Outgassing of a-C

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Progress on a-C coatings
Outgassing of a-C Aging Differences in SEY and
aging Preparation for magnet coating
Ch. Yin-Vallgren, S.Calatroni, P. Costa Pinto,
P.Chiggiato, H.Neupert, I.Wevers
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Pumpdown measurements
Is a measurement of the outgassing of the wall of
the tube
Pressure gauge
Tube with coating sample
calibrated conductance
Turbo-molecular pump
Log(Pressure)
Log(Time)
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Pumpdown curve of a coated tube compared to StSt
tube
Pumpdown after air exposure
10-2 10-3 10-4 10-5 10-6 10-7 10-8
a-C tube CNe12 1h, 1d, 1week air
Pressure Torr
a-C tube CNe18, 1h air
Liner (CNe8 second SPS liner) 1 month air
StSt
a-C tube CNe20, 1h air
102 103 104 105 106
Times
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Aging upon air exposure (samples measured only
once, no cumulative dose)
Red and similar circles are liners Blue and
similar triangles are tubes
Coatings deposited in tube configuration age
faster!
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Magnetron sputtering configuration
Tube versus liner Liner Tube T substrate
- Energy of impinging atoms
- Impact direction many normal Observed
roughness -
Liner
graphite rod
Liner configuration
graphite rod
tube
Tube configuration
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SEY of a-C in tube and Liner configuration
Red and similar circles are liners Blue and
similar triangles are tubes
Emax tubes
Emax liners
Energy eV
-All the tubes have lower Emax and decrease
faster at high Ep -Most of the liners have higher
Emax and more flat dependence on Ep This would be
consistent with rougher coatings in the liners
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Sample from M.Pivi SLAC, macroscopic grooves on
Al (measured with beam scan)
grooves
35 decrease

• grooves made at CERN workshop on copper gave 20
  decrese
• no success for the moment from trials made at
  the CERN workshop on StSt

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Progress on prototype coating
-design approval by end of the week -some delays
foreseen in the installation due to
restructuring of the coating facility at Bdg181
(LHC quadrupole repair)
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• Next
• Coatings
• -change coating parameters (p, power, T ) to get
  a clear picture of the origin of the differences
  in the coatings of tubes and liners
• -degassing rate measurements for various gases
• -measurement of Ne content by laser ablation in
  UHV and mass spectrometry
• Prototype coating of an SPS magnet
• Ordering components for pumping system
• Drawing to be approved this week