<title>Experimental results with cryogenically cooled thin silicon crystal x-ray monochromators on high heat flux beamlines</title>

Abstract

A novel, silicon crystal monochromator has been designed and tested for use on undulator and focused wiggler beamlines at third-generation synchrotron sources. The crystal utilizes a thin, partially transmitting diffracting element fabricated within a liquid-nitrogen cooled, monolithic block of silicon. This report summarizes the results from performance tests conducted at the European Synchrotron Radiation Facility (ESRF) using a focused wiggler beam and at the Advanced Photon Source (APS) on an undulator beamline. These experiments indicate that a cryogenic crystal can handle the very high power and power density x-ray beams of modern synchrotrons with sub-arcsec thermal broadening of the rocking curve. The peak power density absorbed on the surface of the crystal at he ESRF exceeded 90 W/mm<SUP>2</SUP> with an absorbed power of 166 W, this takes into account the spreading of the beam due to the Bragg angle of 11.4 degrees. At the APS, the peak heat flux incident on the crystal was 1.5 W/mA/mm<SUP>2</SUP> with a power of 6.1 W/mA for a 2.0 H X 2.5 V mm<SUP>2</SUP> beam at an undulator gap of 11.1 mm and stored current up to 96 mA.