (HEBT) for the Low Energy Demonstration Accelerator (LEDA), which is part of the Accelerator Production of Tritium (APT) project. The authors used the TRACE 3-D linear design code for the first-order design and performed r-z and 3-D particle-in-cell (PIC) simulations to study the beam distribution and halo. TRACE 3-D predicts rms beam properties well. The PIC simulations are important for determining the presence of beam halo, which is present for some tunes. They propose halo experiments to help validate the simulation codes for modeling nonlinear space charge.
New Low-Profile Applicators for Local Heating of Tissues
A new type of low-profile applicator is described giving efficient power transfer to tissue with low leakage. It consists of a resonant element spaced from a ground plane by low-loss material having high relative permittivity and some relative permeability. This combination is covered by similar material which can be placed in direct contact with the tissue to be heated, or separated from it by a water bolus as required. Laboratory measurements using phantom materials show that these applicators are well matched and produce well defined and relatively uniform heating profiles. Applicators having maximum dimensions of 3-15 cm covering the frequency range 1000-100 MHz, respectively, are described. Penetration depths of at least 4 cm at 100-200 MHz are achieved. Tests on anesthetised pigs and some clinical assessment have confirmed the usefulness of this compact low-frequency type of applicator and have shown that performance compares favorably with that of other recently reported types. The design can be optimized for treatment of specific sites, and suitable choice of dimensions and electrical characteristics of the layer material allow the low-profile concept to be extended over a wide range of operating frequencies.