Recent Experimental Results on Amorphous Carbon Coatings ......3 Conclusions and outlook Conclusions...
Transcript of Recent Experimental Results on Amorphous Carbon Coatings ......3 Conclusions and outlook Conclusions...
Recent Experimental Results on AmorphousCarbon Coatings for Electron Cloud Mitigation
ECLOUD ’10, Cornell University, Ithaca, New York USA
Christina Yin Vallgren
S. Calatroni, P. Chiggiato, P. Costa Pinto, H. Neupert, M. Taborelli,
W. Vollenberg
Vacuum, Surfaces and Coatings Group (VSC), TE-departmentSPS-U team: E .Shaposhnikova, G. Arduini, J. Bauche, F. Caspers, K. Cornelis,S. Federmann, E. Mahner, E. Metral, G. Rumolo, B. Salvant, F. Zimmermann
CERN, CH-1211, Geneva, Switzerland
October 8-12, 2010
MotivationExperiments
Conclusions and outlook
Outline
1 MotivationSPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
2 ExperimentsCoating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
3 Conclusions and outlookConclusionsOutlook
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MotivationExperiments
Conclusions and outlook
SPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
Outline
1 MotivationSPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
2 ExperimentsCoating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
3 Conclusions and outlookConclusionsOutlook
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MotivationExperiments
Conclusions and outlook
SPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
The goal of this work
SPS-U: make the SPS able to deliver the above nominal beams toLHC and reach maximum luminosity.
Find a solution to eliminate e-cloud in the SPS, which
can be implemented in the present SPS-dipoles withoutaperture reduction
does not require bake-out
is robust against air venting (maintenance, installation...)
has a long life time
The condition for the secondary electron yield to avoid e-cloud inSPS dipoles with nominal LHC beam is (G.Rumolo et al.)
δmax < 1.3
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MotivationExperiments
Conclusions and outlook
SPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
Possible remedies for the electron cloud in the beam pipe:
Low Secondary Electron Yield (SEY) thin-film coatings
surface conditioning
clearing electrodes
chamber with grooves or slots
Ti-Zr-V film coating (implemented in straight sections of LHC) haveδmax = 1.1 after activation at temperature higher than 180◦C (24h).
But they cannot be applied to the SPS because the SPS magnet vacuum
chambers are not bakeable.
TiN works well under the effect of photon conditioning in situ.
But no photons in the SPS.
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MotivationExperiments
Conclusions and outlook
SPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
Which material to start with:
Known facts
For air exposed stainless steel, Cu and Al δmax > 2.
In the periodic system, elements with fewer electrons (on theleft side) => lower SEY.
’Beam scrubbed’ surfaces are covered by more carbon(at least Cu and StSt).
Try Carbon, which has few electrons
SEY of graphite is much lower than diamond, so try to makegraphite-like coatings.
Graphite is not very reactive, should be less affected by airexposure.
Graphite-like Amorphous Carbon (a-C) Thin Film Coating.
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MotivationExperiments
Conclusions and outlook
SPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
Which material to start with:
Known facts
For air exposed stainless steel, Cu and Al δmax > 2.
In the periodic system, elements with fewer electrons (on theleft side) => lower SEY.
’Beam scrubbed’ surfaces are covered by more carbon(at least Cu and StSt).
Try Carbon, which has few electrons
SEY of graphite is much lower than diamond, so try to makegraphite-like coatings.
Graphite is not very reactive, should be less affected by airexposure.
Graphite-like Amorphous Carbon (a-C) Thin Film Coating.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Outline
1 MotivationSPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
2 ExperimentsCoating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
3 Conclusions and outlookConclusionsOutlook
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Coating Configurations - DC magnetron sputtering
Different coating configurations were used:
Cylindrical tube with one graphite rod cathode (for lab samples forSEY investigation and vacuum characterization)
Liner in tube with 4 graphite rods (Lab samples, liner for e-cloudmonitors)
MBB magnet chamber in-situ (chamber in the dipole) withMulti-electrode geometry (Version I: coating in-situ in SPS dipoles)
MBB magnet chamber stand-alone with liner configuration(Version II: coating outside SPS dipoles)
Different discharge gases (Ne, Kr, Ar) and different coating parameters
(Temperature of substrate, discharge gas pressure, power) can be used.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Cylindrical tube configurationLab samples for SEY and vacuum characterizations
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Liner in tube with 4 graphite rodsLab samples, liner for e-cloud monitors
The coating chambers were inserted in a solenoid and the magneticfield is parallel to the cathodes and chamber axis.The surface temperature can rise to 250◦C.
