Beam heat load measurements with COLDDIAG at the diamond light source

Understanding the heat load from an electron beam on a cold beam tube (liner) is an open issue of great interest for the cryogenic layout of superconducting insertion devices. COLDDIAG, a cold vacuum chamber for diagnostics was designed and built especially for this purpose. The instrumentation comprises temperature sensors, pressure gauges, mass spectrometers as well as retarding field analyzers with which it is possible to measure the beam heat load, total pressure, and gas content as well as the flux of particles hitting the chamber walls. COLDDIAG was installed in November 2011 in the Diamond Light Source (DLS). Due to a mechanical failure at one thermal transition, it was removed after only one week of operation. A redesign of the faulty transition in COLDDIAG allowed reinstallation in August 2012. In this work, we report on the measurements and results obtained during the first months since reinstallation in DLS.