Choice of the material for - PowerPoint Presentation

Slide1

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

22 April 2013

F. Carra – EN-MME

1Slide2

TCTP RF systemThermal treatment on TT2-111R ferriteOutgassing measurements on ferrite after thermal treatmentFerrite heating during operation: thermal simulationsComments on support materialsConclusions and future actionsOutlook

22 April 2013

F. Carra – EN-MME

2Slide3

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

F. Carra – EN-MME

3Slide4

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;

H

eating/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

F. Carra – EN-MME

4

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.Slide5

Outgassing measurements22 April 2013F. Carra – EN-MME5Treatment at 400 ˚C not sufficient: following

bakeout at 250 ˚C ,

ferrite outgassing at room temperature is larger

than

unfired stainless steel!Slide6

Outgassing measurements22 April 2013F. Carra – EN-MME6After 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).Slide7

Estimated outgassing flow for one TCTP collimator at room temperature:1600 cm2 of ferrite ~ 2∙10-9 mbar∙l/s2300 cm2 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/sTotal (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

F. Carra – EN-MME

7Slide8

Thermal simulations: expected RF losses on ferrite22 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 caseSlide9

Thermal simulations: numerical model22 April 2013F. Carra – EN-MME9Ferrite support

Ferrite

2D analysis: power

loss on

ferrite considered

constant towards longitudinal

coordinate

.

Three materials proposed

for the

supports:

s

tainless steel 316LN, copper OFE, copper OFE

with a

black

c

hrome 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.Slide10

Thermal simulations: material properties22 April 2013F. Carra – EN-MME10

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).Slide11

Thermal simulations: results22 April 2013F. Carra – EN-MME11Pure 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).Slide12

Issues of CrO-coated copper22 April 2013F. Carra – EN-MME12Black 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

∙

cm

2

)



1.28∙10

-8

mbar∙

l/s for one TCTP

coming from black chrome coating (only supports coated).Slide13

Outgassing of a TCTP as a function of ferrite temperature and material of the supports22 April 2013F. Carra – EN-MME13

x

x

x

x

x

x

1.

Nominal

LHC

Cu/

CrO

supports

1.

Nominal

LHC

SS

supports

1

2

3

2

3

1

2. 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

Δ

1

Δ

2

Δ

3

Chrome oxide is effective only for ferrite temperatures

over 100

˚C

, for which the total outgassing rate is anyway

not acceptable! Slide14

Conclusions22 April 2013F. Carra – EN-MME14A 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

.Slide15

Ongoing actions22 April 2013F. Carra – EN-MME15Vacuum 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

).Slide16

Thank you for your attention!Slide17

Backup slidesSlide18

Tests on alternative coatings01.10.2012Federico Carra – EN-MME18The 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!

Slide19

Tests on black chromeBlack 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.”Slide20

Thermal simulations: resultsResults 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