MAGNET SYSTEM FOR W BAND EPR SPECTROMETER

伊利诺斯州EPR研究所的W波段（95 GHz）EPR谱仪 中心被设计成一个多用途的科学仪器。 的 光谱仪的能力已经通过增加快速 磁场扫描系统（最大1000 G扫描， （第二节）和一个专门设计的低温恒温器， 研究（2-300 K）与真空密封微波窗口。 快速 扫掠系统采用室温水冷螺线管和 改进的Techron（Techron，IN）电源。 扫描系统 具有14位分辨率的数字扫描。 一种新 设计了水冷式磁场扫描线圈， 在伊利诺伊大学制造。 新线圈产生18% 在相同的电流下，磁场的扫描比 牛津原创设计 获得高精度、可再现的扫描 围绕中心场，我们修改了原始扫描线圈 由牛津提供。 首先，我们已经取代了原来的扫描线圈 我们自己的设计具有+/- 600高斯的扫描范围，而不是 原来的+/- 500高斯。 第二，因为权力大， 高稳定性的双极电源很难获得， 在原来的基础上增加了一个Danfysik Ultrastab电流传感器 由牛津提供的放大器。 Danfysik传感器在 零磁通原理，可进行电流测量和调节 没有与其固有温度的欧姆连接 大电流下的稳定性问题。 16位D/A转换器允许 以15 mG的步长扫描磁场 测量的可重置性 优于100 稳定性好于10 ppm。 期间 在当前的赠款年度，扫描线圈进行了两次重新设计， 提高隔离度和稳定性。 W波段的系统是可以接入的 用于其他合作或服务用途。 发展和 该系统的改进是一个持续的项目。

The W-band (95 GHz) EPR spectrometer at Illinois EPR Research Center was designed as a multi-purpose scientific instrument. The capabilities of the spectrometer have been extended by adding a fast magnetic field sweep system (maximum 1000 G sweep in a minimum of 1 sec.) and a specially designed cryostat for variable temperature studies (2-300 K) with a vacuum-tight microwave window. The fast sweep system employs a room-temperature water-cooled solenoid and a modified Techron (Techron, IN) power supply. The sweep system features a digital scan with 14 bit resolution. In addition, a new water-cooled coil for scanning the magnetic field was designed and manufactured at the University of Illinois. The new coil produces 18% larger scans of magnetic field at the same current than does the original Oxford design. To obtain high-precision, reproducible sweeps around the center field, we have modified the original sweep coil supplied by Oxford. First, we have replaced the original sweep coil wi th our own design having a sweep range of +/- 600 Gauss, instead of the original +/- 500 Gauss. Second, because high-power, high-stability bipolar power supplies are difficult to obtain, we added a Danfysik Ultrastab current transducer onto the original amplifier supplied by Oxford. The Danfysik transducer operates on the zero flux principle and enables current measurement and regulation without an ohmic connection with their inherent temperature stabilization problem at high current. A 16-bit D/A converter allows sweeping the field in steps as fine as 15 mG. Measured resettability is better than 100 A and the stability is better than 10 ppm. During the current grant year the scanning coil was twice redesigned to improve the isolation and stability. The W-band system is accessible to others for collaborative or service use. Development and improvement of this system is an ongoing project.