Tests of the APS X-ray transmitting beam position monitors at ESRF

Two different types of synthetic diamond-based X-ray transmitting beam position monitor (XBPM) prototypes have been studied with an undulator white beam at the European Synchrotron Radiation Facility (ESRF) ID-6 beamline. Of particular interest was the possibility of designing an integral window and filter/photon beam position monitor for the Advanced Photon Source (APS) high heat flux insertion device beamlines. The photoelectron-emission type transmitting XBPM prototype uses a 25-mm-diameter, 175-micron-thick CVD-diamond disk with O.2-micron-thick electrically isolated patterns of aluminum coating on one side of the diamond disk. The photoelectron emission signal was collected from the aluminum-coat surface to provide the beam position information. A novel photoconductive-type transmitting XBPM prototype uses the same CVD-diamond disk, but patterns of aluminum coating were applied on both sides of the diamond disk. A DC bias voltage was used to generate the current signal, which is based on photoconductive properties of the CVD-diamond. Test results are presented.