Radiation diagnostics and dosimetry modeling for characterization of plasma-beam interactions and x-ray production for a 500kV MILO

The University of New Mexico Electrical Engineering Department has designed and fabricated a Magnetically Insulated Transmission Line Oscillator (MILO) to operate with a 100 ns to 300 ns pulse capability at 500 kV driven by a marx capacitor bank. Its main purpose is to study the interaction between beams and plasmas as they relate to high power microwave production. The coaxial geometry MILO utilizes the self-generated magnetic insulation derived from high electron currents to maintain power flow. This eliminates the need for externally applied magnetic fields. The device the n utilizes a slow wave structure to couple electron energies in to high power microwaves on the order of 1.1 GHz. The operation of the device also results in the production of ionizing bremsstrahlung radiation due to electrons impinging on the aluminum walls of the device. The number of bremsstrahlung photons, the energy of the bremsstrahlung, and the angular distribution of those photons can be analyzed to effectively postulate the behavior of the beam and plasmas evolving from the cathode and anode. This paper presents the design of a tungsten pinhole camera built to identify time inte grated electron impact and x-ray production resulting from firing the MILO; these data will then be correlated with other diagnostics and particle in cell models to gain understanding of the beam plasma interactions within the vacuum chamber. MCNP radiation transport simulations were used in conjunction with measurements taken from thermo luminescent dosimeters and pin-diode radiation detectors in order to determine the radiation dose rates within the laboratory space housing the MILO. This data was then analyzed and used to properly to design adequate shielding as well as safety procedures within the laboratory to eliminate any risk of exposure to radiation exceeding the dose limits outlined in NRC 10CFR20 and university guidelines.