Development of a Very Large CCD Area Detector

一笔赠款已授予埃德温·M博士。Westbrook在芝加哥的分子生物学联盟（MBC），开发一种用于结构分子生物学研究的最先进的X射线探测器。 当原型完成后，它将为未来的此类探测器设定标准。 该探测器的应用是蛋白质晶体学，将在劳伦斯伯克利国家实验室（LBL）的先进光源（ALS）的同步加速器光束线上进行。 蛋白质晶体学正逐步利用美国的同步加速器X射线源，因为它们提供的X射线束比国内实验室的X射线束亮一百万倍，而且光束也窄得多，能量更均匀。 一旦分子生物学学会了使用这些宏伟的光束线，在分子水平上的生物系统结构知识已经取得了巨大的进步。 最近对核糖体亚单位和RNA聚合酶II的分子结构的测定，仅仅是没有同步加速器X射线就不可能获得的结果的例子。 本项目中将开发的探测器将进一步增强其安装的同步加速器光束线的能力。虽然分子生物学科学是开发该探测器的驱动原因，但该项目本身将主要是电子工程。 该探测器将采用最近开发的先进的新型电荷耦合器件（CCD），与以前的CCD相比，其噪声更低，性能更快。 专用集成电路（ASIC）和现场可编程门阵列（FPGA）将被集成到探测器的控制系统中，其读出系统将是新的S-LINK并行光纤接口。 MBC电子集团以其极低噪声的模拟电子产品而闻名，但这款探测器还将采用全新的数字信号处理技术，以降低阅读每个CCD像素的电子电荷的不确定性，允许高达18位的读出配准。新的探测器将有一个每边32厘米的正方形有效区域，可以每0.67秒重复观察一次。 它将具有动态范围-它可以同时检测到的最强/最弱信号的比率-超过250，000：1。 其空间分辨率将允许测量相邻的布拉格斑点，即使它们相距仅0.6 mm，因此该探测器将能够在其32 cm宽度上分辨超过500个斑点。 所有这些特征参数都超过了现有的晶体学探测器，作为一个整体，这种探测器将比现在可用的任何探测器都要好。

A grant has been awarded to Dr. Edwin M. Westbrook at the Molecular Biology Consortium (MBC) in Chicago, to develop a state-of-the-art X-ray detector for structural molecular biology research. When the prototype has been completed, it will set the standard for future detectors in this class. The application for this detector is protein crystallography, to be conducted at a synchrotron beamline of the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory (LBL). Protein crystallography is progressively taking advantage of the nation's synchrotron X-ray sources, because they provide million-fold brighter X-ray beams than can be had at home laboratories, and the beam is also much narrower and of more uniform energy. Once the molecular biology community learned to use these magnificent beamlines, enormous advances have been made in structural knowledge of biological systems at the molecular level. Recent determination of the molecular structures of the ribosome subunits and of the RNA polymerase II are merely examples of results that could not have been achieved without synchrotron X rays. The detector that will be developed in this project will further amplify the capabilities of the synchrotron beamline on which it will be installed.While the science of molecular biology is the driving reason for developing this detector, the project itself will be predominantly one of electronic engineering. The detector will feature advanced new Charge-Coupled Devices (CCDs) that have recently been developed that have lower noise and faster performance than previous CCDs. Application-Specific Integrated Circuits (ASICs) and Field-Programmable Gate Arrays (FPGAs) will be integrated into the control system of the detector, and its readout system will be the new S-LINK parallel fiberoptic interface. The MBC electronics group is well known for its extremely low-noise analog electronics, but this detector will also feature radically new digital signal processing to reduce the uncertainty of reading the electronic charge of each CCD pixel, permitting up to 18-bit readout registration.The new detector will have a square active area 32 cm on each side, that can be repetitively observed every 0.67 seconds. It will have a dynamic range- the ratio of strongest/weakest signals it can simultaneously detect- exceeding 250,000:1. Its spatial resolution will permit neighboring Bragg spots to be measured even when they are only 0.6 mm apart, so this detector will be able to resolve over 500 spots across its 32 cm width. All of these characteristic parameters exceed those of existing crystallographic detectors, and taken together as a whole this detector will be dramatically better than any now available.