Measurement of coating resistivity on Mo coated samples with H011 cavity - PowerPoint Presentation

Slide1

Measurement of coating resistivity on Mo coated samples with H011 cavity

N.Biancacci, F.Caspers, A.Kurtulus

C.Accettura

,

S.Antipov

,

G.Arduini

,

E.Berthome

,

H.Bursali

,

S.Calatroni

, N. Catalan

Lasheras

,

F.Carra

,

F.Di

Lorenzo,

K.Fellag

,

A.Gilardi

,

A.Grudiev

,

J.Guardia

Valenzuela,

I.Llamas

Garcia, B. Louis Schafer,

E.Métral

,

S.Redaelli

,

B.Salvant

,

M.Taborelli

,

W.Vollenberg

,

C.Vollinger

,

M.Volpi

,

C.Zannini

and the mechanic lab bat.152 (

D.Gacon

,

R.Martinez

).

Slide2

Introduction

Accurate measurement of coating surface resistance is needed to characterize the production process of HL-LHC baseline collimators jaws made of 5um Mo coated MoGr.

Extensive characterization studies done in the past by means of

eddy current coils

at low frequency (10kHz – 2MHz).

2

companies called for large production (DTI,

Politeknik

) and compared to CERN

production.

Measurements of resistivity was done on small blocks

based on eddy current testing (see

https://indico.cern.ch/event/773228/contributions/3219381/attachments/1754354/2843771/Outcome_of_recent_Mo_coating_resistivity_measurements.pdf

) with

good outcome for DTI

.

Attempted measurement also on

real (thicker and larger) blocks

:

more sensitivity to bulk not homogeneity

affected the results and triggered the study of an alternative method (

161th HSC meeting

https://indico.cern.ch/event/775773/

)

Alternative approach quickly developed and based on the application of a pillbox cavity optimized for H011 mode operation -> huge transversal team work!

Slide3

H011 cavity

Measurement setup:

Copper cavity with open cap

DUT placed as end cap

: wall resistivity change -> Q change

Cavity w/o end cap

Cavity w/ end cap

Cavity w/ DUT end cap

Many thanks Denis

Gacon

and

Ruan

Martinez for the manufacturing (in only ½ day!).

Slide4

H field of H

011

mode

vacuum

Cu

mitered part

DUT

H011 cavity

[1] Microwave Electronics: Measurement and Materials Characterization, Di L. F. Chen et al. pp. 100-101

[2] Microwave paint thickness sensor, US patent #7898265 B2

https://patentimages.storage.googleapis.com/f1/e8/42/09ab717ddc8033/US7898265.pdf

[3] M. Ye, L. Wang, Y. He and M.

Daneshmand

, "In

SituTest

of Thickness and Sheet Resistance of Conductive Nanomaterial Using Microwave Cavity,"

in IEEE Microwave and Wireless Components Letters, vol. 27, no. 10, pp. 942-944, Oct. 2017.

Measurement setup:

Copper cavity with open cap

DUT placed as end cap

: wall resistivity change -> Q change

Frequency of operation:

mode H011

(most insensitive to cap contacts)

Mitered internal part to separate adjacent E modes

.

Known methodology to make frequency meters (

e.g. [1,2,3]

)

Slide5

Measurement of resonant modes

Excellent agreement of measurements w.r.t. simulations.

A.Kurtulus

Slide6

Simulated Q change vs

end cap resistivityChange in Q vs change in resistivity simulated in CST and reproduced by curve

 

with

,

and

resp. power dissipated in the end cap and rest of the cavity.

 

Example:

Ref

=

C

u

,

16.8

GHz

 

We are

changing only part of the cavity

-> the

gain is less than

!

-> cavity shape

optimized

for the best aspect

ratio to improve Q change sensitivity

.

High frequency of operation (16.8 GHz) above Impedance Lab VNA (max 4.5 GHz). Many thanks to

Nuria

,

Alexej

,

Matteo

and

Hikmet

for the support with the 50 GHz VNA!

 

Slide7

Data acquisition

Probes cross-talk gives “typical” notch pattern after the H011 resonance at 16.5 GHz.Relative Q factor measurement still possible but

minimum Q attainable limited

.

Design refinement can avoid this effect.

Mo on DTI

Mo on CFC

Transmission Q-factor for all acquired samples:

Good Q measurement

Q measurement at the limit

Slide8

Measured Q change

vs end cap resistivity

Measured relative Q change for thick metals

(e.g. Cu, Al, In, Ta, Mo, SS, …) borrowed from TE-VSC-SCC (many thanks!).

Resistivity was accurately measured with the

S

igmameter

(at 900kHz, many thanks Carlotta, Fede and Jorge for the support!)

Curve in excellent agreement with measured data!

Slide9

Measured Q change

vs

end cap resistivity

Measured Q change for Mo coated (6-7um) real blocks

a

llows to deduce the unknown coating resistivity:

(*) DTI block thermal treated at 400 ºC.

(**) CERN and

Politeknik coated blocks had long manipulation history which helped our understanding but probably degraded the surface quality.

DTIPoliteknik

CERN

Mo on Gr

Mo (DTI*)

Mo (CERN**)

Mo (

Politeknik

**)

Mo on Graphite

~

54

nOhm.m

~523

nOhm.m

~418

nOhm.m

~192

nOhm.m

Slide10

Requirements for HL-LHC

All details in

https://edms.cern.ch/document/2016583/1

Quality control during price enquiry foresees:

at DC (4-points, 4-wires on glass)

at

RF (eddy current)

(1.)

i

mplies (2.) based on empirical observations

(e.g.

