Β-ray Spectrometer Research Articles

Numerische rechnungen zweiter und Höherer ordnung zu einem spektrometer mit wendelförmigem magnetfeld

Higher order calculations have been performed for a recently proposed high dispersion β-ray spectrometer with a winding magnetic field. It is shown that the radial aberration terms of ϕr 2 and ϕz 2 simultaneously vanish by a suitable choice of the second field coefficient a 2 and the slope k. In the third, fourth and fifth order approximation a focusing independent of ϕr can be achieved. With a focusing angle of 909.72° and a focusing independent of ϕz 2 and up to the fifth order independent of ϕr, the intensity distributions of point sources at the image plane are calculated. It is shown that, using spark chambers with infinite resolution at the source and detector planes, the resolution depends on the position of the point source, but, for a wide range of source coordinates, is always Δp p < 2 × 10 −5 . In the usual case of β-ray spectroscopy with exit slit the resolution is found to be better than that for corresponding flat spectrometers.

The decay of the K = 3 rotational band of 172Yb based on the 1172.3 keV state

The γ-ray transitions from the K=3 rotational band based on the 1172.3 keV state have been investigated using the Chalk River high-resolution β-ray spectrometer (resolution settings 0.2% and 0.06%) germanium lithium-drifted γ-ray counters and e-γ delayed coincidence techniques. From L conversion-electron subshell intensity ratios, the multipolarities of the following transitions were deduced: 78.74 keV (E2), 90.64 keV (26±3% M1 + 74±3% E2), 112.76 keV (33±5% M1 + 67±5% E2), 134.35 keV (33±12% M1 + 67±12% E2), 181.51 keV (E2), 203.43 keV (E2), 247.14 keV) (E2) and from conversion coefficient measurements, 810.0 keV (M1), 900.7 keV (M1), 912.1 keV (18±12% M1 + 82 ± 12% E2), 929.0 keV (63 ±16% M1 + 37 ± 16% E2) 1002.6 keV (12 ± 11% M1 + 88 ± 11% E2) and 1093.5 keV (E2). The half-lives of the following states were measured: 78.74 keV 1.6 ± 0.4 nsec, 1172.3 keV 7.8 ± 0.4 nsec and 1262.9 keV (≦ 0.6 nsec).

The decay scheme of 165Tm

The electron-capture decay 165 Tm → 165 Er has been investigated with the six-gap β-ray spectrometer as well as Ge(Li) and NaI(Tl) γ-ray detectors. The single γ-ray spectrum, e-γ and γ-γ coincidence spectra have been studied. Some tentative levels have been confirmed and several new established. The structure of the non-rotational states in 165Er is discussed in terms of a model in which the interaction of quasi-particles with quadrupole and octupole phonons is considered. The energy spacing between states with a predominant single-particle character is compared with the energy spacing calculated on the basis of the pairing force theory.

Properties of High Lying Levels in 199Au

The energy level spectrum of 199Au excited in the decay of the 30 min activity of 199Pt was investigated by means of a high resolution, double focussing β-ray spectrometer. The K- and L-conversion ratios of the 196 and 221 keV γ rays show that both are pure E2 transitions. The internal K-conversion coefficients of the 541, 790 and 960 keV γ rays were determined by the internalexternal conversion method, and the following results were obtained: αK (541) =0.059 ± 0.007; αK (790) =0.023 ± 0.003; αK (960) = 0.062 ± 0.008. The multipolarity assignments of these transitions were studied on the basis of the conversion coefficients. These data and the studies of other workers were combined to obtain the spins and parities 5/2 +, 1/2 +, 3/2 + and 9/2 + for the 541, 737, 790 and 960 keV levels in 199Au.

ENERGIES AND HALF-LIVES OF ISOMERIC LEVELS IN THE NUCLEI 139Ce, 141Nd, 161Ho, AND 163Ho

A search has been made for delayed γ rays with 1 second [Formula: see text] minutes following 10.5-MeV proton bombardment of 18 natural metallic targets. The five activities observed are: (1) 139Ce, Eγ = 754.5 ± 1.3 keV, [Formula: see text] second; (2) 141Nd, Eγ = 756.8 ± 1.3 keV, [Formula: see text] second; (3) 161Ho, Eγ = 211 ± 2 keV, [Formula: see text] second; (4) 163Ho, Eγ = 299 ± 2 keV, [Formula: see text] second; and (5) a γ ray of 122 ± 2 keV, [Formula: see text] second which is tentatively assigned to 179Ta. All transitions have been measured using a Ge(Li) γ-ray detector. The internal conversion electrons of the transitions in 139Ce and 141Nd were also studied using an orange β-ray spectrometer. Rotational transition energies in 158Dy, 164Er, 168Yb, and 174Hf were measured in conjunction with the internal conversion studies and are reported in an Appendix.

