The shielding design of BESSY II

BESSY II consists of a 50 MeV microtron, a maximum energy synchrotron and the 1.9 GeV storage ring. The investigations of the radiation types occurring at those machines dependent of the electron energy, target and shielding materials, observating angles and geometric aspects are well established, often condensed in semi-empiric formulas and in good agreement with the results of the Monte Carlo programs EGS4 and FLUKA. But as important as the pure physical aspects of radiation are for a shielding design the operating times and modes and the consideration of possible crash scenarios. We present here a new approach of considering failure operating probabilities at electron storage rings based on years of radiation and operating observations of BESSY I. The shielding design of BESSY II was developed using a C++ class library which includes the most recent models for all radiation types and the new failure operating probability approach. Calculations and first measurement results of the commissioning are presented too.