Engineering Department ENEN Choice of the material for TCTP ferrite supports Collimation Working Group F. Carra, G. Cattenoz, A. Bertarelli, A. Dallocchio, M. Garlaschè, L. Gentini On the behalf of TCTP design, prototyping and manufacturing team 22 April 2013F. Carra – EN-MME1

Engineering Department ENEN  TCTP RF system  Thermal treatment on TT2-111R ferrite  Outgassing measurements on ferrite after thermal treatment  Ferrite heating during operation: thermal simulations  Comments on support materials  Conclusions and future actions Outlook 22 April 2013F. Carra – EN-MME2

Engineering Department ENEN  Ferrite proposed for TCTP collimators: TT2-111R (Trans-Tech).  Curie Temperature: 375 ˚C.  Treatment at high temperature before installation in the machine necessary to decrease outgassing of ferrite. Ferrite Supports TCTP RF system 22 April 2013F. Carra – EN-MME3

Engineering Department ENEN  First cycle (air):  Heating/cooling rates not exceeding 100 ˚C/h;  Plateau of 48 hours at 1000 ˚C;  Estimated duration of the cycle ~ 70 hours.  Second cycle (vacuum):  Vacuum level not higher than mbar for all the duration of the treatment;  Ferrite tiles must remain at 1000 ˚C for at least 48 hours;  Heating/cooling rates shall be adjusted in order to never exceed mbar and shall never exceed 100˚C/h;  Estimated duration of the cycle ~ 180 hours. Proposed thermal treatment on TT2-111R 22 April 2013F. Carra – EN-MME4  All details in EDMS document “Thermal Treatments of Trans-Tech TT2-111R Ferrite for TCTP and TCSP Collimators”  Treatment divided into two cycles: the first one in air, the second under vacuum.

Engineering Department ENEN Outgassing measurements 22 April 2013F. Carra – EN-MME5  Treatment at 400 ˚C not sufficient: following bakeout at 250 ˚C, ferrite outgassing at room temperature is larger than unfired stainless steel!

Engineering Department ENEN Outgassing measurements 22 April 2013F. Carra – EN-MME6  After proposed treatment at 1000 ˚C and following bakeout at 250 ˚C, outgassing at RT is much lower than unfired stainless steel and comparable to “as received” Ferroxcube.  Outgassing rate decreased by 2 orders of magnitude w.r.t. treatment at 400 ˚C!  Data above 100 ˚C are extrapolated (additional measurements ongoing).

Engineering Department ENEN  Estimated outgassing flow for one TCTP collimator at room temperature:  1600 cm 2 of ferrite ~ 2∙10 -9 mbar ∙ l/s  2300 cm 2 of tungsten ~ 2∙10 -9 mbar ∙ l/s  5000 cm 2 of stainless steel ~ 1∙10 -8 mbar ∙ l/s  Total (one collimator): 1.5∙10 -8 mbar ∙ l/s  If the ferrite alone is heated up to 100 ˚C:  1600 cm 2 of ferrite ~ 2∙10 -8 mbar ∙ l/s  Total (one collimator): 3∙10 -8 mbar ∙ l/s  LHC vacuum specification limit 1∙10 -7 mbar∙l/s (EDMS )  This treatment is compatible with LHC operation for a ferrite temperature up to 100 ˚C (over this temperature, we rapidly extinguish the safety margin). The maximum allowed temperature for ferrite is 100 ˚C. But what is the temperature of ferrite during operation? The maximum allowed temperature for ferrite is 100 ˚C. But what is the temperature of ferrite during operation? Maximum acceptable ferrite temperature 22 April 2013F. Carra – EN-MME7

Engineering Department ENEN Thermal simulations: expected RF losses on ferrite 22 April 2013F. Carra – EN-MME8 To be divided by 2 to obtain the load in [W] on each ferrite array Case 1 Case 2 Case 3  RF losses on ferrite evaluated by BE/ABP  Case 1: nominal LHC operation  Case 2: High-Luminosity LHC  Case 3: High-Luminosity LHC, with reduced bunch length (0.5 ns)  Pessimistic case

Engineering Department ENEN Thermal simulations: numerical model 22 April 2013F. Carra – EN-MME9 Ferrite support Ferrite  2D analysis: power loss on ferrite considered constant towards longitudinal coordinate.  Three materials proposed for the supports: 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.  Heat exchange by radiation ~ 99% of total heat exchange.

