1 / 9

MDI Vacuum Status

MDI Vacuum Status. Ray VENESS CERN TE-VSC. Introduction. Pressure requirements for QD0 and the experimental sector Pressure profile for QD0 Vacuum layout in the MDI Post-collision line Conclusions and open questions. Pressure Requirements for QD0 and Experiment.

laurel
Download Presentation

MDI Vacuum Status

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. MDI Vacuum Status Ray VENESS CERN TE-VSC

  2. Introduction • Pressure requirements for QD0 and the experimental sector • Pressure profile for QD0 • Vacuum layout in the MDI • Post-collision line • Conclusions and open questions Warm beampipe - R.Veness

  3. Pressure Requirements for QD0 and Experiment • Requirements from beam dynamics • Recent calculations from Rumolo[1] show that coherent instabilities are not an issue if pressures with pressures in the last 20m of the BDS upto 105nTorr (~1.3x10-4 mbar) • He notes however that incoherent effects and emittance growth should be studied • Requirements from the experiments • ILC simulations [2] suggest that beam-gas background is not an issue at 103nTorr (~1.3x10-6 mbar) • This needs to be confirmed for the CLIC experiments • These pressure requirements suggest that a non-baked solution could be adopted for the QD0, and possibly also the experimental sector [1] G.Rumolo, CLIC-MDI meeting March 2010 [2] T.Maruyama, LCWA 2009 Albuquerque MDI beam vacuum - R.Veness

  4. Unbaked QD0 Vacuum • Geometry • Inner diameter of 7.6 mm • Separation between pumps ~4 m • Assumptions • The system can be pumped for 100h before beam • … or it is not exposed to air during the push-pull operation • Unbaked, but UHV clean system, dominated by outgassing of H20 • Outgassing rates for unbaked systems are variable – uncertainty on result • Assume 1x10-10 mbar.l.s.cm-2 Outgassing rates of water on stainless steel [F.Dylla CAS 2006] Warm beampipe - R.Veness

  5. Unbaked Pressure Profile in QD0 • Static pressures • Average 4.8x10-7 mbar [~3.6x102nTorr] • Peak 8.1x10-7 mbar [~6x102nTorr] • Achievable pressure is dominated by the small conductance of the tube and the outgassing rate • Dynamic pressure components • Additional gas load due to surface bombardment by ions, electrons and photons will increase these static pressures • Some data starting to arrive from A.Sailer, but calculations are time-consuming • Beryllium in the experimental chamber has a high secondary electron yield and may need special coating Static partial pressure of H20 [mbar] along the QD0 beam tube [m] Warm beampipe - R.Veness

  6. Baseline SectorisationScheme • Sectors • Separate machine, QD0, Detector and post-collision for independence and safety during shutdowns • Add additional sector valve to maintain cleanliness in both QD0 and detector • Keep QD0 and experiment either under vacuum or dry gas during push-pull • Essential to reduce pump-down time after detector push-pull in a non-baked system • Possibly add fast shutter to protect detectors from incidents in post-collision Detector Post-Collision Vacuum line Machine Vacuum line QD0 Machine Vacuum line QD0 Post-Collision Vacuum line = Sector valve = Fast shutter valve MDI beam vacuum - R.Veness

  7. QD0-Experiment Layout Is this transition acceptable? We are missing a pump here ..and a pumping port here H.Gerwig, 8th MDI meeting Warm beampipe - R.Veness

  8. Post Collision Line • Absorbers • Latest information from Edda is that the baseline design is for absorber blocks outside the vacuum system • This will mean a ‘reasonable’ gas load on the pumping system, but will require several vacuum windows • Important to maintain contact between post-collision and vacuum system designers Warm beampipe - R.Veness

  9. Conclusions and Open Issues • Unbaked QD0 design presented • Average static pressure 4.8x10-7 mbar [~3.6x102nTorr] • This will need 2 sector valves between QD0 and experiment for rapid recovery after push-pull and pumps on both ends of QD0 • Pumping on both ends of QD0 is essential, as well as a port for pumping the space between the 2 valves • Open issues for pressure profiles • Ion, electron and photon induced desorption rates need to be calculated • Other beam dynamics requirements? • Incoherent effects and emittance growth • Wall impedance requirement for vacuum chambers • low resistivity coatings? • Beampipe geometry transitions? • Trapped RF modes giving coherent/incoherent losses and heating effects • Next steps • Confirm the acceptability of unbaked design in QD0 • Calculate static pressure profile in an unbaked experimental sector Warm beampipe - R.Veness

More Related