Plane Slits Research Articles

Conceptual study on parasitic low-energy RI beam production with in-flight separator BigRIPS and the first stopping examination for high-energy RI beams in the parasitic gas cell

Abstract An in-flight separator performs the important role of separating a single specific radioactive isotope (RI) beam from the thousands of RI beams produced by in-flight fission as well as projectile fragmentation. However, when looking at ``separation'' from a different viewpoint, more than 99% of simultaneously produced RI beams are just eliminated in the focal plane slits or elsewhere in the separator. In order to enhance the effective usability of the RIKEN in-flight separator BigRIPS, we have been developing an innovative method: parasitic laser ion source (PALIS), which implements parasitic low-energy RI beam production by saving eliminated RI beams during BigRIPS experiments. In this paper, we present the expected benefits and feasibility for the PALIS concept and the results of the first stopping examination for high-energy RI beams in the gas cell.

Reply to “Comment on Sochi’s variational method for generalised Newtonian flow” by Pritchard and Corson

In this article we challenge the claim that the previously proposed variational method to obtain flow solutions for generalized Newtonian fluids in circular tubes and plane slits is exact only for power law fluids. We also defend the theoretical foundation and formalism of the method which is based on minimizing the total stress through the application of the Euler-Lagrange principle.

Variational Approach for Resolving the Flow of Generalized Newtonian Fluids in Circular Pipes and Plane Slits

We use a generic and general variational method to obtain solutions to the flow of generalized Newtonian fluids through circular pipes and plane slits. The new method is not based on the use of the Euler-Lagrange variational principle and hence it is totally independent of our previous approach which is based on this principle. Instead, the method applies a very generic and general optimization approach which can be justified by the Dirichlet principle although this is not the only possible theoretical justification. The results that were obtained from the new method using nine types of fluid are in total agreement, within certain restrictions, with the results obtained from the traditional methods of fluid mechanics as well as the results obtained from the previous variational approach. In addition to being a useful method in its own for resolving the flow field in circular pipes and plane slits, the new variational method lends more support to the old variational method as well as for the use of variational principles in general to resolve the flow of generalized Newtonian fluids and obtain all the quantities of the flow field which include shear stress, local viscosity, rate of strain, speed profile, and volumetric flow rate.

Determination of displacements at the boundary of a body due to discontinuities in the medium

The problem of determining the displacements at the boundary of a body due to instantaneous disturbance of the continuity of the medium inside the body, i.e. discontinuities over a certain finite surface S, is of particular interest in connection with the inspection of structural elements, prediction of the probable effects of earthquakes, and the study of other processes. Three-dimensional problems - which more adequately reflect the actual physical processes that take place - are especially interesting in this regard. Here, we use an elastic half-space as an example to study the dependence of the displacements at its boundary on the instantaneous formation of discontinuities inside the half-space over a certain finite plane surface S. To solve this problem with allowance for its three-dimensional nature, we will examine a half-space weakened by plane slits whose opposing surfaces are displaced relative to one another over the period of time t in accordance with a certain law. Conditionally assuming that this law is known, we determine the displacements that these displacements cause at the boundary of the body. The boundary is assumed to be free of external forces.

TESTS OF LIQUID-CRYSTAL SCREENS FOR USE IN MULTI-OBJECT SLIT SPECTROSCOPY

ABSTRACT We examined the use of liquid-crystal (LC) technology to build an easily reconfigurable focal-plane slit system for multi-object spectroscopy (MOS). Several kinds of LC screens were analyzed in a spectrophotometer and at the focus of the spectrograph on the 24-inch telescope at Sommers-Bausch Observatory (SBO) on the CU Boulder campus. Depending on the crystal material used, transmission can be as high as > 80% in the clear state across the visible spectrum, and constrast ratios (ratio of clear- to opaque-state transmission) of >100:1 can be attained, but high contrast and high transmission are not both present in the same LCs. While significant difficulties exist in fabricating LCs as competitive MOS focal plane slits, there exist no fundamental obstacles to implementing this technology in an astronomical setting. The major problems for currently avaiable LCs include: 1. In order to obtain clear-state transmission of > 80% across one free spectral order, even the best contrast ratios currently available for a single screen ( 100:1) are not good enough for faint-object spectroscopy. 2. To use the LC types which yield high clear-state transmission, thin-film transistors (TFTs) must be used to address individual pixels. Currently, development costs for such devices are quite high, though remanufacture costs are low. Based on our tests, by stacking two screens of the best LCs currently available, an LC MOS slit assembly could be configured to give a clear-state transmission of 50-70% across the optical band with off-state opacities approaching 10 magnitudes in that same range. While these specifications are already competitive with other MOS schemes currently in use, the major drawback of an LC MOS at this time appears to be obtaining sufficient opacity between slits to obtain accurate sky subtraction.

Reduction of three-dimensional dynamical elasticity theory problems with arbitrarily located plane slits to integral equations

By generalizing a method described earlier /1/ for reducing three-dimensional dynamical problems of elasticity theory for a body with a slit to integral equations, integral equations are obtained for an infinite body with arbitrarily located plane slits. The interaction of disc-shaped slits located in one plane is investigated when normal external forces that vary sinusoidally with time (steady vibrations) are given on their surfaces. Problems of the reduction of dynamical three-dimensional elasticity theory problems to integral equations for an infinite body weakened by a plane slit were examined in /1, 2/. The solution of the initial problem is obtained in /1/ by applying a Laplace integral transform in time to the appropriate equations and constructing the solution in the form of Helmholtz potentials with densities characterizing the opening of the slit during deformation of the body. The problem under consideration is solved in /2/ by using the fundamental Stokes solution /3/ with subsequent construction of the solution in the form of an analogue of the elastic potential of a double layer.

Determination of the stress-strain state in a space with plane slits

Determination of the stress-strain state in a space with plane slits

Isothermal flow of helium II through plane slits

Measurements are reported on the isothermal, gravitational flow of liquid He II through narrow plane slits. The employed superleak consists of ring-shaped Hostaphan foils packed in layers. The distance between the foils is varied by pressure. The performance of the measurements and the observance of the isothermal conditions are described. The velocity of the superfluid component of He II is calculated in dependence on the width of the slits, the temperature and the hydrostatic pressure. Especially the critical velocity is considered.