1. SPSU 171109 M.Taborelli Results from MD week 45 Views of extracted liners and RF shields M. Taborelli for SPSU team

2. SPSU 171109 M.Taborelli Pressure measurements after coating the RF shields between coated magnets -Start of beam -Pumping speed from p decay? -P change from 1 to 2 batches -P at different bunch spacing

3. SPSU 171109 M.Taborelli Start of MD: week 33 and week 45 Pressure [mbar] co-co un-un co-un 1x72, 26GeV MDw45 MDw33 450GeV No main difference in pressure rise after coating the RF-shields Amplitude is lower for coated (why?)

4. SPSU 171109 M.Taborelli Pressure [mbar] 450GeV 26GeV Effect of acceleration on the shape of the pressure curve

5. SPSU 171109 M.Taborelli 1x72 450GeV 1x12 450GeV Is the pressure recovery different in coated and uncoated magnets ? would be linear on the ln(p) plot if it is only emptying a volume and constant outgassing P=p o exp(-S.t/V)+qsubtract q Pressure [mbar] Assume there is no effect of outgassing from the 12 bunches. Then it

6. SPSU 171109 M.Taborelli after q subtraction….almost linear with same slope for both Pressure [mbar] -from the slope of ln(p) and a volume of 49l we get S=0.15 l/s……??? -the value is too low: it means possibly that we are looking at a part of the curve where the degassing is not constant during time

7. SPSU 171109 M.Taborelli Subtract q Also here the slope gives only S=0.6 l/s, influenced by outgassing and not just emptying a volume (nominal 17 l/s at the RF-shield, which should give a 1/e decay in 2.9s) …again on another time period (beam off) Pressure [mbar]

8. SPSU 171109 M.Taborelli Pressure [mbar] -Normalize the pressure to equal the values of both magnets (…should not affect the exponent of the decay or 1/t behaviour for outgassing) -in the steepest part the decay is quite similar for both magnets, but changes after few seconds Look on the fast decay part:

9. SPSU 171109 M.Taborelli From 1 to 2 batches, 72 bunches 450GeV With a very weak second batch the p decreases: the reason is the cleaning of the ring from protons circulating out of the “buckets” ( e-cloud also decreases……) Pressure [mbar]

10. SPSU 171109 M.Taborelli 3batches 25 ns 1batch 25ns long bunches 1b 50ns 3b 50ns 4b 50 ns Effect of bunch spacing

11. SPSU 171109 M.Taborelli Effect of bunch spacing: summary

12. SPSU 171109 M.Taborelli Liners and RF shields extracted from SPS

13. SPSU 171109 M.Taborelli CKr4 liner cut open: used in scrubbing run w24/2008 Uncoated regions

14. SPSU 171109 M.Taborelli CNe8 liner cut open: used in MD run w28/2008

15. SPSU 171109 M.Taborelli StSt liners (run w24 and w28 or w33+41) Not sure that the visible line is really due to e-cloud

16. SPSU 171109 M.Taborelli RF shield with antenna holes 24mm, extracted from SPS on 6/10/2009 from 51540 (between coated magnets) 30/09/2016 Holger Neupert TE/VSC Shields were inserted in SPS in March 2009, after drilling the holes and chemical cleaning The width is 5 mm, comparable with the most intense region of e-cloud measured for low field (0.4A ~20Gauss nominal) in the monitors 156 mm 6mm 20 40 60 80 100 5mm

17. SPSU 171109 M.Taborelli Side without antenna holes Holger Neupert TE/VSC

18. SPSU 171109 M.Taborelli Conclusions:  We still do not understand the too small difference in dynamic pressure between coated and uncoated magnets: it does not correspond to the expectation from e-cloud monitors and dynamic degassing data from a-C coatings (slides Paolo)  There is e-cloud also in RF shields (visible traces)  The bad result of the first carbon coating in the scrubbing run of 2008 was due to uncoated regions Looking toward 2010: -Magnetic field measurements outside the MBB (J.Bauche) -New setup for degassing measurements of a-C (optimize degassing, since we believe that SEY is sufficiently good) -What to do with SPS tests in 2010? - coat liners in MBB geometry - mass spectrometer?....few chances - longer section of coated magnets? - simulate the p behaviour more precisely?