1. Superconductivity Practical Days at CERN
HTS Leads
Superconductivity
Practical Days at CERN
26th-27th February 2015
Jerome Fleiter and Amalia Ballarino
With the collaboration for the practical exercises of:
P. Denis, E. Seiler and J. Hurte
JUAS /02/2015
J.Fleiter, A.Ballarino

2. Program and Organization
10 to 12 participants
Hands-on practical work in CERN laboratories
Guided by experts
When ? On the 26th and 27th of February
Where ? In the Superconductor Laboratory, Building 163
Program and Organization
Main entrance
B. 163
JUAS /02/2015
J.Fleiter, A.Ballarino

3. Practical Days at CERN (1/2)
Visit of Superconductor Laboratory, Building 163
Test stations for the measurement of:
Critical current of superconductors (strands and cables) at liquid He temperature (1.9 K and 4.2 K, up to 15 T and up to 35 kA);
Magnetic properties of superconductors (magnetization curves) at variable temperatures and fields (VSM);
Residual Resistivity Ratio, Resistivity as function of temperature;
Cabling machine for accelerator Rutherford cables;
Laboratory for analysis of superconductors; Nb-Ti, Nb3Sn, YBCO, BSCCO 2223 and MgB2 strands and cables
Visit of Laboratory, SM 18
Test stations for magnets
JUAS /02/2015
J.Fleiter, A.Ballarino

4. Practical Days at CERN (2/2)
What will you do ?
Measure electrical, magnetic and thermal characteristics of superconducting samples with the purpose of understanding the fundamental characteristics of superconductors
Superconductivity => Cryogenics
JUAS /02/2015
J.Fleiter, A.Ballarino

5. Definitions Superconductivity Superconductor Cryogenics
“Superconductivity is a phenomenon occurring in certain materials at very low temperatures , (the Meissner effect)” characterized by exactly zero electrical resistance and the exclusion of the interior magnetic field from Wikipedia
Superconductor
A conductor that exhibit superconducting properties. It is an assembly of low resistive metal and superconducting material.
Cryogenics
Cryogenic: for Greek “kryos", which means cold or freezing, and "genes" meaning born or produced.
“In physics, cryogenics is the study of the production of very low eye temperature (below –150 °C, –238 °F or 123 K) and the behavior of materials at those temperatures”
from Wikipedia
JUAS /02/2015
J.Fleiter, A.Ballarino

6. Main properties of superconductors
For T<Tc
Zero resistance Perfect conductors
Exclusion of magnetic field Perfect diamagnets
Zero resistance
Onne’s measurement on mercury (1911)
Meissner effect
Discovered by Meissner and Oschenfeld (1933)
Perfect conductivity + perfect diamagnetism = superconductors
JUAS /02/2015
J.Fleiter, A.Ballarino

7. Superconducting state if:
Phase diagram of superconductors
Critical temperature (Tc)
Critical field (Hc)
Critical current density (Jc)
Superconducting state if:
T<Tc
H<Hc
J<Jc
JUAS /02/2015
J.Fleiter, A.Ballarino

8. Various Superconducting materials
Low Temperature Superconductors (LTS)Tc<39K
High Temperature Superconductors (HTS) Tc>39K
Cuprates
Pure metals
Alloys and Intermetallic alloys
JUAS /02/2015
J.Fleiter, A.Ballarino

9. Properties of HTS versus LTS
Bc up to 30 T
Tc up to 39 K
HTS
Bc up to 200 T
Tc up to 120 K
7106 (A/cm2)
Tc=110K
Tc=10K
Bc=15T
Bc=100T
JUAS /02/2015
J.Fleiter, A.Ballarino

10. Superconductivity applications
Generate high DC field: (MRI, NMR, particle Physics)
Current limiters
Electronics, detectors (SQUIDS)
Power transmission
Magnetic levitation (Maglev)
Current leads
RF cavities
JUAS /02/2015
J.Fleiter, A.Ballarino

11. Superconducting devices @CERN
Superconductivity = a core technology of LHC
LHC ring magnets (Nb-Ti):
1232 main dipoles: 8.3 T x 15 m
392 Main quadrupoles 223 T/m (7 T) x 8m
Zoo of 7600 others
LHC detector magnets (Nb-Ti ):
ATLAS: Toroid 4 T, 25 x20 m
CMS solenoid: 4 T, 12 x15 m
LHC current leads (HTS BSCCO)
~1000, rated for I ϵ[0.6,13 kA]
RF cavities (Nb coating)
JUAS /02/2015
J.Fleiter, A.Ballarino

