CALCULATIONS OF THE RADIATION-DOSES TO THE ELECTRONIC EQUIPMENT AND MAGNET COIL INSULATION IN THE PEP-II TUNNEL

The PEP-II collaboration is a new physics project at SLAC that utilize s an existing tunnel to house two accelerator storage rings; a low-ene rgy positron ring (4 GeV, called the LER) atop a high-energy electron ring (10 GeV, called the HER). Both rings are being designed to permit a high circulating current of 3 A, corresponding to a beam particle n umber of 1.38 X 10(14). Dose calculations were made to estimate the po tential for radiation damages to the electronics and magnet coil insul ation in the are section of the tunnel. An analytical code, SHIELD11, was used to calculate the dose from photon and neutron radiations resu lting from beam losses in various modes of operation. Several EGS4 Mon te Carlo user codes were developed to calculate the dose from the sync hrotron radiation escaping the vacuum chamber in stored beam mode. Two different LER vacuum chamber designs were studied: a 0.35-cm-thick co pper wall chamber and a 1-cm-thick aluminum wall chamber with a copper absorber 6 m downstream of every dipole to absorb the synchrotron rad iation in a local spot. The HER has a 0.5-cm-thick copper vacuum chamb er. Shielding from the 5.4-m-long, C-shaped iron bending magnet for th e HER was considered for the beam radiation, while no other structural shielding was assumed for the LER. Furthermore, the dose from all rad iations scattering back from the tunnel concrete wall were also estima ted using the albedo method or the MORSE code. The results of the dose estimations are presented.