organized by EuCARD-AccNet-EuroLumi

1
topical workshop on Anti e-Cloud Coatings
AEC'09
Summary for SPSU by Mauro Taborelli
http//indico.cern.ch/conferenceDisplay.py?confId
62873
organized by EuCARD-AccNet-EuroLumi and SPS
Upgrade Study Team
http//eucard.web.cern.ch/EuCARD/index.html
http//accnet.lal.in2p3.fr/
http//paf-spsu.web.cern.ch/paf-spsu/
2

• TiN as alternative?
• TiN is good if conditioned in the lab (SEY0.85),
  but also other materials have similar
  performance
• The best value presented with moderate
  conditioning (air exp. time unknown) is SEY1.2
  for 10-5C/mm2
• TiN is good if conditioned in machines with
  photons (KEKB, SLACions not quantified)
• Degassing only slightly higher than Cu, improves
  with very moderate bake out (80C)

In KEK LER
Copper
K. Kanazawa
TiN (KEK)
Shibata
TiN (BNL)
3
Conditioning in the lab (S.Kato, KEK)
As received state
Dose of irradiation in the lab at 5KeV electrons
S.Kato
Data consistent with other labs (CERN, SLAC)
S.Kato
After a strong conditioning by an e-beam almost
everything is good
4
Carbon coatings DLC as alternative to a-C?

• it is worse than a-C (not the best DLC according
  to S.Kato, SEY1.1 if sputter cleaned), sp2 is
  relevant
• DLC is not simple SiC or Cr adhesion layer
  stress releasing layer with DLC on top
• ESD is better than Cu
• no air exposure study

As received surfaces
KEKB
Kato DLC
K. Kato and M. Nishiwaki
S.Kato
5
Conditioning of uncoated surfaces Why does StSt
condition to 1.5-1.6 in SPS and to 1.1 in the
lab? No difference for Cu in lab and KEKB
KEKB
Laboratory
0.6C/mm2
S.Kato
S.Kato
6
Conditioning in SPS
SPS transfer sample (StSt)
Measurements in situ on copper (N.Hilleret)
1.4
7
Copper (N.Hilleret)
Cu, LHC type beam in SPS, measured in situ
Photons
Cu lab conditioning
8
Low SEY by rough surfaces (apart of grooves)

• Chemically prepared rough surfaces
• -SEY 1.2 at 800eV, SEY1 at 400eV
• Rough is OK in UHV only if we can bake to reduce
  outgassing
• The surface is mechanically fragile (adhesion?)
• Impedance?
• With insulating particles
• - SEYlt1, higher above 800eV
• Fundamental research necessary, principle still
  not understood
• Would impedance hinder any application or can it
  be optimized?

I.Montero
9

• Magnetically rough surfaces
• The best results are only for Au coated
  particles is there more than the magnetic field
  effect or Au is cutting off the peak at low
  energy ?
• Are there ideal values of magnetization, domain
  size and orientation?
• Probably only for field free regions

Au coated ferrite microparticles (topographicmagn
etic roughness)
Coated (blue) and uncoated (red) particles
10
Simulation of one side of the chamber with low SEY
(G.Rumolo)
Keep in mind this if we put the grooves