1 Blackening of the BGC interaction chamber Johanna Glutting 05022019 Agenda 05022019 Blackening of the BGC interaction chamber Johanna Glutting 2 Context BGC and HEL ID: 777793
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Slide1
Blackening of the BGC interaction chamber
1
Blackening of the BGC interaction chamber Johanna Glutting
05/02/2019
Slide2Agenda
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Blackening of the BGC interaction chamber Johanna Glutting
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Context (BGC and HEL)
Requirements
Blackening options
Which tests are needed?
Slide3Application: Hollow Electron Lens (HEL)
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Blackening of the BGC interaction chamber Johanna Glutting
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Source: Adriana Rossi, BGC collaboration meeting 19 Mar. 2018 (modified);
https://indico.cern.ch/event/712498/
Halo particles can collide with vacuum components and create losses
HEL gives particles out of centre a kick
Halo particles are easier to remove in the collimation system
Monitoring of the concentricity is important
Slide4The BGC for the monitoring of HEL and LHC proton beam
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Blackening of the BGC interaction chamber Johanna Glutting
4
Slide5The BGC for the monitoring of HEL and LHC proton beam
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Blackening of the BGC interaction chamber Johanna Glutting
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Fluorescence image of a single particle beam (e.g. only protons)
Slide6s
kimmer chamber
i
nteraction chamber
d
ump chamber
c
amera with optical components
1
st
skimmer
(Ø180
μ
m
)
2
nd
skimmer
(Ø400
μ
m)
3
rd
skimmer
(4m
m x 0.4mm)
view port
particle beam perpendicular to gas jet and camera axis
333
228.3
20.2
2 ... 17
n
ozzle
(Ø30
μ
m
)
nozzle
chamber
BGC Setup (simplified)
6
Blackening of the BGC interaction chamber Johanna Glutting
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10
-3
mbar
10bar
10
-9
mbar
10
-7
mbar
Slide7Tunnel installation and Planning
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Blackening of the BGC interaction chamber Johanna Glutting
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Installation of the interaction chamber by February 2020
Slide8Requirements
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Blackening of the BGC interaction chamber Johanna Glutting
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Lower the current radiation background by a factor of 200-300
Lower
reflectivity of the surfaces at Neon wavelength
584nm
R(NEG)=45%R
R(coating)=0.15 ... 0.225%ROutgasing rates compliant with LHC vacuum
Solid surface = no UFO production
Suitable for bakeout
Radiation hard
Slide9Geometrical conditions
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Blackening of the BGC interaction chamber Johanna Glutting
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The copper liner will have holes for the gas flow as displayed below
Parts that can be independently coated treated:
Vacuum chamber
Copper liner
Insert in the background of the optics
LHC beam
Gas jet
optics
Holes in the liner for the optics
Background of the optics
Slide10LESS
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Blackening of the BGC interaction chamber Johanna Glutting
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Developed for processing low SEY surfaces by CERN and Dundee
Very rough surface has the effect, that light reflects several times within the surface
higher absorptivity
Tested
samples have the reflectivity 3.5%R for copper and 5.4%R for steel when processed under nitrogen atmosphere
My state of knowledge
There is a robot developed for the processing of beam screens, that will be send from Dundee to CERN within this year
The outgassing tests on LESS samples showed good results (only little more outgassing due to the higher surface)
The question of UFOs is not solved yet
(Ivo Wevers, email contact)
Applied at the inside and possibly outside of the copper liner
Slide11Amorphous carbon
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Blackening of the BGC interaction chamber Johanna Glutting
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Also developed for a low SEY
Reflectivity
= 13%R
Approved for LHC?
Applied at the inside and possibly outside of the copper liner
Slide12LESS coated by amorphous carbon
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Blackening of the BGC interaction chamber Johanna Glutting
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Combination of the absorbtivity of the rough surface and the material
Reflectivity is not tested yet, because of problems with the spectrometer
By eye the surface is darker than before coating (darker than LESS and amorphous carbon)
Applied at the inside and possibly outside of the copper liner
Slide13Multilayer sputtering by
Polyteknik
(DK)
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Blackening of the BGC interaction chamber Johanna Glutting
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Magnetron sputtering process, coating can be adjusted to a certain wavelength
Layers: TiAl, TiAlN, TiAlON, SiO2
≈400nm
Best but most expensive coating with a reflectivity of 0.2%R
Applied at a small insert (50mm x50mm) directly in the background of the region of interest for the optics
Gap between insert and copper liner will prevent the reflection of syncrotron light
at a flat angle
Slide14Chromium Oxide
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Blackening of the BGC interaction chamber Johanna Glutting
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Reflectivity of 15%R
Only suitable for steel
Applied at the inside of the vacuum chamber
Slide15What to do
next for LHC approval?
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Blackening of the BGC interaction chamber Johanna Glutting
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Outgassing tests?
Bakeout tests?
LESS UFO issues?