One of the most innovative x-ray detector designs of the past decade is the microcalorimeter. ... In principle, energy resolutions as good as ~1 eV (FWHM) should be possible. ... In its most basic form a microcalorimeter consists of three parts: a thermal mass that absorbs the x-ray and converts the energy to heat, a thermometer to measure the temperature rise of the thermal mass, and a thermal link to a heat sink to allow the absorbed energy to escape from the thermal mass. ...