Optimizing Cryogenic Systems for RF & Beam Scrubbing: Options & Capacities

1. Cryogenic system in P4:Possible options (Mostly for RF & beam scrubbing) S. Claudet & U. Wagner LHC Workshop, “Chamonix XlV” January 2005

2. Content • Brief recall of present situation • Concerns • Cooling capacity • Pressure stability • Coupling with items operated at higher pressure • Periodic cavity conditioning and developments • Possible alternative cooling schemes • Summary

3. Getting familiar with the subject Interface to be further studied & finalised !!! Global overview ?!? • LHC Design report, p 134 for description of ACS cryogenics and requirements • Schematic views: • Single cavity module: LHCACSGA0006 • QRL sector 3-4: LHCLSQR_0041 • QRL sector 4-5: LHCLSQR_0042 • Minutes of meetings between RF & Cryo • Minutes of LHC Hardware Commissioning

4. Layout UX45, top view ACS QRL QUI QURC

5. Layout UX45, side view ACS QRL WRL QUI

6. Cooling capacity (1/3) “LHC Design report”, recently completed by AB/RF

7. Cooling capacity (2/3) Some margin left at Nominal mode Nominal mode: no need for capacity upgrade Chamonix 2004, p 252 Equivalent capacity [kW]

8. Cooling capacity (3/3) • Lack of capacity • of the 4.5 K • Refrigerators • Ultimate mode: obvious need • for capacity • upgrade Chamonix 2004, p 252 Equivalent capacity [kW]

9. Capacity for beam scrubbing • Turbine upgrade decided in 2004, (contract F529) • Cooling capacity in line with hydraulic capacity of beam screens Chamonix 2004, p 253 Equivalent capacity [kW]

10. Pressure stability (1/2) SM18 Pressure [mbar] LHe level [mm]

11. Pressure stability (2/2) SM18 Pressure [mbar] Request: 1.350 bar ± 15 mbar Try with Line D (60m3) as buffer and return valve in QUI for Pressure control If not OK, then use return control valve of module for Pressure control Nota: LHe level control at low possible value will increase GHe volume for intrinsic pressure stability

12. Coupling via return line D (1/3) • During some operating modes, QRL - Line D will be operated at pressures above Cavities Maximum Allowed Working Pressure Cool-down: 3.5 B to 1.3 B Sector quench: 6 to 15 B Warm-up: 1.3 to 3.5 B 2.0 B Safety device 1.550 B Beam Dump 1.500 B High Voltage off 1.450 B RF off 1.350 B Nominal value

13. Coupling via return line D (2/3) Initial ramp: dTmax* < 75 K Chamonix 2004, p 206 Normal cooldown of a LHC sector • Cool-down of ACS to be started when QRL- line D pressure is low enough • Compatible with overall schedule 300-4.5 K Start of ACS and DFBs cooldown + 2 d to 1.9K * max temp. difference across magnet G. Riddone, AT Department LHC Project Workshop, Session 6 - Chamonix January, 21 2004

14. Coupling via return line D (3/3) Industrial cryogenic check-valve installed in refrigerators, DFB’s

15. Conditioning & tests requirements Not critical, even if frequent quenches at the beginning • Commissioning or conditioning: • After installation before beam: 6 months • After yearly warm-up to 300 K: 1 week • After a short stop (T ≤ 50 K): 1-2 hours • Repeated request: • “Need to have the possibility of doing RF work if machine is down for some time (magnet replacement, …)” Could be a good idea, but not yet the baseline !!!

16. Simplified cooling scheme 4.5 K Refrigerator Warm Compressor Station Warm recovery line (≤300 K; ≤1.1 bar) MP HP LP Cold Box SC Cavities Fall-back for “low intensity” Safety System Back flow limitation D (20 K; 1.3 bar) C (4.5 K; 3.0 bar) QRL QUI Safety System • Open points: • Interface valves located in QRL Service Module • Safety system (control valve, safety valve, bursting disc) • Back flow limitation

17. Alternative cooling schemes, why? • To provide the possibility to discharge helium gas at a lower pressure than nominal 1.350 bar, increasing availability of sc cavities operation • To keep availability at least as it is now • While reviewing possible options, why not giving the possibility to operate the sc cavities independently from the sectors

