High-power beam test of the aps grazing-incidence insertion device x-ray beam position monitor

We present test results of a grazing-incidence insertion device x-ray beam position monitor (GRID-XBPM) at beamline 29-ID. In the vertical direction, the XBPM readout showed little gap dependence for the total undulator beam power from 17 W to 10.6 kW, covering nearly three decades, as one expects from center-of-mass measurements. In the horizontal direction, the calibration factor shows strong gap dependence, as predicted by computer simulations. The XBPM will work reliably near its center position. Monochromatic beam profiles were measured using a liquid-nitrogen-cooled Si (111) doublecrystal monochromator. Their centers correlate strongly with the white-beam positions derived by the XBPM using x-ray fluorescence (XRF). We demonstrated experimentally that the x-ray beam from two different undulators can be centered on the XBPM aperture reliably and reproducibly. Thermal measurements found a maximum of ~ 15°C temperature rise in the chamber walls with the time constant ~ 10 minutes.