Thermal Modeling Techniques forMicrocalorimeter Transition Edge Sensor

Transistion Edge Sensor Microcalorimeters have become an extremely power-

ful tool for rare event searches in recent years (get a ref). By operating a

Superconductor in transition, we can detect fractional miliKelvin fluctuations.

The Ricochet Collaboration intends to implement an array of of such detectors,

along side a set of Germanium detectors, as a means of detecting Coherent

Elastic Neutrino Scattering. An important topic for such experiments is fully

understanding the detector, including both the electrical and thermal proper-

ties. Here we present a characterization technique for such systems. A Thermal

Model describes the energy flow in and out of the detector ensemble, which

includes the TES, the target, and all linking materials. This model is a set

of nonlinear coupled differential equations, expressing the temperature of each

component, each with its own heat capacity and thermal conductance to other

components. By modeling all the interactions, we can extract both the electri-

cal and thermal properties of this detector. One parameter that is relatively

easy to measure is the Complex Impedance. Finding an analytical solution for the complex impedance proves difficult, as it is dependent on both thermal and electrical parameters. Comparisons

between the complex impedance data and complex impedance simulations yield

well-measured detector parameters.