[en] The x-ray beams for the next generation of synchrotrons will contain much more power than is available at present day facilities. The total power in these next generation sources will range from 1 to 10 kilowatts. Cooling the first optical components in these beam lines will require the best cooling technology that one can bring to bear, including specialized filter and apertures. In most cases, when the first optical element is a diffraction crystal more than half of the total power will be absorbed in this crystal. One of the more attractive approaches to cooling these diffraction crystals is to use a liquid metal as the cooling fluid. Gallium, with a low melting point, 29.7 degrees C and its very low vapor pressure make it an easy fluid to handle and its high thermal conductivity and heat capacity make it an excellent cooling fluid. Two series of experiments were performed during 1991 at the CHESS facility at Cornell. The first one, in April of 1991 used the new 24 pole wiggler to investigate cooling of large areas of high power and the second run in June 1991 used the ARGONNE-CHESS undulator. The new liquid gallium pumping system was used to cool the diffraction crystals that delivered three times the flow rate (5 gpm) of the system used in the 1988 tests, at pressures up to 100 psi. The total power of the wiggler beam available in the new F-2 station is 400 watts with 80 milliamps of synchrotron beam. This corresponds to a peak power of 3.4 watts/mm². Three different cooling geometries were used in the cooling crystals, which used both mosaic and near perfect crystals and inclined crystals. Rocking curves were measured as a function of energy, bandwidth, power density, and total power. Similar experiments were performed during the experimental run in June with the undulator beam. The total power in the undulator beam was similar to the wiggler beam (400 watts) but the peak power (perpendicular to the beam) was about ten times as great