Ksenofont Ilakovac

Measurement of the component of the Ge-detector response function due to escape of secondary radiation

Abstract A method of measuring the component of the detector response function due to the escape of secondary photons and electrons from the detector active volume has been investigated. It is based on the use of two detectors that operate in coincidence. The requirement of simultaneity of recorded events in the detectors and the condition of constant energy sum eliminate almost entirely all other components of the detector response function. Results of a measurement of the escape of photons from the active volume of a Ge-detector into the solid angle of about 0.11 sr at the incident energy of 59.537 keV are given. A very clear spectrum was obtained. The results of the calculations considering all relevant single-and double-scattering processes are in good agreement on the absolute scale with the experimental values. The calculations were extended to the entire solid angle for the escape of secondary radiation of 2π.

Cross-talk between two planar germanium detectors in head-on geometry

Abstract Coincident detection of radiation, which, following the interaction of incident radiation in one detector, escapes from it and is absorbed in another detector, was studied. Several prominent peaks due to the transfer of energy by germanium characteristic radiation were observed. Their well defined positions allow accurate calibration of energy scales, and the time spectra corresponding to the peaks make possible a detailed analysis of the operation of the coincidence, a good definition of time intervals and of the coincidence efficiency. The ratios of numbers of pulses in the peaks allow an accurate check of the position of the source between the two detectors. The calculated values of the numbers of counts in the peaks are in agreement with the measured values, presenting an independent check of the efficiency of the coincidence. Among other possible modes of transfer of radiation from one into the other detector bremsstrahlung radiation of photoelectrons ejected in one germanium detector and detected in the other was calculated.

The dependence of the escape of characteristic X-rays from planar germanium detectors on the direction of the incident radiation

Abstract The escape of germanium K α X-rays from two planar germanium detectors for photons of 22.1 keV, incident at angles 0°, ± 10°, s , ± 40° , was measured. Applications of the measurements are discussed.

Hypersatellite and satellite transitions in cobalt

Abstract An accurate measurement of energy shifts and relative intensities of hypersatellite and satellite transitions in cobalt have been made. The use of radioactive 59 Ni, which decays mostly by the nuclear K-electron capture to cobalt and the low-probability processes of ejection of the other K-electron allowed the observation of decays among very pure double inner-shell-hole states. The measurements were made using a pair of high-purity germanium detectors in conjunction with a fast–slow coincidence system and a 128×512×512-channel three-parameter pulse-height analyzer. The results for the hypersatellite shifts are Δ(Kαh)=274.9±1.6 eV and Δ(Kβh)=354.5±4.6 eV, and for the satellite shifts Δ( Kα s L −1 )=25.1±1.4 eV, Δ( Kβ s L −1 )=39.1±4.8 eV and Δ( Kα s M −1 )=8.8±4.2 eV. The results for the intensity ratios are I(Kβh)/I(Kαh)=0.119±0.006, I( Kβ s L −1 )/I( Kα s L −1 )=0.114±0.007 , and I( Kβ s M −1 )/I( Kα s M −1 )=0.092±0.023 . Present results and the available results of earlier work are compared.

Resonance effect in 3d→1s xx decay

In the measurements of emission of photon pairs from many‐electron atomic systems with a vacancy in the K shell (xx decay) resonance effect was observed. The effect was predicted by the second‐order perturbation theory of xx decay in which summation over virtual intermediate states is carried out not only over unoccupied bound and over unbound states, but also over occupied bound states. Stationary intermediate states between the initial and final state, which are a path for ordinary cascade emission of two photons (x rays), cause a large increase of the differential transition probability when energy of the photons due to xx decay approaches values of cascade photons. The effect was observed in 3d→1s xx decay of K‐shell‐vacancy states in silver and hafnium atoms.