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Linac 4 High Power RF

Linac 4 High Power RF. O. Brunner & N. Schwerg. Summary. Installation Phase adjustment campaign High power equipment Procurement of “auxiliaries” New 2.8 MW klystrons LEP klystrons. Installation (1). Klystron hall: WG Phase 1 completed Circulators, RF loads Water distribution

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Linac 4 High Power RF

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  1. Linac 4High Power RF O. Brunner & N. Schwerg

  2. Summary • Installation • Phase adjustment campaign • High power equipment • Procurement of “auxiliaries” • New 2.8 MW klystrons • LEP klystrons

  3. Installation (1) • Klystron hall: • WG Phase 1 completed • Circulators, RF loads • Water distribution • Klystron racks

  4. Installation (2) • tunnel: • WG Phase 2 completed • In process: phase adjustment

  5. Phase adjustment (1) • The distance between the cavities (time of flight of particles) defines the phase difference required between the two RF channels • Adjustment procedure • Measure the actual ΔΦ (i.e. WG electrical length) • Modify WG distribution such to get ΔΦ ≈ 20˚ • Insert a phase shifter(0 - 60˚) in one arm for fine adjustments • Precision of measurements: ≈ 100 ps (≈ 10˚) (circulator comp.: ≈ 100 ps(≈ 10˚)) cavities WG klystron magic T circulators

  6. Phase adjustment (2) => All circulators to be moved (except for PIMS B C & PIMS C D) • ”heavy procedure” • less posts in WG system -> reduces the risk of arcing

  7. High Power equipment: "auxiliaries“(1) • New circulators: contract in preparation (ATF (DE)) (≈ 500kEuros) • RF loads: second batch delivered. On time. • Klystron garages: LEP garages to be refurbished (not started) • RF drive amplifiers: proto under test • Focusing power supplies: Israeli contribution – ok • Arc detectors: proto validated • Blowers: not started • Circulator control units: to be built • Magic Tees: prototype @ CERN. Order placed • Phase shifters: proto validated

  8. High Power equipment: "auxiliaries“(2) • Gun tanks: in production/assembly • Gun tank equipment: resistors, heater transformer & power supplies (TE/EPC)

  9. New 2.8 MW klystrons (1) • Orders were placed in 2011 with CPI and Thales • 4 klystrons each • CPI:first klystron delivered in July. Successfully tested and validated in September. • Thales: first klystron presently under tests at the factory (expected delivery: end of Oct.) • Delivery schedule • CPI & Thales: • second klystron in January’13, • all four klystrons before Fall ‘13

  10. New 2.8 MW klystrons (1) • CPI klystron

  11. LEP klystrons: what de we have? EEV (12) 19 “eligible” LEP klystrons Philips (4) Thomson (3)

  12. LEP klystrons: what do we need for L4? output power 1.3 MW • we need klystrons that can produce > 1.3 MW • we need klystrons that can be run at different working points • The LEP klystron were designed and tuned to reach optimum efficiency (>65%) when operated at well defined operating working points (HV, Icat, drive power, impedance seen by klystron, etc) • The klystrons suffer from instabilities when operated under different conditions

  13. How do we test the LEP klystrons ? PfwdPrfl • DC power settings: 108 kV, 22 A • Increase klystron power as a function of: • Circulator compensation current (impedance change) • Phase variation (to mimic the beam passage) • Detect at which output power the instabilities occur RF load (Cu cavity) circulator klystron Phase shifter RF load

  14. LEP klystrons performance results Joanne: 1300 kW Emily: 1010 kW Alison: 1145 kW Julie: 1050 kW (now dead) Lynda: 1100 kW (3 MeV) Elia: < 1000 kW (SM18)

  15. LEP klystrons: what can we expect? • 5/12 EEV tubes tested: • one is very good :1300kW • others are limited to about 1100 kW or less (one died after the test) • Phillips & Thomson tubes are known to be even more prone to oscillations than EEV klystrons • 1/7 tested: < 1000 kW Question: can one dream of getting significantly more than about 1 MW per LEP klystron ? (in the required operating mode) NO !

  16. Conclusions (1) • Installation: • In progress • Phase adjustments in progress – heavy duty, crucial for future reliability • Adjustments: ≈ 10˚ • High power equipment & auxiliaries • Preparation is ongoing • All “big contracts” placed (new circulators: in preparation) • 3 operational test places (B112, 3MeV, SM18) • New 2.8 MW klystrons • Some delays • First CPI klystron successfully tested and validated at CERN • All klystrons shall be delivered before Q3 2013

  17. Conclusions (2) • LEP klystrons • Preparation and test in progress (slow down to be expected with the departure of Nikolai!) • 1/3rd of the LEP klystrons have been tested: • All are capable of more than 1.3 MW peak power (for well defined WP, as expected!) • All (except one) are unstable in the region 1 – 1.3 MW (as expected!) • Despite all efforts made instabilities could not be suppressed/reduced • One tube died after 6 months of testing: vacuum leak in RF input connector Stability maps (measured according to the L4 mode of operation) show that the LEP klystrons modified for Linac4 are limited to 1 – 1.1 MW • We need clear instructions from Project Leader: • Do we continue spending CERN resources on this effort? • What is the strategy for klystron installation (Do we install them? Which klystron at which position? Is there a power limit?) • How many additional 2.8 MW klystrons that must be ordered ?

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