K-Conversion Coefficients of Transitions in In114 and Cd114

The K-conversion coefficients of the 192 keV isomeric transition in In114 and the 556 and 722 keV transitions in Cd114 have been measured for the first time by means of a high resolution double focusing β-ray spectrometer, using the internal-external conversion method. The results obtained are: αk (192 keV-In114) = 2.3653 ± 0.3075, in excellent agreement with the theoretical value 2.4638 for pure E4 transition calculated by SLIV and BAND, and αK (556 keV-Cd114) = 0.00419 ± 0.00046, αK (722 keV - Cd114) = 0.00207 ± 0.00025, both results in excellent agreement with the theoretical values for pure electric quadrupole radiation 0.00432 and 0.00218 respectively computed by SLIV and BAND. These data confirm the essentially pure E4 character of the 5 + → 1 +, 192 keV transition in In114 and the pure E2 character of the 4 + → 2 +, 722 keV and 2 + → 0 +, 556 keV transitions in Cd114. The conversion coefficient measurements reported here in Cd114 and In114 (Z=48 and 49) and in earlier studies (Z=22 - 28 and 56) indicate that E2-conversion coefficients in the Z region below 60 are in good agreement with theory.

The Internal Conversion Electron Spectrum of 147Nd

The internal conversion electron spectrum following the β-decay of 147Nd has been studied using, an iron yoke and an iron free double focussing β-ray spectrometer at a momentum resolution of about 0.2%. A total of 66 transitions has been ascribed to this decay. On the basis of statistical analysis of sum relationships for the transition energies, combined with earlier reported coincidence results, a decay scheme involving 16 excited levels is suggested. The experimental data indicate a higher state at 763 keV. Its energy is close to the high state observed in other promethium nuclei. The multipolarity assignment for each transition was obtained by comparing the observed conversion line intensity ratios with the theoretical line intensity ratios of SLIV and BAND. From the multipolarity values obtained, the spins and parities of the excited levels in 147Pm are assigned and discussed in terms of recent nuclear models.

M1 and E2 transition rates in 125I and 127I

Using mass-separated sources of 125Xe and 127Xe, time correlations have been measured between K X-rays and conversion electrons. In some cases an orange β-ray spectrometer was used to select the conversion line of interest. The mean lives for the following levels in 125I are: 113.57 keV, τ = 0.87±0.05 ns, 188.43 keV, τ = 0.51±0.01 ns, 243.40 keV, τ ≦ 0.27 ns and in 127 I, 202.83 keV, τ = 0.55±0.01 ns . Utilizing the energies, relative intensities and multipolarities established from separate high resolution studies of the internal conversion electron spectra, the absolute rates of three M1 and five E2 transitions are deduced. These are compared with rates of similar transitions in neighbouring nuclei and the predictions of the Kisslinger-Sorensen model.

Radioactive decay of 129Cs

The decay of 129Cs was investigated with Ge(Li) detectors and with double focusing β-ray spectrometers. Seven new transitions in 129Xe were found. The L-subshell ratios were determined for the 39.6 keV and 93.2 keV transitions. The E2 admixture in the latter is < 1.6%. Two new levels at 321.3±0.2 keV ( 5 2 +) and at 903.1±0.5 keV ( 1 2 + or 3 2 +) and a third possible one at 819±2 keV are reported. The spins 1 2 + and 3 2 + for the 411.1 and 578.8 keV levels, respectively, were determined. The spin 3 2 + for the 944.7 keV level is probable. The comparison with the pairing plus quadrupole model is discussed.

Burnup Analysis of Uranium Dioxide Nondestructive Analysis by External Conversion Method

Fundamental experiments on the nondestructive burnup analysis of UO2 were made by external conversion method using a sector type double focusing β-ray spectrometer. Details of the procedure are described. About 100 mg of UO2 enclosed in an Al-tube was irradiated and analyzed by this method. The fission products used as burnup indicators were 95Zr, 95Nb, 140La and 103Ru. A code for fission product calculation developed in our laboratory was used in burnup determination. The burnup thus determined was 53.07 MWD/t.

