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)
Cryogenic scheme (under discussion)
Cavity/coupler assy
Part of interest
Doub
le-w
alle
d-tu
be
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
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
Fixed support
Sliding support
Inertia beam
Invar longitudinal positioner
External supports (jacks)
RF coupler
Possible supporting schemes“standard” supporting scheme
Fixed support
Sliding support
Inertia beam
Invar longitudinal positioner
External supports (jacks)
RF coupler
Possible supporting schemes“standard” supporting scheme
External supports (jacks)
RF coupler + longitudinal positioner + vertical support
Intercavity support structure
Possible supporting schemesCoupler supporting scheme
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?)
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
• 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)
Mid plane symmetry
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
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
Max sag: “to guide or not to guide?”
Stiffening of coupler/cavity assembly necessary Guiding between cavities is most probably necessary
“standard” supporting
Max. sag minimized at a/L=0.20.
A 3rd central support seems mandatory
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
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
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