A Characterization Procedure for Large Area Spiderweb TES

In this communication, we describe a characterization procedure suitable to extract the most relevant design parameters of a large area absorber TES, designed for Cosmic Microwave Background measurements, very similar to those that will be fabricated for the LSPE/SWIPE balloon-borne experiment. This is a large (8 mm diameter) Au-on-SiN spiderweb designed to collect many modes of the incoming microwave radiation, in the 145-240 GHz range. After obtaining the critical temperature of the Ti/Au TES and its I-V characteristics, we operate it in Negative Electrothermal Feedback (ETF, DC voltage bias) and we record its response after amplification by a SQUID Array Amplifier. Then, in the same conditions, we illuminate the central area of the absorber with a pulsed LED (red visible light), mounted in the cryogenic environment, with pulses short enough to mimic an instantaneous energy deposition. Furthermore, the same LED is driven to produce a slow modulation of the output signal, to explore the bolometric regime of the TES. With this set of measurements we are able to extract its thermal conductance, its natural time constant, and the loop gain associated with the optimal bias point.