Four graphite rods were used to avoid coating in-homogeneity.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Liner in tube with 4 graphite rodsLab samples, liner for e-cloud monitors
The coating chambers were inserted in a solenoid and the magneticfield is parallel to the cathodes and chamber axis.The surface temperature can rise to 250◦C.
Four graphite rods were used to avoid coating in-homogeneity.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Coating for the Electron Cloud Monitor in the SPS
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Coating for the Electron Cloud Monitor in the SPS
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
MBB magnet in-situ with Multi-electrode geometryVersion I: coating in-situ in SPS dipoles
The magnetic field of the dipole was used and was perpendicular
to the cathodes and chamber axis.
The power during coating was kept limited in order to avoidoverheating and damaging of the coil of the dipole.
Three MBBs have been coated.
Disadvantage: in-homogeneity.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
MBB magnet in-situ with Multi-electrode geometryVersion I: coating in-situ in SPS dipoles
The magnetic field of the dipole was used and was perpendicular
to the cathodes and chamber axis.
The power during coating was kept limited in order to avoidoverheating and damaging of the coil of the dipole.
Three MBBs have been coated.
Disadvantage: in-homogeneity.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
MBB magnet stand-alone with liner configurationVersion II: coating outside SPS dipoles
Use the same technique as for liner coating to coat thevacuum chamber outside the SPS magnet.
Three new MBBs have been coated.
Disadvantage: Cut-open SPS dipole magnet and reassembly.(Expensive process!)
Advantage: Perfectly homogeneous coating for large scaleproduction can be done in advance.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
MBB magnet stand-alone with liner configurationVersion II: coating outside SPS dipoles
Use the same technique as for liner coating to coat thevacuum chamber outside the SPS magnet.
Three new MBBs have been coated.
Disadvantage: Cut-open SPS dipole magnet and reassembly.(Expensive process!)
Advantage: Perfectly homogeneous coating for large scaleproduction can be done in advance.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
In the lab: The SEY as a function of PEP: power, p: pressure
200 400 600 800 1000 1200 1400 16000.6
0.7
0.8
0.9
1
1.1
Primary Energy (eV)
SE
Y δ
high P, med phigh P, high phigh P, low pmed P, low pmed P, med plow P, med p
Measured directly afterextraction from thedeposition chamberand transfer to theSEY apparatusthrough air.
The precision of thepresented SEY valuesis estimated to ±0.03.
δmax is between 0.9and 1.1 and Emax =300 eV. (not sensitiveto coating parametersas pressure, power.)
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
In the lab: The SEY as a function of PEP: power, p: pressure
0.8 0.9 1 1.1 1.20
5
10
15
20
25
δmax
of a−C coatings
Nu
mb
ers
of
the
co
atin
gs.
To
tal:
90
sa
mp
les
Measured directly afterextraction from thedeposition chamberand transfer to theSEY apparatusthrough air.
The precision of thepresented SEY valuesis estimated to ±0.03.
δmax is between 0.9and 1.1 and Emax =300 eV. (not sensitiveto coating parametersas pressure, power.)
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Electron Cloud Monitor (ECM) in the SPS
Electron cloud current normalized withbeam intensity v.s time, measured byECM in the SPS.
3-4 batches of nominal LHC beam.(1.15 · 1011 protons/bunch)
0 1 2 3 4 5−6
−5
−4
−3
−2
−1
0
Time(h)
Log1
0(In
tEle
ctro
nCur
rent
/IntF
BC
T)
Normalized e−cloud from the MD runs
a-C nr1 tested in the SPSa-C nr2 tested in the SPSStainless Steel
SEY measurements in thelab.
0 200 400 600 800 1000 1200 1400 1600 18000.5
1
1.5
2
2.5
Primary Energy (eV)
SE
Y δ
a−C nr1 tested in the SPS: δ = 0.92a−C nr2 tested in the SPS: δ = 1.14Stainless Steel: δ = 2.25
Observe!
EC signal is 104 higher onStSt than a-C.
Low SEY ⇒ Low electroncurrent signal.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Ageing observation of a-C liner in the ECM in the SPS
One a-C coated liner has been tested during 3 MachineDevelopment (MD) Runs with 3-4 batches of nominal LHC beamaccelerated to 450 GeV/c.
Vertical unit: nC/1010 protons perbunch
The a-C coated liner was kept inthe SPS for more than one yearoperation. (more than 2 months ofventing, maintenance,installation...)
No sign of ageing in the SPS.
