Radiological considerations for the operation of the Advanced Photon Source storage ring (revised).

Abstract

GeneralThis report deals with the radiological considerations of operations using 7700-MeV positron and electron beams in the storage ring (SR) tunnel. The radiological considerations addressed include the following: prompt secondary radiation (bremsstrahlung, giant resonance neutrons, medium and high energy neutrons, and muons) produced by electrons/positrons interacting in a beam stop or by particle losses in the component structures; skyshine radiation, which produces a radiation field in nearby areas and at the nearest off-site location; radioactive gases produced by neutron irradiation of air in the vicinity of a particle loss site; noxious gases (ozone and others) produced in air by the escaping bremsstrahlung radiation that results from absorbing particles in the components or by synchrotron radiation escaping into the tunnel; activation of the storage ring components that results in a residual radiation field in the vicinity of these materials following shutdown; potential activation of water used for cooling the magnets and other purposes in the SR tunnel; evaluation of the radiation fields due to escaping synchrotron radiation and gas bremsstrahlung. Estimated dose rates outside of the tunnel, in the early assembly area (EAA), and in the Experiment Hall for several modes of operation (including potential safety envelope beam power, normal beam power, and MCI (maximum credible incident) conditions) have been computed. Shielding in the first optics enclosure (FOE) and for the photon beamlines is discussed in ANL/APS/TB-7 (IPE 93), but additional radiological considerations for the ASD diagnostic beamlines are contained in Appendix C. Although the calculations refer to positrons, electron operation would produce essentially the same effects for the identical assumptions. Beam Parameters and Storage Ring Tunnel InformationComputations have been based upon these parameters for normal operations with positrons: 50 nC/pulse, 48 pulses/s and an electron energy of 200 MeV. This results in a beam power of 480 W incident on the tungsten target in the linac. A net conversion factor of 0.005 e + /e -is assumed (0.0083 conversion factor in the W target and 0.6 transmission to the positron linac), resulting in a current of 12 nA of e + , and a beam power of 5.4 W for 450 MeV e + being sent from the positron accumulator ring (PAR) to the synchrotron. In the synchrotron, the accelerated beam reaches 7000 MeV, giving a Design Performance Goal operational power of 84 W. For the case of operation at the linac safety envelope of 1000 W, the e + beam power delivered to the synchrotron has been taken to be 20 W with an e + current of 40 nA and energy of 500 MeV. The safety envelope for synchrotron operation has been set at 308 W. This implies a maximum e + current of 40 nA for 7700-MeV operations (the maximum energy in the synchrotron). As concerns the storage ring, Design Performance Goal operation is considered to be 100 mA of circulating current at 7 GeV e + (2578 J), and the safety envelope is 360 mA of circulating curre...

Shielding design aspects of SR in 3 GeV ILSF

“…where Ḣ is dose equivalent rate (Sv h −1 ), C r is the conversion factor for the rth radiation component (Sv h −1 kW −1 m 2 ), P is the electron power loss (kW), R is the distance between the loss point and the point of observation (m), t i is the thickness of the ith wall (shield thickness) (cm), and λ i,r is the attenuation length of the material of the ith wall for the radiation of type r (cm). The radiation attenuation lengths, which we used for the different radiation components corresponding to shielding materials in the calculations, are given in table 2 [8,9]. The conversion factors taken from Swanson [9] are given in table 3.…”