J.Guardia

Valenzuela in

https://indico.cern.ch/event/751839/contributions/3113528/attachments/1704247/2746297/SEM_Mo_coat_comparison_substrates_aug18.pdf

)

 

Slide11

Requirements for HL-LHC

RF

DC

Measured Mo (DTI)

~54

nOhm.m

[1]

100 nOhm.m [2]Measured Mo (CERN)

~523 nOhm.m [1]210 +/- 20 nOhm*m [3]

Measured Mo (Politeknik)

~418 nOhm.m [1]

Not done by the company

Requirements

~<100nOhm.m

~<250nOhm.m

[1] Measured with H011 cavity at 16.5 GHz

[2] Measured with 4-points on glass by DTI company.

[3] Measured by

Wil

with 4-points method on 6 µm Mo coated on glass: comparable to 250nOhm.m in 4-wires method and ~200

nOhm.m

measured by eddy current (e.g.

J.Guardia

Valenzuela in https://indico.cern.ch/event/751839/contributions/3113528/attachments/1704247/2746297/SEM_Mo_coat_comparison_substrates_aug18.pdf)

Summary of measurements done and requirements: DTI compliant with specs.

Slide12

Requirements for HL-LHC

RF

DC

Measured Mo (DTI)

~54

nOhm.m

[1]

100 nOhm.m [2]Measured Mo (CERN)

~523 nOhm.m [1]210 +/- 20 nOhm*m [3]

Measured Mo (Politeknik)

~418 nOhm.m [1]

Not done by the company

Requirements

~<100nOhm.m

~<250nOhm.m

[1] Measured with H011 cavity at 16.5 GHz

[2] Measured with 4-points on glass by DTI company.

[3] Measured by

Wil

with 4-points method on 6 µm Mo coated on glass: comparable to 250nOhm.m in 4-wires method and ~200

nOhm.m

measured by eddy current (e.g.

J.Guardia

Valenzuela in https://indico.cern.ch/event/751839/contributions/3113528/attachments/1704247/2746297/SEM_Mo_coat_comparison_substrates_aug18.pdf)

Summary of measurements done and requirements: DTI compliant with specs.

DTI compliant with requirements.

Slide13

Summary and outlook

Huge team work effort: many thanks to all people involved, particularly Fritz for the constant follow-up of the measurement developments (we also developed an resonant eddy current meter at ~4GHz which could be useful for quick bulk characterizations).

Thin Mo coating resistivity measured designing and building a H011 cavity

:

H

igh reproducibility (low contact loss)

High sensitivity (high Q factor and optimized aspect ratio)

Fast measurement: could allow quick and clean measurement of all the incoming blocks!Simulations and measurements in good agreement with expectation for operational mode.Known metals used for cross-calibration between instruments (Sigmameter to H011 cavity)Mo coating shows best resistivity on DTI sample (very close to bulk value).

High resistivity on CERN and Politeknick blocks probably due to several manipulations of the blocks.Mo on Graphite in the order of 200nOhm.m

(eddy current showed 350nOhm.m)Mo on CFC induces strong damping -> high resistivity, at the limit of measurability for present setup.

Slide14

Summary and outlook

Improve the cavity design to minimize the probe crosstalk.Produce a second cavity for measuring

smaller samples

(20x20x15).

Investigate measurements in second H mode

insensitive to contacts

at ~20GHz.

Detailed comparison with eddy current testing on known samples.SEM on DTI sample: probing the coating structure to understand the good electrical conductivity.…… and produce a nice document to summarize all the work done!

Slide15

BACKUP

Slide16

Skin depth

Small blocks: magnetic field mostly

outside

bulk material.

Large blocks: magnetic field always

inside

bulk material -> more sensitive to non homogeneity.

Slide17

Slide18

Slide19

Eddy current testing applied to small blocks

Bulk resistivity obtained by changing lift-off to match measured curve.

Coating resistivity obtained by scaling to the peak of simulated/measured data (accounts for lift-off/bulk resistivity error)

Slide20

Eddy current testing applied to small blocks

Slide21

Measurements of Mo on

MoGr

Same procedure applied but large impact on bulk non homogeneity affecting the measurement.

Mo on Graphite

Mo on

MoGr

Graphite

times larger resistivity than

MoGr

:

less sensitive to non homogeneity.

So far only 5 measurements done on random position on the sample.

 

N.Biancacci

et al., 161th HSC meeting

https://indico.cern.ch/event/775773/

Slide22

Introduction

Three producers contacted for Mo on MoGr collimator blocks foreseen for collimators’ HL-LHC upgrade: CERN, DTI, Politeknik.Resistivity of coating characterized by eddy current testing in impedance lab.

Measured small samples (20x20x1.5)mm and collimator-like blocks

.

Mo on Graphite

Mo on

MoGr

(small)

Mo on

MoGr

(large)

Slide23

Slide24

Slide25

Effect of coil lift-off

Coil lift-off position influences magnitude:

C

oil close to surface -> low impedance difference

Coil far from surface -> high impedance difference

Known parameter (within 30% for small distances).

Slide26

Effect of bulk resistivity

Similar to lift-off effect:

The more the resistivity difference w.r.t. bulk, the higher the signal

MoGr

/CFC usually between 1u

m and 5-7u

m resistivity

 

Slide27

Eddy current testing

http://zfp.cbm.bgu.tum.de/mediawiki/index.php/Datei:ECT_tactile_probe.png

Slide28