Energetic Copper Coating on Stainless Steel

Power Coupler for SRF Application

Irfan Irfan, Steve Chapman, Mahadevan Krishnan, Katherine Velas Alameda Applied Sciences Corporation (AASC), San Leandro, California 94577

Walid Kaabi LAL, 91898 Orsay Cedex France

This research is supported at AASC by DOE SBIR Grant: DE-SC0009581

Poster ID: 2131

Motivation:

Stainless steel power coupler parts are required to be coated

with 10 to 30 µm copper film.

Conventional electroplating method has two drawbacks:

:- Inadequate adhesion strength

:- A thin flash layer of Ni (magnetic) film

AASC has developed an energetic coating process (CED)

We demonstrate the potential of the CED process in Cu

coating on power couplers.

Ref: H. Weise, “How to Produce.. ,” WEIB03, Proc. IPAC, Dresden, Germany (2014).

Ref: L. Popielarski et al., “Testing of Copper Plating..,” THP067, Proc. SRF, Paris, France (2013).

RRR of CED Copper Films :1

Four SS strips of 3 mm x 75

mm

1: SS 25 µm

2: SS 100 µm

3: Cu 28 µm/SS 25 µm

4: Cu 28 µm/SS 100 µm

Ref: X. Singer et al., THP18, Proc. SRF workshop, Lubeck, Germany (2011).

If R is the resistance of the sample

(film +substrate), Rcu of Cu film and

RSt of the bare substrate:

1/R = 1/RCu + 1/RSt

RCu = RSt . R / (RSt - R)

Method: R measured from the coated

film, Cu etched by acid and RSt

measured from the bare substrate.

With R and RSt values, RCu can be

calculated.

RRR of CED Copper Films :2

RRR of CED copper films near 50

The E-XFEL acceptable range 30-80

Courtesy: Curtis Crawford, FNAL

# Temp. (K) Res. (Ω) RCu (Ω) RRR

Sub1 298 0.308796

Sub2 298 0.073348

Cu/Sub1 298 0.009492 0.009793 50.9

Cu/Sub2 298 0.008752 0.009938 50.9

Sub1 4.26 0.216840

Sub2 4.26 0.050480

Cu/Sub1 4.26 0.000192 0.000192

Cu/Sub2 4.26 0.000195 0.000195

Adhesion Tests on CED Copper Films :1

Tube 3” ID, 7” long Stainless Steel

304L from Lesker.

Wiped with TCE, acetone, IPA

Coated with a 50 µm Cu film at

300 ºC

Blasted with 1250 psi high purity

water

No deleterious effects of HPWR

test found on the coating.

Courtesy : Curtis Crawford, FNAL

Adhesion Tests on CED Copper Films :2

Three parts stacked in one run

: SS 300 bellows 2” ID (inside)

: Mock CEC tube (inside)

: Mock WIC_1 tube (outside)

Sample 77 K Cold Shock 1200 psi

2” ID Bellows Pass Pass

Mock CEC Pass Pass

Mock WIC_1 Pass Fail

Curtsey: Curtis Crawford, FNAL

Need for a New CED Configuration

Only a small section was coated at a

time. 70% of the Cu was wasted.

Rotation was required to coat the tube.

Uniformity demanded smaller steps.

Anode mesh required

Useful

Old CED Configuration

Waste

New CED Configuration

Useful

Hollow Cu Cathode

Cu Cathode

Tube for Coating Anode Tube

Rotation

Required

Arc Spots

Anode Mesh

15x time efficient. Entire

deposition is useful.

No rotation required.

In-built uniformity in a run.

Tube itself acts as an anode

Test of the New CED Configuration

Large hollow cathode

surrounding a central

anode.

Arcs induced from inside

Cu cathode coats anode

tube from outside.

Parameters

characterized to

understand the new

configuration.

Mock Warm Inner Conductor (WIC)

Top 8-10” coated with 30 µm

copper film.

No vertical non uniform stripes

observed (vs WIC_1 coating).

Coated in 1 day vs 15 days it took

with the old configuration.

A CED coated mock WIC next to a

TTF WIC for comparison.

Courtesy : Walid Kaabi, LAL Orsay

Adhesion Test on WIC_2

Coated mock WIC_2 on FNAL HPWR test stand

1500 psi rinse: no deleterious effects on the Cu coating.

Surface oxides (formed due to an error) removed with an acid soak.

Courtesy : Curtis Crawford, FNAL

Coating of Cold External Conductor (CEC): 1

CEC received from the LAL Orsay group.

Custom adaptors were designed to meet the coating requirements.

Courtesy: Walid Kaabi, LAL Orsay

Coating of Cold External Conductor (CEC): 2

Compare before and after the coating.

Notice the bellows section, color

uniformity and a sharp edge between

the SS face and Cu coating.

Conclusions:

Paper ID THPB083

RRR Value of CED copper films: 50 (meets requirement)

Demonstrated adhesion strength:

:- 1250-1500 psi with HPWR tests

:- 77 Kelvin cold shock tests

Demonstrated a robust coating on a mock coupler part.

Successfully coated a TTF cold external conductor part.

Ready to coat other power coupler parts for RF tests.