Maly Thorsten, Sirigiri Jagadishwar R
Bridge12 Technologies, Inc., Framingham, MA 01702, USA, URL: http://www.bridge12.com.
Appl Magn Reson. 2012 Jul 1;43(1-2):181-94. doi: 10.1007/s00723-012-0360-7.
We present an alternate simplified concept to irradiate a nuclear magnetic resonance sample with terahertz (THz) radiation for dynamic nuclear polarization (DNP) experiments using the TE(01) circular waveguide mode for transmission of the THz power and the illumination of the DNP sample by either the TE(01) or TE(11) mode. Using finite element method and 3D electromagnetic simulations we demonstrate that the average value of the transverse magnetic field induced by the THz radiation and responsible for the DNP effect using the TE(11) or the TE(01) mode are comparable to that generated by the HE(11) mode and a corrugated waveguide. The choice of the TE(11)/TE(01) mode allows the use of a smooth-walled, oversized waveguide that is easier to fabricate and less expensive than a corrugated waveguide required for transmission of the HE(11) mode. Also, the choice of the TE(01) mode can lead to a simplification of gyrotron oscillators that operate in the TE(0n) mode, by employing an on-axis rippled-wall mode converter to convert the TE(0n) mode into the TE(01) mode either inside or outside of the gyrotron tube. These novel concepts will lead to a significant simplification of the gyrotron, the transmission line and the THz coupler, which are the three main components of a DNP system.
我们提出了一种替代的简化概念，用于在动态核极化（DNP）实验中用太赫兹（THz）辐射照射核磁共振样品。该方法使用TE(01)圆波导模式传输太赫兹功率，并通过TE(01)或TE(11)模式照射DNP样品。通过有限元方法和三维电磁模拟，我们证明了使用TE(11)或TE(01)模式时，由太赫兹辐射感应产生并负责DNP效应的横向磁场的平均值，与由HE(11)模式和波纹波导产生的横向磁场平均值相当。选择TE(11)/TE(01)模式允许使用光滑壁、超大尺寸的波导，这种波导比传输HE(11)模式所需的波纹波导更易于制造且成本更低。此外，选择TE(01)模式可以简化以TE(0n)模式运行的回旋管振荡器，方法是在回旋管管内或管外采用轴上波纹壁模式转换器，将TE(0n)模式转换为TE(01)模式。这些新颖的概念将大大简化回旋管、传输线和太赫兹耦合器，它们是DNP系统的三个主要组件。
