Design, fabrication and characterization of a 64 pixel metallic magnetic calorimeter array with integrated, on-chip microwave SQUID multiplexer

Abstract

We report on the design, fabrication and characterization of a 64 pixel metallic magnetic calorimeter array that is read out by an integrated, on-chip microwave SQUID multiplexer. Based on the results of our comprehensive device characterization we refined the state-of-the-art multiplexer model which assumes each associated non-hysteretic rf-SQUID to purely behave as a flux-dependent inductor. In particular, we include the capacitance and the subgap resistance of the Josephson junction as well as screening effects and parasitic mutual couplings between different coils that show up only when a superconducting flux transformer is attached to the SQUID input. Thanks to these modifications, we are able to explain the occurrence of a magnetic flux dependence of the internal quality factor of the microwave resonators as well as to accurately calculate the characteristic multiplexer parameters. When combining the refined multiplexer model with the thermodynamical description of a metallic magnetic calorimeter, we find a reasonable agreement between our measurements and predictions.

Microwave SQUID multiplexing for the Lynx x-ray microcalorimeter

“…This paper will focus on using microwave SQUID multiplexing to readout TESs. Microwave SQUID multiplexing is also the leading candidate to readout large arrays of MMCs 17,18 and the optimization described in this paper would also be useful for MMCs. 19 2 Readout of the LXM Pixels…”

Analytical model of the readout power and SQUID hysteresis parameter dependence of the resonator characteristics of microwave SQUID multiplexers

“…For verification of our µMUX model, data from measurements described in [15] were used. Here, the scattering parameter S 21 (f, Φ ext , Φ rf ) of various channels of a µMUX device for different values of the external fluxe Φ ext and the amplitude Φ rf of the driving signal were measured using a vector network analyzer (VNA).…”

“…Existing models lead to an accurate description of the µMUX characteristics for small readout powers, i.e. P rf → 0 [14,15]. For experimentally more realistic values, i.e.…”

“…For experimentally more realistic values, i.e. when using a µMUX for cryogenic detector readout, large discrepancies between measurements and model predictions are observed [15]. For this reason, existing µMUX models can't reliably be used for optimizing the device performance.…”

Software Defined Radio Based Readout of Microwave SQUID Multiplexed Metallic Magnetic Calorimeter Arrays

“…An efficient readout of large MMC arrays can be achieved through Microwave SQUID multiplexing [7][8][9]. It requires three different components or techniques for proper operation: (1) The actual cryogenic multiplexer which modulates the detector signals onto different carrier signals and combines them into a single readout line, (2) a room temperature readout electronics for operating…”