Redesign of the connection cryostat

1. The future of the Forward Physics at the LHC, Manchester, Dec 13th 2004 Redesign of the connection cryostat D. Macina (TS/LEA) On the behalf of S. Marque (AT/CRI)

2. OUTLINE • Access to the LHC tunnel • Near beam detectors: risk analysis • Connection cryostat: reminder • Proposals for a redesign of the cryostat • Conclusions

3. Access to the DS zone during operational periods

4. ACCESS to DS5 • Travel for ~ 400 m in the LSS and DS • LSS1/5 very radioactive regions (~ KGy/y) • DS : ~ 1 KGy/y foreseen close to the missing magnet and Q11 • Both the passage trough this zone and the work to be done at the cryostat have to be carefully planned with Radiation Protection Group . • At least a few hours are needed before access is granted after a beam dump: • Flush fresh air in the tunnel • RP technician has to inspect the zone

5. Vacuum vessel Beam pipe Beam 2 Beam 1 Integration of near beam detector into the LHC Example: LHCb VErtex LOcator (VELO)

6. VELO Mechanical design Wake field suppressors Detector arrangement along the beam axis IP8 Exit thin window (2 mm thick) RF/Vacuum thin shield Large rectangular bellows: Allow the displacement of detector halves w.r.t. the beam axis Cooled Si sensors in secondary vacuum

7. Vacuum System Layout • 1ary + 2ary vacuum system • No P > 15 mbar allowed • VELO + LHCb beam pipe are one vacuum system • LHCb beam pipe is NEG-coated • Must be possible to: • Bake (without Si) to T ~ 150 oC • Vent with Ne (preserve NEGs) • Work done in close cooperation with CERN/AT-VAC

8. Detector half Silicon CO2 cooling capillaries Operate Si at about –10 oC to reduce radiation damage effects (up to ~1014 1MeV-neq/cm2yr) RF shield Bellows (for decoupling from vacuum vessel)

9. Positioning System • All moving parts are outside the vacuum y x z • Mounted on a y-translation table

10. Risk analysis • General strategy in case of undesired event: have available a set of emergency elements which can rapidly be inserted in place of normal elements so that LHC can readily recover • Risk scenarios identified with the associated level of gravity and occurrence probability: • Rupture of the exit window or beam pipe (Category: major, Frequency: improbable, 7x10-4y-1) • Leak from ambient air to secondary vacuum(Category: severe, Frequency: remote, 4x10-3y-1) • Damage by sudden beam displacement(Category: severe, Frequency: remote, 1.7x10-3y-1) • Loss of electrical power during nominal operation (Category: minor, Frequency: occasional, 3x10-1y-1) • Etc… Even in the improbable case of the most catastrophic scenarios (which would require replacing VELO with an emergency beam pipe) the downtime for LHC would not exceed 2 weeks

11. Reminder: lines to be kept for continuity E C’

12. Ideas • No relevant modifications: detectors at 2 K • Complete redesign of the cryostat: solution “a la TOTEM” with the Roman Pot mechanics in air • Important modifications (Sebastien’s proposal): • External cryostat maintained • Original thermal vacuum maintained • “SAS” to access detectors and mechanics

13. Proposal 2: advantages and disadvantages • Very challenging complete redesign of the cryostat: • Mechanical stability (the structure has to stand Δp = 1 bar and be stable) • Thermal shield needed: it shields elements at T= 2 K from cryostat at ambient temperature (it works in vacuum) • Connection at both end to the “standard’ cryostats (it is complicated and takes away longitudinal space) Very limited space available !

14. Cross section LHC tunnel

15. Proposal 2: disadvantages and advantages • Very challenging complete redesign of the cryostat: • Mechanical stability (the structure has to stand Δp = 1 bar • Thermal shield needed: it shields elements at T= 2 K from cryostat at ambient temperature (it works in vacuum) • Connection at both end to the “standard’ cryostats • Access “a la TOTEM”: free access to both the mechanics and the detectors and no problems related to the warming up/ cooling down of a cryogenics cell Very limited space available !

16. Proposal 3 D. Dattola / S. Marque FP420 - 09/11/2005

17. Proposal 3 D. Dattola / S. Marque FP420 - 09/11/2005 Thermal shield (actively cooled 80K) – 1mm 300K 1.9K Vacuum >= 2mm Vacuum >= 4mm MLI (2x10layers) – 4K/6mm MLI (2x15layers) – 80K/12mm FROM 1.9K to 300K: AT LEAST 25mm

18. Proposal 3 Heat exchanger Vacuum Vessel Cold to warm transition warmtocold transition Beam pipes He II Usable Volume (Tamb) BusBars Support posts (T) S. Marque / D. Dattola FP420 - 09/11/2005

19. Proposal 3:Advantages and disadvantages • Does not require a redesign of the external cryostat and it is in line with all the procedures to assemble and install such cryogenic components in the LHC • Access to the detectors and mechanics possible via “SAS” without a warm up/cool down of the cell • If a number of “small SAS” is not compatible with the mechanics/detector design => • We need to break the thermal vacuum and warm up/cool down the cell to access the detector • We go back to proposal 2

20. Conclusions • A few ideas on the redesign of the connection cryostat have been discussed: • Solution “a la TOTEM” looks very appealing from the point of view of accessibility, however it is technically very challenging given the available space in the tunnel. A feasibility study could be done. • Proposal from AT/CRI does not require a feasibility study and it is in line with all the procedures to assemble and install such cryogenic components in the LHC • In order to start with the redesign of the connection cryostat, the following is needed: • Engineer dedicated to the project • Definition of interfaces between all the major sub-components (i.e. rough definition of the various volumes requested by each sub-component) • Keep in mind that the access to this part of the machine will not be easy