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

Nan Li, Mengjie Song, Sixiao Hu, Wentao Wu, Songqing Liu, Tangchong Kuang, Yudong Gu, Xiangxiang Ren, Xufang Li, He Gao, Zhengwei Li, Congzhan Liu

TL;DR

This work tackles the challenge of ultra-low-noise readout for TES detectors in CMB polarization experiments. It presents a two-stage dc-SQUID readout architecture comprising a 4-cell input SQUID and a 100-cell SSA designed to achieve high gain with minimal noise for TDM TES readout. The authors report a flux noise of about $0.3\,\mu\Phi_0/\sqrt{Hz}$ at $10\,kHz$ and a system-noise-equivalent current of ~$2.4\,pA/\sqrt{Hz}$ at $10\,kHz$, enabled by large flux conversion coefficients $I_\Phi \approx 45\,\mu A/\Phi_0$ and $V_\Phi \approx 10\,mV/\Phi_0$ and by a 100-cell SSA. The results demonstrate that the design meets the stringent TES readout requirements for AliCPT-40G and can be applied to other TES-based detectors, including X/$\gamma$-ray applications, providing a practical route to low-noise cryogenic readout.

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 $0.3$ $μΦ_{0}/\sqrt{Hz}$ 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.

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

TL;DR

This work tackles the challenge of ultra-low-noise readout for TES detectors in CMB polarization experiments. It presents a two-stage dc-SQUID readout architecture comprising a 4-cell input SQUID and a 100-cell SSA designed to achieve high gain with minimal noise for TDM TES readout. The authors report a flux noise of about at and a system-noise-equivalent current of ~ at , enabled by large flux conversion coefficients and and by a 100-cell SSA. The results demonstrate that the design meets the stringent TES readout requirements for AliCPT-40G and can be applied to other TES-based detectors, including X/-ray applications, providing a practical route to low-noise cryogenic readout.

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 in an adiabatic demagnetisation refrigerator (ADR). The the measured magnetic flux noise of the two-stage SQUID circuit system is approximately at . The current noise equivalent to the input coil of input SQUID is about . This result meets the low-noise readout requirements of the CMB TES and other applications with TES detectors.
Paper Structure (4 sections, 5 equations, 8 figures, 2 tables)

This paper contains 4 sections, 5 equations, 8 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Input SQUID and SSA design
  3. Measurement and discussion
  4. Conclusion

Figures (8)

  • Figure 1: Two-stage dc-SQUID circuit for TES readout. The current signal $i_{in,IS}$ flowing through the TES is converted into a magnetic flux signal $\Phi_{in.IS}$ by the input coil $L_{in.IS}$ of the input SQUID. This flux signal cancels the feedback magnetic flux signal $\Phi_{fb.IS}$. Flux-locked loop linearly amplifies the TES signal based on the room-temperature integrating amplifier.
  • Figure 2: Schematic of the dc-SQUID chips. (a) Input SQUID schematic; (b) Input SQUID board layout; (c) SSA schematic; (d) SSA board layout.
  • Figure 3: Input SQUID (a) and SSA (b) are connected to pads of PCB via wire-bonding. They are installed on the $300$$mK$ copper plate in ADR.
  • Figure 4: The $V$–$\Phi$ characteristics of the input SQUID and SSA were measured at $300$$mK$ in ADR. The results correspond to the input coil (a) and feedback coil (b) of the input SQUID, and the input coil (c) and feedback coil (d) of the SSA.
  • Figure 5: The input SQUID is connected to the SSA via wire-bonding. They are installed on the Nb-shielded PCB of Magnicon at the $300$$mK$ copper plate in ADR.
  • ...and 3 more figures