LOW POWER PULSE SPECTROMETER AT 170 & 240 GHZ

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 随着最近购买毫米波频率的强大连续波源，执行低功率脉冲工作的可能性变得有趣。最近用这些源进行的连续波实验表明，在100K到250K的温度范围内，光谱饱和效应可以通过改变入射毫米波功率来观察到。由于源结构的模块化性质，在倍频器链(10-15 GHz)中的方便位置引入廉价、高效的RF开关以在期望的毫米波频率上实现明确定义的脉冲是直接的。还可以在开关的同时引入RF移相器，以实现对这些低功率脉冲执行相位循环操作的能力。由于乘法过程的一致性，这是可能的。这些想法的实施将取决于是否有适当的资金可用。然而，即使在目前的设置下，我们也可以继续探索饱和效应，如果分析得当，可以用来推断纵向弛豫时间，否则在高频下很难获得。具有B1增强功能的介质棒谐振器的进一步发展也将对开展这些研究非常有用。我们在HF/HF CW光谱仪上开发的技术也可能在我们的95 GHz光谱仪上使用，我们将在时间和其他资源允许的情况下探索这些可能性。

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. With the recent purchase of powerful continuous wave (cw) sources at millimeter wave frequencies the possibility of performing low power pulse work becomes an intriguing possibility. Recent cw experiments with these sources have demonstrated spectral saturation effects over a range of temperatures from 100K to 250K which may be observed by varying the incident millimeter wave power. Due to the modular nature of the source construction it is straightforward to introduce inexpensive, efficient, rf switches at a convenient point in the frequency multiplier chain (10 - 15GHz) to achieve well-defined pulses at the desired millimeter wave frequency. It would also be possible to introduce rf phase shifters at the same time as the switches to achieve the capability of performing phase cycling operations on these low power pulses. This is possible due to the coherent nature of the multiplication process. Implementation of these ideas will depend on the availability of suitable funding. Even with the current setup, however, we can continue to explore saturation effects, which, when analyzed properly, may be used to infer longitudinal relaxation times which are otherwise difficult to obtain at high frequencies. The further development of the dielectric rod resonator with its B1 enhancing capabilities will also be extremely useful in pursuing these studies. The techniques we have developed on the HF/HF cw spectrometer may also be of use on our 95GHz spectrometer, and we will explore these possibilities as time and other resources permit.