The half-lives of some short lived low Z nuclei formed by photonuclear reactions

The half-lives of several members of the mirror nuclei series have been measured, using improved scintillation counter detectors and a cycling apparatus which progams the synchrotron beam and several subsequent gated detectors in sequence repetitively. By the use of beta-ray energy discrimination, least squares fitting of decay curves, and by careful correction for background activities, the improved values listed in Table A were found

A proportional counter spectrometer study of the beta-decay of radioactive S-35, Pm-147, Ni-63, and C-14

A proportional counter spectrometer, hereinafter denoted as a p.c.s., of unique design has been constructed for the purpose of measuring beta-spectra whose energies lie below a few hundred Kev. The p.c.s. is well suited for the problem in that thin and uniform radioactive sources which are essential for accurate low energy spectral measurements can be employed. The utilization of radioactive sources of low surface densities is made possible by an allowable source area of a few square centimeters and an ~100 per cent geometrical efficiency for particle detection by the p.c.s. In addition, the p.c.s. obviates a Geiger-Huller counter window of finite thickness which is often associated with the magnetic spectrometers. The penetration of beta-particles through the Geiger-Muller counter window can lead to distortion of the beta-spectrum at low energies

Photodisintegration of light elements in nuclear emulsions

The cross-sections for the reactions C-12 (gamma, 3 alpha) and O-16 (gamma, 4 alpha) have been measured as a function of photon energy from threshold to 50 Mev, and agreement with known levels is good in the former case. New levels are observed in the region 23 to 30 Mev for the latter reaction. The cross section for the reaction N-14 (gamma, 2 alpha) is observed to peak at 25 Mev, with a long tail to 45 Mev. The reaction N-14 (gamma, np)3 alpha occurs at least four times as often as the reaction N-14 (gamma, d)3 alpha

Device for detection and identification of charged particles from photonuclear reactions

A device is described which makes possible the determination of the energy spectrum of protons, alpha particles, or deuterons in the presence of other charged particles. Energy loss per unit path length (dE/dx) and total energy (E) are displayed in the form of voltage pulses of varying amplitudes in quadrature on an oscilloscope screen. The peaks of the pulses are intensitifed, resulting in hyperbolic loci for different types of particles. By masking the oscilloscope screen and using the moving film pulse height analysis technique developed in this laboratory, independent energy spectra may be obtained for each type of particle

Radioactive disintegration spectra of some short-lived nuclides

The beta endpoint energies of several short=lived, low Z radioactive nuclides have been measured with an improved scintillation spectrometer. These values have been combined with recent half-life determinations to give the ft values

Determination of the angular spread of the x-ray beam from the I. S. C. (70-Mev) synchrotron

The radioactivity produced in copper and carbon strips by irradiation with 66 Mev bremmstrahlung is used to determine the angular spread of the X-ray beam. The beam breadth at half maximum intensity indicated an angular spread of 2.03 +/- 0.03 degrees with copper, and a spread of 2.08 +/- 0.04 degrees with carbon detectors. These results are approximately eight per cent smaller than predicted by Schiff\u27s theory for a target of tungsten, 5 mils thick

Decay characteristics of some short-lived nuclides of low atomic number

The short-lived activities in Cl-34, K38, Ca-39, Li-8, He-6, and O-15 formed by high energy bremmstrahlung irradiation have been examined, and some improved values for the half-lives of these nuclides are reported. A detailed description of the apparatus and procedure is included, together with a discussion of the weighted least mean square analysis used

Short-lived synchrotron-induced radioactivities

The use of a scintillation spectrometer for measurement of the energy distribution and half-life of short-lived beta-emitters is described. The instrumentation is especially suited for use with radioactivities of low intensity resulting from photonuclear reactions produced by the Iowa State College 70-Mev synchrotron. Such activities are unsuited for study with a conventional magnetic spectrometer of small solid angle, particularly if the activities are short-lived, but may readily be analyzed with a scintillation spectrometer, for which the solid angle of acceptance is close to 50 per cent

Transmission of 0-5- kilovolt electrons by thin films with applications to beta-ray spectroscopy

The penetration of electrons through matter has long been the subject of both theoretical and experimental investigations. Because of simplicity, the investigation frequently deals with a collimated beam of monoenergetic electrons incident normally upon a planar target. Two of the most useful measurements connected with such an experiment concern the range or depth of penetration of electrons in the target, and the intensity of the transmitted beam as a function of incident energy. One object of this research is to determine experimentally range-energy data for thin films. The other object is to measure the transmission of electrons by a thin film and to apply the data to beta-ray spectra obtained using the film as the window in a G-M counter

The Disintegration of Praseodymium 142

The radiations from Pr-142 have been examined with a thin lens spectrometer. One gamma-ray was found having an energy of 1.576 Mev. The beta-spectrum is complex, the two groups observed having maximum kinetic energies of 2.154 Mev and 0.636 Mev. It is suggested that the high energy beta-group gives a transition to the ground state of Nd-142 and that the gamma-ray follows the low energy beta-transition. The half-life was found to be 19.1 hr. The electron distribution produced by bremsstrahlung, due to the absorption of the beta-rays, was observed