18. Option 1: Warm return • Advantage: • (Cool-down) / Warm-up even if line D > 1.4 bar • Recovery of ACS static losses after sector quench • Allows short period of operation if line D > 1.4 bar 4.5 K Refrigerator Warm Compressor Station Warm recovery line (≤300 K; ≤1.1 bar) MP HP LP ? Cold Box Coupler cooling SC Cavities Safety System D (20 K; 1.3 bar) C (4.5 K; 3.0 bar) QRL QUI Safety System Rather easily implemented

19. Layout UX45, side view ACS QRL Detailed integration study needed to confirm the concept WRL Warm Recovery Line (WRL) always along QRL

20. Option 2: Cold return supply & 4.5 K Refrigerator Warm Compressor Station Warm recovery line (≤300 K; ≤1.1 bar) MP HP LP ? Cold Box Coupler cooling SC Cavities Safety System Kept as back-up ? D (20 K; 1.3 bar) C (4.5 K; 3.0 bar) QRL QUI Safety System • Advantage: • Cool-down / Warm-up even if line D > 1.4 bar • Recovery of ACS static losses after sector quench • Allows quick re-connection after quench • Allows short period of operation if line D > 1.4 bar • Allows operation independently from QRL / Magnets Disadvantage: • New valve box & lines • Intervention on 2 lines • Not easily implemented

21. Layout UX45, top view • Additional lines as by-pass of QUI, via a valve box ACS QRL QUI QPLB - QULA: Lines between refrigerators & QUI • Feasibility to be confirmed • Detailed integration study needed to confirm the concept

22. Option 3: “Process wish” 4.5 K Refrigerator Warm Compressor Station Warm recovery line (≤300 K; ≤1.1 bar) MP HP LP To be defined Cold Box Coupler cooling SC Cavities Safety System Kept as back-up ? D (20 K; 1.3 bar) C (4.5 K; 3.0 bar) QRL QUI Safety System • Advantage: • Cool-down / Warm-up : no limitation • No limitation due to quench • Allows operation independent from QRL / Magnets • Disadvantage: • Not likely to be possible

23. Option 4: Dedicated compressor 4.5 K Refrigerator Dedicated compressor Capacity boost to be defined Warm Compressor Station MP HP LP Cold Box Coupler cooling SC Cavities Safety System Kept as back-up ? D (20 K; 1.3 bar) C (4.5 K; 3.0 bar) QRL QUI Safety System • Advantage: • Cool-down / Warm-up : no limitation • No limitation due to quench • Operation independent from sector Disadvantage: • Coupling with 4.5K Ref. not certain if possible

24. Option 5: Dedicated Ref. (at last!) Dedicated Compressor 4.5 K Refrigerator Warm Compressor Station Dedicated Cold Box MP HP LP Cold Box Coupler cooling SC Cavities Safety System Kept as back-up ? D (20 K; 1.3 bar) C (4.5 K; 3.0 bar) QRL QUI Safety System • Advantage: • Cool-down / Warm-up : no limitation • No limitation due to quench • Operation independent from sector • Disadvantage: • Where and how to install this now ?

25. Layout UX45, top view (5) • ACS • QRL • Cooling capacity critical for ultimate beams, something will have to be done ! • Integration study needed surface-shaft-cavern

26. Summary options Data provided as indications, to be further studied if necessary

27. Summary • The reference solution needs to be implemented, with simple adaptations (control & check valves) to prevent perturbation due to back pressure from line D • A back-up return via the warm recovery line would prevent from major pressure excursions above 1.5 bar Option 1 • Any alternative cooling scheme will need a modification of the corresponding cryogenic distribution line (after concerned service module) • Additional capacity will be triggered by needs for ultimate beams or (bad!) operational experience Option 2,3,4, 5 Option 5

28. Acknowledgements The authors would like to thank all colleagues who contributed to this work: E. Ciapala, R. Losito, P. Maesen, O. Brunner Y. Muttoni L. Serio, G. Riddone, L. Tavian