We have fabricated and tested water jet cooled silicon (111) and (220) monochromators specially tailored for extended wiggler beam and concentrated undulator beam power loadings. The tests were made at the X25 27 pole, 1.1 T hybrid wiggler beam line1 at the National Synchrotron Light Source (NSLS). The wiggler-like line-type loading was produced by the direct, unfocused wiggler white beam, in which 300 W of total power in a 60-mm-wide by 5-mm-high [full width at half maximum (FWHM)] cross section were available in the experimental hutch; this represents a typical power density at existing insertion device beam lines. The undulator-like point-type loading was produced by the focused wiggler white beam, generated via reflection of a portion of the direct white beam from a toroidal platinum-coated silicon mirror, resulting in 75 W of total power in a 0.8-mm-wide (FWHM) by 0.45-mm-high (FWHM) cross section in the hutch. This will be a typical power density at next-generation insertion device beam lines. The monochromator design consists of a thin walled silicon box whose bottom is glued to a stainless-steel water manifold; the coolant is delivered through jet tubes directed perpendicular to the underside of the top, diffracting surface of the box.2 Rectangular monochromators with multiple jets were used for the line power loading studies, and cylindrical monochromators with single jets were used for the point power loading studies. Provisions for simple adaptive corrections to compensate for the inevitable beam-induced thermal deformations, consisting of mechanisms to reverse-bend the top surface, and internal heat baffles to frustrate the cooling at the edges of the crystal (to produce an isothermal top surface), were included in the designs. These required approximate matching of the top surface dimensions to the x-ray footprint. To better understand the thermal strain fields, spatial and angular mapping of both fundamental and harmonic Bragg reflections within the beam footprint were undertaken.3 For the line power loading situation, Bragg angle variations of up to 4 arcsec across the beam footprint were observed, resulting in near-perfect performance for the fundamental.4 The harmonic was more sensitive to these strains;4 the described adaptive methods were used to correct for them.5 For the point loading situation, Bragg angle variations of over 200 arcsec were measured, causing distorted fundamental and harmonic reflectivity curves; again, ≳90% compensation was achieved via adaptive techniques.6 The detailed results show that while, for silicon at room temperature, passive crystal cooling methods are sufficient for the present unfocused insertion device beam lines, adaptive methods will have to be considered for future insertion device beam lines. This work was supported in part by th