Performance analysis of the commissioning filter and window assembly for insertion device beamlines at the Advanced Photon Source

Abstract

Although the Advanced Photon Source (APS) undulator beamlines are designed for windowless operation, a special window assembly will be used during the commissioning phase of the beamlines until sufficient operational experience is gained with the powerful undulator A photon beam. This assembly is called a ‘‘commissioning window.’’ The commissioning window assembly as designed consists of a 300-μm-thick filter (made of graphite), a fixed mask (made of Glidcop), a multipurpose transmitting filter/BPM disk (made of 127-μm-thick CVD diamond), and set of a double windows (made of 250-μm-thick beryllium). Due to the high total power and power density, the filter/window assembly must be carefully designed to guarantee longevity and satisfactory performance throughout its service. Hence extensive analytical work has been conducted on various thermal and structural aspects of the commissioning window assembly. This paper summarizes the analytical results and presents the expected performance characteristics of the as-designed commissioning window.