MICE Absorbers work package MPB – 17/04/15

1. MICE Absorbers work packageMPB – 17/04/15 • RAL • Tom Bradshaw • Vicky Bayliss • Mike Courthold • Matt Hills • Andy Nichols • Roy Preece • Mark Tucker • Steve Watson • DL • Steve Griffith • Trevor Hartnett • Ian Mullacrane • Adrian Oates • Chris White • Oxford • John Cobb • Wing Lau • Stephanie Yang • Imperial College • Victoria Blackmore

2. Contents • Focus Coils • Recap • Contract • Absorbers & hydrogen infrastructure • Hardware progress • Review outcomes • Relief line issue • Schedule

3. FC recap • FC#1 suffers from deficient magnetic performance, probably due to problems with coil potting • Currently mothballed in R9 • FC#2 trained to full current • Currently installed in beamline • Both modules are thermally imperfect and have internal helium leaks • However, the above issues are non-critical

4. FC#2 – PSU problems • During training, the power supply unit (AMI 430) would go into an emergency ramp-down mode after an average of 30 hours • DL have been investigating the cause: • Not due to errant communications from other components in the rack • Unit trips at any current setting, including 0A • Latest theory is that the FC load on the R9 electrical infrastructure made the system too sensitive to mains disturbances (see plot below) • Expectation is that the problem will not be seen in the MICE Hall • 5A • 5.30am

5. FC contract • FC#2 has been accepted for full price • FC#1 has been accepted with a 50% discount on the final payment (£13k) • Both modules were officially accepted on 4th March 2015, initiating the 2 year warranty period • This is important because the LH2 turrets have not been tested • Importantly, MICE have maintained a good relationship with the manufacturer throughout the recent ‘wrangles’

6. LH2 system - review • Held in mid-January, chaired by ISIS • Included attendees from ISIS, RAL SHE group, CERN (Jon Gulley) and Birmingham Uni (John Dowell) • 19 recommendations and 13 comments • Approval given for various proposed system changes • Approval given for final sign-off process (as per R&D programme) • Maintenance plan, training programme for operators and completion of outstanding HAZOP actions • Revisit calculations regarding the ability of the system to cope in the event of absorber window failure

7. LH2 system – relief line • Two failure modes considered by review in considerable detail • Vacuum loss, leading to boil-off of LH2 inside absorber - acceptable • Absorber window rupture, leading to boil-off of LH2 inside vacuum space – some uncertainties • Second scenario was considered by M. Green and S. Yang in 2004 but assuming that the relief system would be of sufficient diameter to effectively negate pipe pressure drop – this is not the physical reality • Calculations by Stephen Harrison of ISIS show that pressure rise is significantly higher than anticipated – calculation needs more refinement but it looks like final answer will be between 5 and 8 bar. • Windows nominally designed for FoS of 4 on PRV pressure (1.6 bar) = 6.4 bar • FEA says windows manufactured to specification will actually burst between 9 and 11 bar • Burst tests carried out to date were at 8 bar

8. LH2 system – relief line cont… • Working group has considered this and tentatively agreed that a Factor of Safety of 2 would be acceptable, pending: • Approval from ISIS and Technology nominated engineers • Discussions with an independent safety expert or consultant • A Factor of Safety of 2 with the current setup would probably require: • Confidence in a pressure rise no greater than 5 bar – unlikely due to small bore welded pipework • Windows that can withstand a minimum of 10 bar – unlikely due to expected optimism in FEA • Plan of action • Use direct and large-bore pumping line as relief line, bypassing turbo pump with a burst disk • Redo calculations accordingly – expected to show a considerably reduced pipe impedance • Carry out further burst tests on windows to better understand FEA errors • Plan for success – install ‘best’ safety windows in the expectation that they will be proved safe

9. Absorbers • Baseline absorber plan is now: • Assume that Step IV starts with LiH absorber • However, until the July shutdown when the LiH absorber would be installed, the hydrogen absorber will remain in the FC to allow commissioning work to progress • This will reduce technical risk from a mid-Step IV hydrogen commissioning period • Downside is that initial “empty” runs will now include an empty hydrogen absorber and 4 beam windows • Hydrogen absorber • Two windows and majority of MLI assembled • Proof testing to be carried out shortly • Insulation over windows tentatively agreed at 5 layers of MLI (~0.19% of one rad length) • LiH absorber • Stored in R9, regularly flushed with argon • Support structure design task ongoing

10. Schedule • March • South PRY installation • April • - Absorber proof tested • - Window burst test • - Absorber installed • May • North PRY installation • - Hydrogen system tested with helium • June • - Hydrogen safety approval • - Completion of hydrogen infrastructure • July

11. Questions?