Storage Ring Vacuum Systems

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Storage Ring Vacuum Systems

• H-C. Hseuh, C. Foerster, J. Hu, G. Mahler, S.
  Pjerov, S. Sharma, J. Skaritka, C. Stelmach,
• October 10, 2006

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Outline
Design Principles Vacuum Cell Layout Cell
Chambers and Material - Al Chamber Cross Sections
and Analysis Vacuum Pumping and Pressure
Profiles Front End Vacuum Summary
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Design Principles

• Adequate Apertures for Beam and Exit Photons
• BSC - 25mm x 70mm
• Chamber cross section precision to 1 mm
• Chamber temperature stability 1oC

• Low Impedance
• Beam channel with smooth cross sections
• Minimize no. of tapers, steps, gaps low Z
• Minimize no. of holes, slots for pumps and
  bellows low Z/n
• Inner wall surface finish to µm

• Low Pressure of lt 1 nTorr ( 50 H2)
• Low outgassing and desorption after in-situ bake
  and pre-conditioning
• Intercept photons at discrete absorbers
• Located absorbers far away from the source
• Lower power density and simpler cooling
• High effective pumping speed (IP TSP) at
  absorber locations

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Vacuum Cell Layout
30 standard cells of 19m eachLSS 15 x 5m and
15 x 8mIsolatable with 60 gate valves
FE
Absorber locations
3m
3m
5m
4m
4m
Cell chamber material extruded aluminum 6063-T5
NSLS and APS experience fabrication cost
thermal/electrical conductivity ease of in-situ
baking 60 bending chambers of 6o each, 3m long
90 multipole chambers of 3 different
lengths/types gt 20 day-one LSS chambers of
various types extruded Al with same cross
sections as cell chambers
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AL-6063 (T5) Extrusion for the Cell Chamber
Comparison of chamber materials
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Fabrication Steps for Cell Aluminum Chambers (G.
Goeppner/E. Trakhtenberg, APS, ANL)
Material () Aluminum 6063-T5 billets, 350mm
diameter Extrusion () only a few available
(interested) vendors in the US (due
to the large cross sections and required
dimensional precision) ? gt 1 yr to develop
the correct parameters for each type
before production can start Stretching to
straighten and eliminate the waviness of inner
surface Roll Bending () to obtain the correct
curvature for bending chambers Machining ()
ports for beam lines, BPMs, absorbers, pumps, .
profiles at multipole, transitions,
Cleaning () to remove surface contaminants
and reduce oxide layer Welding () photon exit
ports, SS-Al bi-metal flanges, etc. Assembly
() BPMs, NEG strips, pumps, gauges,
absorbers, .
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3-D Models of Cell Chambers
Bending chamber, 3m long
3 Multipole magnets/girder
Bending magnet/girder
Multipole chamber 3, 5m long
Special Bending chamber for IR lines
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Chamber cross sections
Dipole extruded cross sections
3mm wall
BSC 25 x 70 mm2
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Chamber cross sections contd
BSC 25 x 70 mm2
Multipole chamber extruded cross section
3.2mm
_at_ sextupole
After Machining
3.9mm
_at_ quadrupole
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von Mises stress at sextupole location
SM 172 MPa (Localized)
SY 144 MPa for Al 6063-T5 SM (D) 54 MPa SM
(Q) 100 MPa
Chien Pai, C-AD
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Deflection at sextupole location
DM 0.6mm x 2
DM (Dipole) 0.36mm x 2 DM (Quad) 0.57mm x 2
Chien Pai, C-AD
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UHV Pumping and Pressure Profiles Pavg lt 1 nTorr
In-situ baking of entire cells at 120 C x 40 hrs
To reduce thermal outgassing to lt 1x10-12
Torr.l/s/cm2 Total ring thermal gas
load of lt 1x10-5 Torr.l/s Pressure will be
dominated by photon stimulated desorption (PSD)
photons from BM 1x1021/s 7x10-5
Torr.l/s Assuming ? (PSD) 2x10-6
mol/hv for Cu after ?hv gt 1024/m
photons from each 7m DW 6x1020/s
with 15 intercepted by the ring absorber ?
7x10-6 Torr.l/s NEG strips 1,400 m _at_ gt 100
l/s/m for active gases Reside in
ante-chambers as in APS Pump thru the photon
slots ( C 200 l/s/m) Ion pumps and TSP of
500 l/s at absorbers 5 IP/TSP per cell 2
for each ID location
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PSD Yield versus Photon Dosage measured at NSLS
U9A X28 beam lines
Cu
Al
100A.hr at NSLS
C. Foerster, et.al, J. Vac Sci. Technol. A14,
1273(1996).
C. Foerster, et.al, J. Vac Sci. Technol. A19,
1652(2001).
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Pressure Profiles (BM only) with Various Pumping
Schemes
By E. Hu F. Makahleh
Using Molflow and VacCal codes
Distributed NEG strips are critical to achieve
low Pavg!
Preliminary
Pavg 1.5 nTorr
Pavg 0.3 0.1 nTorr
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Pressure Profiles with and w/o Damping Wiggler
Radiation
By E. Hu F. Makahleh
Preliminary
Pavg 0.3 nTorr
Pavg 0.27 nTorr
Absorber
IP/TSP
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Beam Line Front End Vacuum
Front end design depends on type of radiation
source (BM or ID) base on experience at
NSLS and APS Details are being developed with the
beam line determination
Front End Vacuum Systems
Pressure of a few nTorr to protect the UHV SR
vacuum from HV beam line with window or
differential pumping Entire FE to be bakeable to
200 C (all metal, UHV material, etc) IP/TSP
combination (same as SR) at high heat load
components
PS photon shutter BS Bremsstrahlung beam stop
IP/TSP ion pump/titanium sublimation pump GV
gate valve
IP/TSP
GV
BS
PS
Typical layout of Day 1 front end w/o beam line.
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Typical layout of hard/soft x-ray beam line front
end.
SS x 2
PM photon mask CO collimator PS photon
shutter BDA beam defining aperture SS safety
shutter
FV
BDA
GV
BPM
GV
PS
BPM
CO
PM
IP/TSP
IP/TSP
IP/TSP
GV gate valve FV fast valve IP/TSP ion pump
and titanium sublimation pump
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Major Goals for FY07 and FY08
Detail layout of cell and ID chambers, absorbers
and pumps Detail design of cell chambers and
absorbers Fabricate or acquire (from APS?) a few
prototype cell chambers Learn and develop
expertise in NSLS-2 chamber fabrication
Establish formal collaboration with APS
colleagues Work with potential extrusion
vendors ASAP Refine the fabrication
technique to meet the specifications
Perform mechanical and vacuum evaluation on
prototype chambers Dimensional precision,
support, alignment NEG strip supports and
installation Vacuum performance
In-situ baking, NEG activation
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Summary
Preliminary layout of cell chambers is
progressing well Improvements are made
together with the lattice Stress and deflection
of chambers at multipole locations are
acceptable Detail chamber design can be
started Ray tracing of SR fan continues to
optimize the absorber design Simulation of the
pressure profiles has started. Including
the PSD gas load from ID devices. To be
refined with the final chamber/absorber design
Pressure of lt 1 nTorr is achievable with
present pumping scheme Need to collaborate with
APS colleagues on chamber fabrication Need to
work with extrusion vendors soon