H. Wollnik

The influence of magnetic and electric fringing fields on the trajectories of charged particles

Abstract The effects of fringing fields of electric and magnetic sector fields on the trajectories of charged particles are determined in a second order approximation. This means that all terms are included which are of the same magnitude as the second order aberrations of ideal fields. The arising effects are either equal for the whole beam of particle trajectories or they are almost independent of the special fringing field distribution. This renders the possibility of calculating an apparatus corrected for image aberrations of second order without a very precise predetermination of the positions of the shielding diaphragms for the fringing fields. From the view of an experimentalist it is thus possible, to a certain amount, to adjust a sector field by changing the positions of the shielding diaphragms without disturbing the correction of the aberrations.

THE INFLUENCE OF AN INHOMOGENEOUS MAGNETIC FRINGING FIELD ON THE TRAJECTORIES OF CHARGED PARTICLES IN A THIRD ORDER APPROXIMATION.

Abstract The deflection of charged particles in the “extended fringing field” of a magnet by conical pole faces is being investigated. Effects originating from an oblique and curved field boundary are being taken into account. All radial effects are calculated in a third order and all axial effects in a second order approximation, since in the radial direction a magnet can accept larger aperture angles than in an axial one.

Third order transfer matrices of the fringing field of an inhomogeneous magnet

Abstract All ion optical fringing field effects of an inhomogeneous magnet are described in the transfer matrix representation. The resulting 49 × 49 matrices include all radial effects due to oblique and curved field boundaries in a third order approximation. The elements of the 10 × 10 axial transfer matrices necessary to describe all corresponding axial effects in a second order approximation are also derived. The necessary radial shifts of the optic axes are determined in a third order approximation.

SECOND ORDER APPROXIMATION OF THE THREE-DIMENSIONAL TRAJECTORIES OF CHARGED PARTICLES IN DEFLECTING ELECTROSTATIC AND MAGNETIC FIELDS

Abstract The radial trajectories of charged particles in electric and magnetic fields between toroidal electrodes and polefaces are known in a second order approximation, if the trajectories under consideration do not deviate very much from a circular main path. In this article the axial trajectories of charged particles are newly derived in a second order approximation and presented together with the radial trajectories.

Principles behind a He-jet system and its application for isotope separation

Abstract The functioning of a He-jet transport system is explained paying special attention to the use of aerosols. Three applications of such a He-jet for an isotope separation are discussed: the use behind a recoil fission product separator, the transportation of activity into the ion source of a conventional mass separator, and the transportation into an α- or gb-recoil time-of-flight spectrometer.

The improvement of a gas-jet system by the use of an aerosol generator

Abstract A gas-jet transport system is greatly improved by loading the sweep gas with aerosols of a specific size. In the thermalization chamber of such a gas-jet system the radioactive atoms are attached to these aerosols. The aerosols then are transported with negligible losses to some collector foil. Optimizing all parameters of the system a stable overall transport efficiency of approximately 80% can be achieved for up to several days, with variations of only ±1.5%.

Multipole elements for the correction of image aberrations

Abstract Multipole elements are discussed as far as their properties of correcting image aberrations are concerned. Limitations of their use are explained. A method of producing multipole elements in a simple but very precise manner is given which employs the technique of etching thin copper foils similarly as for electronic circuits.

The helium-jet technique for inaccessible sources of 252Cf fission fragments and 228Th decay products

Abstract A He-jet system has been developed for the transport of 252Cf fission fragments and 228Th decay products. The essential cluster formation occurs in a cluster breeder separated from the radioactive source. This cluster breeding is accomplished by adding liquids such as H2O or CCl4 to the transport gas and then blowing the mixture past an UV lamp. The efficiency of the transport from the radioactive source to the end of the capillary ranges between 50 and 80%. The efficiency of the skimming process alone is about 50%. K X-ray spectroscopy indicates that the transport of activity is largely independent of the particular element.

The correction of image aberrations of second order for mass or energy separators consisting of one single magnetic sector field

Abstract Image aberrations of second order are presented for mass separators consisting of one homogeneous or inhomogeneous 1–3 ) magnetic sector field, whereby the influence of the fringing fields 4, 5 ) are included in these expressions. Using a graphical method similar to linear programming techniques the derived aberrations can be corrected by proper choice of the curvatures of the entrance and exit boundaries of the magnet. As an example finally such a correction is carried out for a stigmatic focusing symmetric mass separator using a magnetic field with the inhomogeneity factor n = 0.5 and with perpendicular entry and exit of the ion beam into and out of the sector field.

Search for superheavy elements in the interaction of 136Xe and 238U with natU using the gas jet transport technique

Abstract No superheavy elements were observed among gas jet collected reaction products of (natU+136Xe) and (natU+238U) at the UNILAC accelerator. The upper limits for their production are ⋖ 3×10 −33 cm 2 in the half-live range 10 s ⩽T 1 2 ⩽ 1000 s .