High-resolution Magnetic Spectrometer Research Articles

A magnetic spectrometer system for on-line studies of β rays and internal conversion electrons of short-lived mass-separated activities

A π√2 high-resolution magnetic spectrometer has recently become operational at the TRISTAN on-line isotope separator facility. The design and operational modes of the spectrometer have been developed especially for on-line studies of short-lived mass-separated fission product activities. The spectrometer configuration is described, with particular emphasis on the magnetic field control and stabilization, the data collection modes and techniques developed to study nonequilibrium source activities, and the stabilization of the ion-beam deposit position by use of a split-tape ion-beam collector.

Messung des 3H-Betaspektrums und Bestimmung der Obergrenze für die Ruhemasse des elektronischen Antineutrinos / Measurement of the H3-Betaspectrum and Determination of an Upper Limit for the Electronic Antineutrino Rest Mass

The β-spectrum of tritium has been measured with the Heidelberg (π/2)√13 high resolution magnetic spectrometer. A new almost backscatter free source technique and a special proportional counter were developed. Special attention is paid to the problem of energy losses of the electrons in the source layer to get a theoretical expression for correcting the measured spectra in a physically meaningful way. On the basis of the Wilcoxon ranktest an upper limit of 8 6 eV at 90 per cent confidence was obtained for the antineutrino rest mass.

Energy loss measurements of low energy ions in thin carbon foils

The energy losses in thin carbon foils of ions of N, Ne, Ar, Mn, Kr and Xe have been measured at 100 keV and 200 keV using a high-resolution magnetic spectrometer, with a view to improving the accuracy of beam-foil lifetime measurements. For high- Z particles, the results show that a straightforward application of the Linhard-Scharff-Schiott total stopping cross-sections to beam-velocity correction can substantially overestimate the reduction in velocity due to the foil.

A high-resolution magnetic beta-ray spectrometer adapted for on-line work

A 50 cm radius iron-yoke double focussing beta-ray spectrometer has been equipped to work on-line at the charged particle beam from an EN Tandem accelerator. The principal features of the experimental arrangements, including target and detector systems, beam transport and focussing and the background shielding are described. Experimental results from on-line internal conversion measurements on different isotopes are presented. On the basis of the experience gained in these measurements some of the possibilities of high-resolution on-line electron spectroscopy are discussed.

Design of high resolution magnetic spectrometer for use in energy selecting electron microscope

The design of an improved uniform field magnetic electron spectrometer is described. The special choice of ray paths in the second principal section leads to the vanishing of the second order angular aberration term cuased by the fringing field. In analysis of the pencil beams, the resolution of the proposed prism is the best one in comparison with several other dispersive spectrometers. The resolution improvement by shifting the selecting aperture to the plane of minimum trace width is discussed. Finally, the shape of a nonsymmetric magnet, giving a maximum possible resolution for this type of spectrometer, is computed.

The Interaction of Fast Electrons with Aromatic Amino Acids

As part of a program in investigating the interaction of electrons with biological molecules in a field emission scanning microscope, we have studied the energy loss spectra of aromatic amino acids: Tryptophan, Tyrosine and Phenylalanine.The instrument used is the simple multipurpose scanning microscope previously constructed. The high resolution magnetic spectrometer installed in this microscope enables a resolution of ∽.2 ev as limited by the energy spread in field emission only.The energy loss spectra of Tyrosine and Tryptophan are shown in Figs. 1 and 2. In general, they consist of several peaks below ∼l0 ev, a broad one around 25 ev, and some shoulders on the broad peak. The structure below ∽10 ev bears close correlation with UV, far UV or synchrotron radiation spectra, and can be deduced from each other by Kramers-Kronig transformation. For biological specimens, this has more recently been demonstrated for Nuclei-Acid Bases.

The 0 +-0 + transition in 116Sn

The conversion electron spectrum of 116mIn has been measured in a high-resolution magnetic spectrometer. The energy of the first 0 + level in 116Sn is found to be 1757.0 ± 0.2 keV. The E0 transition from this level to the ground state has an intensity of 2.5 ± 0.2 internal K conversion electrons per 10 5 decays of 116mIn. A strength parameter is estimated for this transition.

