EGS4 calculations of the dose to the electronic equipment in the PEP-II ring

The radiation doses to the electronic devices placed under the HER (High Energy Ring) in the PEP-II storage ring were calculated using the EGS4 code. The doses result from a 4-GeV positron and a 10-GeV electron beam uniformly lost around the ring. The annual particle loss per beam was 6.1 × 1017, including both stored beam loss and injection loss. The vacuum chambers (the targets for beam losses) of the LER (Low Energy Ring) and the HER were 1-cm-thick aluminum and 0.5-cm-thick copper, respectively. The shielding from the C-shaped iron bending magnet and the aluminum coil windings of the HER was considered. Both vacuum chambers were located about 1 m from the left wall of the ring (modeled as a 3.5 m wide, 2.9 m high and 100 m long tunnel and with a concrete wall thickness of 60 cm). The LER was 90 cm above the HER, which was 80 cm above the floor. The calculations show that the electronic devices need to be shielded on the left side by 1-cm-thick iron for the dose to remain below a damage threshold of 104 rad, when integrated over a ten-year period. The dose from non-uniform stored beam loss around the ring, due to high vacuum pressure in local regions from the ion avalanche effect, is also analyzed and reported in the Appendix A.