ENEN RF-induced heating on TCTP ferrite: comparison between different support materials F. Carra, A. Bertarelli, A. Dallocchio, M. Garlasche’, L. Gentini Federico Carra – EN-MME1

ENEN  TCTP RF system  Expected RF losses  Thermal simulations  Additional tests performed on ferrite support materials  Conclusions Outlook Federico Carra – EN-MME2

ENEN Federico Carra – EN-MME3  Ferrite proposed for TCTP collimators: TT2-111R Trans-Tech  Curie Temperature: 375 ˚C  What is the best solution for the support material? Ferrite Supports

ENEN Federico Carra – EN-MME4  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 1201 Case Case  RF losses on ferrite evaluated by BE/ABP  Safety factor of 2 considered for the loads reported in the table below

ENEN Ferrite support Ferrite Federico Carra – EN-MME5  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

ENEN Federico Carra – EN-MME6  Emissivity of the analysed materials has been evaluated combining already available data with new measurement results (M. Garlasche’, M. Barnes, L. Gentini) MaterialEmissivity Glidcop0.05 Stainless steel0.3 Copper OFE0.05 Ferrite0.8 Black Chrome0.6

ENEN Federico Carra – EN-MME7  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)

ENEN Black Chrome Graphite Federico Carra – EN-MME 8  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 )  “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.”

ENEN Federico Carra – EN-MME 9  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!

ENEN Federico Carra – EN-MME 10  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

ENEN

ENEN Black Chrome Graphite Federico Carra – EN-MME 12  Outgassing tests of the black chrome have been performed by G. Cattenoz (EDMS n ):  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 ). “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.”

ENEN Federico Carra – EN-MME13  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