ENEN RF-induced heating on TCTP ferrite: comparison between different support materials 01.10.2012...
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Transcript of ENEN RF-induced heating on TCTP ferrite: comparison between different support materials 01.10.2012...
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Federico Carra – EN-MME 1
RF-induced heating on TCTP ferrite: comparison between different
support materials
01.10.2012
F. Carra, A. Bertarelli, A. Dallocchio, M. Garlasche’, L. Gentini
01.10.2012
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Federico Carra – EN-MME 2
TCTP RF system
Expected RF losses
Thermal simulations
Additional tests performed on ferrite support materials
Conclusions
Outlook
01.10.2012
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Federico Carra – EN-MME 3
TCTP RF SYSTEM
01.10.2012
Ferrite proposed for TCTP collimators: TT2-111R Trans-Tech Curie Temperature: 375 ˚C What is the best solution for the support material?
Ferrite
Supports
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Federico Carra – EN-MME 4
EXPECTED RF LOSSES ON FERRITE
01.10.2012
Case 1: nominal LHC operation Case 2: High-Luminosity LHC Case 3: High-Luminosity LHC, with reduced bunch length (0.5 ns) Pessimistic case
More details about the 3 cases in H. Day’s presentation
Heat losses (uniformly distributed along the longitudinal coordinate)
Total power on collimator [W]
Power loss on 1 ferrite array [W]
Case 1 20 1
Case 2 110 6
Case 3 375 20
RF losses on ferrite evaluated by BE/ABP Safety factor of 2 considered for the loads reported in the table below
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Federico Carra – EN-MME 5
THERMAL SIMULATIONS: MODEL
Ferrite support
Ferrite
01.10.2012
2D analysis: power load on ferrite considered constant towards longitudinal coordinate 3 possible materials for the support:
Stainless steel 316LN Copper-OFE Copper-OFE with a black chrome coating
Exchange by conduction and by radiation (thermal resistance between ferrite and support was calculated analytically): radiation is dominant
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Federico Carra – EN-MME 6
MATERIAL PROPERTIES
01.10.2012
Emissivity of the analysed materials has been evaluated combining already available data with new measurement results (M. Garlasche’ , M. Barnes, L. Gentini)
Material Emissivity
Glidcop 0.05
Stainless steel 0.3
Copper OFE 0.05
Ferrite 0.8
Black Chrome 0.6
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Federico Carra – EN-MME 7
THERMAL SIMULATIONS: RESULTS
01.10.2012
Pure copper OFE: worst choice, penalized by copper low emissivity Stainless steel: temperature up to 150 ˚C in the worst case scenario, with a safety ratio > 2 with
respect to the Curie Temperature Copper OFE with CrO coating: best choice from the thermal point of view, temperature on ferrite
decreased by 25-30% with respect to stainless steel (this reduction could be ~ 40% when the upper screen is also coated with CrO)
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TESTS ON BLACK CHROME
Black Chrome
Graphite
01.10.2012 Federico Carra – EN-MME
Black chrome presents a dusty surface (risk of particles detachment) SEM observations performed by N. Jimenez Mena compared morphology and porosity
of Black Chrome and Graphite (EDMS n. 1220547) “The Cr coating shows many cracks and some inhomogeneity on the surface. However, the
porosity and discontinuities in the graphite reference seem to be higher.”
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TESTS ON ALTERNATIVE COATINGS
01.10.2012 Federico Carra – EN-MME
The black coating used for radio tube anodes has been taken in consideration: Very high emissivity, measured with the thermal camera: 0.9 Even more volatile surface than CrO, easily detachable by hand!
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CONCLUSIONS
01.10.2012 Federico Carra – EN-MME
RF losses on ferrite calculated by BE/ABP are used as input for FEM thermal simulations Bad contact between ferrite tiles and supports: thermal exchange by radiation is
dominant Emissivity is the most important parameter for the analysis: ad-hoc measurements
performed on considered materials Three solutions proposed for ferrite support material: Copper OFE, Stainless steel and
Copper OFE with black chrome coating From the thermal point of view, Copper OFE with black chrome coating is the best
solution to decrease maximum temperature on ferrite Highlighted problem: inhomogeneity and volatility of the surface (graphite, often
used for collimator applications, can anyway be more porous) Stainless steel presents a good compromise in terms of efficiency, cost and simplicity of
the solution The other tested coatings, while presenting high emissivity values, are too volatile to be
taken into consideration
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TESTS ON BLACK CHROME
Black Chrome
Graphite
01.10.2012 Federico Carra – EN-MME
Outgassing tests of the black chrome have been performed by G. Cattenoz (EDMS n.1213905): High outgassing rates, but within the limits for LHC vacuum Dusty surface (risk of particles detachment) A SEM observation was performed by N. Jimenez Mena to compare morphology and porosity of
Black Chrome and Graphite (EDMS n. 1220547). “The Cr coating shows many cracks and some inhomogeinities on the surface. However, the porosity and discontinuities in the graphite reference seem to be higher.”