Excited states of 171Yb fed in the electron capture decay of 171Lu

Sources of 171Lu have been produced by the reaction 172Yb (p, 2n) 171Lu at 14 MeV. The excited states of 171Yb fed by the electron capture decay of 171Lu has been investigated using the Chalk River high resolution β-ray spectrometer at a resolution of 0.2% and 0.06%, germanium lithium drifted γ-ray counters and e-γ coincidence techniques. Conversion lines corresponding to 24 transitions in 171Yb were observed with energies in KeV; 9.150, 19.384, 27.126, 46.516, 55.679, 66.718, 72.365, 75.872, 85.59, 91.39, 109.27, 154.72, 163.81, 194.88, 517.7, 627.9, 667.3, 689.3, 712.6, 739.7, 767.5, 780.6, 840.0 and 853.0. The multipolarities of the transitions below 200 keV have been determined from measured L sub-shell conversion intensity ratios and for the higher-energy transitions from measured K-conversion coefficients. From a comparison of the experimental data with Nilsson model the following states have been assigned single-particle orbitals Kπ[ Nn z λ]; the ground state 1 2 −[521] , 95.26 KeV 7 2 +[633] , 122.39 keV 5 2 −[512] , 834.9 keV 7 2 −[514] and 935.2 keV 9 2 +[624] .

Energy levels of 166Er excited in the decay of 166Tm

The electron capture decay 166 Tm → 166 Er has been investigated in a six-gap β-ray spectrometer and with Ge(Li) γ-ray detectors. Conversion lines, single γ-ray spectra and e-γ coincidence relations have been extensively studied. The results with respect to the ground-state band and the gamma-vibrational band of 166Er are in good agreement with those of earlier investigations. Above the gamma-vibrational band, ten levels are definitely established, having the following energies (in keV), spin values and parities: 1460, (2) −; 1516, 3 −; 1574, (4) −; 1920, 3 −; 1941, (2 or 3) +; 1980, (2, 3 or 4) +; 2004, (4 −?); 2135, 3 +; 2162, 3 + and 2218, (1,2, or 3) −. Further three levels are suggested at 1530, 2023 and 2293 keV. The 1590 keV and 1687 keV (5 −) levels found in other investigations are probably also populated in the decay of 166Tm. The decay scheme accounts for 70 of the 90 γ-transitions observed in the present work. The structure of the levels of 166Er is discussed in terms of current nuclear models. In particular, the 1460 keV level is interpreted as an octupole-vibrational K = 2 − state, with the associated rotational band having parameters A = 9.5 keV and B = −10 eV. Evidence for a complicated structure of the 2135 keV 3 + state is presented.

Energy levels of 166Er excited in the decay of 166Tm

The electron capture decay 166Tm → 166Er has been investigated in a six-gap β-ray spectrometer and with Ge(Li) γ-ray detectors. Conversion lines, single γ-ray spectra and e— γ coincidence relations have been extensively studied. The results with respect to the ground-state band and the gamma-vibrational band of 166Er are in good agreement with those of earlier investigations. Above the gamma-vibrational band, ten levels are definitely established, having the following energies (in keV), spin values and parities: 1460, (2) −; 1516, 3 −; 1574, (4) −; 1920, 3 −; 1941, (2 or 3) +; 1980, (2, 3 or 4) +; 2004, (4 −?); 2135, 3 +; 2162, 3 + and 2218, (1,2, or 3) −. Further three levels are suggested at 1530, 2023 and 2293 keV. The 1590 keV and 1687 keV (5 −) levels found in other investigations are probably also populated in the decay of 166Tm. The decay scheme accounts for 70 of the 90 γ-transitions observed in the present work. The structure of the levels of 166Er is discussed in terms of current nuclear models. In particular, the 1460 keV level is interpreted as an octupole-vibrational K = 2 − state, with the associated rotational band having parameters A = 9.5 keV and B = −10 eV. Evidence for a complicated structure of the 2135 keV 3 + state is presented.

Messung des wirkungsquerschnitts für K-ionisierung durch stoss niederenergetischer negatonen und positonen

Absolute cross sections for K ionization in thin foils of Ag, Sn, W, Au and Pb by negaton and positon impact have been measured with the aid of a β-ray spectrometer and a NaI(Tl) scintillation crystal. The negaton and positon energies have been varied from about 100 keV to 400 keV in the cases of Ag and Sn and from 200 keV to 550 keV in the cases of W, Au and Pb. Down to the lowest energies no systematic difference has been found between the values measured with negatons and positons, respectively. A brief discussion of the values obtained in comparison with earlier experimental and theoretical results will be given.

Theorie erster ordnung eines spektrometers hoher dispersion MIT Wendelförmigem magnetfeld

A winding magnetic field is proposed for a high-dispersion β-ray spectrometer. The focusing properties have been investigated with a first-order perturbation theory. It is shown that winding fields at focusing angles of more than 2 π lead to a high dispersion. With a first field coefficient of a 1 = −0.929728 and a slope of k = 0.1 at the radius of the normal orbit the radial focusing angle is found to be I = 913.32° , and the dispersion D = 49.30.

