H. A. Grunder

A 3-Dimensional Beam Scanning System for Particle Radiation Therapy

In radiation therapy treatment volumes up to several liters have to be irradiated. Todays charged particle programs use ridge filters, scattering foils, occluding rings collimators and boluses to shape the dose distribution.1 An alternative approach, scanning of a small diameter beam, is analyzed and tentative systems specifications are derived. Critical components are scheduled for fabrication and testing at LBL.

Performance of the Bevalac

The performance of the Bevalac is reported. The Bevalac uses the LBL SuperHILAC as the heavy ion injector to the Bevatron. Ion species up to 40A have been accelerated to energies of 1.9 GeV/A at modest intensity. Neon has been accelerated to 2.1 GeV/A at an intensity of 4·1010 particles per pulse. The modifications to the SuperHILAC and Bevatron are briefly reviewed and the computer control system is described. Results of the first phase of operation and plans for further improvements are reported.

Design of a Dedicated Heavy Ion Accelerator for Radiotherapy

A new heavy ion accelerator facility for radiotherapy is being designed at the Lawrence Berkeley Laboratory. Performance requirements have been established. Ions from helium to argon can be accelerated to a maximum energy of 800 MeV/nucleon with intensities in the range 108-109 particles per second. The accelerator subsystems consist of a linac injector, a synchrotron and a beam delivery system. Specifications have been developed for many of the technical components, and some details of the technical design are presented.

Advanced Medical Accelerator Design

This report describes the design of an advanced medical facility dedicated to charged particle radiotherapy and other biomedical applications of relativistic heavy ions. Project status is reviewed and some technical aspects discussed. Clinical standards of reliability are regarded as essential features of this facility. Particular emphasis is therefore placed on the control system and on the use of technology which will maximize operational efficiency. The accelerator will produce a variety of heavy ion beams from helium to argon with intensities sufficient to provide delivered dose rates of several hundred rad/minute over large, uniform fields. The technical components consist of a linac injector with multiple PIG ion sources, a synchrotron and a versatile beam delivery system. An overview is given of both design philosophy and selected accelerator subsystems. Finally, a plan of the facility is described.

Acceleration of Partially Stripped Ions at the Bevalac

We present results of the first attempts to accelerate partially stripped heavy ions in the Bevatron. Experiments were performed for hydrogen-like argon and neon ions, and, although the survival time of these ions in the 10-7 torr Bevatron vacuum was not sufficient to achieve full energy, valuable charge-changing cross section information was obtained.

First Phase of Heavy Ion Acceleration at the Bevatron

High Energy Heavy-Ion Beams have become a standard operational feature of the Bevatron. A diver-sified experimental program using these beams complement the traditional proton-physics program, and at present accounts for about one-quarter of the Bevatron operation time. Beams of ion species up to mass number 20 (neon), and with intensities up to 108 particles per pulse for carbon, are available on target in the extracted beam channel. Initial heavy-ion operation began a year-and-one-half ago and for the most part utilized existing Bevatron features and capabilities. Acceleration of ion species heavier than helium-ions, however, required the adaptation of a side-extracted PIG ion-source to the Bevatron pre-injector. The immediate success of this development effort and the concomitant demand for experimental beam time motivated an improvement program to provide higher beam intensities, improved beam control and monitoring, and closed-loop beam control for intensities as low as 106 particles per pulse. Single particle beam dynamics has been invest igated. Predicted operation settings based on these studies are found to be close to actual running parameters. Losses due to recomibination are well explained with existing theories for single electron capture.

A Heavy Ion Facility for Radiation Therapy

The accelerator requirements of particle radiation therapy are reviewed and a preliminary design of a heavy ion synchrotron for hospital installation is presented. Beam delivery systems and multi-treatment room arrangements are outlined.

Pulsed Heavy Ion Source for the Bevatron

A Phillips ion gauge source (Fig. 1) of the type used by the heavy ion accelerator in Berkeley has been adapted for use at the Bevatron. The objective was to achieve high charge state ions (4+, 5+) of carbon and nitrogen. All source parameters are pulsed. The ion source performance regarding linac acceleration is discussed. The light ion (deuteron, alpha) performance of the PIG source and duoplasmatron is compared.

Status and Outlook for Heavy-Ion Accelerator Systems

There are five major heavy-ion centers constructed or funded worldwide; two additional centers are on the verge of being funded. Additionally, there are numerous smaller installations producing excellent science. Most installations aim at 10 MeV/u for the higher mass particles, and as high as possible for lighter ions. Berkeley and Dubna have reached or plan to reach relativistic energies for heavy ions. Studies and proposals for additional relativistic heavy-ion faccilities are pursued at least in five places. Altogether a very large effort is under way which is bound to leave a deep impression on basic science in the decade to come. There is an obvious energy gap in proposed facilities; namely, 30 - 150 MeV/u for high-mass particles. It is apparent that we should be searching for inexpensive magnets for high Bp in circular machines, or for very high, inexpensive electric gradients in linacs. This picture could be dramatically changed with a real breakthrough in ion source development. At least we should satisfy ourselves that we understand ion sources to the extent that we can predict their ultimate performance; only then can we produce optimum accelerator system designs.