PEP-II RF System Status and Upgrades Vojtech Pacak, Heinz Schwarz Klystron Department PEP-II Machine Advisory Committee Review October 25-27 2006

Summary RF system performance Configuration RF aborts - Run 5 List of leading abort causes Klystrons Status of installations and spares RF system upgrades New stations HER 12-4 and HER 4-6 Conclusions

1) RF System Configuration – Runs 5A/B - 6* Cavity Parameter HER LER Oct 2005 PEAK Run 5A Aug 2006 Run 5B PredictedMaximum Run 6 Predicted Maximum RF Voltage/Ring (MV) 13.4 15.4 18.5 4.5 4.05 5.5 Number of Klystrons 9 11 4 Number of Cavities 26 28 8 Gap Voltage/Cavity (kV) 515 592 661 562 507 687 Dissipated Power/Cavity (kW) 36 47 59 42 34 63 Beam Power/Cavity (kW) 242 260 285 264 372 Total RF Power/Cavity (kW) 278 308 344 306 294 435 Klystron Power (kW) 970 989 979 700 713 980 Beam Current (A) 1.74 1.875 2.2 2.94 2.90 4.0 * Number of Bunches (n) 1732 1722 Peak Lumin. (1033 cm-2sec-1) 10.025 12.069 15.1* * 15.1 * * * Prediction before BPM’s failures ** Luminosity predictions assuming y, y* and n remain fixed.

Run 5 Abort Statistics 4/21/05 - 8/18/06 Last event Count Stations Description 03/03/2006 425 ler(4),her(421) IP Vacuum event with/without radiation 01/27/2006 234 ler(215),her(19) didt with transverse 09/05/2005 89 multiple Transverse instability (TFB) 08/14/2006 81 Unknown 66 Cavity 1 arc (RE reported) 07/16/2006 51 Klystron arc 08/17/2006 48 ler(29),her(19) Longitudinal instability 07/30/2006 43 Power dip (Region 8 or 4) 08/05/2006 41 Slow or stuck tuners 08/16/2006 40 Site Power Dip Top 10 events account for 1118 faults (58%) Color code Non-Rf Aborts Courtesy: Dan Van Winkle Station Faults HER non Rf 566 LER non Rf 479 HR21 110 LR44 84 LR43 82 HR25 81 HR26 80 HR22 HR83 78 LR42 77 HR81 75 HR41 52 HR85 41 HR23 32 LR45 25 897 RF aborts/483 days All aborts average per day: 4.0/day The RF related aborts only: 1.8/day Compared to 2.9/day for Run 4

2) RF aborts - Run 5 Cav1(2) arcs, 66 counts Klystron Arcs, 51 counts Majority (~80%) in HER 8-1 and HER 12-1, observed for many years. Blamed on deposit of out gassing debris from the ring arcs into the first RF cavity, compromising the multipactor coating on the window. Typically the operating voltage of these cavities is reduced to limit the trips. Will replace the windows on the first cavities of station 8-1 and 12-1 during the down time Klystron Arcs, 51 counts Observed HV arcing in the gun Philips #7, (LER 4-3). Diagnosed by observing a large drop of klystron perveance. klystron voltage set < 73 kV Failed SLAC klystron #6 – due to arcing at the window Klystron was replaced Stuck Tuners, 41 counts A chronic problem increasing during the very hot days. Tuner stops moving and station trips on high reflected power Problem analyzed by Claudio Rivetta who found the cause. The solution will be implemented during the down time.

2) RF aborts - Run 5 continued Site power dips, 40 counts 230 kV line voltage fluctuation affects all operations Caused by PG&E, not under our control. Region 4 and 8 power dips, 43 counts HV dip in all RF stations in the region, mostly region 8. More thorough investigation is planned after the 2006 down time. HVPS Crowbar SCR’s develop excessive leakage in certain manufacturing lots. Investigated by SLAC and EUPEC, found problem on ~10% devices. Solution: regular testing and elimination of the devices prone to leakage

3) Klystron Issues Spare klystron status Klystron failure: Situation improved since the last January With new SLAC klystrons coming on line we now have several old Philips klystrons as spares. Philips #1, over 50,000 filament hours Philips #2, power limited at ~850 kW, over 50,000 filament hours Philips #5, deformed collector body and is power limited to ~ 600 kW. Philips #6, power limited at ~ 750 kW. Klystron failure: HER 12-2, SLAC #6 broken output ceramic window – first failure of SLAC made tube in operation Failure caused by the insufficient tightening of the inner coax bolt that clamps the center conductor contact on the window vacuum side. Philips klystrons are reaching end of life Several tubes over 50,000 hours. LER 4-5, Philips #3, power limited at ~850 kW, sideband oscillation 3 MHz Region 12 cooling capacity Increased # of SLAC klystrons need increased cooling supply. The problem will be addressed during the down time.

