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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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8

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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9

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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10

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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Backup slides

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12

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.”

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Federico Carra – EN-MME 13

THERMAL SIMULATIONS: RESULTS

01.10.2012

Results showed in slide 7 have been updated with the realistic inputs presented by H. Day (no safety factor considered in this case)

To be divided by 2 to evaluate power on each

ferrite array