Design of a High-Resolution High-Efficiency Magnetic Spectrometer for Electron Spectroscopy

A theoretical design study was carried out for a high-resolution high-efficiency double-focusing magnetic spectrometer intended for general use in electron spectroscopy. With the proposed design it should be possible to operate with good intensity at energy resolutions as high as 0.01%. The air-cored system of coils used in the design gives a fieldform with electron-optical properties very close to those of the 1/r field. The design thus has very good focal-plane properties and, in conjunction with a multichannel detector, should yield data-acquisition rates approximately 100 times higher than in single-channel operation. The present design is superior in this respect to any previous air-cored magnetic spectrometer. All coils in the design are of smaller radii than the electron orbits, giving very high access to the source and detector regions. There appear to be no great difficulties in the construction of a spectrometer with this design. Most features of the design compare very favorably with other spectrometers currently used in electron spectroscopy. The effects of extraneous magnetic field perturbations on the performance of double-focusing spectrometers were also calculated.

Level Scheme ofSm153Based on (n, γ), (n, e−), andβ-Decay Experiments

The $^{152}\mathrm{Sm}(n, \ensuremath{\gamma})^{153}\mathrm{Sm}$ spectrum was measured with the Argonne bent-crystal spectrometer and with a Ge(Li) detector at the in-pile facility at the Argonne CP-5 research reactor. The low-energy bent-crystal spectrum consisted of 251 $\ensuremath{\gamma}$ transitions associated with thermal-neutron capture in $^{152}\mathrm{Sm}$, with energies between 28 and 1041 keV. The $\ensuremath{\gamma}$-ray intensities were normalized to the previously established intensity of the 103-keV line in $^{153}\mathrm{Eu}$ from the $\ensuremath{\beta}$ decay of $^{153}\mathrm{Sm}$. The energies and intensities of 24 other lines associated with this $\ensuremath{\beta}$ decay are also given. The high-energy ($n, \ensuremath{\gamma}$) spectrum, containing 23 lines between 4.5 and 5.9 MeV, was obtained with a Ge(Li) detector. The neutron binding energy of $^{153}\mathrm{Sm}$ was found to be 5869.3\ifmmode\pm\else\textpm\fi{}2.0 keV. The conversion-electron spectrum, measured with the high-resolution magnetic spectrometer at Munich, was used to obtain $K$ and $L$ conversion coefficients and corresponding multipole assignments for 37 of the low-energy $\ensuremath{\gamma}$ transitions. The $\ensuremath{\gamma}$ spectrum in $^{153}\mathrm{Sm}$ following $\ensuremath{\beta}$ decay of $^{153}\mathrm{Pm}$ was measured with Ge(Li) and Si(Li) detectors. The source was made at Darmstadt through the $^{154}\mathrm{Sm}(\ensuremath{\gamma}, p)^{153}\mathrm{Pm}$ reaction. The ($n, \ensuremath{\gamma}$), ($n, {e}^{\ensuremath{-}}$), and $\ensuremath{\beta}$-decay experiments were combined to develop the level scheme of $^{153}\mathrm{Sm}$, in which unique spin and parity assignments are made for 13 of the 28 levels below 750 keV. The energy (keV) and ${J}^{\ensuremath{\pi}}$ of the first 28 levels are: 0.000, ${\frac{3}{2}}^{+}$; 7.535, ${\frac{5}{2}}^{+}$; 35.843, ${\frac{3}{2}}^{\ensuremath{-}}$; 53.533, ${\frac{7}{2}}^{+}$ or (${\frac{5}{2}}^{+}$); 65.475, ${\frac{9}{2}}^{+}$ or ${\frac{7}{2}}^{+}$ or ${\frac{5}{2}}^{+}$; 90.874, ${\frac{5}{2}}^{\ensuremath{-}}$; 112.954, ${\frac{9}{2}}^{+}$ or ${\frac{7}{2}}^{\ifmmode\pm\else\textpm\fi{}}$ or ${\frac{5}{2}}^{\ifmmode\pm\else\textpm\fi{}}$; 127.298, ${\frac{3}{2}}^{\ensuremath{-}}$; 174.17, ${\frac{7}{2}}^{\ensuremath{-}}$; 182.90, ${\frac{5}{2}}^{\ensuremath{-}}$; (194.65), ${\frac{5}{2}}^{\ifmmode\pm\else\textpm\fi{}}$ or ${\frac{7}{2}}^{+}$; 262.33, ${\frac{7}{2}}^{+}$ or (${\frac{5}{2}}^{+}$); (265.93), ${\frac{7}{2}}^{\ensuremath{-}}$ or (${\frac{5}{2}}^{\ifmmode\pm\else\textpm\fi{}}$); 276.71, ${\frac{3}{2}}^{+}$; 321.11, ${\frac{3}{2}}^{+}$; 356.69, ${\frac{5}{2}}^{+}$; 362.29, ${\frac{5}{2}}^{+}$; (371.04), $\frac{9}{2}$ or $\frac{7}{2}$; 405.46, ${\frac{3}{2}}^{\ensuremath{-}}$; 414.91, ${\mathrm{\textonehalf{}}}^{+}$ or ${\frac{3}{2}}^{+}$; 447.07, $\frac{5}{2}$ or $\frac{7}{2}$; 450.04, $\frac{5}{2}$ or $\frac{7}{2}$; 481.08, ${\frac{3}{2}}^{+}$; 524.36, $\frac{5}{2}$; 630.20, ${\frac{3}{2}}^{(\ensuremath{-})}$; 695.83, ${\mathrm{\textonehalf{}}}^{(+)}$ or ${\frac{3}{2}}^{(+)}$; 734.90, $\frac{5}{2}$; and 750.32, \textonehalf{} or $\frac{3}{2}$. The parentheses around a level energy or spin assignment mean that this value is less well established or is less probable if there is a choice. Of special interest is the very low-energy (7.53 keV) first excited state with ${J}^{\ensuremath{\pi}}={\frac{5}{2}}^{+}$, which appears to be the second member of the strongly distorted ground-state rotational band. A good match between the theoretical predictions of the Nilsson model and the observed $\ensuremath{\gamma}$-ray branching ratio was obtained when nine of the eleven levels below 200 keV were assigned to a positive-parity, $K=\frac{3}{2}$, ground-state rotational band and two negative-parity, $K=\frac{3}{2}$, rotational bands with band heads at 35.84 and 127.30 keV.

