95GHZ SPECTROMETER PULSED MODULATOR DESIGN UPGRADES

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。次级项目的主要支助 子项目的主要研究者可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 表示子项目使用的中心基础设施的估计数量， NCRR赠款不直接向子项目或子项目工作人员提供资金。 95 GHz CW/脉冲光谱仪在最初的中心补助金的第一年完成的是一个独特的工具，在目前的ACERT合奏HF ESR光谱仪是。该谱仪的高功率脉冲部分工作在1.2 KW的峰值输出功率下，由CPI公司的扩展互作用速调管（EIK）组成，由ACERT工程组成员设计和制造的快速高压脉冲调制器，以及8个实用通道中分辨率为5 ns的定时模式发生器和分辨率为1 ns的单个高分辨率通道（SpinCore ESR PRO-300，带ACERT定制高分辨率卡）。 这个子项目解决了我们在过去一个月（2009年春季）纳入调制器部分的长期和最近确定的升级。长期以来要进行的改进是：1）修改调制器内部射束门控逻辑，以允许生成射束“开启”时间模式，从而最大限度地减少耗散和死区时间; 2）增加调制器高压开关耗散限制重复率; 3）为调制器外壳提供增强的电磁厄密性。 最近一段时间，我们专门在CW模式下使用主95 GHz频谱仪，这使我们能够移除和拆卸大功率调制器部分，以进行广泛的升级改造。高压开关驱动逻辑已被转换为在门控模式下操作，并且合适的快速定时算法已被硬连线到门控逻辑中以用于EIK保护。为了显著提高高压开关功率耗散极限，在开关模块外壳中增加了电隔离的外部散热器，然后将模块集成到风扇罩中，用于开关输出设备的强制SF6气体冷却。由于调制器盒内同轴电缆屏蔽引起的拾取和外部传导引起的EMI问题已通过改进的接口过渡接地得到纠正。 重新组装后的调制器的台架和初始原位测试表明，我们已经成功地解决了所有上述技术问题，并将EIK输出功率下降降低到接近零。当完成定时软件脚本时，将测量实际脉冲模式死区时间的减少（见子项目211）。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The 95 GHz CW/pulse spectrometer completed during the first years of the initial center grant is a unique instrument in the current ACERT ensemble of HF ESR spectrometers is. Operating at a peak output power of 1.2 KW, the spectrometer's high-power pulse section consists of an extended-interaction klystron (EIK) from CPI, Inc., a fast high-voltage pulse modulator designed and constructed by members of the ACERT engineering group, and a timing pattern generator of 5ns resolution in 8 utility channels and a single high-resolution channel of 1ns resolution (SpinCore ESR PRO-300, with ACERT custom high-resolution card). This Subproject addresses both longstanding and more recently-identified upgrades that we have in the past month (spring 2009) incorporated into the modulator section. Longstanding improvements to be made were 1) modification of the modulator internal beam-gating logic to permit generation of beam "on" time patterns that minimize both dissipation and deadtime; 2) increasing the modulator h.v. switch dissipation-limited repetition rate, and 3) to provide enhanced electromagnetic hermiticity for the modulator enclosure. A recent period of utilizing the main 95 GHz spectrometer exclusively in CW mode allowed us to remove and dismantle the high-power modulator section for the extensive upgrade modifications. The high-voltage switch drive logic has been converted to operation in gated mode and suitable fast timing algorithms have been hardwired into the gated logic for EIK protection. To significantly increase the high-voltage switch power dissipation limit, electrically isolated external heat-sinks were added to the switch module housing and the module was then incorporated into a fan shroud for forced-SF6 gas cooling of the switch output devices. EMI issues due to pickup and external conduction by coax shields within the modulator box have been corrected with improved interface transition grounding. Bench and initial in situ tests of the modulator after reassembly indicate that we have successfully addressed all the above technical issues and have reduced the EIK output power droop to nearly zero. Measurement of the actual pulse mode deadtime reduction will be made when the timing software scripting has been completed (see Subproject 211).