GEANT4 models for the secondary radiation flux in the collimation system of a 300MeV proton microbeam.
In Harbin, we are developing a 300MeV proton microbeam for many applications in space science including upset studies in microelectronic devices, radiation hardness of materials for satellites and radiation effects in human tissues. There are also applications of this facility proposed for proton therapy. The microbeam system will employ a purpose-built proton synchrotron to provide the beam. However there are many challenges to be addressed in the design, construction and operation of this facility. Here we address two important design aspects for which we apply GEANT4 modeling. First, the high energy proton beam interacts strongly with beam line materials, especially the collimation slits, to produce showers of secondary particles which could introduce significant background signals and degrade the resolution of the proton microbeam. Second, the beam transport within the residual vacuum of the beam line may also introduce undesirable background radiation. In both cases mitigation strategies need to be incorporated during the design phase of the new system. We study the use of a dipole magnet following the aperture collimator to reduce the flux of secondary particles incident on the analysis chamber. Monte Carlo simulations are performed using GEANT4 and SRIM. By inserting the dipole magnet, we find as expected a significant reduction in the scattering of protons and other particles, such as neutrons and gamma rays, at the collimation system exit position. Secondary radiation from the residual gas pressure within the beam line vacuum system are also modelled and found to be negligible under the standard operating conditions.
School of Electrical Engineering & Automation, Harbin Institute of Technology, Harbin 150001, China; School of Physics, University of Melbourne, VIC 3010, Australia. Electronic address: douyanxinch@163.com.
Yanxin
Y
Dou
School of Physics, University of Melbourne, VIC 3010, Australia.
David N
DN
Jamieson
Research Center of Basic Space Science, Harbin Institute of Technology, Harbin 150001, China.
Jianli
J
Liu
Microelectronics Center, Harbin Institute of Technology, Harbin 150001, China.
Anlong
A
Li
School of Electrical Engineering & Automation, Harbin Institute of Technology, Harbin 150001, China. Electronic address: liliyi.hit@gmail.com.
Liyi
L
Li
D060328:Magnetic Phenomena; D009010:Monte Carlo Method; D061766:Proton Therapy / Q000379:methods*; D014618:Vacuum
Collimator scattering; Dipole magnet; GEANT4; Proton microbeam