AUSTROMAG: PULSED MAGNETIC FIELDS APPROACHING 70T. R.Grössinger

Transcription

1 AUSTROMAG AUSTROMAG: PULSED MAGNETIC FIELDS APPROACHING 70T R.Grössinger ƒ1

2 AUSTROMAG AUSTROMAG - T.U.Vienna: 10 MW-1s power supply. Regulated DC current over 1s. Maximum available power is limited. Primary power: 16 MVA - transformer 10 kv to 2 840V; Can be switched: series, parallel or antiparallel. ac-current - rectified - bridges 6 thyristors I(t). Maximum dc-power: 10 MW/1 s or 5 MW/2 s or 1 MW/10s Current time profile chosale - 20 free points. Delivers field plateau s or linear dh/dt. ƒ2

3 AUSTROMAG Switching of the thyristor bridges- three types of pulses: i) Parallel switching: 2 x I max = 13600A, U max = 840V: highest current field pulse - one polarity. ii) Serial switching: I max = 6800A, 2 x U max = 1680V: highest voltage field pulse - one polarity 40T. iii) Antiparallel switching: I max = ± 6800A, U max =± 840V. Bipolar pulse - real hysteresis measurements. ƒ3

4 AUSTROMAG Electric circuit ƒ4

5 AUSTROMAG High voltage transformer ƒ5

6 AUSTROMAG Switching the transformer ƒ6

7 AUSTROMAG Seriell - parallel ƒ7

8 AUSTROMAG Thyristors ƒ8

9 AUSTROMAG LC-circuit ƒ9

10 AUSTROMAG Block diagram of the Austromag high field installation. Low temperature system: max. 40 T in 25 mm bore; temperature between 1.5 K and 300K High Temperature system: maximum 35T in 40 mm; 300 K < T < 800K power transformer 16 MVA 2 x 570V/6800A parallel or seriel thyristor rectifier 12-pulses 2 antiparallel bridges 2 x 600V, 8300A/1s passive smoothing LC circuit high-temperature system 300K < T < 800K low-temperature system 1.5K < T < 300K m0h max = m0h max = 35 T 40 T 10 kv 2 x 1700 kva 50 Hz regulating electronic input H(t)! SECURITY! measuring electronics temp. controller test system modulation magnetostriction m0h max = 20 T ƒ10

11 AUSTROMAG Short pulse systems Typical pulse duration 1-50 ms. Energy source: condensator battery - kj. Available power can be varied by the time constant of the system. Consist of: Energy source - C.U 2 /2 charging unit - reproducibility Pulse magnet - diameter, homogeneity measuring device pick-up coils + electronic Data storage + PC ƒ11

12 AUSTROMAG High field magnets Optimized with respect to the available power, the heating of the magnet and the stresses. Heating of the magnet: j(t)...current density j 2 () t dt = T T 1 2 DcT. ( ) ρ( T) dt D...density of the conductor, c(t)...specific heat ρ(t)...specific resistivity of the conductor. ƒ12

13 Austromag Pulse magnet 40T pulse magnet For low temperature measurements ƒ13

14 Austromag High temperature system ƒ14

15 Austromag Pulse magnet Large bore magnet For high temperature measurements ƒ15

16 Austromag Thin foil coil Electrical data of the foil coil 1,4 cm 10,45 cm Inner radius a 1 Outer radius a 1 Length 2b 20 cm Width of the foil 20 cm Thickness of foil 0,15 mm Filling factor λ=0,928 Number of windings 560 Inductivity 10,28 mh ƒ16

17 Austromag Thin foil coil ƒ17

18 Austromag B(t) ƒ18

19 Austromag T(t) ƒ19

20 Austromag Stresses scales with B 2 ƒ20

21 Austromag Coil simulation optimization of regulation parametrs a) ananti-parallel circuit with high proportional amplification factor. Kp = 50, Tn = 150ms Is [A] Antipar. 4kA Trapez,gem.+ ger t [s] ƒ21

22 pressure Pressure cell Cryostat: inner whole 12mm. Outer diameter pressure cell: Smaller than: 12 mm Material: nonmagnetic steel MP35N Aim of pressure: 10 kbar Calculated max. pressure: about 4 kbar. Sample diameter: 2 mm Pick-up system: inside ƒ22

23 AUSTROMAG Increase f the field using the 10 MW/1s power supply + condensator attery. Two coil system. Condensator battery: 440 kj, 8kV Thyristor Diode Pulsed magnet Pickup coil ƒ23

24 Austromag Increase of the field H [T] t [ms] ƒ24

25 AUSTROMAG Condensator battery data ƒ25

26 AUSTROMAG Block diagram of one modul ƒ26

27 Results Application of pulsed high magnetic fields K, x = K, x = K, x = K, x = K, x = K, x = 2 M(Am 2 /kg) YCo 5-x Cu x perpendicular µ 0 H int ƒ27

28 Results Accurate hysteresis measurements on industrial magnets µ 0 M [T] 0,4 0,2 0, µ 0 H [ka/m] -0,2-0,4 PTB - Ferrite cylinder long pulse short pulse dynamic: J H C = 213 ka/m; B r = T PTB: J H C = 208 ka/m; B r = T ƒ28

29 Results Room temperature hysteresis loop of a two phase spherical and a cylindrical Nd-Fe-B sample. The curves were corrected for the demagnetizing factor. µ 0 M (T) 1,0 0,5 0, ,5-1,0 H in (MA/m) cylindre sphere corrected with demagnetizing factor ƒ29

30 Results Anisotropy of nanocrystalline mechanical alloyed Pr-Fe µ 0 H a (T) Pr 18 Fe 76 B 6 Pr 12 Fe 82 B 6 Pr 9 Fe 85 B Temperature (K) ƒ30

31 Results Magnetic viscosity dh/dt [(GA/m)/s)] 20 Cu annealed 1.5 SmCo Cu Cu annealed 5-x x Cu annealed 2.5 Cu annealed 3.0 Cu as-cast 2.0 Cu as-cast H [MA/m] c Coercive field as a function of the sweep rate dh/dt measured in as cast and annealed SmCo 5-x Cu x ƒ31

32 Results Magnetostriction Magnetostriktion [ppm] Bariumferrite HF 24/16 T=300K λ pc λ cc λ pp λ cp B [T] Magnetostriction measurements at room temperature on an anisotropic barium ferrite magnet made by Schramberg (HF24/16). ƒ32

33 Summary Summary of high magnetic fields High magetic fields are necessary for many aspects of sold state physics Pulsed fields allow also smaller laboratories access to medium up to high fields. Measuring technique still has to be impoved. Many applications in the area of magnetism. Magnetization, anisotropy, magnetostriction... ƒ33