Radiation Induced Conductivity in Polyethylene and Teflon

Abstract

The conductivity induced in polyethylene and Teflon by bombardment with x-rays from a 2-Mev Van de Graaff and gamma rays from Co60 has been investigated as a function of time, temperature, geometry, exposure rate, and applied electric field. Within the range of the variables studied, the observed photocurrents were directly proportional to the exposure rate and the applied electric field. The photocurrent could be divided into three components, the current due to the action of monodirectional photons, the increase in this current due to the influence of the electric field, and a component of less than 10% made up of all other possible charge carriers. During irradiation, the conductivity increased by a factor of about 103. Between 78°K and 273°K the photocurrent was nearly independent of temperature. In general, the conductivity of Teflon was greater than that of polyethylene.

Effect of radiation induced current on the quality of MR images in an integrated linac‐MR system

“…4 RIC has been widely reported on in various materials when exposed to various sources of radiation. [5][6][7][8][9] These extraneous currents have the potential to adversely affect MR imaging by distorting the RF signal being measured by the RF coils. Our more recent results have shown that the RIC signal in RF coils can be reduced with the application of appropriate buildup material to the coils.…”

Space charges remaining in polymers after electron beam irradiation and the role of conductivity in their decay profiles

“…2(b). Therefore, we estimated τ 1 by substituting σ = 1.1 × 10 −12 S/m obtained experimentally and the relative permittivity 3.5 [16] into (2). Then, we obtained τ 1 ≈ 29 s for PI.…”

“…Insulating polymers used in radiation environments such as space and nuclear facilities are subjected to radioactive rays such as cosmic rays and γ rays, or high-energy particles such as neutrons and electrons. Therefore, basic research is important to examine the fundamental dielectric or insulating properties of insulating polymers that are exposed to such environments [1][2][3][4][5][6][7][8][9][10]. For this purpose, we irradiated five typical insulating polymers and one conductive polymer with electrons and analyzed the decay profile of the space charges remaining in each sample after the irradiation.…”

Physics Division Summary Report for September Through December 1956

“…H, A. Bethe, Phys, Rev. 103,1353(1956 In recognition of the constantly broadening scope of our activities and of the need to expand them, the Applied Mathematics Section of the Physics Division was transformed into the Applied Mathematics Division on November 1, 1956. Consequently, future reports of our work will be issued by the Applied Mathematics Division.…”