Nuclear Instruments最新文献

Three types of decoupling elements in the transmission line between magnetron and resonator of a microtron are investigated with respect to their power consumption and efficiency: a shunt resistance, an attenuator pad and a ferrite isolator (“Uniline” type S 161 of the firm Cascade Research/USA).

The equations governing the VSWR and the power distribution ratios resonator/load are derived and compared with measurements.

It is shown, that the shunt resistance rules out the attenuator. The uniline type used here does not give a better power efficiency than the shunt resistance. There only remain the other advantages of a ferrite isolator: ease of installation, uncritical setting of the phase shifter, and better isolation of the magnetron in the case of flash-over.

A scaling circuit is described which will operate at frequencies greater than20 Mc/s. Particular attention is paid to reliable triggering.

A long lens beta-ray spectrometer with a pure “triangular” field is here investigated theoretically. A point source as well as a disk source is considered. It is shown that the effect of the source width on the resolution is much smaller with this field than with a uniform field. The spherical aberration is rather large, but the maximum luminosity at a given resolution is larger than with a uniform field. The results are in agreement with experiments.

Some features of the electromagnetic field in a rectangular wave-guide, cut in two by a plane making an angle θ with the guide's longitudinal axis, are examined. The field is excited by a voltage applied across the two halves of the guide. Several values of θ, frequency (between zero and cut-off), and aspect ratio of the cross-section are considered. The problem is of interest for the design of particle accelerators, and, with this particular application in mind, data are presented for the energy and momentum kicks which particles experience when crossing the gap.

The K X-ray escape fraction of a NaI scintillation spectrometer is essentially reduced by letting the collimated X-rays to be studied enter through a narrow well in the crystal.

The construction of an atomic beam resonance apparatus with focusing six-pole magnets for measurements of spins and magnetic moments of radioactive nuclei is reported. The main features are similar to those of the apparatus of Hamilton, Lemonick, and Pipkin^†. The principles of the design and of maximizing the intensity are discussed. The effective solid angle, averaged over the velocity distribution of the beam, has been calculated to be about 3 × 10⁻⁴ steradians in a typical case, which is one order of magnitude larger than can be obtained by the conventional method. The apparatus has been used for measurements on four radioactive bismuth isotopes, which will be reported elsewhere.

An ion source of the oscillating electron type with axial magnetic field and end extraction has been constructed for electromagnetic separation of synchrocyclotron-produced radioactive isotopes. A description of the ion source and the results of some systematic investigations of its properties are given.

The performance of the ion source is illustrated by some recent applications to prepare sources for spallation studies and nuclear spectroscopy.

The results of an experimental investigation concerning the statistical spread of the pulse sizes of the scintillation spectrometer are reported. It was found that for γ-ray energies lower than 800 keV the measured half-width η of the lines fit strictly the relation η² = α + β/E where the two constants α and β vary slightly from one spectrometer to another. At higher energies the half-widths appear to be considerably smaller than predicted from the previous relation. That is due to the fact that at the high energies the γ-rays are absorbed in the phosphor not only by photoelectric effect, but any combination of processes by which the γ-ray is completely absorbed, can happen. All the experimental results are compared with statistical predictions.