BICEP阵列150、220和270 GHz时分复用探测器中的混叠噪声表征与抑制
Aliased noise characterization and mitigation in BICEP Array 150, 220 and 270 GHz time-division multiplexed detectors
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中文总结 AI 辅助
针对BICEP阵列探测器的混叠噪声问题，研究人员揭示其成因并通过调整多路复用率和焦平面温度将噪声等效温度降低约10%，为下一代CMB偏振计提供了关键优化方向。
中文摘要 AI 辅助
BICEP阵列150 GHz（BA2-150）及220/270 GHz（BA3-220/270）接收机的早期观测显示，探测器噪声等效温度（NET）高于预期，且存在显著的探测器间与模块间离散性。在多路复用关闭及高频采样条件下开展的噪声测量表明，该 excess 源于时分复用期间，高频探测器噪声混叠进入科学频段。研究表明，过量高频噪声与异常大的对数TES转变斜率α相关，这会提升电热环路增益，使探测器运行接近稳定边界。α测量值远大于预期，与BA2-150及BA3-220/270探测器采用的倒置TES制备工艺引入的更尖锐超导转变一致。通过提高多路复用率和升高焦平面工作温度两种方案研究了运行抑制策略：更快的多路复用通过将多路复用奈奎斯特频率移至过量噪声滚降之外来减少混叠，而升高冷浴温度可降低TES电功率与环路增益，提升探测器稳定性，使NET降低约10%。这些结果表明，在下一代CMB偏振计中，平衡TES响应度、电热稳定性与多路复用读出性能至关重要。
英文摘要
Early observations with the BICEP Array 150 GHz (BA2-150) and 220/270 GHz (BA3-220/270) receivers revealed detector noise equivalent temperatures (NETs) higher than expected, together with substantial detector-to-detector and module-to-module scatter. Noise measurements acquired with multiplexing off and high frequency sampling demonstrate that this excess originates from elevated high-frequency detector noise that aliases into the science band during time-division multiplexing. We show that the excess high-frequency noise is correlated with anomalously large logarithmic TES transition slopes, α, resulting in elevated electrothermal loop gain and operation near the detector stability boundary. Measurements of α indicate values substantially larger than expected, consistent with the sharper superconducting transitions introduced by the inverted TES fabrication process adopted for BA2-150 and BA3-220/270 detectors. Operational mitigation strategies were investigated through both increased multiplexing rates and elevated focal-plane operating temperatures. Faster multiplexing reduces aliasing by shifting the multiplexing Nyquist frequency beyond the excess noise roll-off, while elevated bath temperatures reduce TES electrical power and loop gain, improving detector stability and reducing NET by approximately 10%. These results demonstrate the importance of balancing TES responsivity, electrothermal stability, and multiplexed readout performance in next-generation CMB polarimeters.
