Β-ray Spectrometer Research Articles

Design and calibration of a beta ray spectrometer for laboratory applications

This article presents the design, construction, and characterization of a low-cost, home-built, open-air magnetic field-based β-ray spectrometer suitable for use in graduate physics laboratories. Prime equipment such as electromagnet and GM tube with counter were characterized for their working. Two types of slits were designed and later one type of slit was used in the measurement. Finally, the working of the spectrometer setup was characterized by β -rays of the ‘204Tl’ source. The measured endpoint energy ‘Emax’ for the ‘204Tl’ source was found to be 0.658 MeV and 0.825 MeV respectively for θ = 30° and θ = 60°. These were only slightly different from the standard value of 0.764 MeV for the ‘204Tl’ source.

Observation of β-ray spectra after penetrating absorbing materials

β-Ray spectra after penetrating absorbing materials of various thicknesses were observed by the use of a scintillation-type β-ray spectrometer equipped with a flat NE-102 plastic scintillator of 5 mm thickness for sources of 60Co, 90Sr– 90Y, 137Cs, 147Pm and 204Tl. Although the spectra changed rapidly with increasing absorber thickness, the average β-ray energy was kept nearly constant for a wider range. These results are consistent in that the β-ray absorption curve becomes quasi-linear in a semi-logarithmic plot. Spectra including scattered β-rays from several materials placed behind the source were also measured for 137Cs and 204Tl. It may be concluded that mean energy measurements by the use of β-ray spectrometer of this kind is useful for the identification of nuclides in radiation protection purposes even in worse source-conditions.

Determination of radiochemical and radionuclide purity of a 131I preparation

The radiochemical purity of a 131I preparation (the iodide fraction) was determined by ascending paper chromatography using a mixture of sodium iodide, sodium iodate, and sodium carbonate as a carrier and aqueous methanol as an eluent. The chromatogram was developed with a scanning β-ray spectrometer. The radiochemical purity of 131I determined by this procedure was 99.98%. The radionuclide purity of the 131I preparation was measured on a γ-ray spectrometer with an ultrapure Ge detector. The content of radionuclide impurities estimated from their detection limits in the 131I preparation isolated from TeO2 in 3–4 days after its irradiation in a reactor was no more than 0.03%. The 75Se content in the preparation aged for 6–7 months (which corresponds to a decrease in the 131I activity by a factor of 106–107 owing to decay) corresponds to 2 × 10−6% of the activity by the end of irradiation.

Positron mass spectrometer design using crossed electric and magnetic fields.

Method of comparing the positron mass with the electron mass by using crossed fields is discussed on the basis of the relativistic calculation to the second order. Remodeling of a high resolution magnetic β-ray spectrometer into a positron-electron mass spectrometer is proposed. The crossed fields in the β-ray spectrometer equipped with a pair of cylindrical electrodes gives the mass dispersion of 1.3 μm/ppm at the optical circle of 0.75 m radius. Simulated peak profiles are presented for the monochromatic source of electrons or positrons and the β-ray source that emits them simultaneously in the continuous distribution.

Decay studies of 237Np with an iron-free π√2 double-focusing β-ray spectrometer of improved efficiency : S.A. Woods, P. Christmas, P. Cross, S.M. Judge and W. Gelletly, Nucl. Instr. and Meth. A264 (1988) 333–356.

A method for the simultaneous horizontal agarose gel electrophoresis on thin layer strips of different gel concentrations was developed for the purpose of generating Ferguson plots at the sub-microgram load level. Seven independent gel strips on a common GelBond support formed by filling channels created by a comb-shaped spacer (polycarbonate) in a vertical multistrip cassette. Electrophoresis on a horizontal Peltier-cooled surface employed commercial apparatus (E-C Apparatus Corp.) with a modified cover which is airtight and holds anodic and cathodic voltage measurement probes for each strip. The application of the apparatus to Ferguson plot analysis in a single experiment wa exemplified on the RNA-containing turnip crinkle virus (TCV) at a load of 50 ng/gel strip, using an optimized silver staining method (a modification of a procedure of FMC Corp. BioProducts) for detection. Within the range of 3.5 to 12.5 V/cm, the plot was found to be independent of field strength. Mobility is also independent of the concentration of detergent (CHAPS) up to 10 mM.

