Transcript Anti e-Cloud Coatings “AEC'09” topical workshop on organized by EuCARD-AccNet-EuroLumi Summary for SPSU

topical workshop on
Anti e-Cloud Coatings “AEC'09”
http://indico.cern.ch/conferenceDisplay.py?confId=62873
organized by EuCARD-AccNet-EuroLumi
http://eucard.web.cern.ch/EuCARD/index.html
Summary for SPSU
by Mauro Taborelli
http://accnet.lal.in2p3.fr/
and SPS Upgrade Study Team
http://paf-spsu.web.cern.ch/paf-spsu/
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)
KEK TiN 04Nov2008
4 10
-3
Near Beam Electron Cloud Density [m ]
11
D(D7)[4,200,3]Cu
D(D7)[4,200,3]TiN
D(D7)[1,1585,3.06]KEKTiN
In KEK LER
Copper
11
3 10
K. Kanazawa
11
2 10
TiN (KEK)
11
1 10
0
0
0.2
0.4
0.6
TiN
0.8
(BNL)
LER Bunch Current [mA]
Shibata
1
1.2
Conditioning in the lab: (S.Kato, KEK)
As received state
Dose of
irradiation
in the lab
at 5KeV
electrons
S.Kato
S.Kato
After a strong conditioning by an e-beam almost
everything is good
Data
consistent
with other
labs (CERN,
SLAC)
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
11
4 10
Electron Cloud Density [m -3]
Cu (1400Ah)
11
Kato DLC
3 10
Graphitized Cu
(1740Ah)
K. Kato and M. Nishiwaki
11
2 10
NEG Coated Cu
(1370Ah)
11
1 10
DLC (1980Ah)
TiN Coated Cu
(1094Ah)
0
0
0.2
0.4
0.6
0.8
LER Bunch Current [mA]
1
1.2
EM-study-FUJI[4-200-3]Cu-DLC.qpc
S.Kato
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
Conditioning in SPS
SPS transfer sample (StSt)
Measurements in situ
on copper (N.Hilleret)
~1.4
Copper (N.Hilleret)
Cu, LHC type beam in SPS,
measured in situ
Photons
Cu lab conditioning
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
2,0
Al2O3 particle
Al2O3 75%+Al 25%+Au
1,8
Al2O3 50%+ Al 50% +Au
1,6
SEY coefficient
Al particle
SEY
Gold coated
Al2O3 25%+ Al 25% +Au
1,4
1,2
1,0
0,8
0,6
0,4
0,2
0,0
0
200
400
600
Primary Electron Energy (eV)
800
1000
Surface top view
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
SEY
1.2
1.60
1.0
1.40
SEY coefficient
SEY coefficient
1.20
1.00
0.80
MnZn/Cu
0.60
0.8
0.6
Ferrita+Au-312º
0.4
NiZn/Cu +Au
Ferrita+Au-342º
Ferrita +Au-300º
0.40
Ferrita +Au-352º
0.2
0.20
0.00
Ferrita +Au-352º
0.0
0
500
1000
1500
2000
2500
3000
Primary Electron Energy (eV)
3500
4000
0
200
400
600
Primary Electron Energy (eV)
800
1000
Simulation of one side of the chamber with low SEY
(G.Rumolo)
Keep in mind this
if we put the
grooves
 =1.50,Height=1.9mm, =20
0
0
2
1.8
1.6
Flat surface
r=0.14mm,B=2 Tesla
r=0.14mm,B=0.2Tesla
r=0.09mm,B=2 Tesla
r=0.09mm,B=0.2Tesla
average,B=2 Tesla
SEY
1.4
1.2
1
0.8
0.6
0.4
Lanfa Wang, SLAC
0.2
0
100
200
300
400
500
Energy (eV)
600
700