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