Workshop on cryogenic & vacuum sectorisation of the SPL Vacuum Sectorisation Paul Cruikshank, CERN Technology Department (TE) Vacuum Surfaces & Coatings Group (VSC)

Topics  Typical Vacuum Instrumentation  Cold & RT beam vacuum  Cryostat insulation vacuum  LHC & LEP inputs  LHC Vacuum sectorisation  LEP cavity experience  Sectorisation Variants for SPL  Advantages / Disadvantages Vacuum Sectorisation

Typical Beam Vac Config 09/11/09 Vacuum Sectorisation 3

Typical Insulation Vac Config  09/11/09 Vacuum Sectorisation 4

LHC; Arcs and LSS Arcs: - 8 x 2.8 km = 22.4 km - cryomagnets in a continuous cryostat LHC arc LHC LSS LSS (Long Straight Sections): - up- and downstream of the experiments - 8 x 2 x 250 m = 4 km - room temp and standalone cryo- magnets Cryogenic distribution line QRL

LHC Vacuum Overview 6 > 300 beam subsectors

LHC Vacuum Overview A few numbers…. CharacteristicQuantity for LHC machine & distribution line (QRL) Insulation vacuum system length22,4 km & 25 km Welds~ ( in-situ) Weld length~ m Elastomer joints~ Elastomer joint length~ m Multi-layer insulation~ m 2 or 200 m 2 /m of cryostat Vacuum subsectors234 Vacuum subsector length214 m (machine) & 428 m (QRL) Vacuum subsector volume~ 80 m 3 Fixed turbo pumps178 Nominal turbo pumping speed0,25 l/s/m of cryostat Fixed vacuum gauges974 Mobile turbo pumping groups36 Mobile primary pumping groups36

LHC Vacuum Sectorisation  LHC Sectorisation Working Group setup in 1995  Consider beam vacuum, insulation vacuum, cryogenic layout  Increased flexibility ?  Reduce down-time ?  Analyse types of intervention  Short – diode replacement, weld repair,instrument repair  Long – change of cryomagnet  Additional equipment required?  Implementation Cost ?  LHC Project Report #60 – September 1996  Quantifications, recommendations, (dis)advantages, costs 09/11/09Vacuum sectorisation8

LHC Sectorisation  Long Straight sections  Low density of cold magnets ( m cryostats in 250m) & lots of RT equipment – needed helium distribution line  Beam vacuum sectorisation at each cold warm transition (CWT)  Arc  Coherent vacuum & cryogenic subsectors to allow local warm- up of 2.8 km continuous cryostat  Vacuum barriers and helium plugs every 214 metres - compromise between staged installation, leak localisation, partial warm-up, additional heat inleaks, limit degraded vacuum  No beam vacuum sectorisation in 2.8 km continuous cryostat  QRL  Separation of QRL vacuum from magnet vacuum to allow staged reception and leak localisation in long cryostats 09/11/09Vacuum sectorisation9

Insulation vacuum sectorisation

Insulation Vacuum (3) 11 LHC magnet cryostat QRL cryostat Jumpers Vacuum barriers

Baseline ‘short interventions’ in insulation vacuum subsectors Scenario from LHC Project Report 60 Vacuum barriers every 214m n-2….floating, cold, under vacuum n-1thermal buffer, RT, under vacuum n intervention, RT, vented, W opened n+1thermal buffer, RT, under vacuum n+2….floating, cold, under vacuum With subsector length of 214m, it is necessary to warm-up 642m of the 2.8 km continuous cryostat n n-1  Eg repairs on diode, busbar, line Y, helium leak….but no intervention on beam vac n-2n+1n+2

Sectorisation of LEP RF Cavities Beam Vacuum Commissioning and installation During the installation and commissioning, the RF cavities shall stay under vacuum to: Limit the contamination by dusts –Without any sectorisation, several venting will be required, increasing the risk of dust contamination. Preserve the RF commissioning on surface –Venting always implies repeating partly the RF commissioning During the pre-commissioning on the surface, absorber blocks have to be installed on the other side of the sector valves to absorb the accelerated electrons emitted by field emission. Once installed in the LEP tunnel, the sector valves were the absorbers. Modules were warmed individually to change tuners or couplers.

