Heavy-ion sources for radiation therapy

Abstract

The usefulness of particle beams for radiation therapy has been well and widely recognized. For the cure of cancer patients, many accelerator facilities have already been utilized, and some new facilities are now being put into operation, or are under construction. Considering the medical and biological requirements, light heavy ions with an energy of several hundred MeV/nucleon are regarded as being the most suitable species. A reasonable choice to this end is an accelerator complex, for an example, one comprising an ion source, an injector linac, and a synchrotron. The ion source is of great importance, since its characteristics strongly affect the overall performance of the accelerator system. A pulsed Penning source (PIGIS) has been successfully used at Lawrence Berkeley Laboratory. Recently, at the National Institute of Radiological Sciences a low-duty pulsed PIGIS for the heavy-ion medical accelerator in Chiba (HIMAC) has been developed; it has both a long lifetime and a high peak intensity. As other types of ion sources, an electron-beam ion source (EBIS) and an electron-cyclotron-resonance ion source (ECRIS) are being developed at several laboratories. An EBIS is basically a pulsed source, and is being successfully used at Saclay. By using an after-glow mode, two ECRISs have made remarkable progress at Grenoble and the Grand Accelerateur National d’Ions Lourds; similar tests are proceeding for the Schwer-Ionen Synchrotron at the Gesellschaft für Schwer-Ionenforschung, the booster at Centre d’Europeen de Recherche Nucleaire, and the HIMAC. These different types of heavy-ion sources are discussed from the viewpoint of their application to radiation therapy.

Review on heavy ion radiotherapy facilities and related ion sources (invited)

“…When the authors first reviewed heavy ion sources for RT, 47 this field was not popular; moreover, HI-RT was not accepted by a large majority of workers and was far from the main stream treatment methods. However, demonstrated medical experiences with HI-RT have recently awakened a worldwide interest.…”

Non-Maxwellian Electron Energy Probability Functions in an Indirectly Heated Cathode Bernas Source

“…These beam electrons produce secondary electrons as a result of the impact ionization process, and the energy exchange via electronelectron collisions with the secondary electrons produces thermalized bulk electrons. The beam electrons that have undergone beam plasma interaction and energy relaxation form a high-energy tail of the EEPF [5,6]; these electrons are classified as the energetic electron group. Eventually, the EEPFs are classified into bulk electron and energetic electron groups based on the cathode voltage.…”

“…The most popular source type among PIG sources is the indirectly heated cathode (IHC) Bernas source [2]. Unlike conventional PIG structures, the IHC source not only has an improved life-time but also has an effective discharge mechanism represented by the confinement of the beam electrons under the electric field combined with the magnetic field [1,2,5,6].…”

“…The plasma discharge initiated by the beam electrons within the electric and magnetic fields exhibits various physical phenomena. Theoretical works have shown the evolution of the electron energy probability function (EEPF) through beam plasma interaction and quasi-linear relaxation of the electrons, and experimental works have reported various physical phenomena related to beam plasma interaction in laboratory-level linear devices [5,6]. However, despite the long history of the sources, authors studying IHC sources focused on finding the plasma discharge conditions that can improve the plasma process yield from an industrial aspect, with no detailed analysis of the electron energy distribution, thus limiting our understanding of the underlying physics in PIG sources.…”

Improvement of Yield and Emittance of Ions from an EBIS/T with rf-Modulated Electron Beam

“…Single-turn injection furthermore allows for a reduction in the ring acceptance, and therefore in the aperture of the magnets, which reduces the cost of the ring construction [39]. In a 1994 review of heavy ion sources for IBT Sato et al [40] mentioned that an EBIS/RFQ injector proposed in [38] "is the most simple system among various combinations which are capable of providing relativistic heavy-ion beams for radiation therapy", however the technological limits, especially on the EBIS side, require further development to make it feasible. Work on improving EBISes for IBT applications was pursued through 1990-s in the group led by R. Becker [41,42].…”