SuperB RF and HOMs Sasha Novokhatski SLAC National

Super-B: RF and HOMs. Sasha Novokhatski SLAC National Accelerator Laboratory XIII Super B General Meeting May 30 – June 5, 2010 INFN, Isola d’Elba, Italy

Super-B: high efficiency, cite independent project. Sasha Novokhatski “RF/Impedance” RF buildings somewhere 2 06/03/2010

Super-B parameters. March 3, 2010 (Bold: computed values) Units Energy Ge. V Circumference Sasha Novokhatski “RF/Impedance” Base Line Parameter m 6. 7 HER (e+) 4. 18 1258. 4 High Current LER (e-) 6. 7 HER (e+) 4. 18 1258. 4 Tau/Charm (prelim. ) LER (e-) 6. 7 HER (e+) 4. 18 1258. 4 LER (e-) 2. 58 1. 61 1258. 4 mm 4. 69 4. 29 4. 73 4. 34 4. 03 3. 65 4. 75 Bunch length (full current) mm 5 5 4. 4 5 5 Beam current m. A 1892 2447 1460 1888 3094 4000 1365 1766 2 2 1 1 2 2 2 2 Ion gap % RF frequency Revolution frequency Hz Hz 4. 76 E+08 2. 38 E+05 4. 76 E+08 2. 38 E+05 Harmonic number # 1998 Number of bunches # 978 1956 N. Particle/bunch # 4. 36 4. 76 E+08 2. 38 E+05 1998 1956 5. 08 E+10 6. 56 E+10 3. 92 E+10 5. 06 E+10 4. 15 E+10 5. 36 E+10 1. 83 E+10 2. 37 E+10 Bunch current Energy Loss/turn m. A Me. V 1. 935 2. 11 2. 502 0. 865 1. 493 2. 11 1. 930 0. 865 1. 582 2. 11 2. 045 0. 865 0. 698 0. 4 0. 903 0. 166 Momentum compaction Energy spread (zero current) 4. 36 E-04 6. 31 E-04 4. 05 E-04 6. 68 E-04 4. 36 E-04 4. 05 E-04 d. E/E 6. 31 E-04 6. 68 E-04 Energy spread (full current) d. E/E 6. 43 E-04 7. 34 E-04 6. 94 E-04 7. 34 E-04 CM energy spread d. E/E Energy acceptance Synchrotron frequency k. Hz 5. 00 E-04 5. 26 E-04 0. 01 0. 01 3. 01 2. 8 2. 97 2. 77 3. 54 3. 26 2. 96 2. 77 0. 0126 0. 0118 0. 0125 0. 0116 0. 0148 0. 0137 0. 0124 0. 0116 3. 99 2. 12 3. 08 1. 63 6. 53 3. 46 0. 55 0. 29 Synchrotron tune SR power loss MW RF Wall Plug Power (SR only) MW 12. 22 Total RF Wall Plug Power MW 17. 08 Number of cavities 9. 43 19. 98 12. 72 0. 01 1. 68 30. 48 3. 11 12 8 20 12 6 4 Number of Klystrons 6 4 10 6 3 2 Total Number of klystrons 10 RF Voltage MV Rs MW Q 0 b 06/03/2010 Low Emittance LER (e-) Bunch length (zero current) N. Buckets distance 3 HER (e+) 7. 01 10 5. 25 6. 88 16 5. 13 9. 3 5 7. 2 2. 54 1. 94

Beam stability Sasha Novokhatski “RF/Impedance” In electric field of a cavity the beam is stable or oscillates near the stable phase if this phase satisfies the condition On the hand high current beam is a periodic force for a cavity, which is naturally an oscillator. This force is a resonance for the main mode of a cavity, so the excited amplitude can be high ~ loaded quality factor of a cavity 4 06/03/2010

Beam stability Sasha Novokhatski “RF/Impedance” To avoid the resonant excitation we detune the cavity relatively to the beam frequency, which is exactly the klystron frequency. The phase of the excited field will also change with detuning The condition that excited field is smaller than the field seen by the beam, which is excited by the klystron is usually called as Robinson criteria 5 06/03/2010

