gms | German Medical Science

48th Meeting of the Particle Therapy Co-Operative Group

Particle Therapy Co-Operative Group (PTCOG)

28.09. - 03.10.2009, Heidelberg

Multiple charged Carbon-Ion Production for the Heavy Ion Therapy

Meeting Abstract

  • A. Kitagawa - Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, Chiba
  • T. Fujita - Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, Chiba
  • M. Muramatsu - Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, Chiba
  • N. Sasaki - Accelerator Engineering Corporation, Ltd., Chiba, Japan
  • W. Takasugi - Accelerator Engineering Corporation, Ltd., Chiba, Japan
  • M. Wakaisami - Accelerator Engineering Corporation, Ltd., Chiba, Japan
  • S. Biri - Institute of Nuclear Research, Debrecen, Anguilla
  • A. Drentje - Kernfysisch Versneller Instituut, Groningen, The Netherlands

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog113

DOI: 10.3205/09ptcog113, URN: urn:nbn:de:0183-09ptcog1136

Veröffentlicht: 24. September 2009

© 2009 Kitagawa et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Background: Although the best ion species principally depends on the type and location of a tumor, a carbon ion beam was finally chosen at HIMAC due to its better biological dose distributions than helium or neon under the typical depth and thickness of a tumor. For almost components of the facility, it's not so different that the accelerated beam is carbon or not. However, for ion sources, the production of carbon ions is harder effort than other ion species. An ECR ion source has been developed and utilized to produce carbon ions for the clinical treatment, because its lifetime is longer than other types of ion sources.

Methods and materials: The performance of the ECR ion source is degraded due to carbon deposition on 1) an electric insulator, 2) the waveguide, 3) the plasma-chamber wall, and most of the other parts. It's easy to prevent 1) since the insulator does not directly face the plasma or the beam. For the prevention of 2), it is effective that a simple rectangular waveguide is connected to the plasma chamber at the far position from the plasma. Microwaves are propagated in free space, and their transmission efficiency is worse in this way. Therefore, the power of the microwave amplifier must be sufficiently high. The deposition on 3) is normally unavoidable. This causes an "anti-wall-coating effect", i.e. a decreasing of the beam, especially for the higher charge-state ions due to the surface material of the plasma-chamber wall.

Results: The record intensity has reached 430 microAe for C4+ under good conditions, just after a cleaning; however, the beam intensity decreases to about 300 microAe caused by rapid carbon deposition after several days. The ion source must be required to produce a sufficiently intense beam under the bad condition in which the wall is completely covered by carbon deposition. As a result, although the intensity was slightly decreasing, the source was able to produce about 240 microAe, even 4 years after without maintenance.

Conclusion: The wall condition varied according to the contaminated ion species or the operation for different ion species before. Since the variation often causes instability or poor reproducibility, it's better to keep two ion sources in order to frequently supply different ion species, especially. In addition, the quality assurance and quality control are indispensable. From analysis of experiences, the failures mainly due to aging deterioration can be managed by replacing any weak parts before their lifetime. Productions of ions with the same charge-to-mass ratio like C6+, N7+, O8+ have a large risk of contamination. It should not be utilized.