0 1 2 3 4 5−1
0
1
2
3
4
5x 10−4
Time(h)
IntE
lectr
on
Cu
rre
nt/In
tFB
CT
Normalized e−cloud from the MD runs
a-C in MD1: 12 August, 2008a-C in MD2: 6-8 October, 2008a-C in MD3: 15-18 June, 2009
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Ageing observation of a-C liner in the ECM in the SPS
One a-C coated liner has been tested during 3 MachineDevelopment (MD) Runs with 3-4 batches of nominal LHC beamaccelerated to 450 GeV/c.
Vertical unit: nC/1010 protons perbunch
The a-C coated liner was kept inthe SPS for more than one yearoperation. (more than 2 months ofventing, maintenance,installation...)
No sign of ageing in the SPS.
0 1 2 3 4 5−1
0
1
2
3
4
5x 10−4
Time(h)
IntE
lectr
on
Cu
rre
nt/In
tFB
CT
Normalized e−cloud from the MD runs
a-C in MD1: 12 August, 2008a-C in MD2: 6-8 October, 2008a-C in MD3: 15-18 June, 2009
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Ageing observation of a-C liner in the ECM in the SPS
One a-C coated liner has been tested during 3 MachineDevelopment (MD) Runs with 3-4 batches of nominal LHC beamaccelerated to 450 GeV/c.
Vertical unit: nC/1010 protons perbunch
The a-C coated liner was kept inthe SPS for more than one yearoperation. (more than 2 months ofventing, maintenance,installation...)
No sign of ageing in the SPS.
0 1 2 3 4 5−1
0
1
2
3
4
5x 10−4
Time(h)
IntE
lectr
on
Cu
rre
nt/In
tFB
CT
Normalized e−cloud from the MD runs
a-C in MD1: 12 August, 2008a-C in MD2: 6-8 October, 2008a-C in MD3: 15-18 June, 2009
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Inspection of FIVE liners extracted from SPSOne Stainless Steel liner and four a-C coated liners
Liner SPS operation δinitial
StSt 1 year 2.25(Reference) (5 MD runs)
C-strip 1 year 0.92(a-C coating of 40mm width) (5 MD runs)
C-Zr 1.5 years 0.95(a-C on rough Zr coating) (9 MD runs)
CNe64 3 months 0.95(a-C coating) (2 MD runs)
CNe65 3 months 0.95(a-C coating) (2 MD runs)
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Inspection of FIVE liners extracted from SPSOne Stainless Steel liner and four a-C coated liners
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Inspection of FIVE liners extracted from SPSOne Stainless Steel liner and four a-C coated liners
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Three MBB dipoles have been coated with a-C coatingin-situ dipole (Version I) inserted in the SPS
Microwave transmission measurements detected e-cloud
related signal in the coated and uncoated magnets.
F. Caspers, S. Federmann
Dynamic pressure rise used to monitor the behavior of
the coated and uncoated magnets. 28 / 42
MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
Three MBB dipoles have been coated with a-C coatingin-situ dipole (Version I) inserted in the SPS
Microwave transmission measurements detected e-cloud
related signal in the coated and uncoated magnets.
F. Caspers, S. Federmann
Dynamic pressure rise used to monitor the behavior of
the coated and uncoated magnets. 29 / 42
MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
E-cloud related measurements/SEY measurements in thelab
Dynamic pressure rise between thecoated and uncoated magnets.
The nominal LHC beam: 1,2,3 and4 batches with 72 bunches at 25 nsspacing.
SEY measurements before/afterinsertion in the SPS.
0 200 400 600 800 1000 1200 1400 1600 18000.5
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
Primary Energy (eV)
SEY
δ
MBB magnet before insertion in the SPS: δ = 1.00MBB magnet after 1 year operation: δ = 1.33
No different in pressure rise.
SEY increases after extraction.
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MotivationExperiments
Conclusions and outlook
Coating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
E-cloud related measurements/SEY measurements in thelab
Dynamic pressure rise between thecoated and uncoated magnets.
The nominal LHC beam: 1,2,3 and4 batches with 72 bunches at 25 nsspacing.
Non-uniform coating color indicatesdifferences in thickness andpossibly composition.
Bad SEY is mostly due to thecoating configuration.
Coat MBB vacuum chamberstand-alone outside dipole!!!(Version II)
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MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Outline
1 MotivationSPS-U: Super Proton Synchrotron UpgradeNew solution → Amorphous Carbon Coating
2 ExperimentsCoating ConfigurationsExperiments in the labImplementation in the SPS: E-cloud experimentsAgeing (increase of SEY) observation of a-C coating
3 Conclusions and outlookConclusionsOutlook
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MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Conclusions
A-C thin films produced by d.c magnetron sputtering show areliable low initial SEY (well below δthreshold = 1.3).
