Thermo-Mechanical Models for the CLIC/LAB Two-Beam Modules

Present Outcome & Future Prospects

22 February 2012

R. Raatikainen

Presentation outline

IntroductionA quick glance to the model configurationsMain differences in the thermo-mechanical model point of view

Modeling principlesCooling schemeConsidered thermal and mechanical loadsApplied boundary conditions

Finite element model description - Towards more efficient modelingMeshing definitionsModeling interconnections

Results Thermal results Structural results Summary

Conclusion & Future steps

Courtesy of D. Gudkov

LAB Module (Type 0-Type 0)

Lab module configuration to be tested without the beam – RF power dissipation is created via heaters

Courtesy of A. Samoshkin

CLIC Two-Beam Module (Type 1)

Current CLIC two-beam module configuration (type 1), frozen for CDR

Cooling scheme in TMM

It should be noted that in TMM, cooling (mass flow) is applied only for the SAS, PETS and waveguides. Thermal conditions for the DB Q, MB Q and loads can be addressed best by using current input from the manufacture or performing CFD analysis separately. This approach is done mainly in computational reasons.

DB

PETS

WG

DB Q/ MB Q Maximum temperature variation of 5°C for the

mock-up magnet was considered (based on the current reference value) – Courtesy of A. Bartalesi

Summary of the thermal dissipations in TMM

MB SAS

39 W

39 W

820 W (corresponding

to unloaded operation)

11W per WG

Thermal condition for the loads in TMM

Based on the 3D CFD cooling simulation performed earlier for the loads, the effect of the loads on the module’s structural behavior was studied (only for the lab configuration) Loads were simplidied into cylinders and the thermal conditions were imported from FLUENT → 1st load undergoes linear temperature variation of about 2.5°C compared to water inlet temperature of 35°C → the surface temperature of the 4th load has thus its highest value of about 45°C

Boundary conditions

LAB module CLIC module

Meshing definitons

Most of the thin geometrical features are modelled as shells instead of solid shells or solids → Part of the elements used in the model contains three d.o.f. (solids) and the other six d.o.f (shells) → Interconnections must be created manually and taken into account in the APDL (Ansys Parametric Design Language) script as MPC (Multibody Constraint, shell to solid interface) Both membrane and bending stiffnesses are taken into account for the shells (Reissner-Mindlin)

20-node hetrahedral solid element

10-node tetrahedral solid element

3 d.o.f.s results into 3 force components

6 d.o.f.s results into 3 force and 2 momentum components

coupledTotal amount of nodes about 3 million → over 15 million d.o.f.s !

4-node shell element

500 MPa (with a force of only few Newton!)

Low stiffness is lateral direction Ansys Bushing Joint:

Stiffness coefficients as a direct input (BOA metal bellows cataloque)

+User does not need to use any elements when defining the flexible contact+The method is numerically very stable and LINEAR!+Allows the user to probe the forces (and moments) directed to the bellows in different load configurations.

Interconnections

Two different techniques was tested for modeling the interconnections between module components; equivalent cylinderical tube and ANSYS bushing joints, where the given stiffness coefficients are input as 6x6 matrix with 3 translational and 3 rotational parameters. Both techniques resulted in the same outcome (difference only few percents) but the equivalent tube approach encountered several numerical problems → using a linear material model for such a thin (nanometer scale) membrane results into large strains/stresses already in very low loading values.

Illustration: equivalent tube VS. Bushing joint

→In the future TMM configurations, an alternative solution for the bellows could be taken into account.

Structural behavior of the bellows(equivalent tube) under RF-load

Structural behavior of the bellows(Bushing joint) under RF-load. Smooth behavior!

