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Outlook

Choice of the material for TCTP ferrite supports Collimation Working Group 22.04.2013 F. Carra , G. Cattenoz, A . Bertarelli, A. Dallocchio, M. Garlaschè , L. Gentini On the behalf of TCTP design, prototyping and manufacturing team . Outlook. TCTP RF system

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Outlook

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  1. Choice of the material for TCTP ferrite supportsCollimation Working Group 22.04.2013F. Carra, G. Cattenoz, A. Bertarelli, A. Dallocchio, M. Garlaschè, L. GentiniOn the behalf of TCTP design, prototyping and manufacturing team F. Carra – EN-MME

  2. Outlook • 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 F. Carra – EN-MME

  3. TCTP RF system Ferrite Supports • 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. F. Carra – EN-MME

  4. Proposed thermal treatment on TT2-111R • All details in EDMS document 1276976“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. • 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 10-4 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 10-4 mbar and shall never exceed 100˚C/h; • Estimated duration of the cycle ~ 180 hours. F. Carra – EN-MME

  5. Outgassing measurements • Treatment at 400 ˚C not sufficient: following bakeout at 250 ˚C , ferrite outgassing at room temperature is larger than unfired stainless steel! F. Carra – EN-MME

  6. Outgassing measurements • After proposed treatment at 1000 ˚Cand 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). F. Carra – EN-MME

  7. Maximum acceptable ferrite temperature • Estimated outgassing flow for one TCTP collimator at room temperature: • 1600 cm2 of ferrite ~ 2∙10-9mbar∙l/s • 2300 cm2 of tungsten ~ 2∙10-9mbar∙l/s • 5000 cm2 of stainless steel ~ 1∙10-8mbar∙l/s • Total (one collimator): 1.5∙10-8mbar∙l/s • If the ferrite alone is heated up to 100 ˚C: • 1600 cm2 of ferrite ~ 2∙10-8mbar∙l/s • Total (one collimator): 3∙10-8mbar∙l/s • LHC vacuum specification limit 1∙10-7 mbar∙l/s (EDMS 428155). • 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? F. Carra – EN-MME

  8. Thermal simulations: expected RF losses on ferrite Case 1 Case 2 Case 3 To be divided by 2 to obtain the load in [W] on each ferrite array • 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 F. Carra – EN-MME

  9. Thermal simulations: numerical model Ferrite Ferrite support • 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. F. Carra – EN-MME

  10. Thermal simulations: material properties • The emissivity of the analysed materials has been evaluated combining already available data with new measurement results (M. Garlasche’ , M. Barnes, L. Gentini). F. Carra – EN-MME

  11. Thermal simulations: results • 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 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 also the upper screen is coated with CrO). F. Carra – EN-MME

  12. Issues of CrO-coated copper • 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 • The CrO-coated support itself has a high outgassing rate (G. Cattenoz, EDMS n. 1213905). • Outgassing rate per unit surface: 2∙10-11mbar∙l/(s∙cm2)  1.28∙10-8mbar∙l/s for one TCTPcoming from black chrome coating (only supports coated). Graphite F. Carra – EN-MME

  13. Outgassing of a TCTP as a function of ferrite temperature and material of the supports 3 x Δ3 Chrome oxide is effective only for ferrite temperatures over 100 ˚C, for which the total outgassing rate is anyway not acceptable! 3 x 2 1 x x Δ2 Δ1 2 x 1 x 3. HL-LHC 0.5 ns b.l. Cu/CrOsupports 1. Nominal LHC SS supports 1. Nominal LHC Cu/CrOsupports 2. HL-LHC SS supports 3. HL-LHC 0.5 ns b.l. SS supports 2. HL-LHC Cu/CrOsupports F. Carra – EN-MME

  14. Conclusions • 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 OFEwas 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. Tferrite~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. F. Carra – EN-MME

  15. Ongoing actions • 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). F. Carra – EN-MME

  16. Thank you for your attention!

  17. Backup slides

  18. 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

  19. 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

  20. 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

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