Precise intensity measurements of internal conversion lines in the decay of 207Bi and systematic comparison with theoretical predictions

Relative intensities of internal conversion lines of the 569.6, 897.3, 1063.6 and 1770.2 keV transitions in the decay of 207Bi were precisely determined by spectrographical measurements with position-sensitive electron detectors installed on the focal plane of the INS iron-free π√2 β-ray spectrometer. Internal conversion coefficients were deduced with the measured relative electron intensities and with the recent precise γ-ray data, where we assumed that the ICC of the 569.6 keV K-line is equal to the theoretical α k(E2) value. The experimental ICC thus obtained were systemati- cally compared with those by Rösel- Fries-Alder- Pauli (RFAP) and found to be satisfactorily in agreement with the theoretical values. L- and M-subshell ratios, and K- through O+P-shell ratios of the 569.6 and 1063.6 keV transitions determined for the first time in the present work were also found consistent with the predictions by RFAP.

Decay studies of 237Np with an iron-free π√2 double-focusing, β-ray spectrometer of improved efficiency

The efficiency of the NPL magnetic β-ray spectrometer has been increased by a factor ∼ 240 so that the decay of long-lived actinide nuclei may be studied. This large increase in efficiency was achieved by the use of a large area multistrip source in the manner of Bergkvist, together with the development of a sixteen element proportional counter. These modifications to the β-ray spectrometer have permitted the study of internal conversion following the decay of 237Np. The low-energy scheme of 233Pa has been determined on the basis of these measurements and the results of complementary singles and coincidence γ-ray studies.

中性子放射化分析法および蛍光Ｘ線分析法によるリョウブ標準試料のけい素およびりんの定量

Silicon and phosphorus contents in Pepperbush standard reference material were determined by neutron activation and X-ray fluorescence methods. In neutron activation analysis, β-ray spectra of 32P produced by 31P (n, γ) 32P reaction on Pepperbush and standard samples were measured by a low background β-ray spectrometer. In X-ray fluorescence analysis, the standard samples were prepared by mixing the Pepperbush powder with silicon dioxide and diammonium hydrogenphosphate. Characteristic X-rays from the samples were analyzed by a wavelength dispersive X-ray fluorescence spectrometer. From the β and X-ray intensities, silicon and phosphorus contents in Pepperbush were determined to be 1840±80 and 1200±50μg g-1, respectively.

Flight-Time Spread of Uniform Field Sector Magnet System for Use in Nuclear Life-Time Measurements

A nuclear life-time measurement apparatus incorporating a deflecting β-ray spectrometer with electron pre-accelerator has been constructed. A new arrangement consisting of two double angular focusing sector magnets based on the principle of symmetry has been devised so as to reduce the time spread in the spectrometer, which up till now has been the weak point of such systems. The time spread in the spectrometer was estimated to be \\cong0.1 ns by a simulation method, and good agreement was obtained between this estimated value and the experimental value. A prompt time resolution of 1.25 ns (FWHM) was obtained. The half-lives of the 199 and 401 keV levels in 75As were measured with an acceleration voltage up to 30 kV to check the reliability of the apparatus. The values were found to be 0.87±0.04 ns and 1.74±0.05 ns, respectively, in good agreement with previous measurements.

