Post on 24-Dec-2015
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F. Carra – EN-MME 1
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
22 April 2013
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F. Carra – EN-MME 2
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 2013
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F. Carra – EN-MME 3
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 2013
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F. Carra – EN-MME 4
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.
Proposed thermal treatment on TT2-111R
22 April 2013
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.
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F. Carra – EN-MME 5
Outgassing measurements
22 April 2013
Treatment at 400 ˚C not sufficient: following bakeout at 250 ˚C , ferrite outgassing at room temperature is larger than unfired stainless steel!
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F. Carra – EN-MME 6
Outgassing measurements
22 April 2013
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).
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F. Carra – EN-MME 7
Estimated outgassing flow for one TCTP collimator at room temperature: 1600 cm2 of ferrite ~ 2∙10-9 mbar∙l/s 2300 cm2 of tungsten ~ 2∙10-9 mbar∙l/s 5000 cm2 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 cm2 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 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?
Maximum acceptable ferrite temperature
22 April 2013
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F. Carra – EN-MME 8
Thermal simulations: expected RF losses on ferrite
22 April 2013
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
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F. Carra – EN-MME 9
Thermal simulations: numerical model
22 April 2013
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.
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F. Carra – EN-MME 10
Thermal simulations: material properties
22 April 2013
Material Emissivity
Glidcop 0.05
Stainless steel 0.3
Copper OFE 0.05
Ferrite 0.8
Black Chrome 0.6
The emissivity of the analysed materials has been evaluated combining already available data with new measurement results (M. Garlasche’ , M. Barnes, L. Gentini).
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F. Carra – EN-MME 11
Thermal simulations: results
22 April 2013
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).
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F. Carra – EN-MME 12
Issues of CrO-coated copper
22 April 2013
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. 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.”
The CrO-coated support itself has a high outgassing rate (G. Cattenoz, EDMS n. 1213905). Outgassing rate per unit surface: 2∙10-11 mbar∙l/(s∙cm2) 1.28∙10-8 mbar∙l/s for one
TCTP coming from black chrome coating (only supports coated).
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F. Carra – EN-MME 13
Outgassing of a TCTP as a function of ferrite temperature and material of the supports
22 April 2013
x
x
x
x
x
x
1. Nominal LHCCu/CrO supports
1. Nominal LHCSS supports
12
3
2
3
1
2. HL-LHCCu/CrO supports
2. HL-LHCSS supports
3. HL-LHC 0.5 ns b.l.Cu/CrO supports
3. HL-LHC 0.5 ns b.l.SS supports
Δ1
Δ2
Δ3
Chrome oxide is effective only for ferrite temperatures over
100 ˚C, for which the total outgassing rate is anyway
not acceptable!
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F. Carra – EN-MME 14
Conclusions
22 April 2013
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. 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.
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F. Carra – EN-MME 15
Ongoing actions
22 April 2013
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).
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TESTS ON ALTERNATIVE COATINGS
01.10.2012 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!
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TESTS ON BLACK CHROME
Black Chrome
Graphite
19
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.”