Magnetic Squeeze Research Articles

Equilibrium of non-neutral plasmas in a Malmberg–Penning trap with quadrupole field errors

The effect of small quadrupole magnetic and electrostatic perturbations on the equilibrium of a non-neutral plasma confined in a Malmberg–Penning trap is analyzed on the base of the parallel current constraint derived recently [Kotelnikov and Romé, Phys. Plasmas 15, 072118 (2008)]. The constraint is generalized to the case of nonuniform plasma temperature. Analytical solutions for the electric potential variations inside the trap and Pfirsch–Schlüter currents are found in the paraxial limit for stepwise radial density profiles of the plasma. It is shown that the equilibrium distorted by a magnetic quadrupole is qualitatively different from that perturbed by an electric quadrupole. In particular, a magnetic quadrupole squeeze perturbs the plasma potential only within a localized region, whereas an electric quadrupole squeeze perturbs the potential in the entire plasma column. On the other hand, axially variable parts of the perturbed potential have similar radial profiles for both electric and magnetic quadrupoles.

Experimental studies on nonequilibrium plasma flow in a convergent–divergent magnetic field

We applied convergent–divergent (C–D) magnetic fields to nonequilibrium argon and hydrogen plasma flows, and investigated the variation of the plasma properties by emission spectroscopy measurements. From the observation of the emission patterns, the C–D magnetic field is found to compress and squeeze the plasma flow, causing the emission region to elongate downstream. It is clearly shown from the captured images that the extent of the compression and squeeze gets larger by applying a stronger magnetic field. Emission spectroscopy of argon plasmas shows that the electronic excitation mode is almost frozen. Emission spectroscopy of hydrogen plasmas shows that the rotational temperature decreases downstream, whereas the vibrational mode is almost frozen. Furthermore, it is demonstrated that the heat loss from the wall can be reduced with the applied C–D magnetic field, because compression and squeeze by the applied magnetic field keeps the plasma away from the wall.

Accessibility research at the department of mechatronics at Darmstadt University of Technology

Before the first author joined the department, the research group around Prof. Nordmann exclusively focused on 'classic' Mechatronics issues, such as active magnetic bearings and squeeze film dampers . This changed in 2004, when the first author -- who had developed a hands-free control system for an electric wheelchair within the framework of his PhD thesis (see [1]) -- became an active part of the group.

Magnetic fluid-based squeeze film between rough porous truncated conical plates

Efforts have been made to analyse the performance of a magnetic fluid-based squeeze film between rough porous truncated conical plates. The lubricant used here is a magnetic fluid and the external magnetic field is oblique to the lower plate. The bearing surfaces are assumed to be transversely rough. The roughness of the bearing surfaces is modelled by a stochastic random variable with non-zero mean, variance, and skewness. An attempt has been made to average the associated Reynolds equation with respect to the random roughness parameter. The concerned non-dimensional equation is solved with appropriate boundary condition in dimensionless form to get the pressure distribution, which is then used to obtain the expression for load carrying capacity, paving the way for the calculation of response time. The results are presented graphically as well as in tabular form. This investigation reveals that the bearing system admits an improved performance as compared to that of a bearing system working with a conventional lubricant. The results suggest that the pressure, load carrying capacity, and response time increase with increasing magnetization parameter. It is observed that although the bearing suffers owing to transverse roughness in general, there is scope for obtaining better performance in the case of negatively skewed roughness. This performance further enhances especially when negative variance is involved.

Solid ring armature experiments in a transaugmented railgun

The UTSI 2.4 m long, 11 mm diameter, transaugmented (separately augmented) railgun was used to accelerate solid aluminum ring armatures to velocities up to 3 km/s. The armature consisted of a 15 mm long aluminum tube with a tapered nose and wall thickness of 1 mm. The 1.2 to 1.3 g armatures were tested in a series of both conventional and augmented experiments to evaluate performance, transition velocity and transition action. Precise transition location was determined by correlation of muzzle voltage and the armature light emission measured by a PIN diode looking down the muzzle. The electromagnetic forces in this armature were determined using the MEGA 3-D finite element code. The ring armature produces a magnetic squeeze in the insulator plane which, because of the high compliance of the thin ring, loads the ring against the rails to increase the contact force. Augmentation increases the contact force and increases the transition velocity. This armature configuration may have application in all velocity ranges since it appears to operate as a true hybrid after transition with no plasma armature formation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic fluid-based squeeze film

Squeeze film lubrication of a magnetic fluid between two approaching surfaces is considered in the presence of an externally applied magnetic field that is oblique to the lower surface. The upper one is a rigid rectangular smooth plate, and the lower one is a porous rectangular plate composed of three thin layers with different porosities. Explicit solutions for the velocity, pressure, and the load-carrying capacity are obtained. The time for the upper plate to come down is found to be longer than for viscous squeeze film. This shows that magnetic fluid-based squeeze film is definitely better.