CASCA: A readout ASIC for a TPC based X-ray polarimeter
CASCA: A readout ASIC for a TPC based X-ray polarimeter
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DOI：
10.1109/nssmic.2015.7582002
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
H. Zhang;Z. Deng;L. He;H. Li;H. Feng;Y. Liu
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文献类型：
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作者：
H. Zhang;Z. Deng;L. He;H. Li;H. Feng;Y. Liu
本文介绍了一种用于基于TPC的X射线偏振仪(XTP)的原型ASIC(CASCA：带开关电容阵列的电荷放大器)。它用一维条读数测量入射X射线光子产生的二维光电子轨迹。另一个维度由来自信号波形的漂移时间计算。为了达到100MSPS m的磁道分辨率，使用了精细的节距条，这需要具有20MSPS波形采样能力的高密度读出电子设备。CASCA集成了32个通道全功能信号处理电路，采用0.18μm cmos工艺制造。每个通道由电荷灵敏前置放大器、峰值时间为25 ns的CR-RC整形器、基线保持器、鉴别器和单元开关电容阵列组成。在以前的原型中，模拟前端和SCA电路已经在两个独立的芯片上实现和验证。还进行了几项改进，例如使用本地NMOS电容器来存储样本和改变开关电容电路的结构。CASCA的测试结果表明，当输入电容为14.5pF时，等效噪声电荷(ENC)约为1500e。积分非线性优于0.6%，质心时间抖动小于3 ns。
The paper presents a prototype ASIC (CASCA: Charge Amplifier with Switched Capacitor Array) for a TPC based X-ray Polarimeter (XTP). It measures two dimensional photoelectron tracks generated by the incident X-ray photons with one dimensional strip readout. The other dimension is calculated by the drift time from the signal waveform. In order to achieve 100 μm track resolution fine pitch strips are used, requiring high density readout electronics with 20 MSPS waveform sampling capability. CASCA integrates 32 channel full function signal processing circuits and is fabricated in a 0.18μm CMOS process. Each channel consists of a charge sensitive preamplifier, a CR-RC shaper with a peaking time of 25 ns, a baseline holder, a discriminator and a 64-cell switched capacitor array (SCA). The analog front-end and the SCA circuits have been implemented and verified in two separate chips in the previous prototypes. Several modifications have also been made, such as using native NMOS capacitor to store the samples and changing the structure of the switched capacitor circuits. The test results of CASCA show that the equivalent noise charge (ENC) is about 1500e with 14.5pF input capacitance. The INL (Integrated Nonlinearity) is better than 0.6% and the center-of-gravity time jitter has been measured to be no more than 3 ns.