1. RF-induced heating on TCTP ferrite: comparison between different support materials01.10.2012F. Carra, A. Bertarelli, A. Dallocchio, M. Garlasche’, L. Gentini Federico Carra – EN-MME

2. Outlook • TCTP RF system • Expected RF losses • Thermal simulations • Additional tests performed on ferrite support materials • Conclusions Federico Carra – EN-MME

3. TCTP RF system Ferrite Supports • Ferrite proposed for TCTP collimators: TT2-111R Trans-Tech • Curie Temperature: 375 ˚C • What is the best solution for the support material? Federico Carra – EN-MME

4. Expected Rf losses on ferrite • RF losses on ferrite evaluated by BE/ABP • Safety factor of 2 considered for the loads reported in the table below • 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 Federico Carra – EN-MME

5. thermal simulations: model Ferrite Ferrite support • 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 Federico Carra – EN-MME

6. material properties • Emissivity of the analysed materials has been evaluated combining already available data with new measurement results (M. Garlasche’ , M. Barnes, L. Gentini) Federico Carra – EN-MME

7. Thermal simulations: results • 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 CrOcoating: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) Federico Carra – EN-MME

8. Tests on black chrome • 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.” Black Chrome Graphite Federico Carra – EN-MME

9. Tests on alternative coatings • 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! Federico Carra – EN-MME

10. conclusions • 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 Federico Carra – EN-MME

11. Backup slides

12. Tests on black chrome • 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.” Black Chrome Graphite Federico Carra – EN-MME

13. Thermal simulations: results • 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 evaluatepower on each ferrite array Federico Carra – EN-MME