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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
ISTITUTO NAZIONALE DI FISICA NUCLEARE
LABORATORIO NAZIONALE DI LEGNARO
Laboratorio di Superconduttività
THIN FILMS AND NEW IDEAS FOR SRF
OCTOBER, 2014
Content
Research framework
Specific research aims
Recent developments at LNL
Conclusions and further works
Framework
Cavities with
accelerating field of 6 MV/m with a
Q-value of at least 5X108
Our goal
Develop a magnetron sputtering configuration source to deposit QWRs for
HIE-ISOLDE
Copper substrates Nb/Cu QWR
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.
How to do that????
Magnetron sputtering
Main Advantage
Main Disadvantage
High deposition rate
Erosion of material
not uniform
Magnetron sputtering vacuum system
Stainless steel cathode
Stainless steel dummy cavity
Magnetron sputtering depositions
Stainless steel
onto quartz
samplesStainless steel onto
copper strips
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
Magnetic field confinement
0
1
2
3
4
5
6
-20 -15 -10 -5 0 5 10 15 20
Thic
kne
ss (
µm
)
Sample position
Stripping test
t=0 After 3 hours
Niobium cathode
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 1750,6 337
30 YES
101x10-2
21 65,8 332 30 YES
111x10-2
25 74,8 340 30 YES
I magnetic
confinement
II magnetic
confinement
III magnetic
confinement
IV magnetic
confinement
Thickness results
0
0.2
0.4
0.6
0.8
1
1.2
1.4
-20 -10 0 10 20 30
Thic
kn
ess
(µ
m)
Sample position
I magnetic confinement
Thickness results
0
1
2
3
4
5
6
-20 -15 -10 -5 0 5 10 15 20
Thic
kn
ess
(µm
)
Sample position
II magnetic confinement
Thickness results
0
1
2
3
4
5
6
-20 -15 -10 -5 0 5 10 15 20Thic
kn
ess
(µ
m)
Sample position
III magnetic confinement
Thickness results
0
1
2
3
4
5
6
-20 -15 -10 -5 0 5 10 15 20
Thic
kne
ss (
µm
)
Sample position
IV magnetic confinement
Magnetic field configurations
A new configuration has developed in
order to increase the thickness on the top
of the cavity
Thickness results
0
1
2
3
4
-20 -15 -10 -5 0 5 10 15 20
Thic
kn
ess
(µ
m)
Sample position
2±1µm
Superconductive properties
Quartz
sample
RRR and Tc measurements
𝑅𝑅𝑅 =𝑅(300𝐾)
𝑅(10𝐾)
Superconductive properties
RRR and Tc measurements
0
10
20
30
40
50
60
70
0 10 20 30 40
RR
R
Power (kW)
I configuration
II configuration
III configuration
IV configuration
Superconductive properties
RRR and Tc measurements
Thin film morphology
500nm 400nmGJ
External conductorInternal conductor
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
Deposition of Nb/Cu QWR
An important parameter:
The cavity was heated at 450°C during the process
Deposition of Nb/Cu QWR
QWR after surface treatment
(SUBU)
QWR after magnetron
sputtering deposition
Cleaning and mounting
High pressure rinsing
100 bar
Cavity during
the Nb/Cu
plate mounting
Test cryostat
RF performance
0,0 5,0x105
1,0x106
1,5x106
2,0x106
106
107
108
109
18W
@1,8K
@4,2K
Q
EAcc
[MV/m]
First Magnetron Sputtered Nb/Cu QWR Isolde
44W
105W
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.
Aknowledgements
Special thanks to:
W. Venturini Delsolaro
Sergey Stark
Anna M. Porcellato
Thanks for your attention
