CLIC meeting Accelerating structure thermomechanical behavior G Riddone
CLIC meeting Accelerating structure thermomechanical behavior G. Riddone. 25. 06. 2010 Contribution from R. Nousiainen, J. Huopana, T. Charles
Content � Recall of main issues � Recall of module heat dissipation � Module cooling scheme � Thermo-mechanical analysis: � Accelerating structures � Two-beam modules � Remarks 2 GR, BE-RF, 25/06/2010
Main issues • Tolerances must be preserved in static and dynamic conditions (RF and beam dynamics constraints): � shape accuracy for machining: ± 2. 5 mm, � pre-alignment: 14 um @ 1 s � water induced vibrations • Optimization of several parameters: temperature stabilization, pressure drop, volumetric flow, Re, heat transfer coefficient, … 3 Compromise between opposite requirements from several technical systems GR, BE-RF, 25/06/2010
Accelerating structure heat dissipation Cell-by-cell heat dissipation Accelerating structure EDMS 964717 • Thermal load is not constant through an accelerating structure • Considered unloaded condition and loaded conditions Distribution of heat flux over 480 mm: superstructure Unloaded 821 W Loaded 672 W 4 GR, BE-RF, 25/06/2010
Module heat dissipation (water cooled) For details, see EDMS# 910399 5 GR, BE-RF, 25/06/2010
CLIC Workshop 2007 Total per linac (2007): 65 MW Baseline: one access point for inlet and outlet pipes J. Inigo-Golfin R. Nousiainen Action: reduce mass-flow rate, increase temperature difference between supply and return pipes 6 GR, BE-RF, 25/06/2010
Module cooling scheme Still one inlet/outlet access point close to IP (§CES WG Dec 2008) 35 ˚C 25 ˚C 45 ˚C Twater_in = 25 ˚C [± 2 ˚C] Re = 5800 (d = 7 mm) h = 3750 W/m 2/K V= 70 l/h [per AC. STR. ] V = ~350 l/h [per MODULE] V = 3500 m/h [per LINAC] 7 GR, BE-RF, 25/06/2010
Super accelerating structure Max 39. 7 °C Unloaded Max 38 °C Loaded Thermal analysis Temperature difference Unloaded to Loaded 1. 9 K [K] 0. 8 K 8 GR, BE-RF, 25/06/2010
Accelerating structure Beam pipe deformation: unloaded to loaded structural effect beam Structural analysis Fixed Max 2, 5 µm Transverse movement induced by thermal expansion (volumetric flow can be adjusted to limit this effect) 9 GR, BE-RF, 25/06/2010
Two-beam module: definition � TMM model: Static thermal � Static structural � � Loading conditions Gravity � Vacuum � Nominal unloaded RF load � � 8 accelerating structures brazed into one 2 -m long unit Component Girder Geometry of Baseline configuration RF structure supports RF structures Vacuum system 10 Material Si. C E [Gpa] 420 α [µm/m-°C] 5 Al EN AW 7075 Cu OFE Stainless steel 72 110 200 23. 6 16. 4 17. 3 GR, BE-RF, 25/06/2010
Two-beam module: unloaded case Surrounding air: 30˚C Thermal � Girders are at different temperature, reference T = 25 ˚C � � analysis Hottest spot in the AS – 40˚C (loads omitted) 11 GR, BE-RF, 25/06/2010
Two-beam module: unloaded case Structural analysi Gravity + Vacuum + RF (unloaded) Notice lateral deformation and wave guide deformation 12 GR, BE-RF, 25/06/2010
Influence of T difference 2007 2010 V = 2 m/s Tunnel pipe diameter: case of unique access point 13 GR, BE-RF, 25/06/2010
14 GR, BE-RF, 25/06/2010
Remarks � Estimation of power dissipation: temperature difference across structures compromise between several technical constraints � Thermal issues are big challenge for micrometric precision of structures � During RF ramp up ~15 K variation in temperature is expected Large deformations � � Unloaded to loaded ~2 K variation in temperature Thermally caused deformations linearly proportional to temperature variation Minimize temperature fluctuations mass-flow adjusted accordingly � Module thermo-mechanical analysis based on input from technical experts � Combines separate simulations results Shows fundamental thermo-mechanical behavior Helps defining current improvement points � 15 Vacuum and RF ramp up (thermal variations) causes significant deformations Thermo-mechanical effect mitigation is essential GR, BE-RF, 25/06/2010
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