© 2010-2014 SarFTI NRNU MEPhI

Measurement methods of substance properties in high pulsed magnetic fields

Inductive magnetization measurements

Inductive (compensation) method for the magnetization measurement allows investigating oscillation effects and metamagnetic phase transitions at high magnetic fields. It was widely used for research in ultra-high magnetic fields.

Astrophysical magnetic fields and their simulation

A possibility of appearance of a dynamo effect at compression of a hollow, conducting, spherical, and rapidly rotating shell by high pulsed magnetic field. A process of azimuth magnetic field generation is qualitatively described and estimated by a differential rotation, appearing at a shell implosion in the pulse magnetic field; and the magnetic fields generation process using αω-dynamo effect.

Generation of the azimuth magnetic field with the differential rotation (left image) and poloidal magnetic field with a gyrotropic turbulence(right image)

Dielectric permittivity and conductivity of isentropically compressed hydrogen up to multi-megabar pressures

are shown below (figures show pressure in Mbar)

High-frequency method of conductivity measurement

The method is used for conductivity and dielectric permittivity measurements of samples. It has high noise immunity. It was used for investigations of phase transitions in pulsed magnetic fields and at isentropic compression of substances.

ВЧ сигнал проводимости FeSi в сверхсильном магнитном поле – переход полупроводник металл (FeSi).

Helical solenoids

Works with the solid-turned helical solenoids made of bronze and brass (peak fields are up to 45 T at pulse length of about 200 mks) are carried out at the facility.

Left image shows a solenoid helix in technological mount, right image does elements of the solenoid.

Physics and technique of high magnetic fields

Technology of high magnetic fields generation

High magnetic fields facility

The facility consists of:

• capacitor battery (energy is 300 kJ, charging voltage is 10 kV),
• charging device HVPSystems (10 kV,10 kW)
• semiconductor switch based on reverse-switching dynistor (maximum working current is 30 kA at length up to 10 ms, maximum emergency current is 70 kA at length of 2 ms)
• wire solenoid
• control and measurement complex National Instruments
• oscilloscopes and measurement equipment.

The Laboratory has own cryogenic equipment:

· Helium machine CryoMech LP-12

· Different types of cryostats including optical helium cryostats.

By the end of 2010 we are planning to launch the first stage of the facility with the peak magnetic filed up to 55 T at a working volume diameter of  20 mm.

Mechanic stresses, which appear under effect of the ponderomotive forces, cause the most complicated problems at construction of nondestructive solenoids of high magnetic fields. The Laboratory develops and fabricates prestressed solenoids.

Technologies of wire solenoids

The Laboratory has own workshop. Equipment of SarFTI and RFNC-VNIIEF is also used.

Winding of the wire solenoids is made with a microcomposite wire Cu-Nb having nanocrystalline structure, made by A.A.Bochvar VNIINM, LLC. This conductor has a unique combination of high strength (up to 1300 MPa) and conductivity (up to 65% IACS, i.e. from the conductivity of annealed copper), that are necessary for creating the high magnetic fields solenoids.

Mechanic stresses, which appear under effect of the ponderomotive forces, cause the most complicated problems at construction of indestructible high magnetic fields solenoids.

There are several methods to preserve the construction from mechanical failure: (a) principle of dynamic confinement: the magnetic field is created during a very short period of time and the winding material does not undergo the deformation; (b) the solenoid is segmented and the mechanic stresses do not exceed the stress limit of the material and do not pass from one section to another; (c) reinforcement with stainless steel or dielectric materials; (d) the solenoid with a quasi-forceless configuration of the magnetic field, when a combination of azimuth and axial magnetic fields leads to equilibrium of radial magnetic forces; (d) prestressed solenoid.

Wire solenoids of strong magnetic field SSMF-55-19

• 30 T peak magnetic field (SSMF-55-19-1)
• Close to 40 T peak magnetic field (SSMF-55-19-3 and SSMF-55-19-4)
• the bore diameter is 19 mm
• the operation temperature is 77 K

Increase of the peak magnetic field up to 55 T is planned.

Time dependencies of field pulses for experimental solenoids. Corresponding current pulses are shown on inset.

Magnetization of Nd2Fe14B powder embedded into epoxide compound. Initial magnetization of specimen is oriented along applied field (black curve) and against it (grey curve). Inset – signal from the compensating coils corresponding to opposite directions of initial specimen magnetization and external field.

SSMF-55-19-1

SSMF-55-19-3

SSMF-55-19-4