Bizel-Bizellot, L. Ellis, M. Pattalwar, S.M. Pendleton, M.D. Smith, P.A. Wheelhouse, A.E. JACoW Geneva, Switzerland 978-3-95450-191-5 10.18429/JACoW-SRF2017-TUPB060 English 520-523 TUPB060 ion cavity SRF operation cryogenics Contribution to a conference proceedings 2018 2018-01 https://doi.org/10.18429/JACoW-SRF2017-TUPB060 http://jacow.org/srf2017/papers/tupb060.pdf Testing SRF cavities in a vertical cryostat is the first step in qualifying the performance of SRF cavities before being integrated into a cryomodule. The European Spallation Source (ESS) requires 84 high-beta 5 cells, 704 MHz cavities which will be manufactured and qualified for their RF performance in a vertical cryostat at Science and Technology Facility Council (STFC) Daresbury Laboratory (United-kingdom). Taking a conventional approach each vertical test would require a large cryostat demanding more than 7000 litres of liquid helium per test for testing 3 cavities simultaneously. In order to reduce the overall operating cost, we plan to develop an alternative method to divide the liquid helium consumption by 5 by filling liquid helium only in each individual helium vessels enclosing each cavity placed horizontally in the cryostat. Therefore the test is performed in more realistic conditions such as in a cryomodule and reduces the operating time. This also reduces the mass flow-rate to be handled by a factor 10, leading to 2 g/s, thus reducing the size of the associated components such as the 2 K pumps, the safety device, the valves and transfer lines.