Robinson criteria Sasha Novokhatski “RF/Impedance” To avoid the resonant excitation we detune the cavity relatively to the beam frequency, which is exactly the klystron frequency. The phase of the excited field will also change with detuning and we can get a stable phase 6 06/03/2010

Sasha Novokhatski “RF/Impedance” Optimal conditions for RF power No reflected power 7 06/03/2010

Cavity frequency shift and optimal coupling factor Sasha Novokhatski “RF/Impedance” • Matching main mode 8 06/03/2010

Sasha Novokhatski “RF/Impedance” Coupling factor and frequency shift for high current regime 9 06/03/2010

Sasha Novokhatski “RF/Impedance” Changing the coupling factor b from 3. 6 to 6 of the PEP-II cavity by modifying the coupling box. 10 06/03/2010 b l /4 Changing the waveguide size

Parked cavity Sasha Novokhatski “RF/Impedance” Voltage from the beam 11 06/03/2010 We need large detuned angle

Low-level feedback Sasha Novokhatski “RF/Impedance” Transfer function 12 06/03/2010 Impedance Loaded Q

Sasha Novokhatski “RF/Impedance” HOMs in RF cavities longitudinal modes 13 06/03/2010

Sasha Novokhatski “RF/Impedance” Transverse modes, may be important for synchro-betatron oscillations. 14 06/03/2010

Sasha Novokhatski “RF/Impedance” Cavity loss factor and power above cut-off 15 06/03/2010

Sasha Novokhatski “RF/Impedance” HOMs power due to cavities 16 06/03/2010

Sasha Novokhatski “RF/Impedance” Beam pipe chamber For these beam pipe geometries loss factor is almost the same, because Al part of LER has larger size. 17 06/03/2010

Sasha Novokhatski “RF/Impedance” Resistive wake 18 06/03/2010

Resistive wall power Sasha Novokhatski “RF/Impedance” LER 19 06/03/2010 HER

Sasha Novokhatski “RF/Impedance” Longitudinal kicker 20 06/03/2010

Sasha Novokhatski “RF/Impedance” Transverse kicker 21 06/03/2010

NEW DAFNE INJECTION KICKER From Fabio Marcellini, ILC’ 08 Sasha Novokhatski “RF/Impedance” Input ports BEAM 22 06/03/2010 Elliptical cross section HV feedthrough Output ports (LOAD) Tapered stripline Strip ceramic supports

Sasha Novokhatski “RF/Impedance” New Injection Kicker Impedance 23 06/03/2010

Sasha Novokhatski “RF/Impedance” SLAC-type Injector and Abort kickers 24 06/03/2010

Sasha Novokhatski “RF/Impedance” Collimators 25 06/03/2010

Sasha Novokhatski “RF/Impedance” HOMs power in Super-B Interaction Region 26 06/03/2010

RF cavity limits Sasha Novokhatski “RF/Impedance” • Cavity voltage and forward power 28 06/03/2010 – Voltage in a cavity is limited by sparks and breakdowns • SLAC PEP-II experience: voltage should be less than 0. 75 MV per cavity – Forward power into a cavity and reflected power are limited by sparks in RF windows • SLAC PEP-II experience: transmitted power should be less than 500 KW per cavity and reflected power less than 10%

Sasha Novokhatski “RF/Impedance” Super-B RF plug power. 29 06/03/2010 Base Line.

Sasha Novokhatski “RF/Impedance” Super-B RF plug power. 30 06/03/2010 Low emittance.

Sasha Novokhatski “RF/Impedance” Super-B RF plug power. 31 06/03/2010 High current.

Sasha Novokhatski “RF/Impedance” Super-B RF plug power. Tau/Charm. Beta=6 32 06/03/2010

Sasha Novokhatski “RF/Impedance” Multi-bunch beam stability 33 06/03/2010 • Threshold for a cavity impedance

Sasha Novokhatski “RF/Impedance” Summary 34 06/03/2010 • A small modification of a coupler box of the PEP-II RF cavities will considerably improve the RF performance of the Super-B. • RF and bunch by bunch feed-back may allow to go to higher currents adding more cavities.