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

Cyclone C230 performance improvements

Meeting Abstract

  • P. Verbruggen - Ion Beam Applications s.a., Belgium, Louvain la Neuve, Belgium
  • M. Abs - Ion Beam Applications s.a., Belgium, Louvain la Neuve, Belgium
  • S. de Neuter - Ion Beam Applications s.a., Belgium, Louvain la Neuve, Belgium
  • Y. Jongen - Ion Beam Applications s.a., Belgium, Louvain la Neuve, Belgium

PTCOG 48. Meeting of the Particle Therapy Co-Operative Group. Heidelberg, 28.09.-03.10.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. Doc09ptcog216

DOI: 10.3205/09ptcog216, URN: urn:nbn:de:0183-09ptcog2161

Published: September 24, 2009

© 2009 Verbruggen et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.


Outline

Text

Background: The Cyclone C230 cyclotron is currently installed in ten proton therapy centers around the world, with nine additional machines at different stages of construction and test at the moment. Continuous efforts are made to improve the systems performance, availability and maintainability. With such a large installed base, emphasis is put throughout every redesign on retrofitability.

Material and methods: The main objective was to increase the amount of available beam while reducing the time required and difficulty to optimize the accelerator. The poster focuses on four significant modifications.

1.
An adjustable dowel pin system was designed and implemented to displace the upper yoke with respect with the lower yoke in order to correct for a tilt between the beam acceleration plane and the mechanical median plane.
2.
The electrostatic deflector septum curvature was optimized through 2D simulations and particle tracking to increase extraction efficiency.
3.
Pencil Beam Scanning (PBS) requires very high beam current modulation speeds. This capability was obtained by an original method that consists of modulating the accelerating dee voltage between the central region cut-off voltage and nominal dee voltage instead of modulating the ion source arc current.
4.
Internal beam losses during acceleration have been significantly reduced by relatively simple mechanical redesign.

Results: Being able to easily displace the beam and managing more room for it has reduced internal beam losses by an order of magnitude. Vertical beam loses during acceleration are now below a percent. Tests have shown that these improvements lead to a significant increase in extraction efficiency, several tens of percents higher. Beam current modulation using the RF system allows regulating the beam between 100pA and 300nA within 1% error, with a bandwidth exceeding 8kHz and a rise time smaller than 50 µs.

Conclusions: Over the last years, several improvements on the design of the first generation C230 cyclotron have been designed, implemented and validated successfully. These improvements were driven by more stringent beam related requirements needed for active scanning techniques, like PBS, as well as various quality related requirements aiming at improving safety and facilitating system's maintenance.