Storage Ring Vacuum Systems

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Storage Ring Vacuum Systems
H. Hseuh, Vacuum Group ASAC Review of NSLS-II
July 17-18, 2008
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Outline

• Vacuum System Requirement and Layout
  
• Vacuum Chamber Design
• Prototype Chamber Fabrication
• Ray Tracing, Absorbers and Pressure Profiles
• Layout of Straight Sections for ID, Inj. and RF
  
• Development in Bellows, BPM Buttons, NEG Strip
  Support
• Development in In-situ Bake and Ozone Cleaning
• Summary

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Vacuum Requirements

• Vacuum Chambers - Adequate Apertures and Low
  Impedance
• Beam aperture 25 mm (V) x 76 mm (H)
• Chamber straightness - lt 1 mm / 5 m
• Smooth cross section changes inclination angle lt
  10o
• Minimum steps or cavities lt 1 mm
• Mechanical stability 1 fixed 2 flexible invar
  supports at BPMs

• P(avg) lt 1 nTorr (gt 50 H2, lt 50 CO, CO2, CH4,
  ),
• ? (beam-gas) gt 40 hr (inelastic scattering)
• Local pressure bumps ? bremsstrahlung radiation
• Intercept BM photons at discrete absorbers
• To protect un-cooled flanges and bellows
• Large ion pump and TSP (or NEG cartridge) at
  absorbers
• Two NEG strips in antechamber to provide linear
  pumping

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Cell Vacuum Chamber Layout
ID Beamline
S2
S3
BM Beamline
S1
S4
L.S.
Absorbers/pumps
S5
S1
S6
S.S.
Aluminum Cell Chambers
Stainless chambers
S2 - 3.6m
Dipole chamber, 6o bend
S3 - 3m
Multipole chamber
S4 3.3m
S5 3m
S6 3.7m
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Cell Chamber Cross Sections and Analysis
Multipole Chamber
Dipole Chamber
Extruded
Extruded cross section
3 mm wall
Bended and machined
At Quadrupole
Maxi. d 0.3 mm x2 Max. S 42 MPa
Machined at pole locations
At Sextupole
3.1 mm wall
Maxi. d 0.27 mm x2 Max. S 64 MPa
Syield (A6063T5) 145 MPa Sstress (A6063T5)
186 MPa
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Aluminum Cell Chamber Fabrication
L. Doom
Extrusion ? bending ? machining ? cleaning ?
welding ? assembly .






V 1,2
V 3
V 4, 5, 6
APS
APS
BNL
End plate
Machining
Extrusions
Machining
End Assy
End plate bi-metal flanges
Test extrusion with two vendors completed
Fabricate two S4 chambers by Sept Machining
by CS and by vendor started Weld development
by APS started Bending of dipole extrusions
starts soon
Welding at APS
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Ray Tracing of Photon Fans

• To define photon fans and absorber locations
• ? To ensure adequate apertures for photon
  fans
• ? To protect un-cooled flanges and bellows
• ? To estimate power, density and ?T for
  absorbers, and P profile

