1. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 M.Valentino, C. Bonavolontà Coherentia CNR -INFM, Naples, Italy V. Palmieri Istituto Nazionale Fisica Nucleare, Legnaro National Laboratories, Legnaro (PD), Italy Magnetometry and Non Destructive Evaluation

2. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Outline:  Sensors for magnetometry  Design of high sensitivity magnetic sensors working in unshielded environment  Giant Magneto Resistance (GMR) sensors  GMR devices for magnetic field detectors and Eddy- current measurements  Real time correlation between magnetic signal and corrosion on bulk Niobium  Real time magnetic detection of fatigue stress in metals  2D high sensitivity magnetic image

3. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Magnetic field (Tesla) Magnetic sensors & applications 10 -4 10 -5 10 -6 10 -7 10 -8 TT 10 -9 10 -10 10 -11 nTnT 10 -12 pTpT 10 -13 10 -14 10 -15 fTfT Magnetometer field resolution Applications NDE Biomagnetic applications Hall Flux-gate HTS LTS GMR corrosion Fatigue

4. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Main magnetic sensors characteristics SensorRange Temperature stability Sensitivity (Unsh.Environment) Cost Hall probe± 10 mTlow 0.8  T /  Hz @ 1Hz low Flux Gate ± 70  T low 236 nT/  Hz @ 1Hz medium GMR ± 50  T high 320 pT /  Hz @ 1Hz low SQUID ± 5  T low 176 pT/  Hz @ 1Hz high

5. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 GMR Sensors Principles Alloy and base transition metal targets (Ni/Fe, Co/Fe, Co/Cr/Pt, Pt/Mn, Ta, Cu, Au) Ferromagnet Co Non magnetic metal Cu No external Magnetic Field J J High Electrical Resistance J J Low Electrical Resistance Ferromagnet Co Non magnetic metal Cu Applied external Magnetic Field Giant Magneto Resistance, (1988)

6. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006  R/R ~ 10%-20% GMR Sensors Principles Electrical resistance variation due to the magnetic field

7. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 magnetic field noise responses in magnetic unshielded environment Comparison between magnetic field responses of magnetometer, 1 st and 2 nd order gradiometer

8. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 m r b  2  1 z 1 st order Radial gradiometer m r b  2  1 z 1 st order off axis gradiometer m r b  2  1 z 1 st order transverse gradiometer Useful Gradiometers configuration m r b  3  1 b  2 z 2 nd order transverse gradiometer

9. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 detector reference 1 2 3 4 5 Experimental set-up. 1) Niobium disk; 2) Teflon vessel filled with 40ml of Acid solution; 3) Fluxgate magnetometers sensors housed in a Plexiglas holder: detector and reference magnetometers are in a first order gradiometer configuration; 4) Aluminium shields; 5) mu-metal shield. Niobium Buffered Chemical Polishing BCP Solution : -Hydrofluoric acid -Phosphoric acid

10. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Niobium corrosion BCP 1:1:1 to BCP 1:1:2 increasing the H 3 PO 4 percentage the magnetic signal Intensity increase

11. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 The average magnetic field is plotted versus etching rate. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 11.522.53 Etching Rate [micron/min] nT/Hz 1/2 Niobium corrosion

12. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Cell width (mm) w[g] at 4V weighing w[g] at 4V field w[g] at 7V weighing w[g] at 7V field 80,0120,0110,0250,048 160,0230,0200,0350,020 240,050,0320,130,035 Corrosion rate Corrosion Rate evaluation According to Faraday law cells 50 mm long Not explained by Faraday law

13. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Curve cathode Magnetic field distribution Flat cathode Line-scan Cells with different cathode geometries Optimization of the Cu-polishing Cells with different cathode geometries Optimization of the Cu-polishing

14. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 GMR 2 nd order gradiometer GMR 2nd order electronic gradiometer. It detects the in plane magnetic field component reducing the environmental noise 1 st GMR 2 nd GMR 3 th GMR 2 nd order Radial gradiometer m r b  3  1 b  2 z 2 2 dz Bd x

15. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 GMR testing on the electropolishing The solution used: 55% Phosphoric acid 45% n-buthanol Flux gate 1 st order gradiometer imagingGMR 2 nd order gradiometer imaging

16. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 5 mm 4 mm GMR sensors for Eddy-current probe Circular excitation coil to induce eddy current into the specimen

17. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Back side Surface GMR Eddy current probe has been tested using a specimen of AL-Ti alloy with rivets and artificial slots GMR Eddy Current probe testing Slot 1Slot 2 Slot 1Slot 2

18. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 50 mm 20 mm Detection of sub- millimetric scratch on Niobium surface 20 mm 50 mm Artificial sub millimetric scratches have been produced on the Nb surface Test sampleGMR imaging

19. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Working frequency: 3MHz 50 mm 20 mm Test sample Eddy Current induction coil imaging 50 mm 20 mm Comparison with conventional Eddy current induction system

20. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Physical etching of titanium surface

21. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 mm GMR Eddy current Probe detection

22. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Magnetic field scanner to detect fatigue effect in metals System characteristics  Speed: 3mm/s (0-6/mm/s)  Spatial resolution: 0,1mm  Position Reproducibility :  0,05mm  Magnetic field signal Reproducibility  0.01%

23. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Detection of the localized Fatigue process in steel Monitoring the Magnetic field … around the cut …20 mm far from the cut

24. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Sub-millimetric Magnetic field imaging 9,5 kN 0,0 kN 23 kN 0,0 kN 0,1 mm

25. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Surface plastic deformation imaging, preliminary results GMR responses, spatial resolution: 50  m Magnetic field resolution: 1nT/Hz 1/2 mm 0,1 mm

26. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Conclusions Emerging magnetic sensors, like GMR, allows to detect with high sensitivity the magnetic field produced during the following process:  The ongoing corrosion of the metals electropolished as Cu and Nb.  The Fatigue stress effects in steels.  2D magnetic field imaging of sub-millimetric defects and plastic deformation in metals with a spatial resolution better than 100 micron.  Development of GMR Eddy current probe  Detection of surface sub-millimetric defects and scratches with depth less than 0.1 mm in Niobium plate.  Detection of corrosion effect with a depth less than 100micron, due to Ion etching on Titanium surface. Prospective Development of magnetic sensors array to measure the magnetic field during the electropolishing process of metals on non- planar geometry.

27. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Microscopic Magnetomechanical effect M=0 M≠0M≠0 σcσc σcσc  c is the compressive strain M≠0M≠0  t is the tensile strain σtσt σtσt No applied strain metallic materials: steel and metallic alloy

28. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 The simulated gradiometric output vs depth at different values of the normalized baseline b/z Probe modeling 1 st order Radial gradiometer 1 st order off axis gradiometer 1 st order transverse gradiometer 5 43210 Depth (cm) b/z=1.2 b/z=1 b/z=0.5 b/z=0.2 b/z=1.2 b/z=1 b/z=0.5 b/z=0.2 b/z=1.2 b/z=1 b/z=0.5 b/z=0.2 5 43210 Depth (cm) 5 43210

29. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 1.2 cm 1.4 cm f 0 = 120 Hz f 1 = 40 Hz  f= 100 Hz Dipole distance = 2 cm The Best Baseline

30. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006

31. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Giant Magnetoresistance (GMR)

32. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006

33. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 GMR bandwidth

34. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 The H-V Characteristics of Elecropolishing just replies the I-V polarization curve Static measurements Fixing the probe on the electrode and driving in voltage it is possible to measure: Flux Gate Anode Cathode

35. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Basic Considerations In the BCP process there is not metal dissolution …… The H 3 PO 4 works as a reaction moderator The detected magnetic field is proportional to the dissolution rate The Nb is oxided by HNO 3 The oxide is reduced by HF in a soluble salt All these processes are based on a charge transfer If there is a charge transfer a magnetic field is detectable

36. The International Workshop on THIN FILMS APPLIED TO SUPERCONDUCTING RF AND NEW IDEAS FOR PUSHING THE LIMITS OF RF SUPERCONDUCTIVITY M. Valentino, Padova-Italy, October 9 – 12, 2006 Campione di Titanio con fori (ALTRAN) Fori tipo A Fori tipo B Bobina 2 mm di diametro a 26.6 kHz = 133 mA, viene riportata la Parte reale 3-2-06