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.