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DW and BM Photon Fans at S1-S4 Region
M. Ferreira
S2
S3
S4
DW ABS gt 15 kW
S2
S3
S3
Larger bellows and RF fingers to accommodate
canted DW fan
Vertical fan hitting Top/bottom wall
S4B
S4A
Source Location P(W)
BM S3, S6 5EPU S1-S3 lt 35 IVU20
S1 160 DW S1 166
S2 280 S3 270
Large SR power intercepted here Limited space
for pumping ports and multipoles
on magnet shields
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Simulation of DW vertical power using SPECTRA8
M. Ferreira
S2
S1B
S3
S1A
DW 1
DW 2
h 10 - 25 mm
h 15 - 25 mm
h 9 mm
From DW1
1.8 mrad
P 166 W
P 274 W
P 230 W
From DW2
- 1.8 mrad
P 6 W
P 40 W
?P lt 0.3 W/cm2
DW fan profile
?P lt 0.5 W/cm2
Power and density are not excessive for S2 and S3
chambers Flange absorbers may be added at
S1A-S1B, S1B-S2, and S2-S3? to trim
vertical fan effectively, still with reasonable
impedance
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Photon Absorbers (8-10 per cell)
Flange
Stick
Crotch
Crotch in dipole
Stick in multipole
Damping Wiggler Absorber
lt 3 W/mm2, Tmax 68oC
lt 12 W/mm2, Tmax 200oC
BM Absorber Positions and Power
Absorber brazing development started
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Absorber Positioning vs. Aperture Requirement
W. Guo
-- 3 aperture ? ABS X position
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Molflow Code (R. Kersevan/ESRF)
Pressure Profile with and without DW
E. Hu
Local ?P w/ 15 DW fan ? bremsstrahlung radiation
To be updated
Pavg 0.25 nT
SS
LS
3 GeV, 0.5A, ? 1x10-5
Pavg 0.13 nT
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Layouts for Insertion Device Straights
ID Chamber Design Chamber inner height magnet
gap - 3 mm Extruded Al with NEG strips in
antechamber Or extruded Al w/NEG coated
h 7.5 mm, 1.25 mm wall
APS ID chamber
h 8 x 57 mm, 1mm wall
ESRF NEG coated chamber
9.3 m straight for 2 x 3.5 m DW
6.6 m straight for 2 x 2 m EPU
Limited space for stand-alone ID BPMs
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Layouts for Injection and RF Straights
Bellows transition
Injection Straight
RF Straight
Working closely with AP, Diag, Magnet and other
systems on the layout of special components
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Choice of RF Shielded Bellows
M. Ferreira
RF Bellows Requirements Max mis-alignment 2 mm
Max comp/extension 12 mm Max angle
deviation 15 mrad
Inside fingers Outside fingers (APS, LNLS)
(Soleil, Diamond, etc) Simple, reliable Lower
impedance
inside fingers
outside fingers
inconel springs
Outside fingers Wider fingers Fewer fingers
3D model for impedance simulation
Inside or outside fingers?
Be-Cu fingers
Solid sleeve
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Impedance of Other Vacuum Components
Work closely with AP on vacuum components
impedance simulation and approval
A. Blednykh
S4A chamber with absorber and shielded pumping
ports
S4A absorber and pump port
GV RF shields
Multipole chamber with stick absorber and pumping
ports
Dipole chamber with crotch absorber and pumping
ports
Flange absorber
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Mounting of BPM Buttons/Flanges
P. Cameron
Optimum design 7 mm Ø buttons, 16 mm apart? (O.
Singhs talk)
50
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CD-2 Design 10mm Ø button /34 mm Ø flange
/Helicoflex seal
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12 mm wall may be too thin for bolts/inserts
sealing 15 mm wall?
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Rectangular flange? Sealing reliability?
7mm Ø 12 mm apart w/ 44 mm Ø flange
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NEG strip supports
L. Doom, K. Wilson
Riveted mounting every 10cm, with alumina
insulators on carrier plates Prototype to be
tested on APS chambers for reliability and
flexibility
NEG strips in Antechamber
NEG support development using APS chambers
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In-situ Bake with External Heaters
M. Ferreira, F. Lincoln
T 120oC achievable with foil heaters mounted at
drift space (lt 1 kW/m) Need to optimize power,
heater temp, non-magnetic, insulation,
etc Eliminate the needs of high P, hot water
system, a major ESH concern
APS chambers for bakeout development
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Ozone Cleaning Development
K. Wilson
Flush chamber with lt 500 ppm O3 in O2 to break
and remove contaminants
Process developed by T. Momose, KEK Final
cleaning prior to installation (after
alignment) Extensive O3 monitoring to meet ESH
requirements System being assembled for testing
Ozone system flow diagram
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Summary

• Cell vacuum chamber design is well advanced
• Test extrusion of both cross sections completed
  with two vendors
• Machining and weld development of prototype
  chambers are underway
• Ray tracing and absorber development continues
• Straight section layouts for ID, RF and Inj has
  started
• RF shielded bellows design has started
• Work with AP on vacuum component impedanace
• Work with Diag. on finalizing BPM
  button/feedthru design.
• NEG strip supports developed and is being tested
• Chamber bakeout with foil heaters is successful
• Ozone cleaning system developed and is ready for
  evaluation