Vacuum in LER and HER. First estimation for the pumping system requirements A.Variola for B.Mercier, C.Prevost, F.Letellier

Approximation of the pressure distribution in Cell LER #2 at SuperB under static conditions Basic vacuum parameters Effective pumping speed? Nature of gas ? Neg strip or coat ?, …….? Same shape in all sections Conductance chamber (N2 at 20°C)  43 l.m.s-1 Perimeter chamber  54 cm Input data for VASCO program In all sections / baked copper in situ (A. G Mathewson et al, LHC project note 21 CERN) adjacent quadrupoles / effective pumping speed for unsatured starcell in dipoles and drift sections antechamber Holding pumping Half Holding pumping LAL Vacuum group - B. Mercier

Approximation of the pressure distribution in Cell LER #2 at SuperB after in situ baked copper chamber and static conditions With distributed pumping in dipoles and drift sections antechamber Without distributed pumping H2 H2 Pressure (mbar) Pressure (mbar) CO CH4 CO2 CO CH4 CO2 Distance (cm) Distance (cm)

Approximation of the pressure distribution in Cell HER #2 at SuperB under static conditions Basic vacuum parameters Effective pumping speed? Nature of gas ? Neg strip or coat ?, …….? Same shape in all sections Conductance chamber (N2 at 20°C)  35 l.m.s-1 Perimeter chamber  28 cm Input data for VASCO program In all sections / baked copper in situ (A. G Mathewson et al, LHC project note 21 CERN) adjacent quadrupoles / effective pumping speed for unsatured starcell Distributed NEG pumping in drift sections Distributed ion pumping in dipoles Holding pumping Half Holding pumping LAL Vacuum group B. Mercier

Approximation of the pressure distribution in Cell HER #2 at SuperB after in situ baked copper chamber and under static condition With distributed ion pumping in dipoles and with distributed NEG pumping in drift sections Without distributed pumping H2 H2 Pressure (mbar) Pressure (mbar) CO CH4 CO2 CO CH4 CO2 Distance (cm) Distance (cm)

Measurement of the intrinsic conductance of the LER dipole vacuum chamber by the Monte Carlo method (Molflow plus program) L = 1m Vm = 470.7 m.s-1 (N2@20°C ) average velocity for a Maxwell-Boltzman distribution A = 52.13 cm2 cross sectional area of the inlet aperture P = 7.6 % transmission probability Intrinsic conductance C  50 l.s-1 N2@20°C

Conclusions 1) First estimations for pumping system efficiency in HER and LER 2) W and Wo distributed pumping 3) Distributed pumping => LER = NEG, HER = Ionic. 4) Main partial pressure H2. ~few 10-10 5) LER methane stays at 10-11 level with NEG (HER no due to pumping). This should be the principal responsible for beam lifetime in Gas scattering (scales linear with mass number and quadratic with the charge number of the gas) 6) Need input of photon on walls, electron on walls to determine dynamic vacuum.