UPDATE OF THE SPS KICKERS

Transcription

1 UPDATE OF THE SPS KICKERS B. Salvant and E. Métral APC action (0//06): The Committee but it stressed the importance of evaluating the effect of the resonance peaks observed at low frequency on the longitudinal and transverse stability of the 25 ns and 75 ns LHC beams before going any further in the programme of modification of the extraction kickers Longitudinal impedance of all the SPS kickers Vertical impedance of all the SPS kickers Analysis of the effect of metallic stripes on the MKE-L0 Appendix: Vertical impedance î Tsutsui vs. Zotter Appendix2: Vertical impedance of each kicker in 2006 Elias Métral, APC meeting, 27/04/07 /22

2 TABLE OF THE KICKERS APERTURES IN 2006 AFTER CROSS-CHECK CHECK WITH E. GAXIOLA (G. Arduini,, 0/06/06) KICKERS IN PARTICLE %06s PC %le GAMMA %le LENGTH %le GAMMATR %le Q %le Q2 %le DQ %le DQ2 %le ORIGIN %9s MAD-X DATE %08s TIME %08s * NAME s [m] LENGTH [m] BETX [m] DX [m] BETY [m] FULLAPERX [mm] FULLAPERY [mm] $ %s %le %le %le %le %le %le MKQH.653** MKQV MKDV.73 MKDVA MKDV.736 MKDVB MKDH.75 MKDHA MKDH.754 MKDHA MKDH.757 MKDHB MKPA.93 MKPA MKPA.936 MKPA MKPC.952 MKPC MKP.955 MKP MKE.463 MKEL MKE.4634 MKEL MKE.4637 MKES MKE.465 MKES MKE.4654 MKEL MKE.663 MKEL MKE.6634 MKEL MKE.6637 MKES MKE.665 MKES ** inner dimensions of the ceramic insert Length of the ferrite ~ 20% smaller Elias Métral, APC meeting, 27/04/07 2/22

3 KICKERS IN 2007 Discussion with L. Ducimetiere (26/04/07) The spare kicker MKE-L0 (all ferrite cells equipped with serigraphed interleaved metallic stripes) has been put in 663 (replacing the MKE-L8 which has been removed) The MKE-S3 in 6637 has been removed and replaced by the MKE-S6 in 665 (with impedance reduction on 2 cells only) î Conclusion: Only 8 MKE kickers in the SPS in 2007 (9 in 2006) - 6 not shielded (8 in 2006) - fully shielded (not present in 2006) - shielded on 2 cells only (present in 2006) Elias Métral, APC meeting, 27/04/07 3/22

4 MKE AND MKP KICKERS Example of cross sections of the SPS MKE and MKP kicker magnets (F. Caspers, Chamonix X) î From the impedance point of d view, a SPS kicker can be b approximated by the following a sketch Beam Vacuum Ferrite Perfect conductor Elias Métral, APC meeting, 27/04/07 4/22

5 F. Caspers et al., CERN- SL (AP) LONGITUDINAL IMPEDANCE (/4) Comparison between longitudinal measurements in 2000 and in 2006 Tsutsui Measurements on SPS MKE Kicker on 0/2000 Z 2006 measurements Measurements on SPS MKE Kicker on 0/2000 Tsutsui Elias Métral, APC meeting, 27/04/07 5/22

6 LONGITUDINAL IMPEDANCE (2/4) H. Tsutsui, CERN-SL (AP) Re [Z // /L] Im [Z // /L] Re [Z // /L] Im [Z // /L] î a (with the perfect conductor) is very important as found by Tsutsui, F. Caspers and Tsutsui s formula should be used Elias Métral, APC meeting, 27/04/07 6/22

7 LONGITUDINAL IMPEDANCE (3/4) Confirmed by the new formula from Benoit (round geometry) Should be close to the round case! Round chamber Re [Z // /L] Im [Z // /L] Re [Z // /L] Im [Z // /L] Elias Métral, APC meeting, 27/04/07 7/22

8 LONGITUDINAL IMPEDANCE (4/4) Real part for each kicker Im. part for each kicker î ~ 5-6 Ω at low frequency Elias Métral, APC meeting, 27/04/07 8/22

9 TRANSVERSE IMPEDANCE (/3) Comparison between measurements and theory Meas. by F. Caspers, T. Kroyer & E. Gaxiola Im MKE kicker Zotter Burov-Lebedev 2-wire 2-wire ê shielded Res. loop HReL ê shielded Re Theory plotted before the measurements! Elias Métral, APC meeting, 27/04/07 9/22

10 TRANSVERSE IMPEDANCE (2/3) Plot of the vertical impedance for all the 20 SPS kickers in 2006 (taking into account the flat chamber + betatron function at the kicker) Zotter s formalism 8 6 Real part Im. part Elias Métral, APC meeting, 27/04/07 0/22

11 TRANSVERSE IMPEDANCE (3/3) Zoom between 0 and 500 MHz Real part Im. part î ~ 7 MΩ / m at low frequency î ~ 7 (3 / 2) = 0.5 MΩ / m should be measured (from kickers) when measuring the vertical coherent tune vs. intensity (dipolar + quadrupolar) H. Burkhardt measured ~ 24 MΩ / m for the whole SPS machine (APC 0//06) Elias Métral, APC meeting, 27/04/07 /22

12 METALLIC STRIPES ON MKE-L0 Courtesy of E. Gaxiola (APC, 0//2006) Elias Métral, APC meeting, 27/04/07 2/22

13 LONGITUDINAL IMPEDANCE OF MKE-L0 Courtesy of T. Kroyer (APC, 0//2006) î Significant reduction of the (real part here of the) longitudinal impedance (and associated power loss) Elias Métral, APC meeting, 27/04/07 3/22

