Effective dose and organ doses due to gas bremsstrahlung from electron storage rings

Bremsstrahlung on residual gas is an important source of beam losses in ele ctron-positron storage rings. The bremsstrahlung photons are emitted in a n arrow cone in the forward direction, which produces a "hot spot" of dose at the end of a straight section. Estimates of radiation hazard due to gas br emsstrahlung have so far been performed by calculating the maximum dose equ ivalent (MADE) or similar quantities. However, the use of quantities concei ved for broad parallel beams in the case of very narrow beams significantly overestimates the organ doses and effective dose. In this paper a more sop histicated computational model was used to calculate the values of effectiv e dose and absorbed doses in various organs due to gas bremsstrahlung X-ray s generated by 0.1-10GeV electrons. The bremsstrahlung photons generated by the interaction of a monoenergetic electron beam in a Im long air target w ere made to impinge on a selected organ of an hermaphrodite anthropomorphic mathematical model placed at 1 and 10 m distances from the end of the targ et. Organ dose and effective dose were calculated for five representative o rgans, namely right eye, ovaries, breast, testes and thyroid. Fits to the c alculated values are given, as well as the dependence of photon fluence and dosimetric quantities on various parameters. The results are compared with previous estimates based on MADE and with values of ambient dose equivalen t. (C) 2001 Elsevier Science B.V. All rights reserved.