Engineering Department ENEN Thermal simulations: material properties 22 April 2013F. Carra – EN-MME10 MaterialEmissivity Glidcop0.05 Stainless steel0.3 Copper OFE0.05 Ferrite0.8 Black Chrome0.6  The emissivity of the analysed materials has been evaluated combining already available data with new measurement results (M. Garlasche’, M. Barnes, L. Gentini).

Engineering Department ENEN Thermal simulations: results 22 April 2013 F. Carra – EN-MME11  Pure copper OFE: worst choice, penalized by copper low emissivity.  Stainless steel: T ~ 60 ˚C at High Luminosity, 95 ˚C if the bunch length is reduced to 0.5 ns.  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 also the upper screen is coated with CrO).

Engineering Department ENEN Issues of CrO-coated copper 22 April 2013 F. Carra – EN-MME12 Black Chrome Graphite  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.”  The CrO-coated support itself has a high outgassing rate (G. Cattenoz, EDMS n )  Outgassing rate per unit surface: 2 ∙ mbar∙l/(s ∙ cm 2 )  1.28∙10 -8 mbar∙l/s for one TCTP coming from black chrome coating (only supports coated).

Engineering Department ENEN Outgassing of a TCTP as a function of ferrite temperature and material of the supports 22 April 2013 F. Carra – EN-MME13 x x x x x x 1. Nominal LHC Cu/CrO supports 1. Nominal LHC SS supports HL-LHC Cu/CrO supports 2. HL-LHC SS supports 3. HL-LHC 0.5 ns b.l. Cu/CrO supports 3. HL-LHC 0.5 ns b.l. SS supports Δ1Δ1 Δ2Δ2 Δ3Δ3 Chrome oxide is effective only for ferrite temperatures over 100 ˚C, for which the total outgassing rate is anyway not acceptable! Chrome oxide is effective only for ferrite temperatures over 100 ˚C, for which the total outgassing rate is anyway not acceptable!

Engineering Department ENEN Conclusions 22 April 2013 F. Carra – EN-MME14  A thermal treatment has been defined for TT2-111R ferrite to decrease its outgassing rate before installation in the LHC.  Tests performed by G. Cattenoz show, that after firing, TCTP outgassing is acceptable for a maximum temperature on ferrite of 100 ˚C.  Heating of ferrite has been evaluated in three scenarios (nominal LHC, HL-LHC, HL-LHC with 0.5 ns bunch length), for supports made of different materials:  Pure copper OFE was ruled out because of its low emissivity (high temperatures induced on ferrite);  Copper OFE with a coating of chrome oxide is the best solution from the thermal point of view, BUT:  inhomogeneity and volatility of the surface (graphite, often used for collimator applications, is anyway even more porous);  high outgassing rate: compared with stainless steel solution, total outgassing of TCTP is higher in all the three identified scenarios;  Stainless steel minimizes the TCTP total outgassing, also presenting advantages in terms of efficiency, cost and simplicity of the solution. T ferrite ~60 ˚C at High Luminosity, 95 ˚C if the bunch length is reduced to 0.5 ns.  Other coatings have also been studied but, while presenting high emissivity values, are too volatile to be taken into consideration.

Engineering Department ENEN Ongoing actions 22 April 2013 F. Carra – EN-MME15  Vacuum Group:  Outgassing measurement on 1 ferrite tile (TT2-111R) at temperatures higher than 100 ˚C;  Outgassing tests on a 40-pieces batch;  Outgassing tests on a TCSP jaw (without ferrite)  completed, report under approval.  RF team:  Simulations and RF measurements on other ferrite products (e.g. 4E2 from Ferroxcube).

Engineering Department ENEN

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ENEN Federico Carra – EN-MME 18  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!

Engineering Department ENEN Black Chrome Graphite 19  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.”

Engineering Department ENEN  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