Abstract

The intense photon beams of the next generation of synchrotron sources (Argonne’s APS) will deliver large thermal loads (1 kW to 10 kW) to the first optical elements. Considering the problems that present synchrotron users are experiencing with beams from recently installed insertion devices, new and improved methods of cooling these first optical elements, are clearly needed. Calculations were performed to test the efficiency of new cooling geometries and various cooling fluids. The best results were obtained with liquid Ga metal flowing in channels just below the surface of the crystal. Ga was selected because of its good thermal conductivity and thermal capacity, low melting point, high boiling point, low kinetic viscosity, and very low vapor pressure. Its very low vapor pressure, even at elevated temperatures, makes it especially attractive in UHV conditions. A series of experiments were conducted at Cornell in February and June of 1988 that compared liquid gallium cooled silicon diffraction crystals with waer cooled crystals using photon beams from a wiggler and the new ANL/CHESS undulator. A special high pressure electromagnetic induction pump, recently developed at Argonne, was used to circulate the liquid gallium through the silicon crystals. The liquid metal cooling performed 3 to 5 times better than the water cooling.

© 1989 Optical Society of America