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Fast Vacuum Valves at CERN

Fast Vacuum Valves at CERN. Introduction to fast valves History of fast valves in use/used at CERN LEP fast shutters Fast valves for LHC?. OLAV Workshop 11/04/2005 W. Maan. Introduction to Fast Valves. Fast Acting Valves or Fast Shutters Safety devices to protect sensitive equipment from:

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Fast Vacuum Valves at CERN

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  1. Fast Vacuum Valves at CERN Introduction to fast valves History of fast valves in use/used at CERN LEP fast shutters Fast valves for LHC? OLAV Workshop 11/04/2005 W. Maan OLAV 1 Workshop CERN

  2. Introduction to Fast Valves • Fast Acting Valves or Fast Shutters • Safety devices to protect sensitive equipment from: • pressure shocks • particle or dust contamination • heat load on a cold system Detecting element Trigger generator Fast shutter controller Fast shutter Gate Valve System to protect Type A Type B OLAV 1 Workshop CERN

  3. CERN Fast Valves: ISR • ISR Fast Shutter (‘60 & ’70) • Developed by Dr. J. Delfosse • PhD “Protection des anneaux de stockage contre les irruptions d’air” OLAV 1 Workshop CERN

  4. CERN Fast Valves: SPS • SPS Fast Shutters early eighties: • Circular Aperture 150 mm • Spring actuation • Closing time about 25 ms • Conductance of 1 mbarl/s • Circular Aperture 250 mm • Compressed air on large piston actuation • Closing time about 50 ms • Conductance of 1 mbarl/s • SPS Fast Shutters for protection of sensitive equipment like: • Kicker Magnets • Electrostatic Septa • Super Conducting Cavities • Machine functionality • No major incidents • Several justified closures linked to small leaks • Adjustment of detection levels needed during machine operation. OLAV 1 Workshop CERN

  5. CERN Fast Valves: LEP • The first fast valve at CERN late eighties • Mechanical problems • 2 valves installed around one LEP experiment • Machine functionality? OLAV 1 Workshop CERN

  6. di/dt P di/dt P di/dt P di/dt P CERN Fast Valves: LEP2 • LEP Fast Shutters mid-nineties. • Protection of the Super conducting cavities: • Ultra clean vacuum • Cryogenic heat loads & discharge • Functionality during last LEP runs • Poor confidence in the reliability of the product • Non controlled closures with important consequences Super conducting cavities Ion pump Fast Shutter EXP Arc Arc OLAV 1 Workshop CERN

  7. CERN Fast Valves: LEP2 • Functional problems and solutions • Mechanical: • Deformation of shutter blade • Radiation damages on • Electro-magnetic actuator • Electro-pneumatic distributor • Electrical: • Closing of shutter due to power cuts and other perturbations • Low radiation resistance of part of the electronics • Solutions: • Re-design of shutter blade • New shutter controller • Replacement of low radiation resistant parts Radiation zone Controller Valve box Fast shutter OLAV 1 Workshop CERN

  8. CERN Fast Valves: AD ring • Recent installed (1997) Fast Valve in the AD ring • Commercial available system • Aperture 63 mm, ~15 ms overall closing time • Equipped with five detecting elements around the different experiments in the extraction lines (20 to 35 m away from valve, each individual detecting element generates a trigger to close) • To protect: • AD baked UHV main ring vacuum system. • Septa, Kicker magnets and other delicate equipment. • Machine functionality after 7 runs: • No real incidents • Many Fast Valve closures related to pollution of the detection element OLAV 1 Workshop CERN

  9. CERN Fast Valves: LHC? • Fast Valves / Shutters for the LHC? • The goal of the fast valves will be to protect the LHC machine from the potential dangers of the LHCb- experiment. • Two independent vacuum systems, separated with 0.25 mm AlMg3 foil (supports only 10 mbar pressure difference) • 2 mm thick, ~Ø650 mm, concave exit foil (beam vacuum inside, atm pressure outside) OLAV 1 Workshop CERN

  10. CERN Fast Valve : LHC? • Closing scenarios LHC Fast Valves Fast Valve Closed Machine Secured Detection and Trigger Generation Start Beam Dump Beam Dump OK Valve chain broken Fast Valve Closing A t1A t2A t3A t0 t1B t2B t3B Time line Start Beam Dump Beam Dump OK Fast Valve Closed Machine Secured Detection and Trigger Generation Valve chain broken B Fast Valve Closing to= trigger/interlock signal arrives. t1= beam dump OK. t2= fast valve 1/2 closed. t3= fast valve closed, machine secured. Scenario A only valid for LHCb if t3A < 20 ms Scenario B only valid if: t1B<t2B OLAV 1 Workshop CERN

  11. CERN Fast Valves: LHC? • A fast valve or shutter should never tough the LHC beam: • Destruction of fast valve • Quenches of magnets • Important damage to machine electronics in the tunnel • Damage to the detector of the experiment involved • Important radioactivity in this part of the machine SPS beam interaction with fast shutter plate OLAV 1 Workshop CERN

  12. Summary • Fast Acting Valves/Shutters = Compromise • Installing a security element to protect the vacuum system of a high energy accelerator • Installing an element with potential risks to disturb the operation of a high energy accelerator • Fast, precise and sensitive detection will result in fast closures and security to system • But: • High risk of false triggers • Many unnecessary closing of fast shutters • Increase of machine down time Installation of Fast Acting Valves/Shutters in the LHC is not confirmed OLAV 1 Workshop CERN

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