Farias Nicole, Adkins Tylor, de Haan Tijmen, Lee Adrian T, Lonappan Anto, Russell Megan, Suzuki Aritoki, Siritanasak Praween, Takatori Sayuri, Westbrook Benjamin
University of California Berkeley, Berkeley, CA 94720 USA.
Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801 Japan.
J Low Temp Phys. 2024;216(1-2):352-362. doi: 10.1007/s10909-024-03143-9. Epub 2024 May 26.
Cosmic microwave background (CMB) experiments have deployed focal planes with transition edge sensor (TES) bolometers cooled to sub-Kelvin temperatures by multiplexing the readout of many TES channels onto a single pair of wires. Digital Frequency-domain Multiplexing (DfMux) is a multiplexing technique used in many CMB polarization experiments, such as the Simons Array, SPT-3 G, and EBEX. The DfMux system studied here uses LC filters with resonant frequencies ranging from 1.5 to 4.5 MHz connected to an array of TESs. Each detector has an amplitude-modulated carrier tone at the resonant frequency of its accompanying LC resonator. The signal is recovered via quadrature demodulation where the in-phase (I) component of the demodulated current is in phase with the complex admittance of the circuit and the quadrature (Q) component is orthogonal to I. Observed excess current noise in the Q component is consistent with fluctuations in the resonant frequency. This noise has been shown to be non-orthogonal to the phase of the detector's responsivity. We present a detailed analysis of the phase of responsivity of the TES and noise sources in our DfMux readout system. Further, we investigate how modifications to the TES operating resistance and bias frequency can affect the phase of noise relative to the phase of the detector responsivity, using data from Simons Array to evaluate our predictions. We find that both the phase of responsivity and phase of noise are functions of the two tuning parameters, which can be purposefully selected to maximize signal-to-noise (SNR) ratio.
宇宙微波背景（CMB）实验通过将许多过渡边缘传感器（TES）通道的读出信号复用至一对导线上，部署了冷却至亚开尔文温度的焦平面。数字频域复用（DfMux）是一种在许多CMB极化实验中使用的复用技术，如西蒙斯阵列、SPT-3G和EBEX。这里研究的DfMux系统使用谐振频率范围为1.5至4.5 MHz的LC滤波器连接到TES阵列。每个探测器在其伴随的LC谐振器的谐振频率处有一个调幅载波信号。信号通过正交解调恢复，其中解调电流的同相（I）分量与电路的复导纳同相，正交（Q）分量与I正交。在Q分量中观察到的过量电流噪声与谐振频率的波动一致。已证明这种噪声与探测器响应度的相位非正交。我们对DfMux读出系统中TES的响应度相位和噪声源进行了详细分析。此外，我们利用西蒙斯阵列的数据来评估我们的预测，研究对TES工作电阻和偏置频率的修改如何影响相对于探测器响应度相位的噪声相位。我们发现响应度相位和噪声相位都是这两个调谐参数的函数，可以有目的地选择它们以最大化信噪比（SNR）。
