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 Tc 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 at cryogenic temperatures (∼ 70 mK) where thermal noise is minimal. This TES has demonstrated ∼ 1.5 eV resolution around Cu L₃ edge (932.7 eV). We present first results of using this detector to study elastic diffuse scattering and charge orders from a single crystal of stripe-ordered La_2-xBa_xCuO₄ (x=0.125). Use of this detector for studying excitations and models of rejecting fluorescence background will be further discussed.