organized by EuCARD-AccNet-EuroLumi

and SPS Upgrade Study Team

topical workshop on

Anti e-Cloud Coatings “AEC'09” http://indico.cern.ch/conferenceDisplay.py?confId=62873

http://accnet.lal.in2p3.fr/

http://eucard.web.cern.ch/EuCARD/index.html

http://paf-spsu.web.cern.ch/paf-spsu/

Summary for SPSUby Mauro Taborelli

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 with photons (KEKB, SLAC…ions

not quantified)-Degassing only slightly higher than Cu, improves with very moderate bake out

(80C)

0

1 1011

2 1011

3 1011

4 1011

0 0.2 0.4 0.6 0.8 1 1.2

KEK TiN 04Nov2008

D(D7)[4,200,3]CuD(D7)[4,200,3]TiND(D7)[1,1585,3.06]KEKTiN

Nea

r Bea

m E

lect

ron

Clo

ud D

ensi

ty [m

-3]

LER Bunch Current [mA]

TiN (KEK)

TiN (BNL)

Copper

In KEK LER

K. Kanazawa

Shibata

Conditioning in the lab: (S.Kato, KEK)

As received state

Dose of irradiationin the lab at 5KeV electrons

After a strong conditioning by an e-beam almost everything is good

Data consistent with other labs (CERN, SLAC)

S.Kato

S.Kato

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

0

1 1011

2 1011

3 1011

4 1011

0 0.2 0.4 0.6 0.8 1 1.2

Ele

ctro

n C

loud

Den

sity

[m-3

]

LER Bunch Current [mA]

Cu (1400Ah)

NEG Coated Cu(1370Ah)

TiN Coated Cu(1094Ah)

Graphitized Cu(1740Ah)

DLC (1980Ah)

EM-study-FUJI[4-200-3]Cu-DLC.qpc

K. Kato and M. Nishiwaki

KEKB

Kato DLC

S.Kato

As received surfaces

Conditioning of uncoated surfacesWhy 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

0.6C/mm2

Laboratory

KEKB

S.KatoS.Kato

Conditioning in SPS

Measurements in situ on copper (N.Hilleret)

SPS transfer sample (StSt)

~1.4

Cu, LHC type beam in SPS, measured in situ

Cu lab conditioning

Photons

Copper (N.Hilleret)

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?

SEY

0,0

0,20,4

0,6

0,81,0

1,2

1,4

1,61,8

2,0

0 200 400 600 800 1000Primary Electron Energy (eV)

SEY

coef

ficie

nt

Al2O3 75%+Al 25%+Au

Al2O3 50%+ Al 50% +Au

Al2O3 25%+ Al 25% +Au

Al particleAl2O3 particle

Surface top view

Gold coated

I.Montero

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

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800 1000Primary Electron Energy (eV)

SEY

coef

ficien

tFerrita+Au-312º

Ferrita+Au-342º

Ferrita +Au-300º

Ferrita +Au-352º

Ferrita +Au-352º

Au coated ferrite microparticles(topographic+magnetic roughness)

SEY

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 500 1000 1500 2000 2500 3000 3500 4000Primary Electron Energy (eV)

SEY

coeff

icien

t

MnZn/CuNiZn/Cu +Au

Coated (blue) and uncoated (red) particles

Keep in mind this if we put the grooves

0 100 200 300 400 500 600 7000.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Energy (eV)

SEY

0=1.50,Height=1.9mm, =200

Flat surfacer=0.14mm,B=2 Teslar=0.14mm,B=0.2Teslar=0.09mm,B=2 Teslar=0.09mm,B=0.2Teslaaverage,B=2 Tesla

Lanfa Wang, SLAC

(G.Rumolo)

Simulation of one side of the chamber with low SEY