Neutron Production and Leakage from Medical Electron Accelerators

Download or read book Neutron Production and Leakage from Medical Electron Accelerators written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For medical accelerators operating above about 10 MeV, there is an unavoidable production of photoneutrons which add to the head leakage. The yield of photoneutrons produced by electron beams incident on thick targets has been calculated and found to increase rapidly with primary electron energy up to approximately 25 MeV, and more slowly thereafter. Dividing the neutron fluence for W (or Pb) by the photon absorbed dose for the same conditions gives the ratio plotted. This ratio, representing the maximum achievable with practical materials, becomes nearly constant above about 25 MeV incident electron energy where its value is about 2.1 x 105 neutrons cm−2 rad−1. Measurements that fall significantly below the curve are likely due to photon absorption in components that are not high-Z materials, or measurements made with the moveable jaws open. Points that fall significantly above probably mean there is substantial loss of electron beam elsewhere than the intended target.