ELECTRON NUCLEAR DOUBLE RESONANCE RESONATOR FOR DNP & ENDOR AT 5 TESLA

电子核双共振实验需要两个很强的 样品位置处的微波场和射频场。一个 典型的DNP设置针对核磁共振通道进行了优化，而微波是 只需在核磁共振线圈中喷洒到样品上，从而浪费 相当大的入射微波功率。在一个标准中 高场Endor探头，优化微波信号通道 使用外置核磁共振的高Q微波谐振器 线圈，导致射频效率的大幅损失 由于金属谐振器的屏蔽。我们开发了一种新的 双谐振谐振器，可实现两种微波的高效率 和射频辐射。该设计是基于圆柱形的 腔运行在TEO，模式。与传统的 设计中，微波腔的实体被替换为一个 缠绕扁线，形成核磁共振线圈，同时保持较高的 微波辐射品质因数(Q10aded-1000)。在DNP中 用4-氨基TEMPO作为偏光剂的实验表明 这种谐振器的使用，结合了低微波功率 设置(17 MW)导致‘H-信号增强F-=300-400。 以前，这个数量级(F=185)只能通过以下方式获得 使用我们的高功率微波回旋管(1-5瓦)。对于Endor 实验表明，射频脉冲长度减小了1倍~4 与标准Endor设置相比，Endor设置允许大量 对低Y核Endor的敏感性较高。演出很精彩 用13C-Endor显示在铁簇蛋白上，其中短 由于电子弛豫时间很短，所以需要照射时间 铁(S=1/2)团簇的倍数，以及与H-Endor在A 全氚BDPA稳定自由基。

Electron Nuclear Double Resonance experiments require both strong microwave and radio frequency fields at the sample position. A typical DNP setup is optimized for the NMR channel and microwaves are simply sprayed onto the sample in the NMR coil, thereby wasting a significant amount of the incident microwave power. In a standard high field ENDOR probe, the microwave signal channel is optimized using a high Q microwave resonator with an externally mounted NMR coil, resulting in a substantial loss of radio frequency efficiency due to the shielding of the metal resonator. We have developed a new double resonance resonator allowing high efficiency for both microwave and radio frequency irradiation. The design is based on a cylindrical cavity operating in the TEO,, mode. In contrast to the conventional design, the solid body of the microwave cavity has been replaced by a wound flat wire, which forms the NMR coil while maintaining a high quality factor for microwave irradiation (Q10aded - 1000). In DNP experiments using 4-amino TEMPO as polarizing agent, we have shown that the use of this resonator, combined with a low microwave power setup (17 mW) leads to a 'H-signal enhancement of F-=300-400. Previously, this order of magnitude (F-=185) could be obtained only by using our high power microwave gyrotron (1-5 Watt). For ENDOR experiments the RF pulse lengths are reduced by a factor ~! 4 compared to the standard ENDOR setup, which allows for substantial higher sensitivity on low Y-nuclei ENDOR. The performance was demonstrated with 13 C-ENDOR on an iron-cluster protein, where short irradiation time is required due to very short electronic relaxation times of the iron (S=1/2) cluster, as well as with 2 H-ENDOR on a perdeuterated BDPA stable radical.