MICE Collaboration Meeting RAL 31 May – 3 June 2009 AFC status By Wing Lau, Oxford University

1. MICE Collaboration Meeting RAL 31 May – 3 June 2009 AFC status By Wing Lau, Oxford University

2. Everything you want to know about the AFC, but didn’t know how to ask. • Let me unfold this to you in the following sequence. • Issues, Hiccups & points of interest • Progress since last reported • Current schedule • Contract variance

3. Issues:- • Quench Issue on the AFC Module • There has been some discussion in the context of the AFC module as the best method to control quench. There are basically two approaches were considered: • Active system • The use of an active system where there are heaters embedded in the coils. Upon detection of a quench electronics provide power to these heaters which dissipate the stored energy. • Pros • Doesn’t rely on thermal contact between the coils and the former – a slip plane can be used. • Cons • Expensive • More complex as heaters have to be installed in the coils • The price tag – over £100K!!!

4. Quench Issue on the AFC Module (cont.) • Passive (Quenchback) • This relies on there being good thermal contact between the coils and the former. A quench induces currents in the former which heat the inner surface of the coils and dissipates the energy. • Pros • Simple construction • No complicated electronics • Passive • Cons • Need good and reliable thermal contact between the coils and the former • For MICE we will need a separate power supply for each module • Baseline solution • The systems above were reviewed in the context of MICE and as a baseline, the passive system was chosen. Tesla have been charged with coming up with a design that ensures there is adequate thermal contact between the coils and the former

5. The Hiccups

6. Hiccups so far:- Space envelope clashes:- This came about when we agreed to Tesla increasing the bobbin end plate thickness from 25mm to 35mm. As a result, the following happened:

7. 422.0 362.0 7.0 5.0 2.0 12.5 47.5 13.5 24.0 25.0 309.5 Thermal radiation shield bobbin Magnet cryostat 39.0 Large End Flange 386.0 The leading dimensions shown on the interface drawing to both KEK and Tesla

8. Clash between LH2 pipe and magnet cryostat !!! The design as it stands 422.0 377.4 5.0 14.5 4.0 32.1 12.5 9.4 Constraint from Tesla:- 8.6 35.0 309.5 Tesla needs 10mm for the extra thickness for the bobbin end plate. They also increased the gap at and thicken up the thermal radiation shield sheet metal. This extends their space envelope by as much as 15.4mm. Foul!! Thermal radiation shield bobbin Magnet cryostat 39.0 Large End Flange 386.0 The constraint from KEK: Hydrogen Absorber and the feed pipes are already made and tested.

9. If nothing done, the following will happen:

10. The Large End Plate will stick out of the AFC cryostat flange face by 15.9mm 15.9mm 447.9 377.9 5.0 14.5 4.0 12.5 47.5 9.4 24 35.0 310 Thermal radiation shield bobbin Magnet cryostat 39.0 Large End Flange 10.0 386.0 The absorber has to be shifted by 15.9 mm upstream

11. The solution:

12. 0.4mm Negligible stick out Agreed change with Tesla:- 1) Reduce space between Magnet cryostat & radiation shield; 2) Local thinning of Large End flange to give H2 pipe a clearance gap of 47.5mm 422.4 372.4 5.0 9.0 4.0 47.5 9.4 2.5 24 35.0 310 Thermal radiation shield bobbin Large End Flange locally thinned down to 2.5mm Magnet cryostat 39.0 Large End Flange 396.0 Absorber stays at coil centre Agreed change with KEK:-The LH2 feed pipe to be extended by 10mm

13. Details of the local thinning of the large flange end plate at the LH2 pipe area

14. Arrangement for the local hatch of the Large Flange end plate

15. Justification for the local thinning on the large end plate – by FEA

16. Applied pressure:- 1 bar Local peak stress:- 90.5 MPa Max. bending stress:- 62 MPa Pro-rata to the design pressure of 1.5 bar (Table 1.8 of tech,spec), the max. bending stress = 93 MPa. Allowable bending stress for Al T6061 at room temp = 1.5 x 78 = 117 MPa. End load effect (from Safety window) is accounted for and is applied onto this area This area has a thickness of only 2.5mm Stress in the thinned down area does not seem to be affected – mainly because of the reinforcement effect from the rest of the plate which is 12.5mm thick.

17. The issue has been addressed by the Technical Board who has accepted the technical proposal for the change.

18. Issues of interests

19. Points worth highlighting here:- HTS Leads SS shunts are incorporated. Each is 225mm long and has an area of between 38.2mm2 and 59.6mm2. We still need to establish how long will it take for the power supply to react in the case of a lead quench Cryocooler:- Power supply - we opted for 280 / 420VAC; 3 phase at 50 Hz. Beam height Now fixed at +1544mm from mounting platform. AFC support to be made with a tolerance of +0,-30mm. This allows the module to be shimmed at site. Coil Cooling Indirect cooling is now incorporated. SS banding wire on the outside any space outside the coil is filled up with epoxy to ensure good thermal contact between coil and bobbin – a requirement for the passive

20. Progress on PRR

29. The schedule

32. Money issues

33. Contract variance:- • Two contract variance were raised by Tesla so far; • On the Bobbin design and indirect cooling etc. • This has resulted in a cost variance of £16K and a schedule delay of 2 months. • This has been resolved and MICE has accepted the request. • On the space envelope • Tesla has submitted a cost variance in the region of £11K and a schedule delay of a further 2 months. It is not clear what the £11K include. Clarification is being sought. • Approval is needed from the MICE PM board to accept the variance request.