Measurement of the beta-ray spectra of 90Sr- 90Y

The β-ray spectra of 90Sr and 90Y have been remeasured with the CBNM magnetic β-ray spectrometer. From the measurements the endpoint energies (W 0 [m oc 2] and E 0 [keV]), the spectrum shapes (coefficient, a, of the shape-correction factor, l+aW), and the ratio of the numbers of β particles emitted in the decays of respectively 90Y and 90Sr, ( I β 1 I β 2 ), have been determined. The results are for 90Y, β 1 transition : W 0 1 = 5.4608 ± 0.0058E 0 1 = (2279.5 ± 2.9) keVa 1 = −(0.0078 ± 0.0024), 90Sr, β 2 transition: W 0 2 = 2.0685 ± 0.0032E 0 2 = (546.0 ± 1.6) keVa 2 = −(0.032 ± 0.007). The ratio of the numbers of emitted β particles is I β 1 I β 2 = 1.00 ± 0.01 . Corrections to the measured data and the estimates of uncertainties are discussed.

K/LM+ internal-conversion ratios for pure E2 transitions in the decays of 152Eu and 192Ir

Measurements have been made with a magnetic β-ray spectrometer in order to determine the internal-conversion ratio R = K/LM+ for pure E2 transitions of 244.7 and 344.3 keV in the decay of 152Eu and of 205.8 and 316.5 keV in the decay of 192Ir. The results from several experimental runs for each transition are respectively, R = 2.92 ± 0.05, 3.43 ± 0.05, 1.05 ± 0.04 and 1.71 ± 0.05. A comparison has been made with previously published results as well as with theoretical values deduced for pure E2 multipolarity from the most recent tabulations of internal-conversion coefficients.

The energy spectra and the quantum efficiencies of electrons emitted from the metallic elements irradiated by 60Co gamma rays

The energy spectra, angular distributions, and the absolute quantum efficiencies of forward emission electrons from 60Co γ-ray irradiated metallic elements have been measured using a double focusing β-ray spectrometer. Samples measured were C, Al, Cu, Mo, Sn, W, and Pb. Their thicknesses were chosen about equal to the maximum range of a 1.33 Mev photoelectron so as to ensure electron equilibrium. Similar spectral shapes were observed for samples with similar atomic numbers, but energy spectrum for the large atomic number sample was different from the small atomic number one. Photoelectron peaks were observed in the spectra for W and Pb. An empirical equation which gives the quantum efficiency as the function of atomic number was obtained. The efficiencies computed from this equation were in good agreement with experimental results and numerical calculations.

A high resolution position detecting system with a SWPC for electron spectroscopy

A position sensitive single wire proportional counter (SWPC) by a charge division method has been developed for a focal plane detector of the INS π√2 iron-free β-ray spectrometer ( ϱ = 75 cm). Good position resolutions, 0.3 mm (fwhm) for electron energy higher than 200 keV and 1 mm for 40 keV electrons, have been obtained with an integral position linearity of 0.2%. Analytical expressions of the charge division mechanism for proportional counter pulses, which have a logarithmic rise, are presented. The relations between the performance parameters, which are position resolution, linearity and counting rate, and the characteristics parameters of the wire, charge amplifier and shaping network are also given. A new effect, namely that the effective counter depth becomes one-half of the actual depth, was found. This effect (half depth effect) is useful for detection of the position of low energy electrons. A new high accuracy (0.1%) and high speed (15 μs) digital divider system has been developed with the use of successive approximation type ADCs.

The Decay of 137Cs Determined by β-Ray Spectrometry

The internal conversion coefficients of the 662 keV transition in 137Ba have been determined by the PBS method using an iron-free, double-focusing β-ray spectrometer. The results, with overall 68% confidence limits, were αT = 0.1092 ± 0.0008 and αK = 0.0888 ± 0.0007. In addition, the intensities per disintegration of the high-energy β-branch and of the 662 keV γ-ray were determined to be (6.21 ± 0.07)% and (84.56 ± 0.08)% respectively, and the value (513.89 ± 0.26) keV was obtained for the endpoint energy of the inner β-branch.