A complete suppression of e-cloud can be achieved by coatingof liners with a-C.
The coating of liners does not show ageing (increase of SEY)after more than 1 year of exposure in the SPS.
Magnetron sputtered a-C film is a potential solution toeliminate e-cloud.
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MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Conclusions
A-C thin films produced by d.c magnetron sputtering show areliable low initial SEY (well below δthreshold = 1.3).
A complete suppression of e-cloud can be achieved by coatingof liners with a-C.
The coating of liners does not show ageing (increase of SEY)after more than 1 year of exposure in the SPS.
Magnetron sputtered a-C film is a potential solution toeliminate e-cloud.
34 / 42
MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Conclusions
A-C thin films produced by d.c magnetron sputtering show areliable low initial SEY (well below δthreshold = 1.3).
A complete suppression of e-cloud can be achieved by coatingof liners with a-C.
The coating of liners does not show ageing (increase of SEY)after more than 1 year of exposure in the SPS.
Magnetron sputtered a-C film is a potential solution toeliminate e-cloud.
35 / 42
MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Conclusions
A-C thin films produced by d.c magnetron sputtering show areliable low initial SEY (well below δthreshold = 1.3).
A complete suppression of e-cloud can be achieved by coatingof liners with a-C.
The coating of liners does not show ageing (increase of SEY)after more than 1 year of exposure in the SPS.
Magnetron sputtered a-C film is a potential solution toeliminate e-cloud. ✓
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MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Outlook
The future activities will be focused on:
modifying the coating system in order to find an efficient andeconomical solution to coat beam pipes in a large scale withthe same quality of coating as in the ECMs.following the ageing development of the liners and getting adeeper understanding of a-C thin film both in the lab and inthe SPS.following the ageing development of the new version of MBBcoating and getting a deeper understanding of the relationshipbetween dynamic pressure rise and e-cloud effect.
The first implementation in a large scale with this type of a-Ccoating is now planned to be performed in the SPS magnet oftotal 200 m during the shutdown 2012.
37 / 42
MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Outlook
The future activities will be focused on:
modifying the coating system in order to find an efficient andeconomical solution to coat beam pipes in a large scale withthe same quality of coating as in the ECMs.following the ageing development of the liners and getting adeeper understanding of a-C thin film both in the lab and inthe SPS.following the ageing development of the new version of MBBcoating and getting a deeper understanding of the relationshipbetween dynamic pressure rise and e-cloud effect.
The first implementation in a large scale with this type of a-Ccoating is now planned to be performed in the SPS magnet oftotal 200 m during the shutdown 2012.
38 / 42
MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Outlook
The future activities will be focused on:
modifying the coating system in order to find an efficient andeconomical solution to coat beam pipes in a large scale withthe same quality of coating as in the ECMs.following the ageing development of the liners and getting adeeper understanding of a-C thin film both in the lab and inthe SPS.following the ageing development of the new version of MBBcoating and getting a deeper understanding of the relationshipbetween dynamic pressure rise and e-cloud effect.
The first implementation in a large scale with this type of a-Ccoating is now planned to be performed in the SPS magnet oftotal 200 m during the shutdown 2012.
39 / 42
MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Outlook
The future activities will be focused on:
modifying the coating system in order to find an efficient andeconomical solution to coat beam pipes in a large scale withthe same quality of coating as in the ECMs.following the ageing development of the liners and getting adeeper understanding of a-C thin film both in the lab and inthe SPS.following the ageing development of the new version of MBBcoating and getting a deeper understanding of the relationshipbetween dynamic pressure rise and e-cloud effect.
The first implementation in a large scale with this type of a-Ccoating is now planned to be performed in the SPS magnet oftotal 200 m during the shutdown 2012.
40 / 42
MotivationExperiments
Conclusions and outlook
ConclusionsOutlook
Outlook
The future activities will be focused on:
modifying the coating system in order to find an efficient andeconomical solution to coat beam pipes in a large scale withthe same quality of coating as in the ECMs.following the ageing development of the liners and getting adeeper understanding of a-C thin film both in the lab and inthe SPS.following the ageing development of the new version of MBBcoating and getting a deeper understanding of the relationshipbetween dynamic pressure rise and e-cloud effect.
The first implementation in a large scale with this type of a-Ccoating is now planned to be performed in the SPS magnet oftotal 200 m during the shutdown 2012.
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Thanks
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