The objective of this research is the deposition of a superconductive thin film onto copper Quarter Wave Resonator cavities that can be used in the HIE-ISOLDE facility at CERN. To do this, it was developed an innovative magnetron configuration source. Our experience has shown the efficiency of this particular configuration in order to deposit a uniform thin film, and also improve the superconductive properties of the niobium (Residual Resistance Ratio and Critical Temperature). This presentation presents the recent improvement of the niobium thin film properties and the procedure used to deposit and measure the first resonator at LNL of HIE-ISOLDE type.

1. ISTITUTO NAZIONALE DI FISICA NUCLEARE
LABORATORIO NAZIONALE DI LEGNARO
Laboratorio di Superconduttività
STATUS AND DEVELOPMENTS OF SPUTTERED Nb/Cu
QWRs AT LNL-INFN
D. Franco Lespinasse, G. Keppel, S. Stark, A.A. Rossi, A.M. Porcellato, F.
Stivanello, C.Pira and V. Palmieri
THIN FILMS AND NEW IDEAS FOR SRF
OCTOBER, 2014

2. Content
Research framework
Specific research aims
Recent developments at LNL
Conclusions and further works

3. Framework
Cavities with
accelerating field of 6 MV/m with a
Q-value of at least 5X108

4. Our goal
 Develop a magnetron sputtering configuration source to deposit QWRs for
HIE-ISOLDE
Copper substrates Nb/Cu QWR

5. Specific research aims
 Develop a magnetron sputtering configuration source to deposit QWRs for
HIE-ISOLDE
Deposit a uniform thin film coating over the
cavity.
Improve the Tc and RRR values
Deposit and measure the first resonator at LNL of
HIE-ISOLDE type.

6. How to do that????
Magnetron sputtering
 Main Advantage
 Main Disadvantage
High deposition rate
Erosion of material
not uniform

7. Magnetron sputtering vacuum system

8. Stainless steel cathode

9. Stainless steel dummy cavity

10. Magnetron sputtering depositions
Stainless steel
onto quartz
samples
Stainless steel onto
copper strips

11. Stainless deposition
Run Pressure
(mbar)
Power (Kw) Current (A) Voltage (V) Time (min)
1 8x10-3 3 8,1 370 30
2 8x10-3 6 14,5 415 30
3 2x10-2 6 19 320 30
4 5x10-2 6 20,5 290 30
5 2x10-2 6 20,5 280 60
6 8x10-3 10 23,1 453 45
7 8x10-3 10 15 450 60

12. Magnetic field confinement
6
5
4
3
2
1
0
-20 -15 -10 -5 0 5 10 15 20
Thickness (μm)
Sample position

13. Stripping test
t=0 After 3 hours

14. Niobium cathode

15. Niobium depositions
Run
Pressure Power Current Voltage Time Heating
(mbar) (kW) (A) (V) (min) 200°C
1 1x10-2 3 10,2 280 25 NO
2 1x10-3 3 9,9 300 25 NO
3 1x10-2 3 10,8 270 35 NO
4 1x10-2 5 16,5 290 30 NO
5 1x10-2 10 33,2 300 30 NO
6 1x10-2 15 50,5 310 30 NO
7 1x10-2 15 49,8 305 30 YES
8 1x10-2 17 50,68 333 30 YES
9 1x10-2 17
50,6 337
30 YES
10
1x10-2
21 65,8 332 30 YES
11
1x10-2
25 74,8 340 30 YES
I magnetic
confinement
II magnetic
confinement
III magnetic
confinement
IV magnetic
confinement

16. Thickness results
I magnetic confinement
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Thickness (μm)
-20 -10 0 10 20 30
Sample position

17. Thickness results
II magnetic confinement
6
5
4
3
2
1
0
Thickness(μm)
-20 -15 -10 -5 0 5 10 15 20
Sample position

18. Thickness results
III magnetic confinement
6
5
4
3
2
1
0
Thickness (μm)
-20 -15 -10 -5 0 5 10 15 20
Sample position

19. Thickness results
IV magnetic confinement
6
5
4
3
2
1
0
-20 -15 -10 -5 0 5 10 15 20
Thickness (μm)
Sample position

20. Magnetic field configurations
A new configuration has developed in
order to increase the thickness on the top
of the cavity

21. Thickness results
4
3
2
1
0
Thickness (μm)
-20 -15 -10 -5 0 5 10 15 20
Sample position
2±1μm

22. Superconductive properties
Quartz
sample
 RRR and Tc measurements
푅푅푅 =
푅(300퐾)
푅(10퐾)

23. Superconductive properties
 RRR and Tc measurements
70
60
50
40
30
20
10
0
0 10 20 30 40
RRR
Power (kW)
I configuration
II configuration
III configuration
IV configuration

24. Superconductive properties
 RRR and Tc measurements

25. Thin film morphology
500nm 400nmGJ
Internal conductor External conductor

26. Deposition of Nb/Cu QWR
 The sputtering process was carried out taking into account the
following parameters:
 Sputtering:
Power 30 kW
Voltage 408V
Sputt. Pressure 6x10-3 mbar
Current 72,57 A
Time 40 min

27. Deposition of Nb/Cu QWR
 An important parameter:
 The cavity was heated at 450°C during the process

28. Deposition of Nb/Cu QWR
QWR after surface treatment
(SUBU)
QWR after magnetron
sputtering deposition

29. Cleaning and mounting
High pressure rinsing
100 bar
Cavity during
the Nb/Cu
plate mounting

30. Test cryostat

31. RF performance

32. First Magnetron Sputtered Nb/Cu QWR Isolde
0,0 5,0x105 1,0x106 1,5x106 2,0x106
109
108
107
106
18W
@1,8K
@4,2K
Q
E
Acc
[MV/m]
44W
105W

33. Conclusions and further works
 The cavity has been deposited with a good homogeneity (2±1)
 Superconductive properties (Tc and RRR) were improved with a new
magnetron configuration source
 The first cavity of HIE ISOLDE type has been deposited succesfully at
Legnaro
 A test cryostat has been built to measure the cavity performance
 The RF performance is below the specification, however new depositions
will be done.

34. Aknowledgements
 Special thanks to:
 W. Venturini Delsolaro
Sergey Stark
Anna M. Porcellato

35. Thanks for your attention