Gamma intensities in the decay of187W

A study of the relative intensities of the γ-rays from the decay of187W to187Re has been performed using the external conversion method. The photo-electrons from uranium converter are analysed in a double-focusing β-ray spectrometer. Twenty nine γ transitions in the energy region of ∼200 keV to one MeV have been observed, and their energies and intensities have been measured. A modification of the previously reported scheme of levels is proposed after the addition of the new fifteen γ-rays found with energies (197.30±0.03), (201.14±0.04), (211.64±0.05), (220.71±0.23), (223.12±0.22), (225.63±0.30), (252.20±0.31), (302.18±0.42), (437.51±0.5), (466.94±0.32), (473.76±0.27), (478.23±0.30), (601.15±0.32), (749.71±0.50) and (878.23±0.30) keV.

0 + states in the N=82 nuclei

Targets of 140Ce, 142Nd and 144Sm have been bombarded with 12 MeV protons and deuterons. The spectra of high-energy conversion electrons were studied in a six-gap β-ray spectrometer, and the inelastical scattered particles from 142Nd and 144Sm were observed in a heavy-particle spectrograph. Four E0 transitions were observed, one in 140Ce, one in 142Nd and two in 144Sm. These E0 transitions are interpreted as transitions from excited 0 + states to the 0 + ground state. The energies of the excited 0 + states are 140Ce 1.90±0.02 MeV, 142 Nd 2.21±0.02 MeV, 144 Sm 1.67±0.02 MeV and 2.45±0.02 MeV . The inelastic-particle spectra show five levels in 142Nd below 2.8 MeV excitation energy and seven levels in 144Sm below 2.8 MeV excitation energy.

K auger spectra and atomic level widths of Yb ( Z=70)

The K-LL Auger spectrum of 70Yb observed in the electron capture decay of 71Lu 171 and 71Lu 172 has been studied with the Chalk River π√2 β-ray spectrometer at an instrumental resolution of 0.06% in momentum. The K-L IL III ( 3P 1) line and its nearby satellite K-L IL III ( 3P 2) were resolved. A comparison has been made of the measured line energies with the non-relativistic theoretical predictions of Asaad and Burhop as modified by Hörnfeldt. Except for the K-L IIL II line the overall agreement is better than 3 parts in 10 4. A comparison of the measured relative intensities and the relativistic calculations of Listengarten has also been made. Although these predicted intensities are in much better agreement with the experimental data than the non-relativistic calculations of Asaad and Burhop, the agreement is still only qualitative. A curve folding technique has been used to determine the natural widths of atomic states in 70Yb from the measured shapes of low energy internal conversion lines. The measured values of the widths of atomic states characterized by a vacancy in either the K, L I, L II or L III shells are 32, 5.0, 4.0 and 5.0 eV, with an uncertainty of ≈ 20%.

Study of the decay of Cs 134 with a high resolution Ge(Li) γ-ray spectrometer

The γ-ray spectrum of Cs 134 has been studied with a 3.5 mm deep by 18 mm diameter Ge(Li) γ-ray spectrometer. The conversion line spectrum has also been studied in a high resolution β-ray spectrometer and the K conversion coefficients of the transitions measured using a mixed source of Cs 134 and Cs 137. The energies in keV, relative intensities in percent per disintegration, and dominant multipolarities of the γ-transitions are: 475.26 (1.5%, E2); 563.11 (8.3% E2); 569.24 (14.3%, M1); 604.64 (98.0%, E2); 795.80 (88.0%, E2); 801.80 (8.8%, E2); 1038.46 (1.0%, M1 + E2); 1167.65 (2.0%, E2); and 1364.97 (3.4%, E2). The present data are consistent with levels in Ba 134 at 0 (0 +), 604.6 (2 +), 1167.7 (2 +), 1400.4 (4 +), 1643.0 (3 +), and 1969.6 keV (4 +). There is no evidence for previously reported levels at 1570 and 1773 keV.

Automatische mess- und entmagnetisierungseinrichtung für das Siegbahn-Slätis zwischenbild-beta-spektrometer

This article describes an automatic control system for the Siegbahn-Slätis β-ray spectrometer, built in the electronics division of the Reactorcenter Seibersdorf. This system is similar to that described by Konopasek and Connor. But in addition to a control system for automatic measurements, here a system for automatic demagnetisation too is described. Because of the simplicity of the stepping device, the author would not miss a description of that one. The whole system has been running since summer 1962 without any defects worth mentioning.