Nuclear Instruments最新文献

A simple method is described allowing to transform a pulse spectrum pattern displayed as binary numbers on a cathode ray screen of a multichannel analyzer into a recorded curve.

A general relativistic analysis of the properties of spherical electrostatic analyzers is presented, and applied to some special cases of interest. An important limitation on the allowable kinetic energies is shown to exist: for energies greater than a certain kinetic energy T_max, the spherical analyzer is not an effective focusing instrument. Expressions for the velocity and energy dispersions, and for the resolving power, are derived. A special case, in which the central angle of the analyzer is greater than $\text{3π}\text{2}$, and which has desirable focusing properties, is briefly discussed.

A new method has been developed to measure the spectra of gamma radiation emitted in cascade disintegrations. Use is made of a two-crystal scintillation spectrometer and a gated multi-channel analysing device. The pulses produced by summing the outputs of the two crystal-photomultiplier combinations are selected by a single-channel differential discriminator. The output of this differential discriminator gates the multi-channel analyser whenever the sum pulse corresponds to the release in the crystals of the full energy available in the cascade. The spectrum displayed is that of either of the two detectors. The most important features of the technique are:

1. 1.

   (a) only “full-energy” peaks are detected;

2. 2.

   (b) improved resolution is obtained especially at higher gamma-ray energies;

3. 3.

   (c) one γ-γ or p-γ-γ angular correlation experiment determines the angular correlation of the gamma rays of all double cascades deexciting a given level.

Details of operation and typical spectra are presented. It is suggested that the technique be called the “sum-coincidence” method.

For light nuclei reactions, the energy of the emitted particle depends appreciably on the emission angle with a double focusing spectrometer using a large entrance angle, this variation can be of several %. Our experiments allowed to test for the first time this improvement of energy resolution with our astigmatic system (n = 0.57) and with a variable tilting angle of exit slit (after suggestion of Curt Mileikowsky).

Methods for the reduction of grid current noise and leakage currents in direct-coupled preamplifier circuits are discussed. It is shown that, by combining a cathode follower pream-plifier with a negative feedback output circuit, input grid resistors of very high value can be used. The construction and performance of an amplifier using these principles is described. Features of this circuit are a high zero stability and an adjustable time constant.

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 new type of detector has been built to distinguish between He³ and He⁴ particles of a continuous energy spectrum ranging from about 10 to 30 MeV. It consists of two gridded ionisation chambers which measure the total energy of the particle in two fragments $\text{“E}{}_1\text{”}\text{and}\text{“E}{}_2\text{”}$, in general E₁ being < E₂. The information is displayed in a cathode ray oscilloscope by a series of spots whose co-ordinates are proportional to the values of E₁ and E₂ for each particle. The positions of the spots are compared to calculated positions to determine the total energy and mass of the particle concerned. The apparatus has been used to study the reaction γ + He⁴ → π⁰ + He⁴ by picking up the recoil α-particle amidst a large background of He³ and singly charged particles. It is currently being used to investigate the photodisintegration of oxygen, argon and krypton at high energies.