Sectorisation of LEP RF Cavities Beam Vacuum RF processing is required to increase the accelerating field above 6 MV/m Injection of helium ( mbar, reading on the gauge) onto the cold (4.5 K) RF cavity. Sequence is as follow: Installation of a pumping group with an helium injection line (4 h) Bake out (24 h) Helium injection (3 h) …RF processing… Helium pump down (10 h minimum) needs a partial warm-up to release the condensed helium  Need that each module is sectorised to allow for an RF processing

SPL Sectorisation Variants 09/11/09Vacuum sectorisation15 Continuous Segmented Option B Segmented Option A

Typical Insulation Vac Config  Cost for vacuum system:  Draft estimate from S. Calatroni  Includes instrumentation, controls, cabling, in-situ leak test  Insulation vacuum subsector ~ 90 kCHF  Beam vacuum ‘cell’ ~ 90kCHF (cold) + 90kCHF (RT with valves) 09/11/09Vacuum sectorisation16

SPL Sectorisation Variants Volume types Max ‘Segmented’Max ‘Continuous’ Insulation vacuum volumes - cryomodule 35 ((10+5)+6+(12+2)) 3 200m+90m+212 m Beam vacuum volumes - cryomodule + intermodule Insulation vacuum volumes - helium distribution line 5 ? 106m*5 0 or 1 530m Total vacuum volumes Vacuum sectorisation17

Design aspects – vacuum  Advantages  More modular design  Minimise cold equipment – access, alignment, repairs, upgrades, unecessary outgassing, leaks, etc  Modules are complete & tested before installation  Disadvantages  More vacuum equipment eg cold to warm transitions, intermodules  More vacuum instrumentation  Advantages  Compact longitudinal layout – fewer CWT, fewer RF contacts  Helium transfer line can be integrated – less vac systems  Disadvantages  Beam vacuum sectors long- cold sector valves don’t exist!  Some sensitive equipment is imprisoned in cryostat - needs vacuum compatibility and validation Vacuum Sectorisation18 SegmentedContinuous

Installation aspects – vacuum  Advantages  Minimise tunnel work and problems - modules are complete and tested before installation  Fewer problems treated on- line  Staged acceptance tests  Decoupling of problems  Disadvantages  Beam and insulation vacuum systems are exposed to tunnel environment – dust contamination? Vacuum sectorisation19 SegmentedContinuous

Repair aspects – vacuum  Advantages  Reduced search zone  Decoupling of repair and other activities  Limit zones of warm-up and opening of vacuum system – cost & downtime  Disadvantages  Difficult access at cold to warm transitions – not std interconnect design  Advantages  Less tasks for systematic repairs on modules – venting, repumping..  Disadvantages  Equipment will see more thermal cycles – create leaks? Vacuum Sectorisation20 SegmentedContinuous

Commissioning aspects – vacuum  Advantages  Precommissioning before installation  Staged tests – smoothing of resources, earlier identification of problems  Decoupling of problems  Recommissioning of ‘weak’ module possible  Disadvantages  More volumes to commission  Disadvantages  Cavities need to be recommissioned if vented  RF processing with helium required for field above < 6 MV/m – complicated  Movable blocks or valves to absorb field emission electrons? Vacuum Sectorisation21 SegmentedContinuous

Operational aspects – vacuum  Advantages  Limit zone of degraded ins vacuum (helium leak)  Easier diagnosis of problems  Disadvantages  More equipment (fixed pumping systems & valves)  More interlocks  More risk of equipment failure  More maintenance  Advantages  Simpler controls  Redundancy in fixed pumping systems  Disadvantages  MCI would affect more equipment Vacuum Sectorisation22 SegmentedContinuous

SPL Vac Sectorisation – next steps  Which sectorisation variants are not possible?  Strong vacuum constraints need to be identified & investigated – eg can we expose cavity to tunnel air, etc.  Constraints for other technologies to be confirmed  For retained variants, advantages and disadvantages presently expressed qualitatively, now need to be quantified in time, manpower and expenditure.  Are there other vacuum aspects to add?  Continue to get feedback from other operational machines Vacuum Sectorisation23

Last Slide Thanks for your attention Vacuum Sectorisation24

ITER/CERN Collaboration - LHC Insulation Vacuum - Paul Cruikshank - 25 June 2009 Semi-standalone cryo-magnet - typical installation and leak test sequence - HELIUM CIRCUIT JUMPER CRYO-MAGNET CRYOGENIC DISTRIBUTION LINE (QRL) CRYO-MAGNET BEAM VACUUM TUBES PUMP + DETECTOR DETECTOR