1. 1 Vacuum in LER and HER. First estimation for the pumping system requirements (part II) A.Variola for B.Mercier, C.Prevost Annecy - Mars 2010

2. 2 synchrotron radiation from only dipoles E = 4 GevI = 2.28 A  = 28 m  = 4.3.10 19 ph/s/mEc = 5.1 KeVP = 11 KW/m LER E = 7 GevI = 1.3 A  = 139 m  = 8.5.10 18 ph/s/mEc = 5.5 KeVP = 2.3 KW/m HER LER Distance m  (ph/s/m) Rt = 47,5 mmRt = 25 mm Approximation of the pressure distribution in Cell LER #2 and HER #2 at SuperB with synchrotron radiation Distance m [ref]: O.B. Malyshev and all EPAC 2002 Paris 10 19

3. 3 and Ec = 4,5 KeV photodesorption Yield  at machine start-up For baked Cu 150°C Input data HER#2 HER#2 With distributed pumping + SR Too important pressure !!! Neg pump saturation Decrease of the intensity in the starting up Pressure mbar 10 -6 H2H2 CO CO 2 CH 4 Approximation of the pressure distribution in Cell HER #2 with synchrotron radiation at machine start-up Distance m gas  (mol/ph) H2H2 ~ 1.10 -3 CH 4 ~ 1.10 -4 Co ~ 5.10 -4 Co 2 ~ 3.10 -4 Gröbner and all, JVSTA 12(3) 1994 Distributed pumping inside antechamber

4. 4 After conditionning baked Cu 150°C Gröbner and all, JVSTA 12(3) 1994  = 0.84 conditioning gas  (mol/ph) H2H2 ~ 6.10 -7 CH 4 ~ 2.5.10 -8 Co ~ 2.5.10 -7 Co 2 ~ 2.5.10 -7 D = photon dose 10 25 photons/m  360 A.h ( seen by all the surfaces ) Approximation of the pressure distribution in Cell HER #2 with synchrotron radiation after machine conditioning

5. 5 With distributed pumping + SR after machine conditioning H2H2 CO 2 CO CH 4 HER#2 10 -9 Pressure mbar Distance cm P m (H 2 ) = 1.4.10 -9 mbar Approximation of the pressure distribution in Cell HER #2 with synchrotron radiation after machine conditioning P m (CO 2 ) = 5.10 -10 mbar Goal P m ~ 6.10 -10 mbar Possible improvement  (mol/ph) ~10 -7 (PEPII) Neg coating in the drift tubes Pumping speed increase, time conditionning decrease, low secondary emission but impedance chamber ?? P m (H 2 ) = 3.10 -10 mbar

6. 6 With distributed pumping + SR Input data LER#2 at machine start-up LER#2 10 -5 Pressure mbar Distance cm H2H2 CO 2 CO CH 4 Approximation of the pressure distribution in Cell LER #2 with synchrotron radiation at machine start-up gas  (mol/ph) H2H2 ~ 1.10 -3 CH 4 ~ 1.10 -4 Co ~ 5.10 -4 Co 2 ~ 3.10 -4 and Ec = 4,5 Kev For baked Cu 150°C photodesorption Yield  at machine starting Distributed pumping inside antechamber Too important pressure !!! Neg pump saturation Decrease of the intensity in the starting up

7. 7 After machine conditioning gas  (mol/ph) H2H2 6.10 -7 CH 4 2.5.10 -8 Co2.5.10 -7 Co 2 2.5.10 -7 D = photon dose 10 25 photons/m  160 A.h ( seen by all the surfaces ) P m (H2) = 10 -8 mbar P m (CH4) = 2.10 -9 mbar With distributed pumping + SR after machine conditioning LER#2 10 -8 Pressure mbar H2H2 CO 2 CO CH 4 Approximation of the pressure distribution in Cell LER #2 with synchrotron radiation after machine conditioning Goal P m ~ 6.10 -10 mbar Possible improvement  (mol/ph) ~10 -7 H 2, CO,CO 2 (PEPII) Neg coating in the drift tubes P m (H 2 ) = 2.10 -9 mbarP m (CH 4 ) = 8.10 -10 mbar ~10 -8 CH 4 P m (CO) = 5.10 -10 mbar SR absorbeurs + holding pumps Distance cmdistributed pumping speed inside dipole chamber

8. 8 Approximation of the pressure distribution in Cell LER #2 with synchrotron radiation after machine conditioning New input data  (mol/ph) ~10 -7 H 2, CO,CO 2 (PEPII) ~10 -8 CH 4 For Neg coating in the straitght section gas Sticking coefficients (distributed pumping l.s -1.m -1 )  (mol/ph) H2H2 ~ 0.0005 (120)~ 2.5.10 - 7 CH 4 ~ 0~ 2.5.10 - 9 Co~ 0.1 (6700)~ 1.2.10 -8 Co 2 ~ 0.1 (5380)~ 1.2.10 -8 P. Chigiatto, R. Kersevan Vacuum 60 (2001) For dipole chamber with antichamber (Neg strip) A. Rossi LHC Project report 783 With distributed pumping + SR after machine conditioning P m (H2) = 1.5.10 -9 mbar P m (CH4) = 6.10 -10 mbar in this case Neg is not enough effective SR absorbeurs + with high pumping speed for H 2, inside and/or at each extremity of dipole chamber solution LER#2 10 -9 Pressure mbar H2H2 CO 2 CO CH 4 Distance cm

9. 9 Conclusions 1- First estimations for pumping system efficiency in HER and LER under synchrotron radiation from dipoles 2- in HER after machine conditioning, with ionic distributed pumping inside dipole antechamber, Neg strip distributed pumping inside drift antechamber and with photodesorption yield of 10 -7, we obtain P m (H 2 ) = 3.10 -10 mbar OK! 3- in LER after machine conditioning, with Neg strip distributed pumping inside dipole and drift antechamber, and with photodesorption yield of 10 -7 for H 2 and 10 -8 for CH 4 and, we obtain P m (H 2 ) = 2.10 -9 mbar and P m (CH 4 ) = 8.10 -10 mbar Possible improvement add holding pumps with high pumping speed for H 2, CH 4 (sublimation pumps, Ion pump) in/near dipole chambers to check Need input for synchrotron radiation from quadripoles Determine exactly the effective pumping speeds of Neg strip in antechamber for all gas? Ion desorption Electron desorption 4- other considerations to be taken into account E-cloud ……… HOM heating

10. 10 P. Chigiatto, R. Kersevan Vacuum 60 (2001) For NEG(Ti-Zr-V) Ec =20 Kev photodesorption Yield 