N15(He3,d)O16Reaction and Structure of Oxygen-16

The structure of ${\mathrm{O}}^{16}$ has been studied by means of the ${\mathrm{N}}^{15}({\mathrm{He}}^{3},d){\mathrm{O}}^{16}$ reaction. The experiments were performed with 16.00- and 24.90-MeV ${\mathrm{He}}^{3}$ beams from the tandem Van de Graaff accelerator at Rochester. Reaction products were analyzed and recorded automatically by means of a high-resolution magnetic spectrometer equipped with a sonic-spark counter connected to an on-line computer system. In the region of excitation up to about 22 MeV, 14 lines have been identified with levels of ${\mathrm{O}}^{16}$, all having odd parity except the ground state (which was strongly excited), the first excited state (which was weakly excited), and the third excited state (which was barely detectable). Many well-known states were not seen. The experimental data have been analyzed by use of distorted-wave Born-approximation (stripping theory) calculations, and the results have been compared with expectations from wave functions of the shell model and of the "mixed model" exemplified in the work of Brown and Green and of Kelson. The strengths of the transitions are mostly found to be in good agreement with predictions of the mixed model and, where applicable, the shell model, although the $J={2}^{\ensuremath{-}}$, $T=0$ state at 12.53 MeV seems somewhat too strongly excited. However, a strongly excited state tentatively identified as a ${J}^{\ensuremath{\pi}}={3}^{\ensuremath{-}}$, $T=0$ state of ${\mathrm{O}}^{16}$ lying at 13.12 MeV is not predicted by any of the theories used in the comparisons.

