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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/.

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slide1

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/

slide2

TiN as alternative?

  • TiN is good if conditioned in the lab (SEY=0.85), but also other materials have similar performance
  • The best value presented with moderate conditioning (air exp. time unknown) is SEY=1.2 for 10-5C/mm2
  • TiN is good if conditioned in machines withphotons (KEKB, SLAC…ions 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)

slide3

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

slide4

Carbon coatings: DLC as alternative to a-C?

  • it is worse than a-C (not the best DLC according to S.Kato, SEY=1.1 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

slide5

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

slide6

Conditioning in SPS

SPS transfer sample (StSt)

Measurements in situ on copper (N.Hilleret)

~1.4

slide7

Copper (N.Hilleret)

Cu, LHC type beam in SPS,

measured in situ

Photons

Cu lab conditioning

slide8

Al particle

Al2O3 particle

Gold coated

Surface top view

Low SEY by rough surfaces (apart of grooves)

  • Chemically prepared rough surfaces
  • -SEY =1.2 at 800eV, SEY=1 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
  • - SEY<1, higher above 800eV
  • Fundamental research necessary, principle still not understood
  • Would impedance hinder any application or can it be optimized?

I.Montero

slide9

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

(topographic+magnetic roughness)

Coated (blue) and uncoated (red) particles

slide10

Lanfa Wang, SLAC

Simulation of one side of the chamber with low SEY

(G.Rumolo)

Keep in mind this

if we put the

grooves