Item   ValueMax temp. of MB 43 ˚CMax temp. of DB 35.7 ˚CWater output temp MB 34.8 ˚CWater output temp DB   29.8 ˚C

Thermal results – LAB module

Item x y zMax. def. at MB line, RF 183 μm 8 μm 9 μm

Item x y zMax. def. at MB line, RF (compact loads included)

189 μm 8 μm 10 μm

Environment at 25°C

Structural results – RF – LAB module

x-direction y-direction z-direction

Item x y zMax. def. at DB line, RF 46 μm -8 μm 7 μm

Environment at 25°C

x-direction y-direction z-direction

Structural results – RF – LAB module

Item x y zMax. def. at MB line, Vacuum 10 μm -27 μm 9 μmMax. def. at DB line, Vacuum 2 μm 130 μm 12 μm

Structural results – Vacuum – LAB module

Displacement in y-direction

Item x y zMax. def. at MB line, Gravity -5 μm -2 μm -26 μmMax. def. at DB line, Gravity 0 μm -4 μm -40 μm

Actual deflection < 6 µm (actuator stiffness → ∞)

”drop” of the module, when actuator stiffness (snake system) is notified

Structural results – Gravity– LAB module

Item Unloaded LoadedMax temp. of the MB 42.5 ˚C 40.7 ˚CMax temp. of the DB 34˚C 34˚CWater output temp MB 35.0 ˚C 34.9 ˚CWater output temp DB 28.2 ˚C 28.2 ˚C

Thermal results – CLIC module

x-direction y-direction z-direction

Structural results – RF – CLIC module

Item x y zMax. def. at MB line, RF, unloaded

-45 μm 1.6 μm 15 μm

Max. def. at MB line, RF, loaded

-38 μm 1.4 μm 12.4μm

Environment at 30°C

Item x y zMax. def. at DB line, RF 15 μm 0 μm 6 μm

x-direction y-direction z-direction

Structural results – RF – CLIC module

Environment at 30°C

Item x y zMax. def. at MB line, Vacuum 0 μm -130μm -4μmMax. def. at DB line, Vacuum 3 μm 53 μm 10 μm

Structural results – Vacuum– CLIC module

Structural results – Gravity – CLIC module

Item x y zMax. def. at MB line, Gravity 0 μm -8 μm -22 μmMax. def. at DB line, Gravity 2 μm -10 μm -35 μm

”drop” of the module, when actuator stiffness (snake system) is notified

Conclusion

The temperature of the module in both configurations rises over 40°C due to the RF-power dissipation The water temperature rise is about 10°C in MB and about 5°C in DB side at the most Under RF heat dissipation, the structural deformation has significantly larger values in the lab configuration (longitudinal about 180 µm) than in the CLIC configuration (longitudinal about 45 µm) due to different supports/interconnectionsThe transversal defomation of the CLIC module from unloaded to loaded operation is less than 3 µmVacuum created displacement are turning the beams towards each other. The vacuum is not uniformly distributed especially on the DB side and thus, possible tilt in the beam axis is seen. However, the vacuum created displacement could be further studied by improving the supporting system and interconnections.Under gravity load the module is ”dropped” about 20-40 µm. The actual deflection of the RF structures can be calculated assuming infinite stiffness for the actuators.

Further studies

Comparative test results are required to verify the current results → Improved understanding of the module’s thermo-mechanical behavior and its simulation model can then be propagated to the following module generationsThe current TMM has been numerically/technically significantly improved if compared to the very first TMM version → As a next step, transient phenomena could be studied more closely (e.g. What is the time required to reach fully steady-state thermal condition between unloaded and loaded operation for the module? How the module acts in coupled transient thermal-structural enviroment (currently possible in ANSYS 14.0)? Furthermore, structural optimization should be considered → What kind of supporting for the RF components including interconnections would lead into a minimum deformation?Other configurations...

Continuing TMM towards any transient/iterative cases using a such complex model presented here requires still signigicant computing resources – What is the work needed vs. the gain? - As it best the model should be considered to predict the very global response of the module. Test Module (type 1) – vacuum

reservoir replaced by minitanks

Extra – Heat dissipation - LAB

4 x 11W for waveguides

Extra – Considered heat dissipation – CLIC (Type 1)

Integrated total thermal dissipation along the beam line per AS are about 410W and 336W for unloaded and loaded operation, respectively

In loaded operation the total heat for AS is 336W instead of 420W

3 x 11W for waveguides