Comparison of results of explorer XXXI direct measurement probes

Intercomparison measurements of the major ionospheric parameters of ion and electron density and temperature and ionic species made by direct measurement probes on the Explorer XXXI satellite are presented. Plasma density results are compared with simultaneous data from the Alouette II satellite. Probe results are from the following experiments: planar ion trap, planar electron trap, cylindrical electrostatic probes, high resolution magnetic ion mass spectrometer, planar Langmuir plate, and spherical ion probe. The plasma densities measured by the various probes generally agree with simultaneous Alouette II sounder values to within 20 percent. Electron temperatures measured by three different types of probes generally agree within 10 percent. Ion composition measurements by the planar ion trap and spherical probe show good agreement with the high resolution magnetic mass spectrometer. Ion temperature measurements from the ion trap are consistently higher than spherical ion probe results.

Microwave planar triodes in preamplifiers of nuclear magnetic resonance spectrometers

Microwave planar triodes are investigated as low-noise devices for preamplifiers of high-resolution nuclear magnetic resonance spectrometers in the frequency band from 10 to 100 MHz. Noise sources, noise figures and a preamplifier circuit for planar triodes are considered. Planar triode noise performance is realistically evaluated by measurements under actual operating conditions. Comparison with other competitive low-noise devices in the frequency band from 10 to 100 MHz are given. A microwave planar triode preamplifier with high amplification stability has been designed; when operated with the optimum value of source conductance, it has a minimum noise figure of 0.35 dB at 24.3 MHz.

Etude experimentale de la diffusion inelastique proton-deuton a 155 MeV

Measurements of the inelastic proton-deuteron cross section and polarization in a region of small momentum transfer have been made with a high resolution magnetic spectrometer. The amplitude Σ s and the polarization P 8 associated with the transition which leaves the target nucleons in a singlet S- state have then been obtained following Cromer's treatement of inelastic p-d scattering. The results are generally in good agreement with the theoretical predictions confirming Cromers theory which introduces final interaction between the target nucleons. These parameters have also been compared with the differect solutions of nucleon-nucleon interaction with isospin T = 0. The best fit was obtained with the Hamada-Johnston potential.

Rate of energy loss for positive and negative pions

With the use of a high-resolution magnetic spectrometer, the ranges of pions in nuclear emulsions have been measured at two momenta: 78 MeV/c and 90 MeV/c. The pions were produced in the CERN synchrocyclotron. It was found that the ranges of positive and negative pions are equal within ±0.5%. Any possible difference in the rate of energy loss must have saturated at a much lower momentum.

Nuclear Magnetic Resonance Spectroscopy in Superconducting Magnetic Fields

The first high-resolution nuclear magnetic resonance spectrometer operated at 30 Mcy/sec (7.05 kilogauss). The magnets constituted the only major obstacle to raising the frequency, but by continuous development over 10 years this frequency for proton resonance was increased to 100 Mcy/sec (23.4 kilogauss). Now, in one step, a system has been made to operate at twice this frequency and field intensity. It is not expected that superconducting magnets will generally replace iron magnets, but it is interesting to note that very few laboratories use the 30- and 40-Mcy/sec proton systems today. Notwithstanding the cost and operating problems of the superconducting magnet system for the nuclear magnetic resonance spectrometer, the fact that this is the only practical means of developing both a stable and a high-intensity field puts it in a class by itself. For this reason, even though the maintenance of spectrometers with superconducting magnets requires rather specialized skills, this type of instrumentation will clearly have an important role in advancing scientific knowledge, by making possible analyses which have not been possible with presently available instruments.

