Development of Low-Noise Two-stage dc-SQUID for TES Detector Readout

TL;DR

This paper presents a low-noise two-stage dc-SQUID amplifier designed for TES detector readout, achieving high signal gain and low noise levels suitable for cosmic microwave background measurements.

Contribution

The development of a two-stage dc-SQUID circuit with high gain and low noise for TES detector readout in CMB experiments is introduced.

Findings

Measured flux noise of 0.3 μΦ₀/√Hz at 10 kHz

Input coil current noise of 2.4 pA/√Hz

System noise meets low-noise requirements for TES applications

Abstract

Direct-current superconducting quantum interference devices (dc-SQUIDs) are one of the most sensitive magnetic detectors. These sensors are extensively used in the readout of superconducting transition edge sensors (TESs), which are used for the detection of weak signals. A cosmic microwave background (CMB) polarization telescope operating in 22-48 GHz is currently under developing. The TESs calorimeter of the telescope will be readout by a time-division multiplexer (TDM) SQUID readout system. We develop a two-stage dc-SQUID amplifier circuit, comprising an input-stage SQUID with 4 SQUID cells and a series SQUID array (SSA) with 100 SQUID cells. This configuration has been shown to achieve extremely high signal gain while effectively controlling system noise. We assess the system noise at $300$ $mK$ in an adiabatic demagnetisation refrigerator (ADR). The the measured magnetic flux noise of the two-stage SQUID circuit system is approximately $0.3$ ${\mu}\Phi_{0}/\sqrt{Hz}$ at $10$ $kHz$. The current noise equivalent to the input coil of input SQUID is about $2.4$ $pA/\sqrt{Hz}$. This result meets the low-noise readout requirements of the CMB TES and other applications with TES detectors.