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 (Hi gh Energy Ring) in the PEP-II storage ring were calculated using the E GS4 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 bea m was 6.1 X 10(17), including both stored beam loss and injection loss . The vacuum chambers (the targets for beam losses) of the LER (Low En ergy Ring) and the HER were 1-cm-thick aluminum and 0.5-cm-thick coppe r, respectively. The shielding from the C-shaped iron bending magnet a nd the aluminum coil windings of the HER was considered. Both vacuum c hambers 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 devic es need to be shielded on the left side by 1-cm-thick iron for the dos e to remain below a damage threshold of 10(4) rad, when integrated ove r 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 a valanche effect, is also analyzed and reported in the Appendix A.