95GHZ SPECTROMETER PULSED MODULATOR DESIGN UPGRADES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 95 GHz CW/PULSE光谱仪在最初的中心资助的最初几年中完成，是目前Acert高频ESR光谱仪中的唯一仪器。该光谱仪的高功率脉冲部分以1.2 KW的峰值输出功率运行，包括CPI，Inc.的扩展相互作用速调管(EIK)、由Acert工程小组成员设计和建造的快速高压脉冲调制器、8个实用通道中分辨率为5 ns的定时模式发生器和1 ns分辨率的单个高分辨率通道(带Acert定制高分辨率卡的SpinCore ESR PRO-300)。 这个子项目解决了我们在过去一个月(2009年春季)合并到调制器部分的长期和最近确定的升级。要进行的长期改进是：1)修改调制器内部波束选通逻辑，以允许产生使耗散和死区时间最小化的波束“开启”时间模式；2)增加调制器H.V.开关损耗受限的重复频率，以及3)为调制器外壳提供增强的电磁赫密性。 最近一段时间，主95 GHz光谱仪完全在CW模式下使用，这使得我们可以移除和拆除高功率调制器部分，进行广泛的升级改造。高压开关驱动逻辑已转换为门控模式，并在门控逻辑中硬连线了合适的快速时序算法，以实现EIK保护。为了显著提高高压开关的功率消耗极限，在开关模块外壳中添加了电隔离的外部散热器，然后将模块合并到风扇护罩中，以强制对开关输出设备进行SF6气体冷却。通过改进接口过渡接地，调制器盒内的同轴屏蔽产生的拾取和外部传导引起的EMI问题已得到纠正。 重新组装后的调制器的台架和初步的现场测试表明，我们成功地解决了所有上述技术问题，并将EIK输出功率下降几乎为零。计时软件脚本编写完成后，将测量实际脉冲模式死区时间减少(参见子项目211)。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. 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 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).