MICE hydrogen review Commissioning, testing and operations

Commissioning progress Transfer line manufactured and (roughly) fit-checked Vacuum line manufactured and fit-checked Absorber assembly – Window – absorber indium seals made – 2 MLI blankets applied

Testing Pre-sign off – Pressure test of absorber/window assembly* – Pressure test of newly installed pipework – Leak testing of overhauled relief circuit Pre-cryogenic operation – Leak test of modified sub-assemblies – Leak test of entire system – Turbo pump run-in test in isolation* – Test of gas detection system – Systematic test of valve and instrumentation operation Pre-experimental operation – Purge sequence* – Fill/empty cycle with helium* – Fill/empty cycle with hydrogen

Absorber system pressure test LH2 Vacuum Gas panel Two failure scenarios – Heat load into absorber, causing rapid boiling of LH2 through absorber relief line – Absorber window rupture, causing rapid boiling of LH2 predominantly through vacuum relief line AbsorberVacuum Both PRV Δ0.5 bar

Absorber system pressure test Heat load scenario – Significant heat can only feasibly come from a vacuum failure but… A safety window rupture would not cause a vacuum failure The surrounding vacuum vessels are substantial and unlikely to fail in a catastrophic way Small leaks, such as from seal degradation, would not result in rapid boil-off – Nevertheless, if such a vacuum failure were to occur, two estimates of the heat load into the LH2 were made: Film boiling i.e. maximum possible rate of heat transfer, regardless of ΔT ~ 19kW CERN paper with experimental data suggesting actual max heat transfer would be ~5kW – The latter figure was taken, doubled, and used to calculate a boil-off rate of kg/s – This was used to calculate a total pipe pressure drop from absorber to flame arrestor of 1.92 bar – PRV pressure is 1.5 bara. 1.1 x 1.25 x 1.5 bar = 2.06 bar, so a pressure test to this will be adequate. Note, windows have already been burst tested to above 8 bar

Absorber system pressure test Window failure scenario – Boiling rate from hydrogen spill would be considerable but has not been calculated with similar rigour to previous scenario (estimated at 0.12 kg/s in worst case) – However… Absorber and vacuum relief lines are effectively in parallel in this scenario, thus halving the pipe impedance There is a ‘bucket’ in the vacuum space to reduce the surface area which a spillage would be subject to The safety windows are 0.21mm at their thinnest point, as oppose to 0.18mm in the absorber windows The most likely window failure scenario is a crack or small breach, resulting in a much slower rate of heat transfer than in a full-scale rupture – MICE argues that testing to a higher pressure for the safety windows is unnecessary A burst test as per the absorber windows should be carried out however

Turbo pump Failures experienced – Pictured failure was seemingly random (and also not our pump!) – However, also had bearing problems due to excessive periods of inactivity Preventative maintenance programme – Gradual run in every 6 months – Pumps in storage for longer than 1 year sent to Leybold for bearing replacement – Project also has multiple spares now

System tests Helium purge – Pressurises with helium and pumps out three times – Tests operation of the gas panel, pumps, pressure gauges and control system Helium fill – no liquid – Uses the control valve to maintain helium pressure in the absorber vessel as it cools – Radiative heat load means the system will not reach 4.2K – Tests operation of the temperature sensors and cryocooler and provides an indication as to the cryogenic performance of the system as it cools down – Will have to be manually terminated Hydrogen vent – Replaces the old hydrogen empty sequence – Opens the vent line valve and switches the heater onto the absorber – won’t be particularly representative with cold helium but will still test the interlocks, valve operations etc

Milestones November December January February March April May June PRY installation 2015 FC contractual acceptance Absorber assembly FC#2 to MICE Hall Hydrogen safety review Vacuum and leak testing Pressure testing of absorber Cryogenic (helium) testing Hydrogen safety sign-off Cryogenic (hydrogen) testing Magnet testing begins

Operations General principle is that only designated ‘hydrogen experts’ interact with the system when hydrogen is present – Broadly speaking, this statement also stands during helium operations Hydrogen experts are: – Myself – Mike Courthold (part-time) – Phil Warburton (based at DL) – Mark Tucker (based at RAL) R&D tests took 4 weeks and required 14 people to staff 24/7 Same coverage will be required for: – Hydrogen commissioning – Active hydrogen sequences during operation – …but not for remainder of user runs – this will covered by on-call arrangements

Operations Run schedule handled by Steve Boyd (Warwick Uni)