Speaker
Description
Conventional white beam photon beam position monitors (XBPMs) in light source front-ends detect the beam by measuring the drain current from illuminated metallic materials (photoelectric). Another common method is the use of semiconductors like Diamond or SiC (photoconduction) however rarely (if any) for white beam due to the high power density. The most recented and novel development has been the GRID-XBPM at the APS* making use of X-ray fluorescence. The Australian Synchrotron has been developing XBPMs for new beamlines however mechanical tolerances due to a much smaller upstream mask has resulted in a rethink of how the photon BPM could be done.
For the first time we propose a method to measure the power density profile via photoabsorption in 0.5 mm thick CVD diamond probes in a cross configuration, referred to as a thermal photon BPM (T-BPM). By measuring the temperature differences between probes the centroid of the beam can be calculated. This report will present the analysis and results of a prototype T-BPM that has achieved a position resolution of $<0.4 \mu$m and $0.3 \mu$rad for a 2.2 m separation between two T-BPMs at a bandwidth of 20 Hz. From cold to full beam, thermal equilibrium is achieved in $<$ 3 minutes. In this prototype we will also present the challenges encounted at this early stage with long term drifts and discuss developments in place to realised a T-BPM solution in the fron-end optics for the MX3 and Nano beamlines.
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