spl rf coupler: integration aspects
DESCRIPTION
SPL RF coupler: integration aspects. V.Parma, TE-MSC with contributions from WG3 members: Th.Renaglia, U.Wagner, P.Coelho, N.Bourcey, A.Vandecraen . Review of SPL coupler, CERN 16th-17th March 2010. β =1 cryo -module in SPL layout ( drwg SPLLJL__0014). - PowerPoint PPT PresentationTRANSCRIPT
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SPL RF coupler: integration aspects
V.Parma, TE-MSC
with contributions from WG3 members:Th.Renaglia, U.Wagner, P.Coelho, N.Bourcey, A.Vandecraen
Review of SPL coupler, CERN 16th-17th March 2010
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β=1 cryo-module in SPL layout(drwg SPLLJL__0014)
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Cryogenic scheme (under discussion)
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Cavity/coupler assy
Part of interest
Doub
le-w
alle
d-tu
be
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Coupler integration functionalities (non-exhaustive list)
Functionality Requirement CommentRT/atm. to 2K/vacuum penetrations
-minimise static HL;- leak-tight penetration (o-ring);- mechanical decoupling from vacuum vessel (if not a support);
- Optimise thermal design
Isolation between coupler and beam vacua
- leak tight window- vacuum gauge outside cryostat
- Single ceramic window for HP RF
Gas cooling of double-walled tube (5 K-300 K)
- minimise static HL;- cryostat feedthrough of cooling line:
- leak-tight- avoid atm. moisture (T>dew
point)
- externally-mounted manual valves (presetting);- Heater for control (Ofelia’s talk)
Coupler maintenance Maintenance-free No in-situ intervention
Coupler as support (option under study)
-support/position cavities;- coupler flange mechanically fixed to vacuum vessel;- fix longitudinal position of cavities;- mechanical support of thermal shield
- impact of gas cooling on position (Ofelia’s talk);- Vacuum vessel as mechanical reference
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Transversal position of cavities inside cryostatBUDGET OF TOLERANCE (preliminary)
Step Sub-step Tolerances (3σ) Total envelopes
Cryo-module assembly
Cavity and He vessel assembly ± 0.1 mm (TBD)Positioning of the cavity
w.r.t. beam axis ± 0.5 mm
Supporting system assembly ± 0.2 mm (TBD)
Vacuum vessel construction ± 0.2 mm (TBD)
Transport and handling (± 0.5 g any
direction)N.A. ± 0.1 mm (TBD)
Stability of the cavity w.r.t. beam axis
± 0.3 mmTesting/operation
Vacuum pumping
± 0.2 mm (TBD)
Cool-down
RF tests
Warm-up
Thermal cycles
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Fixed support
Sliding support
Inertia beam
Invar longitudinal positioner
External supports (jacks)
RF coupler
Possible supporting schemes“standard” supporting scheme
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Fixed support
Sliding support
Inertia beam
Invar longitudinal positioner
External supports (jacks)
RF coupler
Possible supporting schemes“standard” supporting scheme
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External supports (jacks)
RF coupler + longitudinal positioner + vertical support
Intercavity support structure
Possible supporting schemesCoupler supporting scheme
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Coupler position: top ...?Contras:• Interferes with bi-phase tube move
sideways• Waveguides/coupler more exposed to
personnel/handling (damage, breaking window?)
Pros:• Easier connection of waveguides• Easier access (needed?)
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Coupler position: ...or bottom?Contras:• Space needs for waveguides under
cryostat• If coupler not a support (bellows)
support on top, i.e. centered tube not possible
Pros:• Centered bi-phase tube symmetry• Waveguides/coupler protected
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• Defines minimum diameter of “pipeline” type vessel:– Lenght of double-walled tube– Integration of thermal shield
RF coupler assembly constraints
Note: drwgs for information only (concept not final)
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Mid plane symmetry
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Need guiding?
l
2l
- If sag small enough- If strenght OK- isostatic
- couple cavities- hyperstatic
mid cavities most critical: sag reduces only to ½
No
Yes
Equivalent sketchLayout
inter-cavity guides
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Mass loads on internal supports(preliminary)
Description Load Comment
Cavity/he vessel/tuner ~2.0 kN per assembly (x 8 per cryomodule)
Piping/thermal shield/MLI 0.8 kN equally shared on coupler tube
Transport accelerations ± 0.5 g each direction
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Max sag: “to guide or not to guide?”
Stiffening of coupler/cavity assembly necessary Guiding between cavities is most probably necessary
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“standard” supporting
Max. sag minimized at a/L=0.20.
A 3rd central support seems mandatory
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comparing solutionsA) Coupler supporting scheme B) “standard” supporting scheme
Pros ContrasDesign simplicity Vacuum vessel:
- Stiffness (thickness, stiffeners)- Dim. stability- Precision machining- Cost
Single cavity adjustment at assy
Positioning stability (thermal, weld relieving...)
Inter-cavity guiding
Mid cavities guiding sufficient?
Pros ContrasCavities mechanical isolation from external perturbations: dim. changes (thermal, weld relieving), vibrations...
Design complexity
Vacuum vessel simplicity:-Reduced machining precision- reduced thickness
Central support needed (?)
Complex cavity adjustment at assy
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Summary• Coupler length (double-walled tube) sets
minimum diameter of cryo-module• Coupler could be used as cavity support and is an
interesting option• Vacuum vessel become of paramount importance
for mechanical positioning/stability• Guiding between cavities probably needed
(relieve cantilever)• In case of “standard” supporting solutions,
coupler design considerations still valid mechanical decoupling with bellows