• S. Boucher, X.D. Ding, A.Y. Murokh
  RadiaBeam, Marina del Rey

Self-contained irradiators are used for a number of applications, such as blood irradiation to prevent Graft-Versus-Host-Disease, biomedical and radiation research, and detector calibration. They typically use a sealed Cs-137 source to irradiate an item within a treatment compartment. The US National Research Council has identified as a priority the replacement of such high-activity sources with alternative technologies, in order to prevent them from falling into the hands of terrorists for use in a Radiological Dispersal Device ("dirty bomb"). RadiaBeam Technologies is developing a novel, compact, low-cost linear accelerator "the MicroLinac" for use in self-contained irradiators in order to effectively replace Cs-137 in such devices. A previous version of the MicroLinac, originally developed at SLAC, was designed to produce 1 MeV electron energy and 10 μA of average current. RadiaBeam has redesigned the linac to produce 1.5 MeV and 20 μA current, in order to match the penetration and dose rate of a typical blood irradiator. This paper describes the new design of the MicroLinac and our future development plans.

• I. Jovanovic, Y. Yin
  Purdue University, West Lafayette, Indiana
• S. Boucher, R. Tikhoplav
  RadiaBeam, Marina del Rey
• G. Travish
  UCLA, Los Angeles, California

One approach for detecting special nuclear material (SNM) at a distance is to use highly penetrating gamma-rays (>6 MeV) to produce photofission. We are investigating inverse gamma-ray sources (IGS), based on inverse Compton scattering (ICS) of a laser pulse on a relativistic electron bunch. Nearly monochromatic gamma rays with high brightness, very small source size and divergence can be produced in IGS. For the interaction drive laser recirculation it is necessary to meet the repetition rate requirements. Three implementations of laser recirculation are proposed for the interaction drive laser, which can significantly reduce the requirements on the interaction drive laser average power. It is found that the recently demonstrated recirculation injection by nonlinear gating (RING) technique offers unique advantages for beam recirculation in IGS.

• X.D. Ding, S. Boucher
  RadiaBeam, Marina del Rey

The distribution of electromagnetic fields in an RF cavity is primarily determined by the geometry of the RF cavity. The quality factor (Q-factor) of an RF cavity characterizes RF losses in the cavity: an RF cavity having a higher Q-factor is a more efficient user of RF power. However, a cavity having a lower Q-factor can operate on a wider range of frequencies, shorter filling time and may be more stable and less sensitive to input power perturbations. A method is discussed in this paper for an RF cavity that provided a desired Q-factor for the cavity while enabling a desired field distribution for electron acceleration within the cavity. The structure forming the inner wall of the RF cavity may be comprised of different types of material(such as copper and steel). Using different materials for different portions of the inner walls forming a cavity will cause different Q-factors for the cavity while the shape of the cavity remains constant.

contact: ding@radiabeam.com