A Completely New Camera for Cryo-EM

描述（由申请人提供）：该项目的总体目标是设计和建立一个最先进的相机系统，基于直接检测主动像素检测器（APD），为生物电子显微镜的数据直接数字记录提供一个大大改进的胶片替代品。该系统可立即应用于大分子的低温电子显微镜（cryo-EM）研究。新的APD将有一个非常均匀的表面和格式为3500 × 4000像素在5微米× 5微米间距。作为直接入射电子探测器，该装置不需要限制分辨率的磷光闪烁屏。APD的每个像素将有一个二极管，该二极管将收集入射电子在其通过敏感p外延层时沉积的电荷。它将在暴露期间整合收集的电荷。在帧结束时，传感器阵列的内容被读出、数字化并存储。所有的集成和读出电子器件都在0.25微米CMOS芯片表面不到1微米的范围内实现，并且对入射电子是透明的。“填充因子”，即对入射电子敏感的每个像素区域的比例，是100%，因为敏感的p外延层位于读出电路下面，并且是连续的。我们已经取得了重大突破，实现了512 x 550像素5微米间距的APD原型。该探测器对每个入射电子（在100-400 keV范围内）产生的信噪比约为10/1（与CCD相比为1/1）。空间分辨率也要好得多（FWHM为2.5微米，而FWHM为30微米）。更好的空间分辨率使该探测器能够以比CCD低得多的放大倍率拍照。需要资金来制造更大的芯片（高达3.5K x 4K像素），芯片上的ADC允许非常高的帧读出（高达100帧/秒）。还需要资金来试验更小的像素间距（3微米x 3微米）。完成后，这种探测器将使研究人员能够快速收集数十万张图像的数据，大大提高所研究大分子的3D结构的分辨率。这种探测器将极大地帮助研究感染哺乳动物、昆虫和植物宿主的球形病毒。这些研究将在与疾病的斗争中产生非常关键的结果。

DESCRIPTION (provided by applicant): The overall aim of this project is to design and build a state-of-the-art camera system, based on a Direct Detection Active Pixel Detector (APD) to provide a vastly improved film substitute for direct digital recording of data for biological Electron Microscopy. Such a system will be immediately applicable and beneficial to cryo-Electron Microscopy (cryo-EM) of macromolecules. The new APD will have an extremely uniform surface and format of 3500x4000 pixels at 5 micron x 5 micron pitch. As a direct incident electron detector, this device will not require a resolution limiting phosphorescent scintillation screen. Each pixel of the APD will have a diode that will collect the charges deposited by an incident electron in its passage through a sensitive p-epitaxial layer. It will integrate the collected charges during an exposure period. At the conclusion of the frame, the contents of the sensor array are then read out, digitized and stored. All of the integration and read out electronics are implemented within less than 1 micron of the surface of a 0.25 micron CMOS chip, and are transparent to the incident electrons. The "fill factor" i.e. the proportion of each pixel area that is sensitive to the incident electrons, is 100% due to the fact that the sensitive p-epitaxial layer lies beneath the readout circuitry and is continuous. We have made a big breakthrough with the realization of a prototype APD having 512 x 550 pixels of 5 micron pitch. This detector yields a signal-to-noise ratio for each incident electron (in the 100-400 keV range) of 10/1 approximately (versus 1/1 with a CCD). The spatial resolution is also much better (2.5 micron versus 30 micron for FWHM). The better spatial resolution allows this detector to take pictures at a much lower magnification than with a CCD. Funding is requested to make larger chips (up to 3.5K x 4K pixels) with on chip ADC allowing very high frame readout (up to 100 frames/sec). Funding is requested also to experiment with even smaller pixel pitch (3 micron x 3 micron). When finished, this kind of detector will allow researchers to quickly gather data on hundreds of thousand of images, greatly improving the resolution of 3D structures of the studied macromolecules. This detector will greatly help the studies of spherical viruses that infect mammalian, insect, and plant hosts. These studies will yield very critical results in the fight against disease.