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First design of a PS2 prototype vacuum chamber Edgar Mahner thanks to Sebastien Blanchard, Cedric Garion, Giuseppe Foffano. Main magnet apertures (baseline) Vacuum chamber geometry for dipoles optimization parameters geometry, FE model, behavior under vacuum first prototype fabrication - PowerPoint PPT Presentation
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Edgar Mahner 1
First design of a PS2 prototype vacuum chamberEdgar Mahner
thanks to Sebastien Blanchard, Cedric Garion, Giuseppe Foffano
PS2 meeting, 11.06.2009
• Main magnet apertures (baseline)• Vacuum chamber geometry for dipoles
– optimization parameters– geometry, FE model, behavior under vacuum– first prototype fabrication
• Possible bakeout solutions• Conclusions
Edgar Mahner 2
PS2 main magnet apertures
• Proposal for outer dimensions of the vacuum system in the main magnets, now including alignment and heating jackets!– Status 16.04.2009 (MB, PS2 meeting)– Dipoles half sizes: 60 mm horizontal, 40 mm vertical– Quadrupoles half sizes: 65 mm horizontal, 45 mm vertical – First consideration for a PS2 prototype dipole vacuum chamber by C. Garion
PS2 meeting, 11.06.2009
Dipole gap:80 120 mm2
Dipole length: 4.20 m
Installation/alignment:≈1 mm (tbs)
Bakeout system:≈5 mm thick (tbs)
Maximum outer dimensions of the dipole vacuum chamber: ≈68 108 mm2
C. Garion (April 2009)
Edgar Mahner 3
Principle of the vacuum chamber geometry
PS2 meeting, 11.06.2009
34
54
dy
dx
R=5Vertical aperture reduction(or equivalent thickness)
• Objective: vacuum chamber for maximum h/v beam aperture – Shape close to a rectangular (shoe-box type) vacuum chamber with following
main parameters used for calculations:• Thickness, dy, dx
– Main assumptions:• Stainless steel (almost mandatory)• Plane stresses (axial free: required for a baked solution)• No installation pre-stress
C. Garion (April 2009)
Edgar Mahner 4
Parameters
PS2 meeting, 11.06.2009
• Assumption – The aperture is defined by the inner wall of the vacuum
chamber minus a geometrical tolerance, 0.5 mm assumed (tbc)• This tolerance could be, for example, a shape and/or straightness
deviation; under discussion with EN-MME
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.62.9
3
3.1
3.2
3.3
3.4
3.5
3.6
Wall thickness [mm]
Thic
knes
s + d
y +
0.5
The minimum vertical aperture reduction is obtained for a stainless steel wall thickness of 2mm; dy = 0.65 mm; dx = 0.1 mm
C. Garion (April 2009)
Optimization guidelineFind the smallest vacuum chamber thickness to obtain the largest beam aperture but satisfying mechanical stability (stiffness).
Edgar Mahner 5
Geometry, FE model, andMechanical behavior under Vacuum
PS2 meeting, 11.06.2009
Concept: the vacuum chamber is slightly biconvex, under vacuum it becomes almost flat no aperture reduction
Stability checked; equivalent (von Mises) stress under vacuum: 100 MPa
Stainless steels 304L: 175 – 200 MPa; 316L: 200 MPa; 316LN: 300 MPa
– Safety factor with respect to the yield stress? – But: eddy current forces have to be
estimated during the magnet ramp (1.7 T/s) and considered for the design.
Obtained beam apertures– Vertical 62.7 mm– Horizontal 103.8 mm– not including geometrical
tolerances of the vacuum chamber
= 53.9 mm
= 31
.35
mm
2
C. Garion (April 2009)
Edgar Mahner 6
PS2 prototype vacuum chamber – to be coated
PS2 meeting, 11.06.2009
G. Foffano (June 2009)
Three chambers for coating tests (Cu, a-C, TiZrV)316LN st.st. (2 mm wall thickness)3020 108 68 mm3 (with two DN 150 CF)Reduced length fabrication is possible @ CERN
DRAFTunder discussion with EN-MME
Edgar Mahner 7
PS2 prototype vacuum chamber under vacuum
PS2 meeting, 11.06.2009
G. Foffano (June 2009)
Concept: the vacuum chamber is flat, under vacuum it becomes slightly biconcave small aperture reduction
Edgar Mahner 8
Possible bakeout solutions for PS2 dipoles
PS2 meeting, 11.06.2009
S. Blanchard (June 2009)
Blue: dipole vacuum chamberRed: dipole gap (120 80 mm2)
Blue: dipole vacuum chamberRed: dipole gap (120 80 mm2)
• Conclusions – A 5 mm thin bakeout system, which was a first assumption, needs development work to increase its reliability
(problems found in LHC (warm magnets) with 4.3 mm system); a 6.7 mm thin bakeout system is o.k. (good experience, e.g. in LEIR).
– A 1 mm gap between the bakeout equipment and the dipole magnet seems (too) small, risk to damage it during closure of the upper magnet cover.
– Important assumption (agreed with GdR): bolted-type PS2 dipoles and quadrupoles, avoids to slide vacuum chambers with heating elements into magnets, no need to cut/weld flanges (very important in many aspects)
– Next steps: material/dimensions/fabrication methods/tolerances of vacuum chambers, deformation under vacuum as well as bakeout options need more studies to optimize for maximum beam aperture but also to build a (very) reliable system.