Signal and noise of diamond pixel detectors at high radiation fluences
Signal and noise of diamond pixel detectors at high radiation fluences
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DOI：
10.1088/1748-0221/7/09/p09009
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发表时间：
2012-09-01
影响因子：
1.3
通讯作者：
Wermes, N.
中科院分区：
文献类型：
--
作者：
Tsung, J-W;Havranek, M.;Wermes, N.
CVD 金刚石是大型强子对撞机顶点探测器的一种有吸引力的材料选择，主要是因为其具有大带隙和强晶格，具有很强的抗辐射能力。特别是，在相互作用点附近工作的像素探测器受益于金刚石的微小漏电流和小像素电容，从而与硅相比，噪声系数较低。另一方面，金刚石中穿过高能粒子的电荷信号比硅中小约 2.2 倍。因此，在能量密度超过 10(15) n(eq) cm(-2) 时定量测定金刚石与硅的信噪比 (S/N) 非常重要，这对于大型强子对撞机 (LHC) 升级来说是很重要的。根据辐照钻石传感器的测量以及 FE-I4 像素读出芯片的设计和性能，我们确定了高粒子注量辐照的钻石像素探测器的信号和噪声。为了表征辐射损伤对材料和信号减弱的影响，载流子的平均自由程 lambda(e/h) 的变化被确定为辐射注量的函数。我们利用为 ATLAS 升级开发的 FE-I4 像素芯片来实际估计预期的噪声系数：给定注量下的预期漏电流是通过校准计算得出的，并使用专门开发的芯片 (PixCap) 测量像素电容。我们使用已发布的电荷损失测量值和与金刚石相同的外推方法，将所得的信噪比与平面硅像素探测器的信噪比进行比较。结果表明，具有大型强子对撞机典型像素间距的金刚石像素探测器的预期信噪比在注量超过 10(15) 粒子 cm(-2) 时超过了平面硅像素的预期信噪比，确切值仅取决于辐照硅像素探测器假定的最大工作电压。
CVD diamond is an attractive material option for LHC vertex detectors mainly because of its strong radiation-hardness causal to its large band gap and strong lattice. In particular, pixel detectors operating close to the interaction point profit from tiny leakage currents and small pixel capacitances of diamond resulting in low noise figures when compared to silicon. On the other hand, the charge signal from traversing high energy particles is smaller in diamond than in silicon by a factor of about 2.2. Therefore, a quantitative determination of the signal-to-noise ratio (S/N) of diamond in comparison with silicon at fluences in excess of 10(15) n(eq) cm(-2), which are expected for the LHC upgrade, is important. Based on measurements of irradiated diamond sensors and the FE-I4 pixel readout chip design and performance, we determine the signal and the noise of diamond pixel detectors irradiated with high particle fluences. To characterize the effect of the radiation damage on the materials and the signal decrease, the change of the mean free path lambda(e/h) of the charge carriers is determined as a function of irradiation fluence. We make use of the FE-I4 pixel chip developed for ATLAS upgrades to realistically estimate the expected noise figures: the expected leakage current at a given fluence is taken from calibrated calculations and the pixel capacitance is measured using a purposely developed chip (PixCap). We compare the resulting S/N figures with those for planar silicon pixel detectors using published charge loss measurements and the same extrapolation methods as for diamond. It is shown that the expected S/N of a diamond pixel detector with pixel pitches typical for LHC, exceeds that of planar silicon pixels at fluences beyond 10(15) particles cm(-2), the exact value only depending on the maximum operation voltage assumed for irradiated silicon pixel detectors.