A NEW BEAM INTENSITY MONITOR, BASED ON AVALANCHE PHOTO DIODE

基于雪崩光电二极管的新型光束强度监视器

• 批准号: 7598187
• 负责人: MARC NIEBUHR
• 金额: $ 0.79万
• 依托单位: STANFORD UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-01 至 2008-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7598187
• 关键词: Collection; Computer Retrieval of Information on Scientific Projects Database; Count; Development; Electronics; Elements; Funding; Grant; Housing; Institution; Ions; Measurement; Mica; Monitor; Nitrogen; Photons; Positioning Attribute; Research; Research Personnel; Resources; Scheme; Source; Specimen; Standards of Weights and Measures; Thick; United States National Institutes of Health; Vacuum; absorption; base; design; detector; improved; prototype; success

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. We have designed and built a prototype of a new intensity monitor to replace the existing standard miniature ion chamber placed immediately upstream of the specimen position. The new monitor combines the avalanche photodiode (APD) detector that we had developed for ultra-small-angle x-ray scattering (USAXS) and a 12 ¿m thick Kapton foil placed in the beam. The low level Kapton x-ray scattering, which is proportional to beam intensity, is photon-counted by the APD. The new monitor is intended to eliminate both the beam absorption and the low-level background scattering from the ion chamber due to the mica windows and the short nitrogen path. As a part of this development project we improved the shielding and grounding scheme of the electronic components in the APD and successfully eliminated false photon counts. The very weak level of Kapton foil scattering is practically eliminated by two sets of guard slits since the prototype intensity monitor is installed immediately downstream of the beam defining slit. The new beam intensity monitor is in routine use at BL4-2, and has resulted in satisfactory improvements in beam quality, i.e., substantially reduced scattering background and increased photon flux at the specimen position by ca. 20%. Given this success, we have recently acquired a new APD element and are developing a more compact dedicated intensity monitor APD detector, so that it can be placed much closer to the Kapton foil for higher photon collection efficiency to improve statistical significance of the beam intensity measurement. A dedicated in-vacuum housing for the Kapton foil is also being designed for further optimization.

该副本是使用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这是调查员的机构。 我们设计并建造了新的强度监视器的原型，以替换现有标准的微型离子室立即放置在样品位置的上游。新的监视器结合了我们为超小角X射线散射（USAXS）和放置在梁中的12？m厚的Kapton Foil开发的雪崩光电二极管（APD）检测器。与梁强度成正比的低水平Kapton X射线散射是由APD计数的。新的监视器旨在消除由于云母窗口和短氮路径而导致的离子室的束吸收和低级背景散射。作为该开发项目的一部分，我们改善了APD中电子组件的屏蔽和接地方案，并成功消除了错误的光子计数。由于原型强度监视器立即在梁定义狭缝的下游安装，因此实际上，两组防护板缝被消除了非常弱的Kapton箔散射。新的光束强度监视器在BL4-2处进行常规使用，并导致梁质量的令人满意的改善，即，大幅减少了散射背景和在标本位置的光子通量增加。 20％。鉴于这一成功，我们最近获得了一个新的APD元素，并正在开发更紧凑的专用强度监视器APD检测器，因此它可以将其放置在Kapton Foil的距离上，以提高光子收集效率，以提高光束强度测量的统计学意义。 Kapton箔的专用内部外壳也正在设计用于进一步优化。