Dynamic vacuum zero-order Dynamic vacuum requirement H 2 and CO 2 partial pressures < 1 nTorr (G. Rumolo and D. Schulte) BD meeting1Sergio Calatroni From Cedric BD meetingSergio Calatroni !!!! Based on outgassing (H 2 O): mbar.l.sec -1 cm -2 for 100h pumping (Paolos vacuum course: 2* for 100 h) Structure test layout BD meetingSergio Calatroni e - on faraday cup Model Only one cell is modelled Electrons are field-emitted, then accelerated and distributed uniformly in the cell Dynamic vacuum by ESD: desorbed molecules fill the whole cell volume, or only the beam channel No pumping BD meetingSergio Calatroni e - on faraday cup e - are uniformly distributed inside the cell e - on faraday cup Cell [mm]dimensionsouter areabeam areacopper areavolume [mm3]beam channel [mm3] Ext diam Iris diam6 volume [liters]beam channel [liters] Length E E-04 Faraday cup measurements - T18_VG24_Disk_2 - KEK BD meetingSergio Calatroni Pulse 173 ns ESD data No much data on unbaked copper (N. Hilleret, CAS Vacuum School G. Vorlaufer CERN-Thesis (2002) ) BD meetingSergio Calatroni Data BD meetingSergio Calatroni Total e- current [A]Pulse duration [ns]Total charge [C]Number of electrons Solid angle (one cell, one side) Total electrons on copperDose per pulse (e- /cm2) 1.00E E E E E+08 ESD coefficient for H2 (unbaked copper) Total H2 molecules per RF pulse Equivalent pressure at RT (total volume) Equivalent pressure at RT (beam channel)G. Vorlaufer CERN-Thesis (2002) 2.00E E E E-07 ESD coefficient for CO2 (unbaked copper) Total CO2 molecules per RF pulse 6.00E E E E-08 ESD coefficient for H2 (copper baked 250 C) Total H2 molecules per RF pulse 250 C / 24h Benvenuti et al LEP E E E E-09 ESD coefficient for CO2 (copper baked 250 C) Total CO2 molecules per RF pulse 6.00E E E E-09 ESD coefficient for H2 (copper baked 300 C) Total H2 molecules per RF pulse Mathewson-JVSTA15(1997)3093.pdf 3.00E E E E-09 ESD coefficient for CO2 (copper baked 300 C) Total CO2 molecules per RF pulse 1.60E E E E pulses to start conditioning times maximum allowed times maximum allowed Molecule speed BD meetingSergio Calatroni Atomic massMass [kg] Molecule 300 K [m/s] Molecule displacement in RF pulse [m] H223.32E E-04 H2O E E-04 CO E E-05 CO E E-05 Mauros vacuum course BD meetingSergio Calatroni Water desorption due to pulsed heating RF pulse duration = s >> =1/ 0 = s Desorption depends on the sojourn time as a function of temperature Pulse heating: 300 K 350 K ( T 50 K) Sojourn time: 6 s 0.06 s Dynamic desorption : mbar.l.sec -1 cm -2 mbar.l.sec -1 cm -2 BD meetingSergio Calatroni Desorbed flux [mbar.l.sec-1cm-2]Pulse duration [s] Specific amount [mbar.l.cm-2] Total amount [mbar.l] Equivalent pressure cell [mbar] Equivalent pressure beam [mbar] 1.00E E E E E E-12