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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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Thank you for your attention!

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Backup slides

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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.”

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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 evaluate power on each

ferrite array