Precise Shape Measurements of Beta Spectra ofY90andY91

Precise measurements of the detailed shapes of the beta spectra of ${\mathrm{Y}}^{91}$ and ${\mathrm{Y}}^{90}$ were made in order to determine better to what extent the theory of beta decay in its present approximation is adequate to describe the distributions which are observed for these unique, $\ensuremath{\Delta}I=2$, party changing transitions. The use of an integrally biased semiconductor as the detector in a high resolution magnetic spectrometer provided an extremely low background which facilitated the accurate determination of the end points with a minimum amount of extrapolation. A proper end-point determination is necessary for a meaningful shape-factor analysis. In both cases, it was found that the experimental shape factor shows a small but definite deviation from the theoretical expectation. For a theoretical shape factor, ${L}_{0}{q}^{2}+9{L}_{1}$, with ${L}_{0}$ and ${L}_{1}$ based on exact electron radial wave functions including the effects of a finite nuclear radius, the necessary correction can be supplied by an empirical factor of the form $1+\frac{b}{W}$ with $0.3\ensuremath{\le}b\ensuremath{\le}0.4$. The end points of the ${\mathrm{Y}}^{91}$ and ${\mathrm{Y}}^{90}$ spectra were determined to be 1.545\ifmmode\pm\else\textpm\fi{}0.005 MeV and 2.273\ifmmode\pm\else\textpm\fi{}0.0005 MeV, respectively.

LEVELS IN Ne20 FROM THE C12(C12, α)Ne20 REACTION

A high-resolution magnetic spectrometer which compensates for dE/dθ effects has been used to examine levels in Ne20 produced in the C12(C12,α) Ne20 reaction, using the C12 beam from the Chalk River tandem accelerator. Levels were observed at excitations (Mev) of 4.25, 4.97, 5.62, 5.79, 6.71, 7.02, 7.17. 7.21, 7.43, 7.85, 8.46, 8.71, 8.79, 8.87, 9.04, 9.11, (9.31), 9.48, and 10.24 all with an estimated error of ± 0.02 Mev.

The high-resolution nuclear magnetic resonance spectrometer in the Central Laboratory for Automatics

The high-resolution nuclear magnetic resonance spectrometer in the Central Laboratory for Automatics

High-resolution nuclear magnetic resonance desk spectrometer, model JNM-C-60

High-resolution nuclear magnetic resonance desk spectrometer, model JNM-C-60

Slightly Inelastic Proton-Deuteron Scattering

Measurements of the inelastic $p\ensuremath{-}d$ cross section, in the region of very small momentum transfer, have been made at laboratory scattering angles of 5\ifmmode^\circ\else\textdegree\fi{}, 10\ifmmode^\circ\else\textdegree\fi{}, 15\ifmmode^\circ\else\textdegree\fi{}, and 20\ifmmode^\circ\else\textdegree\fi{}. The elastic $p\ensuremath{-}d$ cross section has also been measured at these angles and compared with Postma's data. These measurements have been performed with a high-resolution magnetic spectrometer designed especially for this experiment. The $p\ensuremath{-}d$ cross sections have been obtained by normalizing the $p\ensuremath{-}d$ spectra to $p\ensuremath{-}p$ spectra obtained by filling the same target with liquid hydrogen. The shape of the $p\ensuremath{-}p$ spectrum, at a particular angle, was used to effect the separation of the inelastic $p\ensuremath{-}d$ from the elastic $p\ensuremath{-}d$ spectrum. The over-all energy resolution at small angles was about 0.75%.A comparison of the elastic $p\ensuremath{-}d$ data with the impulse-approximation calculation of Kerman, McManus, and Thaler yielded a value of ${\ensuremath{\Sigma}}_{t}$, the triplet amplitude sum, at the four angles measured. The singlet amplitude sum, ${\ensuremath{\Sigma}}_{s}$, was obtained by fitting Cromer's theory to the inelastic $p\ensuremath{-}d$ cross section. The experimental values of the parameters ${\ensuremath{\Sigma}}_{s}$ and ${\ensuremath{\Sigma}}_{t}$ are compared with the predictions of the most recent phase-shift analyses. ${\ensuremath{\Sigma}}_{s}$ appears to be particularly sensitive to the values of the $T=0$ amplitudes and thus experimental values of ${\ensuremath{\Sigma}}_{s}$ may be useful in future phase-shift analyses.