Author: Winklehner, D.
Paper Title Page
TUB01
 Status of the Development of a Fully Iron-free Cyclotron for Proton Beam Radiotherapy Treatment  
 
  • D. Winklehner
    MIT, Cambridge, Massachusetts, USA
  • L. Bromberg, J.V. Minervini, A. Radovinsky
    MIT/PSFC, Cambridge, Massachusetts, USA
  
  Funding: This work was supported by the US Department of Energy under award number DE-SC0013499.
Superconducting cyclotrons are increasingly employed for proton beam radiotherapy treatment. The use of superconductivity in a cyclotron design can reduce its mass by an order of magnitude and size by a factor of 3-4 over conventional resistive magnet technology, yielding significant reduction in overall cost of the device, the accelerator vault, and its infrastructure. In the presented work, we go a step further and remove the iron yoke, generating the magnetic field with a combination of superconducting coils only. Eliminating the iron yoke has two key benefits. First and foremost, the overall weight can be reduced by almost another order of magnitude. Secondly, eliminating all magnetic iron from the flux circuit results in a linear relationship between field and coil current, which allows smooth scaling of the magnetic field and thus the output energy, thereby removing the need for a degrader. Here we describe the status of the design of such an iron-free cyclotron, currently under development at the Plasma Science and Fusion Center at MIT, with coil and cryostat calculations as well as beam dynamics studies and treatment plan considerations pertaining to this type of cyclotron. 		 
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WEB05
 Beam dynamics and preliminary design of the RFQ Direct Injection Project  
 
  • D. Winklehner
    MIT, Cambridge, Massachusetts, USA
  
  Injecting beam into a compact cyclotron from an external ion source usually requires a low energy beam transport line (LEBT) with several beam shaping elements (magnets and a buncher), the transfer through the cyclotron axial bore hole, and finally, bending the beam into the median plane using a spiral inflector. In the RFQ Direct Injection Project we are combining LEBT, buncher, and axial transfer within one element, the RFQ (Radio Frequency Quadrupole), which is inserted axially into the cyclotron yoke. This is a very compact solution that offers an excellent bunching efficiency. To accommodate the small diameter that is available in the axial bore hole together with a low RF frequency of 32.8 MHz, a split-coaxial RFQ type was chosen. Longitudinal and transverse de-bunching are mitigated by an internal re-bunching cell, and an external electrostatic quadrupole, respectively. The preliminary design phase of this project has been concluded and the RFQ is currently under construction at Bevatech GmbH in Germany. Here, we present the beam dynamics simulations, showing the feasibility of the system, and the preliminary design of the RFQ and test cyclotron with central region.  
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