The design of a frequency multiplexed Ir-Au TES array

The IrAu TESs which have been developed in Genoa in past years, will be assembled in large numbers in a detector to reach the required accuracy in neutrino mass measurement (by beta decay of Re-187). When the number of bolometers increases a multiplexed readout is needed to reduce the thermal load on the low temperature refrigerator and to keep low the cost of SQUID electronics. We present the scheme of the circuit that distributes the AC supply to the TESs in the array and collects the signal from a row of devices, decoding the address by the signal frequency. The TESs are polarized by voltage sources of different frequencies. The TES working at different frequencies can be read by a single SQUID, which reads the current induced in a Superconducting transformer, and feeds in the transformer itself a feedback flux. The signal from the TES in the idle state will be compensated. The circuit will be built with planar film technology and will act as heat sink for each TES. The requirements for the SQUID will be discussed. The construction of a small prototype of the circuit is under way.