14 TRANSVERSE IMPEDANCE OF MKE-L0 (/7) Zoom between 0 and 500 MHz (of the picture in page 9) Im Re Zotter Burov-Lebedev 2-wire 2-wire ê shielded Res. loop HReL ê shielded Elias Métral, APC meeting, 27/04/07 4/22

15 TRANSVERSE IMPEDANCE OF MKE-L0 (2/7) Zoom between 0 and 200 MHz.5 Im Re Zotter Burov-Lebedev 2-wire 2-wire ê shielded Res. loop HReL ê shielded Elias Métral, APC meeting, 27/04/07 5/22

16 TRANSVERSE IMPEDANCE OF MKE-L0 (3/7) Fit of the most critical resonance by a resonator Resonator : R y = 5 MΩ/m, f r = 90 MHz, Q = 4 Resonator 2: R y = 5 MΩ/m, f r = 90 MHz, Q = 0 î Worst case R e H Z y L@MWêmD R e H Z y L@MWêmD Elias Métral, APC meeting, 27/04/07 6/22

17 TRANSVERSE IMPEDANCE OF MKE-L0 (4/7) Resonator wake-field and coupled-bunch instability rise-times for batch of 72 bunches (.5 0 p/b) at 26 GeV/c spaced by 25 ns êhpc m mld Resonator Resonator 2 êhpc m mld î Rise-time = Infinity! Bunch spacing = 25 ns = 7.5 m î Rise-time = 233 turns (260 ms) N.B.: The effect of the b-function is neglected here, but the b s are smaller than the average one of 42 m (î conservative approach) Elias Métral, APC meeting, 27/04/07 7/22

18 TRANSVERSE IMPEDANCE OF MKE-L0 (5/7) For 9 shielded MKE kickers (and worst case) êhpc m mld 0 êhpc m mld î Rise-time = 73 turns (27 ms) Bunch spacing = 25 ns = 7.5 m î Rise-time = Infinity! Bunch spacing = 75 ns = 22.5 m Elias Métral, APC meeting, 27/04/07 8/22

19 TRANSVERSE IMPEDANCE OF MKE-L0 (6/7) î The SPS RW coupled-bunch instability rise-time at 26 GeV/c is ~ 90 turns, i.e. much smaller than what computed previously î Should be OK! Elias Métral, APC meeting, 27/04/07 9/22

20 TRANSVERSE IMPEDANCE OF MKE-L0 (7/7) Example of the wake-field induced by the classical Broad-Band impedance in the SPS: R y = 0 MΩ/m, f r =.3 GHz, Q = W êhpc m mld Only m! Elias Métral, APC meeting, 27/04/07 20/22

21 CONCLUSION (/2) The longitudinal impedance of the SPS kickers seems well described using Tsutsui s formula (considering both ferrite plates on top&bottom + metallic plates on both sides) The vertical impedance of the SPS kickers seems well described using Zotter s formalism (considering only the ferrite plates on top&bottom) The serigraphed interleaved metallic stripes reduce considerably the longitudinal impedance (and associated power loss) and slightly the vertical one, introducing some resonances at low frequency, which seem not too harmful î Could be extended to the other kickers! Elias Métral, APC meeting, 27/04/07 2/22

22 CONCLUSION (2/2) The low-frequency imaginary longitudinal impedance Z l / n of all the 20 kickers in 2006 is ~ 5-6 Ω The low-frequency imaginary vertical (dipolar) impedance of all the 20 kickers (taking into account the flat chamber + betatron function at the kickers) is ~ 7 MΩ / m Elias Métral, APC meeting, 27/04/07 22/22

23 Appendix: Vertical impedance î Tsutsui vs. Zotter (/4) Zotter s formalism a = 67 mm MKE KICKER Elias Métral, APC meeting, 27/04/07 23/22

24 Appendix: Vertical impedance î Tsutsui vs. Zotter (2/4) Zotter s formalism with perfect conductor outside (as Tsutsui) Elias Métral, APC meeting, 27/04/07 24/22

25 Appendix: Vertical impedance î Tsutsui vs. Zotter (3/4) Scan in half gap a using Tsutsui s formula a = 0 mm a = 6 mm a = 20 mm a = 40 mm Elias Métral, APC meeting, 27/04/07 25/22

26 Appendix: Vertical impedance î Tsutsui vs. Zotter (4/4) a = 68 mm a = 00 mm a = 500 mm a = 000 mm Elias Métral, APC meeting, 27/04/07 26/22

27 Appendix2: Vertical impedance of each kicker in 2006 (/5) (taking into account the flat chamber + betatron function at the kicker) MKQH.653 MKQV MKDV.73 MKDV Elias Métral, APC meeting, 27/04/07 27/22

28 Appendix2: Vertical impedance of each kicker in 2006 (2/5) MKDH.75 MKDH MKDH.757 MKPA Elias Métral, APC meeting, 27/04/07 28/22

29 Appendix2: Vertical impedance of each kicker in 2006 (3/5) MKPA.936 MKPC MKP.955 MKE Elias Métral, APC meeting, 27/04/07 29/22

30 Appendix2: Vertical impedance of each kicker in 2006 (4/5) MKE.4634 MKE MKE.465 MKE Elias Métral, APC meeting, 27/04/07 30/22

31 Appendix2: Vertical impedance of each kicker in 2006 (5/5) MKE.663 MKE MKE.6637 MKE Elias Métral, APC meeting, 27/04/07 3/22