用于宏观低温量热计阵列的微波SQUID多路复用概念
A microwave SQUID multiplexing concept for macro-cryogenic calorimeter arrays
AI总结：
本研究提出将微波SQUID多路复用（μMUX）技术应用于大规模低温量热计阵列，推导了其噪声模型，显示该技术可在多路复用因子达1000时劣化分辨率不足2%，适用于CEνNS和暗物质搜寻的多塔阵列单元设计。
AI中文摘要：
由过渡-edge传感器（TES）读出的大规模低温量热计可达到电子伏特级的基线分辨率，但在稀有事例搜寻中传统使用的单通道直流SQUID读出方式，每个探测器搭配一条放大器链和数根导线，使得实用阵列仅能容纳几十个通道。我们提出将为快速X射线和中微子质量微量热计开发的微波SQUID多路复用（μMUX）技术，应用于工作在约20mK的大规模BGO（Bi₄Ge₃O₁₂）量热计；蓝宝石和TeO₂吸收体也可采用同一套方案。基于已有的大规模TES量热计的热与噪声模型，我们推导了多路复用读出的噪声模型，其包含高电子迁移率晶体管（HEMT）、两能级系统及SQUID的贡献，以及噪声随多路复用因子Nₘᵤₓ的缩放关系。由于热信号变化缓慢，每个通道仅需约千赫兹的采样率，因此限制要求并非带宽，而是输入线圈灵敏度需达到（0.1至1）μA/Φ₀，这一数值比当前的μMUX器件高出10至30倍，与探测器电流噪声（9至10）pA/√Hz相匹配，该噪声与吸收体质量无关。在总通量噪声约为1.2μΦ₀/√Hz的情况下，当Nₘᵤₓ达到1000时，该读出方式对基线分辨率的劣化小于2%，与TES限制的分辨率相比可忽略不计。这些结果被应用于单塔设计：52块100克的BGO晶体和1个HEMT放大器。该塔是多塔阵列的单元，总质量达数千克，旨在用于相干中微子原子核散射（CEνNS）和暗物质搜寻。
英文摘要：
Massive cryogenic calorimeters read out by transition-edge sensors (TES) can reach eV-scale baseline resolution, but the single-channel dc-SQUID readout conventionally used in rare-event searches, with one amplifier chain and several wires per detector, limits practical arrays to a few tens of channels. We propose to apply microwave SQUID multiplexing ($μ$MUX), developed for fast X-ray and neutrino-mass microcalorimeters, to massive BGO (Bi$_4$Ge$_3$O$_{12}$) calorimeters operated at $\simeq 20$~mK; sapphire and TeO$_2$ absorbers are covered by the same framework. Using the established thermal and noise model for massive TES calorimeters, we derive a noise model for the multiplexed readout, including the HEMT, two-level-system and SQUID contributions, and its scaling with the multiplexing factor $N_{\rm mux}$. Since the slow thermal signals require only about a kHz of sampling per channel, the limiting requirement is not bandwidth but an input-coil sensitivity of $( 0.1$ to $1)\,μ$A$/Φ_0$, a factor of $10$ to $30$ beyond current $μ$MUX devices, matched to the detector current noise of ($9$ to $10$)~pA$/\sqrt{\rm Hz}$, which is independent of the absorber mass. With a total flux noise of $\simeq$$1.2\,μΦ_0/\sqrt{\rm Hz}$, the readout degrades the baseline resolution by less than $2\%$ up to $N_{\rm mux}=1000$, negligible compared with the TES-limited resolution. These results are implemented in a single-tower design: 52 BGO crystals of 100~g each and one HEMT amplifier. The tower is the unit of a multi-tower array of several kilograms aimed at CE$ν$NS and dark matter searches.