Transitions in123Sb

The X- and γ-ray and electron spectra associated with the (41.8 ± 0.5) min123Snm decay were measured by using high-resolution Ge(Li) and six-gap β-ray spectrometers. The123Snm activity was produced by irradiating enriched isotopes,122Sn (97.8%) with thermal neutrons and124Sn (96%) with fast neutrons. The present investigation besides confirming the weak transitions yields a hitherto unreported 170.9 keV γ-ray associated with the123Snm decay. A modified decay scheme of123Snm incorporating the new 170.9 keV γ-ray is proposed. TheK andK/L conversion coefficients for the 160.0 keV transition in123Sb have been measured for the first time. The results obtained are α K = 0.15 ± 0.01 andK/L = 7.6 ± 0.6. Our conversion data interpret the 160.0 keV transition to be almostM1.

Electric Monopole Transitions from Excited 0+ States in 156Gd

Internal conversion electron spectra from the decay of 156 Eu were measured at high resolution with an air-core, β-ray spectrometer. The source of 156 Eu was made through the double neutron capture process by irradiating separated 154 Sm with thermal neutrons and was chemically separated. Our data were combined with recent gamma-ray data to deduce conversion coefficients for 47 transitions. The 0 + states at 1049.4, 1168.1 and 1715.2 keV were confirmed. Spins and parities of other states were also assigned or confirmed. A method of analysis for β-band de-excitations is developed with ratios of E2/E0 matrix elements. The β-ground mixing parameter of 156 Gd is obtained to be 0.014, while the β-γ mixing parameter 0.029 for the 2 + β state and 0.005 for the 4 + β state.

An isotope separator beam position stabilizer of high sensitivity

A family of ion beam stabilizers in use on the TRISTAN isotope separator facility at the Ames Laboratory Research Reactor is described. The evolution of the concept is presentred, a detail;ed discussion is given od a beam stabilizer for a magnetic β-ray spectrometer, and design variations appropriate for isotope high voltage power supply stabilization and beam switching magnet power supply stabilization are presented.

Ghost peaks in a sector-focusing magnetic β-ray spectrometer

Zero-, single- and double-loop trajectories in a magnetic sector field, H = H φ ∼ 1 r , have been investigated. The focusing of single- and double-loop trajectories has been calculated for a K = 0.82 β-ray spectrometer with a symmetric entrance and exit profile shape. The trajectories are represented graphically. The counting ratio N 1/ N 0 of single-loop electrons/zero-loop electrons has been measured depending on the spectrometer entrance angle ψ s and the detector width Δz. An important decrease of N 1/ N 0 was achieved by a radial baffle S r placed in the central plane z = 0 of the spectrometer gap. The maximum length Δr max ( Δz, ψ s) of S r was found from the condition that the transmission T 0 ( Δz, ψ s) of the zero-loop electrons is unaffected by S r. Minimum obtainable values (N 1/N 0) min = ƒ min (Δz, ψ s ) are reported.

The 4s electron densities of Fe impurity atoms in some transition and noble metals

From internal conversion experiments and the Mossbauer effect measurements, the 4s electron density and isomer shift for Fe impurity atoms in Cr, Ni, Cu, Pt and Au metals were studied. The M and N shell conversion electron spectra of the 14.4 keV transition of57Fe were measured using a high resolution β-ray spectrometer and analyzed using a deconvolution methods. The Mossbauer effect measurements were performed by a standard spectrometer with a moving absorber. Most of the samples showed isomer shift values consistent with the published ones.

Automatic control and data acquisition of magnetic β-ray spectrometer measurements

The development of a versatile electronic system for control and data acquisition in connection with a goniometer-type magnetic β-ray spectrometer is described. Beside the commercially available transistorised power supply the electronic system consists of a magnet current control unit including an automatic demagnetisation routine and a read-out control unit. Use has been made of CAMAC standard equipment as much as possible. Experimental tests are performed on stability and reproducibility of the complete installation.