CHARACTERIZATION OF CCD DETECTOR ELECTRONICS FOR RECORDING WEAK X-RAY SCATTERING

用于记录弱 X 射线散射的 CCD 探测器电子器件的特性

• 批准号: 7370628
• 负责人: MARC NIEBUHR
• 金额: $ 1.37万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-03-01 至 2007-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7370628
• 关键词: CHARACTERIZATION; CCD; DETECTOR; ELECTRONICS; RECORDING

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The BL4-2 MarCCD165 detector displays a relatively large A/D converter offset fluctuation, making it highly challenging to record very weak signal levels accurately, despite the significant improvements in data precision due to radial integration of scattering signals. This is in fact a universal problem with almost all of optic fiber coupled CCD x-ray detectors. A project was initiated to determine the exact level of electronic stability required for actual solution x-ray scattering experiments. We measured offset level fluctuation as a function of time and assessed the exact degree of signal fluctuation with respect to the level of scattering signals from dilute protein and buffer solutions. We observed offset fluctuation of as much as 2-4 AD converter unit per pixel on average, corresponding approximately to 2-4 12 keV x-ray photons. We implemented a blank offset level measurement immediately prior to each x-ray exposure in Blu-ICE, and we have as a result been able to record weak signal levels more accurately on many occasions. We communicated our results to the detector manufacturer, who as a result implemented two major improvements within our annual maintenance contract: replacing some of key electronic components in the read out electronic circuit and implementing a compensation algorithm in the programmable field gate array in the circuit. Furthermore, measures were taken to stabilize the temperature of the detector electronics inside the BL4-2 experimental hutch in order to further stabilize the performance of the temperature-sensitive electronic components primarily responsible for the offset fluctuation. The detector now performs with improved stability and gives much more reliable buffer subtraction in most solution scattering studies.

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。BL4-2 MarCCD165探测器显示相对较大的A/D转换器偏移量波动，这使得精确记录非常弱的信号电平具有极大的挑战性，尽管由于散射信号的径向积分显著提高了数据精度。事实上，这是几乎所有光纤耦合CCDx射线探测器的普遍问题。启动了一个项目，以确定实际溶液X射线散射实验所需的电子稳定性的确切水平。我们测量了作为时间函数的偏移量水平波动，并评估了信号波动相对于来自稀释蛋白质和缓冲溶液的散射信号水平的准确程度。我们观察到平均每个像素高达2-4个AD转换单位的偏移量起伏，大约相当于2-4个12keV的X射线光子。我们在BLU-ICE的每一次X射线曝光之前立即实施了空白偏移量水平测量，因此我们能够在许多情况下更准确地记录微弱信号水平。我们将我们的结果传达给了探测器制造商，他们因此在我们的年度维护合同中实施了两项主要改进：更换读出电子电路中的一些关键电子元件，以及在电路中的可编程现场门阵列中实施补偿算法。此外，还采取措施稳定BL4-2实验舱内探测器电子元件的温度，以进一步稳定主要引起偏移量波动的温度敏感电子元件的性能。该检测器现在的稳定性得到了提高，在大多数溶液散射研究中提供了更可靠的缓冲减法。