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PEP-II Machine Advisory Committee Meeting SLAC, April 15-17, 2004 HOM Issues in LER Ring and IR. Recent measurements and calculations. Sasha Novokhatski.

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Presentation on theme: "PEP-II Machine Advisory Committee Meeting SLAC, April 15-17, 2004 HOM Issues in LER Ring and IR. Recent measurements and calculations. Sasha Novokhatski."— Presentation transcript:

1 PEP-II Machine Advisory Committee Meeting SLAC, April 15-17, 2004 HOM Issues in LER Ring and IR. Recent measurements and calculations. Sasha Novokhatski SLAC

2 SN 15-April-2004 PEP-II MAC Session 2 More LER & HER currents – more HOM Heating LER ring –TSP feed-through & Bellows –Vacuum pumps & NEGs (new) HER ring –Bellows (new) Interaction region –Vertex bellows & near bellows

3 SN 15-April-2004 PEP-II MAC Session 3 Fight against high temperatures Water and air cooling –Fans for bellows in all LER and HER regions –Special cooling for vertex bellows Damping High Order Modes by water cooled RF absorbers –HOM absorber in LER arc chamber Improving RF screens

4 SN 15-April-2004 PEP-II MAC Session 4 HOM measurements and computer simulations HOM spectrum measurement: –Signals from BPMs –RF antenna near TSP feed-through –RF antenna near HV cable in vacuum pumps HOM power measurement: –Thermocouples on input and output water cooling system with water-flow measurement Computer simulation: –Calculations with MAFIA and other wake field programs

5 SN 15-April-2004 PEP-II MAC Session 5 HOM absorber in region 4 HOM Absorber TSP 1162 Bellows 2012

6 SN 15-April-2004 PEP-II MAC Session 6 Absorber: ceramic tiles with large loss tangent and water cooling tube

7 SN 15-April-2004 PEP-II MAC Session 7 Effect of absorber on TSP feed-through Temperature LER current Nov. 2002-Apr. 2004

8 SN 15-April-2004 PEP-II MAC Session 8 TSP in the next arc chamber 1153 Nov. 2002-Apr. 2004

9 SN 15-April-2004 PEP-II MAC Session 9 Analog TSPs in region 12 do not have high temperatures Artem Kulikov HOM detectors installed in June 2003

10 SN 15-April-2004 PEP-II MAC Session 10 HOM spectrum measurement: antenna and spectrum analyzer near TSP 1163

11 SN 15-April-2004 PEP-II MAC Session 11 HOM power measurement: digital water flow meter and thermocouples

12 SN 15-April-2004 PEP-II MAC Session 12 Power relations Now we are here

13 SN 15-April-2004 PEP-II MAC Session 13 The hottest bellows in the LER LER Bellow 2012 PR04 with ‘super” fan Nov. 2002-Apr. 2004

14 SN 15-April-2004 PEP-II MAC Session 14 Examples of RF modes. S. Weathersby Magnetic fieldElectric field

15 SN 15-April-2004 PEP-II MAC Session 15 Proposal for absorber for arc bellows Copper buttons Absorber tiles Water cooling tubes

16 SN 15-April-2004 PEP-II MAC Session 16 MAFIA. Stephen Weathersby computation. Comparison of 1-tile thick covered flange absorber with azimuthal 2x3-tile mount and the no absorber Q values.

17 SN 15-April-2004 PEP-II MAC Session 17 HOM spectrum in IP region.

18 SN 15-April-2004 PEP-II MAC Session 18 Vertex bellows Bellow Cavity bunch field ‘‘Mode Converter”

19 SN 15-April-2004 PEP-II MAC Session 19 Vertex bellows. RF Modes. Vertex bellows. RF Modes. Stephen Weathersby computation.

20 SN 15-April-2004 PEP-II MAC Session 20 Quadruple mode

21 SN 15-April-2004 PEP-II MAC Session 21 Damping HOMs in vertex bellows. Simulation study by S. Weathersby. Decreasing Q-value of a bellow cavity by placing absorber Best position of absorber. Low Q decreases power dissipation.

22 SN 15-April-2004 PEP-II MAC Session 22 Power dissipation a bellow cavity

23 SN 15-April-2004 PEP-II MAC Session 23 Absorber on the one side does not well damp modes!

24 SN 15-April-2004 PEP-II MAC Session 24 Absorber on the other side. Still not good damping.

25 SN 15-April-2004 PEP-II MAC Session 25 Absorber on the wall

26 SN 15-April-2004 PEP-II MAC Session 26 Power in a cavity

27 SN 15-April-2004 PEP-II MAC Session 27 HOMs in vacuum pumps

28 SN 15-April-2004 PEP-II MAC Session 28 Vacuum pump (LER PR2:3044) HOM spectrum. Frequency range 0-10 GHz Antenna in HV connector

29 SN 15-April-2004 PEP-II MAC Session 29 Frequency range 3-6 GHz

30 SN 15-April-2004 PEP-II MAC Session 30 Q-value estimation

31 SN 15-April-2004 PEP-II MAC Session 31 RF screen for vacuum pump

32 SN 15-April-2004 PEP-II MAC Session 32 RF screens for NEGs

33 SN 15-April-2004 PEP-II MAC Session 33 Other screen

34 SN 15-April-2004 PEP-II MAC Session 34 Summary More water and air cooling Damping High Order Modes by water cooled RF absorbers Simulation studies on improvement of beam chamber elements and RF screens


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