HYBRID PULSED FIELD GRADIENT COIL DRIVER

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 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 为了进一步提高我们在脉冲ESR显微镜中的仪器能力，与c.w.不同， 实验者可以直接测量许多关键参数，例如自扩散、磁探针的弛豫时间、粘度、精确的O2浓度等，我们已经设计了具有先进能力的可编程脉冲场梯度线圈驱动器。基于由我们现有的门控半正矢线圈激励方案和快速开关恒流源组成的混合拓扑结构，新的梯度线圈驱动器设计可以在可编程的“矩形”模式下操作，以适应我们在脉冲序列期间对时不变梯度的需求，或者在先前的快速“半正矢”梯度激励模式下操作。快速脉冲矩形梯度的主要优点在于，其可以例如仅在每个成像脉冲序列期间被开启，这使得操作者能够避免在频率编码成像应用的维度之一中产生恒定梯度的热的问题。 最终，随着进一步的发展，我们希望能够产生短矩形梯度脉冲约100纳秒，0.5%的稳定性。这样的梯度可以在特定的微波脉冲期间选择性地开启，这将允许，例如，切片选择成像能力的可能性。此外，当在我们目前的半正矢电流驱动器的模式下操作时，新的混合设计将能够实现更强和更短的脉冲场梯度，这对于支持具有100 μ m的T2的氮氧自由基的ESRM研究是必要的。  400 ns范围。在梯度驱动器的计划开发和改进之后，预计成像探头将能够产生持续时间约为80 ns的半正矢脉冲场梯度。 一个双通道的原型“混合”脉冲场梯度线圈驱动器已经设计和建造，目前正在测试中。在未来的一年中，该装置将取代现有的半正矢线圈驱动系统，并将继续进行开发升级，并在现场进行评估。

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. To further enhance our instrumentation capability in pulsed ESR microscopy, where unlike c.w., the experimenter can directly measure many key parameters such as self diffusion, relaxation times of the magnetic probe, viscosity, accurate O2 concentration, etc., we have designed a programmable pulsed field gradient coil driver of advanced capability. Based on a hybrid topology consisting of our existing gated-haversine coil excitation scheme and a fast-switched constant-current source, the new gradient coil driver design can be operated in either a prgrammable "rectangular" mode to accommodate our need for time-invariant gradients during the pulse sequence, or the previous fast "haversine" gradient excitation mode. The main advantage of a fast pulsed rectangular gradient is that it can be turned on, for example, only during each imaging pulse sequence, which enables the operator to avoid the problem of a heat producing constant gradient in one of the dimensions for frequency-encoded imaging applications. Ultimately, with further development, we expect to be able to produce short rectangular gradient pulses of ca 100ns at 0.5% stability. Such gradients can be selectively turned on during a specific microwave pulse which would permit, e.g., the possibility for slice selection imaging capability. Furthermore, when operating in the mode of our present haversine current driver, the new hybrid design would be capable of stronger and shorter pulsed field gradients which are necessary to support ESRM studies of nitroxide radicals with T2's in the 100  400ns range. After the planned developments and improvements in the gradient drivers, it is anticipated that the imaging probes will be able to generate haversine pulsed field gradients with durations of ~80 ns. A two-channel prototype "hybrid" pulsed field gradient coil driver has been designed and constructed and is presently under test. During the coming year, this unit will replace the existing haversine-only coil driver system, and continuing developmental upgrades will be incorporated and evaluated in situ.