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Pressure data from SPS MDw35 H.Neupert, M.Taborelli

Pressure data from SPS MDw35 H.Neupert, M.Taborelli. For SPSU, 23/09/2010. No RF shields. MBB. MBB015. MBB. MBB 289 51530. MBB 188 51490. MBB177 51550. QD. P. P. P. 51340. 51480. 51540. Comparison of p-rise for 50 ns and 25 ns in MBB.

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Pressure data from SPS MDw35 H.Neupert, M.Taborelli

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  1. Pressure data from SPS MDw35 H.Neupert, M.Taborelli For SPSU, 23/09/2010

  2. No RF shields MBB MBB015 MBB MBB 289 51530 MBB 188 51490 MBB177 51550 QD P P P 51340 51480 51540

  3. Comparison of p-rise for 50 ns and 25 ns in MBB 4x 36 (50 ns) and 4x72 bunches, 450GeV, almost same number of ppb

  4. Let us look at this on a linear scale since the important is the absolute p increase, not relative (if we assume that the p increase is not related to the background p) The absolute increase (peak value Dppeak) by comparing the two cases: un-uncoated (1.8 E-7) > co-coated (1E-7 mbar) un-uncoated (1.8 E-7) > co-uncoated (1.4E-7) > co-coated (1E-7 mbar) NB: the co-uncoated region has not RF shield (effect is neglected here)

  5. However…50 ns: The ranking of the signals changes with different intensities of the bunches More protons gives more pressure rise for all The rise is un-uncoated< co-uncoated < co-coated: The coated are more sensitive to ppb increase

  6. Again more clear in linear scale Dppeak un-un (2E-8) < Dppeak co-un (3E-7) < Dppeak co-co (4.2 E-7)

  7. In conclusion The uncoated-uncoated MBB have a largest absolute Dp when going from 50 ns to 25 ns --We know (ECM) that for StSt there is more e-cloud at 25 ns than 50 ns --This suggests that in a situation with more e-cloud the absolute pressure rise is larger in the uncoated If we increase the number of protons at fixed spacing (50 ns) there is only marginally more e-cloud (ECM data presented before) in StSt: this is consistent with the observed small change in Dp un-un But in the coated the increase of peak pressure with the number of protons is large: either e-cloud increases there more strongly than in StSt (?) or there is another mechanism of Dp rise, not related to e-cloud

  8. Proposal for next MDs Do a systematic run by looking at Δp and ECM signal as a function of the protons by trying to change as few parameters as possible: try to change the number of protons in two different ways, as protons per bunch and as number of bunches

  9. Future SPS liners and magnets No intervention until december/january --beginning 2011: Insertion of 2 MBA and one quadrupole with coating to build a coated half cell: the goal is to show that we can coat also chambers of those shapes, may be we can even just coat them without insertion? --for 2012 the present view is to insert some 20 coated magnets (to be decided if we do only dipoles or all the types?) by coating the chambers separately --liners 2011: -insert in 2011 an a-C coated with one of the new techniques (permanent magnet, loops, CVD…..) -extract DLC liner? Yes, may be not in first run -extract StSt liner? Put a new one as refernce -extract CNe13 :cut and inspect -leave inside the half coated --Dump beam of ions in a coated drift chamber or dipole

  10. ….and in addition • Pumpdown curves for StSt, MBB chamber coated, MBA coated…. • Try to insert a pick-up for electrons in the RF shield region (modified port, cabling to 51340 51480, electronics = one channel of ECM…); not easy for noise, it was already tried, but may be at larger bandwidth

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