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

P P P MBB MBB MBB015 MBB QD MBB No RF shields

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

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 p peak ) 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)

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

Again more clear in linear scale p peak un-un (2E-8) < p peak co-un (3E-7) < p peak co-co (4.2 E-7)

In conclusion The uncoated-uncoated MBB have a largest absolute p 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 p 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 p rise, not related to e-cloud

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

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

….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 , electronics = one channel of ECM…); not easy for noise, it was already tried, but may be at larger bandwidth