4) Klystron Manufacturing Schedule Start bake Scheduled Test Complete Comment SLAC #8A completed 3/6/06 HER 12-1, installed Apr 2006, replaced Philips #6. SLAC #7B 4/11/06 HER 12-2, installed May 2006,replaced SLAC #6 with broken window. SLAC #9B 5/17/06 HER 4-1, installation 2006 shutdown, replaced Philips #2. SLAC #10A 6/23/06 HER 12-5, installation 2006 shutdown, replaced Philips #1. Philips #8C n/a 10/20/06 HER 4-6, new station installation 2006 shutdown, (klystron rebuilt at CPI), Processing problems – gassy. Philips #4B 11/10/06 LER replacement, (klystron rebuilt at CPI). SLAC #11A 12/1/06 HER 12-4, new station installation 2006 shutdown. SLAC #12A 12/15/06 2/23/07 LER replacement. SLAC #6B 2/15/07 4/15/07 Courtesy: Chris Pearson, KLY

4) Klystron Replacement Schedule Shutdowns Power Limited Station Q3 2005 Q4 2005 Q1 2006 Q2 2006 Q3 2006 Q4 2006 >Q1 2007 LER 4-2 Marconi 4 LER 4-3 Philips 7 SLAC 12 LER 4-4 Marconi 1 SLAC 6 LER 4-5 Philips 3 Philips 4 HER 4-1 Philips 2 SLAC 9 HER 4-6 N/A Philips 8 HER 8-1 SLAC 5 HER 8-3 SLAC 3 HER 8-5 SLAC 4 HER 12-1 Philips 6 SLAC 8 HER 12-2 SLAC 7 HER 12-3 SLAC 1 HER 12-4 SLAC 11 HER 12-5 Philips 1 SLAC 10 HER 12-6 Philips 5 SLAC 2 New Installation SLAC Tubes Run 5A Run 5B Run 6 NOW

5) PEP-II RF Station Installation HER Presently Nov 2006 LER Oct 2006 4-1 2 4-2 4-6 4-3 8-1 4 4-4 8-3 4-5 8-5 12-1 12-2 12-3 12-4 12-5 12-6 Installation 2006 shutdown Total Kly/Cav 9/26 11/28 4/8

4) RF Stations/Upgrades New RF stations HER 12-4 split 4-cavity old station HER 12-3 SLAC #11 ready for testing PEP installation Nov – Dec 2006 New station HER 4-6 2 cavities assembled and currently conditioning klystron Philips #8 tested Klystron replacement – total of 4 this year HER stations 4-1, 12-1, 12-2, 12-5 3 are SLAC klystron, 1 Philips klystron rebuilt at CPI Installation Apr – Dec 2006

Conditioning of the cavity

5) Conclusions PEP RF systems worked reliably this last run! For Run 5: PEP RF systems worked reliably this last run! RF related abort rate average 1.8/day, compared to 2.9/day for Run 4. Run 5 started with only one spare klystron and four power limited operating klystrons. Since March, new klystron delivery one every ~ 5 weeks. Two new SLAC klystrons installed during the run in HER ring. The most frequent RF aborts: Arcing and vacuum trips of cavity #1 in stations HER 8-1 and 12-1. Lowered cavity voltage when arcing Will replace ceramic windows in cav1 of 8-1 and 12-1 Klystron arcs in LER 4-3 and HER 12-6. operates with lowered klystron voltage on LER 4-3 replaced klystron in 12-6 Stuck tuners. Found and implemented solution – (Claudio Rivetta) For Run 6: Two new HER RF stations, HER 12-3 split and new 2-cavity HER 4-6. Only one power limited klystron in LER 4-5 remaining. Three more new/repaired klystrons will be available for installation in LER.

Acknowledgements To all members of the PEP-II RF Systems Taskforce Specific thanks to Alan Hill, Chris Pearson, Dan Van Winkle, Claudio Rivetta and Marc Larrus for their input to this presentation.