12. Superconductors in form of tape or wire
CERN
Only few superconducting materials could be used as superconductor for large scale application
Low Temperature Superconductors:
Nb-Ti (Tc=9K, Bc=15T) LHC machine
Nb3Sn (Tc=18 K, Bc=30T) Hi Lumi-LHC (2017)
MgB2 (Tc=39K, Bc=30T) Hi Lumi-LHC (2022)
High Temperature Superconductors:
Bi2Sr2Ca2Cu3O10+x(Tc=108 K, Bc>100 T) LHC machine
Bi2Sr2CaCu2O8+x(Tc=95 K, Bc>100 T) High energy-LHC (>2030)
YBa2Cu3O7-x (Tc=93K, Bc>100 T) High energy-LHC (>2030)
Superconductors in form of tape or wire
used to make cables
JUAS /02/2015
J.Fleiter, A.Ballarino

13. LTS => Liquid Helium HTS =>Liquid Helium or Liquid Nitrogen
Superconductors needs Cryogens
LTS => Liquid Helium
HTS =>Liquid Helium or Liquid Nitrogen
Saturated
Vapor/liquid
Triple point
(K)
Boiling
point
(1 atm)
Critical
Point
Methane
90.7
111.6
190.5
Oxygen
54.4
90.2
154.6
Argon
83.8
87.3
150.9
Nitrogen
63.1
77.3
126.2
Neon
24.6
27.1
44.4
Hydrogen
13.8
20.4
33.2
Helium
-point
4.2
5.2
JUAS /02/2015
J.Fleiter, A.Ballarino

14. Superconductivity Practical Days at CERN
We will work with cryogenics and superconductivity to understand and verify the unique properties of superconductors
YBCO 123 bulk
BSCCO 2223 tape
SmCo, NeFeB magnets
Liquid nitrogen
………
Levitation
Flux pinning
Zero resistance
Jc,Tc,Hc
………
JUAS /02/2015
J.Fleiter, A.Ballarino

15. Experiments Experiments will be performed with HTS superconductors
1.Levitation experiment
2.Flywheel demonstration
3.Critical temperature experiment
4.Zero resistance experiment
5.Critical current experiment
6.Resistive transition experiment
JUAS /02/2015
J.Fleiter, A.Ballarino

16. Superconductors you will use for the experiments at CERN:
HTS
Liquid nitrogen
Superconductivity
Cryogenics
Superconductors you will use for the experiments at CERN:
YBCO 123 Melt Textured Bulk .Tc= 93 K
BSCCO 2223 Tape Tc= 110 K
You will use Nitrogen
78% of atmosphere
Boiling point (1 atm): 77 K (-196 C)
Colorless, odorless, non-toxic
Dealing with LN2: safety first (skin burn, splashing..)
HTS
SmCo
4 mm
0.2 mm
JUAS /02/2015
J.Fleiter, A.Ballarino

17. Levitation experiment
Appreciate the intensity of the max levitation force !
Understand the Meissner effect and flux pinning
HTS
SmCo
JUAS /02/2015
J.Fleiter, A.Ballarino
Levitation experiment

18. Critical temperature experiment
Measurement of critical temperature by using the Meissner effect.
The critical temperature is defined as the temperature measured on the superconductor when the permanent levitating on it comes to complete rest on the superconductor’s surface.
JUAS /02/2015
J.Fleiter, A.Ballarino
Critical temperature experiment

19. Zero resistance experiment
Zero resistance DC experiment
A superconducting tape and a pure silver tape are connected in series, Measure the voltages (resistances) as the specimens are inserted into liquid nitrogen and cooled to 77 K.
A see-through glass walled dewar is used for the LN2.
Ag(293 K)1.46∙10-6 Ω∙m
Ag(77 K) 0.2∙ Ag(293 K)
HTS:BSCCO 2223 multi-filamentary tape in silver alloy matrix.
JUAS /02/2015
J.Fleiter, A.Ballarino
Zero resistance experiment

20. Critical current experiment
DC Critical current experiment
HTS Leads
Critical current (Ic): current at which a specified electric field criterion Ec, or resistivity criterion c is achieved in the specimen. Losses through a Type II superconductors (Hc1<H<Hc2) depend on the sample geometry and on the vortex pinning.
VIn
n=n-value
N reflects the abruptness of the transition from superconducting to normal state
H=const
T=const
JUAS /02/2015
J.Fleiter, A.Ballarino
Critical current experiment

21. We are looking forward to
working with you at CERN !
JUAS /02/2015
J.Fleiter, A.Ballarino