Dynamic nuclear polarization (DNP) increases the sensitivity of nuclear magnetic resonance (NMR) spectroscopy by using high frequency microwaves to transfer the polarization of the electrons to the nuclear spins. The enhancement in NMR sensitivity can amount to a factor of well above 100, enabling faster data acquisition and greatly improved NMR measurements. With the increasing magnetic fields (up to 23 T) used in NMR research, the required frequency for DNP falls into the THz band (140- 600 GHz ). Gyrotrons have been developed to meet the demanding specifications for DNP NMR, including power levels of tens of watts; frequency stability of a few megahertz; and power stability of 1% over runs that last for several days to weeks. Continuous gyrotron frequency tuning of over 1 GHz has also been demonstrated. The complete DNP NMR system must include a low loss transmission line; an optimized antenna; and a holder for efficient coupling of the THz radiation to the sample. This paper describes the DNP NMR process and illustrates the THz systems needed for this demanding spectroscopic application. THz DNP NMR is a rapidly developing, exciting area of THz science and technology.

中文翻译：

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太赫兹动态核极化核磁共振

动态核极化 (DNP) 通过使用高频微波将电子极化转移到核自旋，从而提高了核磁共振 (NMR) 光谱的灵敏度。NMR 灵敏度的增强可以达到远高于 100 的倍数，从而实现更快的数据采集并大大改进 NMR 测量。随着核磁共振研究中使用的磁场（高达 23 T）不断增加，DNP 所需的频率落入太赫兹频段（140-600 GHz）。已开发回旋加速器以满足 DNP NMR 的苛刻规范，包括数十瓦的功率水平；几兆赫的频率稳定性；和持续数天至数周的 1% 的功率稳定性。超过 1 GHz 的连续回旋管频率调谐也已被证明。完整的 DNP NMR 系统必须包括一条低损耗传输线；优化的天线；以及用于将太赫兹辐射有效耦合到样品的支架。本文描述了 DNP NMR 过程，并说明了这种要求苛刻的光谱应用所需的太赫兹系统。太赫兹 DNP NMR 是太赫兹科学技术中一个快速发展、令人兴奋的领域。