Mass Flow Control Improves Electron Collider
The Cornell Electron Storage Ring (CESR) is a 768 meter former electron-positron collider which is hidden beneath the school’s Alumni Field and a parking area. Throughout the 1990’s the CESR was the world’s highest luminosity electron-positron collider. The CESR now acts as an x-ray storage location for CHESS (Cornell High Energy Synchrotron Source). During its long and distinguished history the CESR has provided radiation materials which have allowed hundreds of scientists and scientists-in-training to collect data for their research.
Historically the CESR at Cornell had been run in a vacuum state. The problem is that “absolute” vacuum can never be achieved and so stray molecules of unknown composition were having a negative effect on experiment results both in terms of quality of measurement and non-repeatability.
The Bronkhorst solution was to provide a known atmosphere within the CESR through water injected in a vapor state. The water is added via a highly accurate low flow Coriolis Flow Meter directly coupled to a Controlled Evaporator Mixing (CEM) system. This solution ensured that precisely the desired mass of water was injected into the ring atmosphere and that it was added in a complete vapor state. The CEM system allows for the accurate control of a liquid such that a specific mass of that liquid is vaporized. Because the CEM system can provide such accurate control of the vapor those responsible for the CESR are able to maintain a stable atmosphere within the ring. The possibility of stray molecules, which can affect the energy beams in unpredictable ways, is greatly reduced which leads to repeatable results and better data for research. The water vapor also allows better purging of stray molecules during vacuum draw-down allowing for more repeatable results.