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RF for the LHeC

RF for the LHeC. 1.3) RF design for the ring-ring option 2.1) RF design for the ring- linac options. E. Ciapala CERN. 1.3) RF design for the ring-ring option:. i . RF design RF Power and Voltage, Margins Frequency choice, # Cavities, # klystrons Footprint

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RF for the LHeC

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  1. RF for the LHeC 1.3) RF design for the ring-ring option 2.1) RF design for the ring-linacoptions E. Ciapala CERN RF Systems - LHeC Meeting 5th July 2010

  2. 1.3) RF design for the ring-ring option: • i. RF design • RF Power and Voltage, Margins • Frequency choice, • # Cavities, # klystrons • Footprint • ii. Space estimate for the alcoves / bypasses for cavities and klystrons • iii. Crab Cavity - Rama Calaga (CERN), Grame Burt (CI) RF Systems - LHeC Meeting 5th July 2010

  3. Energy = 70 GeV (50 GeV) RF and beam parameters – 2008/9 Workshops • Energy loss / turn @ 70 (50) GeV= 707 (184) MeV • Beam current Ib= 74 mA • Beam Power Pb= 54 (14) MW (Losses due to synchrotron radiation) • Total RF voltage Vrf= 900 (250) MV • (Overvoltage for QL, + Some Reserve ....) • Frf= 1002 MHz, h = 89100 • Fs = 1406 (1124) Hz, Qs = ~0.125 (0.1) RF Systems - LHeC Meeting 5th July 2010

  4. Energy (RR) = 60 GeV (50 GeV) New RF and beam parameters 27.7.2010 RF Systems - LHeC Meeting 5th July 2010

  5. Energy = 60 GeV RF system from parameters list 27.7.2010 • Energy loss / turn @ 60 GeV= 379 MeV • Beam current Idc= 131 mA • Beam Power Pb= 50 MW(Losses due to synchrotron radiation) • (NOTE – At 104 GeV LEP had ‘only’ 20 MW....) • Total RF voltage Vrf= 430 MV gives QL 100 hrs • Overvoltage for QL, + Some Reserve => 500 MV • Total RF power needed (margins – WG loss, LLRF, critical coupling, other) • => 60 MW cw (t.b.c) • Note 40 % efficiency Wall Plug to RF... (Factor 2.5 in electricity...) • # cavities ? • # klystrons ? depending on frequency ?.... RF Systems - LHeC Meeting 5th July 2010

  6. Energy = 60 GeV, 400 MHz RF500 MV, 60 MW.Like 400 MHz LHC RF (3 MV / cavity maximum) RF system at 400 MHz • h = 35640 (1 bunch per 10 buckets) • 168 cavities, 3MV/cavity => 42 LHC style 4-cav SC modules (8m long) => 168 m + 20% • 350 kW/cavity, within LHC power coupler ratings • => RF Config: 168 klystrons, or 84 700 kW klystrons, each driving 2 cavities PC Power Converter PC D. Valuch SPL layout example RF Systems - LHeC Meeting 5th July 2010

  7. Energy = 60 GeV, 721.4 MHz RF, 500 MV, 60 MW. Use SPL type cavity = > slightly smaller than SPL 704 MHz cavity, use same cryostat, tuner, couplers etc RF system at 721 MHz • h = 64152 (1 bunch per 18 buckets) • Assume 250 kW per coupler, 240 cavities (Reasonable) • 2.1 MV/cavity only needed, i.e. single cell (SPL spec is 25 MV for 5 cells) • 8 single cell cavities in a 30 8 m cryomodule ? Total length = 30 * 8 = 240 m • Feed 2 cavities with one 500 MW klystron, 120 klystrons • Large beam current - HOMs ? - Studies needed • Not an efficient option, since limited by coupler power. RF Systems - LHeC Meeting 5th July 2010

  8. 2.1) RF design for the ring-linacs option: • i. RF design • RF Power and Voltage, Margins • Frequency choice, • # Cavities # klystrons • ii. Space estimates in the tunnels RF Systems - LHeC Meeting 5th July 2010

  9. RF design for the linacs I-III • total length, required cavities, power etc.) RF Systems - LHeC Meeting 5th July 2010

  10. RF design for the linacs I-III Parameters (Frank) RF Systems - LHeC Meeting 5th July 2010

  11. RF design for the linacs I-III – More Parameters RF Systems - LHeC Meeting 5th July 2010

  12. Energy = 30 GeV, Use 701.4 MHz RF, allowed by 50 nS bunch spacingPulsed 10 Hz 5 ms, Ipk = 16 mA, Iav = 0.64 mA SPL cavity = > Very close to SPL 704 MHz cavity, use same cryostat, tuner, couplers etc. Linac p-60 RF system at 701 MHz • 25 MV/m (SPL) cf 31.5 (ILC) • 1.06 m/cavity => 26.6 MV/cav => 1132 cavities (!) • Ipk = 16mA => Pcavpk = 420kW per cavity (similar to 20 mA SPL @ 500 kW/cavity) • Iav = 0.64 mA, Pcavav = 17 kW per cavity (low) – no issue for power couplers • Total average klystron power/cavity = 19.2 MW (Low) • Run with one 2 MW klystron per four cavities, not ideal but best for economy • => 284 klystrons + their modulators for pulsed operation!! • 8 cavities in a 15 m cryomodule (SPL design V. Parma) Total length = 2km + 20% • A very impressive linac .... RF Systems - LHeC Meeting 5th July 2010

  13. Energy = 2 * 10 GeV/pass, 701.4 MHz RF, allowed by 50 nS bunch spacingCW 10 mA SPL cavity = > Close to SPL 704 MHz cavity, use same cryostat, tuner, couplers etc ERL RF system at 701 MHz • 20 MV/m (SPL) (More conservative than p-60) • 1.06 m/cavity => 21.2 MV/cav => 944 cavities (!) • Ipk = Iav = 10 mA • Ptot = 22 MW (losses in arcs ?) => 23 kW per cavity - very low • No challenge for power couplers, power sources • Again, 8 cavities in a 15 m cryomodule (SPL design V. Parma) Total length = 2km + 20% • A very impressive linac, but a less impressive power system RF Systems - LHeC Meeting 5th July 2010

  14. Conclusions • Ring • Huge synchrotron rad losses in ring version at the 131 mA current • Best to stick to low frequency cavity for this current (power couplers) • One or two cavities per klystron • Don’t forget wall plug to RF power efficiency … • Linacs • p-60 needs a lot of hardware, cavities, klystrons, power modulators • Better to stay with 25 MV/m in estimates • ERL … looks attractive.. • Need to set up small group for further study…. RF Systems - LHeC Meeting 5th July 2010

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