XHV Instrumentation Activities at the Jefferson Lab
Ganapati Myneni
Jefferson Lab
Newport News Virginia 23606
Continuous Electron Beam Accelerator Facility (CEBAF) at the Jefferson Lab is one of the worlds largest Extreme High Vacuum (XHV) system in the world. With the present day vacuum instrumentation we have no way of measuring the pressure in these 2 K Linacs. The estimated pumping speed for hydrogen in this system is ~6´ 106 ls-1. For reliable operation of the accelerator we had to make sure that the 2 K beam line vacuum system is free from helium leaks. To accomplish such a daunting task a very high sensitivity helium leak detection method has been developed and used1. Based on this work a prototype extreme high sensitivity leak detector was designed and built. Further, a need for XHV instrumentation is recognized and systematic studies are undertaken to gain an understanding of the associated problems in order to develop reliable instrumentation. As a part of this study we have used Spindt filed emitters in extractor gauges and residual gas analysers2. Under a joint Cooperative Research and Development Agreement (CRADA), Varian Vacuum Technologies, Old Dominion University and Jefferson Lab are working to develop low outgassing and reliable cold electron sources for vacuum instrumentation. In this paper a review of these XHV instrumentation activities will be presented. Further, a simple XHV instrumentation calibration system will be discussed.