Magnetic Flux Gradient Research Articles

Simulation of electron transport in newly designed large volume ion source.

Numerical simulation for electron transport in newly designed large volume ion source is carried out by simultaneously solving several differential equations. It should be noted from the computation that the electron produced by rf discharge at the circumferential region of large volume ion chamber transports to the central region of chamber by the gradient of magnetic flux density. This computational result is supported quantitatively by experimental results published recently.1 It is also found that the increase in rf frequency decreases the cyclic drift distance in x (circumferential) direction and increases the frequency of cyclic drift motion.

Magnetic susceptibility effects in imaging: Distortion-free images of plant tissue in soil

Magnetic susceptibility effects (MSE) in NMR spectra are well known, and indeed the NMR technique has frequently been applied to measure magnetic susceptibility. In the case of imaging, MSE can lead to image distortion when the sample is heterogeneous. We have performed experiments on a soil sample (iron content ≈ 2%) containing plant tissue which gave a NMR signal that was spread over about 15 kHz in the 1H spectrum. We present some results from a 128 × 128 × 128 3D 1H image (voxel size = 150 × 150 × 150 μm 3) generated by the stray field imaging (STRAFI) technique in which the use of a 5 kG cm −1 magnetic flux density gradient reduced the magnetic susceptibility distortion to less than 10 μm.

Direct Observation of Magnetic Flux Behavior in High-Tc Oxide Superconductors

The magnetic flux behavior in YBa 2 Cu 3 O x specimens under various applied fields was observed at 10K and 77K using the Faraday effect of an iron garnet film with stripe magnetic domains. The magnetic flux distribution was determined by optical observation of the domain structure in the iron garnet film placed on the sample. The magnetic flux gradients in a crystal fabricated by the Melt-Powder-Melt-Growth (MPMG) method and in a thin film were in good agreement with those predicted by the critical state model at both 10K and 77K. On the other hand, in a sintered sample the flux penetrated through the superconducting weak-link regions, and no flux gradient was observed at 77K.

Direct observation of magnetic flux behavior in high- Tc YBa 2Cu 30 x superconductors using the magneto-optical effect of iron garnet films

The magnetic flux behavior in YBa 2Cu 3O x , specimens at various applied fields was observed at 10 and 77 K using the Faraday effect of iron garnet films with perpendicular magnetization and stripe magnetic domains. Magneto-optical observation of the domain structure in the iron garnet film placed on the sample revealed the magnetic flux distribution. The magnetic flux gradients in melt processed crystals at both 10 and 77 K are in good agreement with that predicted by the critical state model. On the other hand, in a sintered sample the flux penetrated through the superconducting weak-link regions and no flux gradient was observed at 77 K. However, the critical state was weakly held for the macroscopic sample volume at 10 K due to the increase of intergrain critical currents.

Displacement sensor for a gravitational redshift experiment with 67Zn Mössbauer resonance

A displacement sensor was constructed to monitor the motion of a piezoelectric Doppler velocity transducer in a gravitational redshift experiment with 67Zn Mössbauer resonance. The sensor uses a dc superconducting quantum interference device (SQUID) to detect small displacements of a permanent magnet. To meet the stringent requirements of the redshift experiment, the magnetic flux gradient and the pickup coil of the sensor are designed in such a way that the SQUID flux noise of 7 × 10−6 Φ0/√Hz corresponds to a displacement resolution of 6 × 10−14 m/√Hz. However, resolution up to 3 × 10−15 m/√Hz in the frequency band of 20–20 000 Hz is demonstrated. The linearity of the displacement sensor and the piezoelectric transducer are considered in detail and the resulting uncertainties associated with the Doppler modulation in the Mössbauer experiment are evaluated.

酸化物高温超電導体の磁束挙動の直接観察

The magnetic flux behavior in YBa2Cu3Ox specimens at various applied fields was observed at 10 and 77 K using the Faraday effect of an iron garnet film with stripe magnetic domains. Optical observation of the domain structure in the iron garnet film placed on the sample revealed the magnetic flux distribution. The magnetic flux gradients in a Melt-Powder-Melt-Growth (MPMG) processed crystal and in a thin film are in good agreement with that predicted by the critical state model at both 10 and 77 K. On the other hand, in a sintered sample the flux penetrated through the superconducting weak-link regions and no flux gradient was observed at 77 K.

Observation of attractive forces in zone-melted YBa 2Cu 3O 7− x

Attractive forces between zone-melted YBa 2Cu 3O 7− x (YBCO) samples and a magnet beneath the samples were observed. Attractive forces were observed only among the samples with large magnetic hysteresis loops. The magnitude of the observed attractive forces is related to the sample's critical current density, J c , and the magnetic flux gradient the sample experiences.

The flux jumps in high T cBi 1.7Pb 0.3Sr 2Ca 2Cu 3O y bulk superconductor

There was giant flux jumps in high Tc Bi 1.7Pb 0.3Sr 2Ca 2Cu 3O y bulk superconductor. The relaxation time, τ, decreased with both the increase of magnetic field and the rise of temperature. The maximum τ was about 40 min.. The average-dM/dt increased with both the increase of magnetic field and the rise of temperature. The minimum average-dM/dt was about 4.1×10 −2G/min.. The flux jump weakened with time. It was dependent on the decrease of gradient of magnetic flux density dn/dx in the sample.

Magnetic instabilities of a rotating gas

We explore two types of instability which may develop when a highly conducting gas rotates rapidly in the presence of a radial gravitational force and an azimuthal magnetic field. Beyond a critical radius (equal to twice the isothermal scale height) a decrease of magnetic flux (per unit mass) outwards leads to the appearance of eastward-propagating waves by the mechanism of ‘magnetic buoyancy’. Within the critical radius an increase of magnetic flux outwards leads to westward-propagating waves by a totally different mechanism. Provided that the effects of Ohmic dissipation are not too large, either instability may set in for quite modest magnetic flux gradients, even when the magnetic energy of the system is very much smaller than the rotational energy.