Resonant Soft X-ray Scattering studies with Transition Edge Sensors

Resonant Soft X-ray has been one of the key techniques to study charge orders in high $T_c$ cuperates. To solve the issue of unwanted enhancement of inelastic florescence background at resonance, we have developed an energy-resolving superconducting Transition-Edge Sensor microcalorimeters. These superconducting sensors obtain exquisite energy resolution by exploiting the superconducting-to-normal transition to photon energy and by operating at cryogenic temperatures ($\sim$ 70 mK) where thermal noise is minimal. This TES has demonstrated $\sim$ 1.0 eV resolution below 1 keV. We present first results using this detector to study the (002) Bragg peak and specular elastic scattering from a single crystal of stripe-ordered \ce{La_${2-x}Ba_xCuO_4$} (x=0.125). Use of this detector for studying excitations and rejecting background fluorescence will be discussed.