Modular filter design for the white-beam undulator/wiggler beamlines at the Advanced Photon Source

Abstract

A new filter has been designed at Argonne National Laboratory that is intended for the use in undulator/wiggler beamlines at the Advanced Photon Source. The water-cooled frame allows up to four individual filter foil banks simultaneously in the beam path. Additionally, the bottom of each frame holds two thin (20 pm) uncooled carbon filters in tandem for low-energy filtering. Therefore, a maximum of 625 filter selection combinations is theoretically possible. The design is intelligent, compact and modular, with great flexibility for the users. To prevent accidental movement of the filter, effort has been taken to provide a mechanically locked, fail-safe actuator system. Programming aspects are under development as part of our general personnel and equipment protection system. Aspects of the design and operational principles of the filter are presented in this paper. Conceptual Design The effective use of filters in a general experimental beamline requires a large variety of different filters to cover the entire beam spectrum. The filter assembly described is designed to provide filtering with cutoffs up to 30 keV and above. To provide additional flexibility to the experimenters, a modular design was required. This allows the option of adding or exchanging individual filters with minimum effort. In addition, this Esembly earl be build as a double filter bank assembly or a quadruple filter bank assembly, depending on the needs of the individual beamline. The design had to be UHV compatible. Water cooling was requited for each filter foil (Fig.l and Fig.2). Finally, the requirements called for individual motor controlled actuators for each filter bank. These actuators are to be linked to the APS equipment protection system.