Untersuchung von40Ca mit der Reaktion39K(p, γ0)40Ca

Excitation functions of the reaction³⁹K(p, γ ₀)⁴⁰Ca at 0° and 90° have been taken in the proton energy range 2.5–6.0 MeV corresponding to an excitation of⁴⁰Ca between 10.8 and 14.1 MeV. Positions and strengths of several resonances appearing in the excitation functions are given. The structure of⁴⁰Ca is compared with predictions from 1 particle — 1 hole calculations.     

Spektroskopie der Protonen aus der Reaktion Ni(n,p) Co bei einer Neutronenenergie von 14 MeV mit einem Teleskop aus Halbleiterdetektoren

Protons from nuclear reactions induced by 14 MeV neutrons are analysed with solid state detectors. A high background is caused by nuclear reactions in silicon. The application of a telescope with twodE/dx- detectors allows to suppress this background extensively. Proton identification is made by use of a two-dimensional analyser. The telescope is tested by recoil protons with polyethylene. This arrangement may also be used as a neutron spectrometer. The proton spectra from the reaction Ni(n, p)Co in forward direction (0°) and on an angle of 90° are compared. Nuclear temperature and level-density parameter are evaluated from statistical theory plots. The contribution of direct processes is estimated.     

Untersuchung der Anregungen von186Re nach der (n, γ)-Reaktion

Prompt and delayedγ-γ-coincidences were measured after slow neutron capture in¹⁸⁵Re by use of Ge(Li)-detectors. New isomers were found at 99.4 keV (T_1/2=27±7ns) and at ≈330keV (T_1/2=17.4±0.7 ns). The evaluation of coincidence data established 10 rotational bands with band heads below 700 keV. The level scheme is discussed in detail: Nilsson assignments are proposed for the band configurations, and calculations of Coriolis mixing andγ-transition probabilities are presented which reproduce the experimental level energies and transition intensities very satisfactorily.     

Zur Asymmetrie der Reaktion139La(n,α)136Cs mit polarisierten Neutronen

Experimental and theoretical investigations have been performed to determine the thermal conductivity of hydrogen in the temperature range between 2000 and 7000 °K. For this purpose the radial temperature distributions for various currents and theE-I-characteristic of a low current wall-stabilized hydrogen arc have been measured. In the dark region of the arc outside the bright core the temperature and the thermal conductivity between 2000 and 4500 °K were found by means of the schlieren technique. The electron temperature in the core of the arc results from spectroscopic measurements. The gas temperature has been calculated with a formula, derived from the kinetic theory of gases. Assuming a constant collision integralQ _eH ¹¹ the radial distribution of electric conductivity has been calculated according to Langevin's formula. The valueQ _eH ¹¹ =30·10^?16 cm₂ results by comparing the integrated conductance with the measured one. Since now the radial distribution of power input and the temperatures are known, the thermal conductivity between 4500 and 7000 °K can be determined as well. The total course of the heat conductivity shows a strong peak at the temperature of 3740 °K characteristic for the dissociation process.     

Messung der Neutronenpolarisation bei der Reaktion12C(d,n 0)13N mit Hilfe der Mott-Schwinger-Streuung

The polarization of neutrons produced in the reaction¹²C(d, n ⁰)¹³N was measured. Deuterons from the Karlsruhe isochronous cyclotron were used to induce this reaction at 51,5 MeV laboratory energy. The degree of polarization was determined by using the special features of Mott-Schwinger scattering. With an uranium scatterer analysing efficiencies of up to 0.92 can be obtained at very small angles (0.23°). The analysing efficiency can be calculated if the differential cross section at 0° and the total cross section is known. These quantities were experimentally determined. The differential cross section for 49.4 MeV neutrons, scattered by uranium, was measured between 0.88° and 2.10°. By an extrapolation the value 43.4±2.6 b/sr was found for the nuclear differential cross section at zero degree. A total cross section ofσ _t=4.80±0.22 b was obtained. The neutron polarization was measured at a reaction angle of 24.5° and the result isP=?0.45±0.07. This value is fairly above the semiclassical 1/3 limit and can be only explained, if spin orbit forces are taken into account. For (d, n) reactions this is the first neutron-polarization measurement above an energy of 20 MeV.     

Untersuchung der niedrigliegenden Niveaus des54Fe durch die (p,p′γγ)-Reaktion

The low-lying levels of⁵⁴Fe were studied. The method ofγ γ-triple-correlations was used. Angular distributions were also measured. The levels at 2.5 MeV were found to be a doublett, withI=0(⁺) for the 2563 keV-level andI=4(⁺ or 2(⁺) for the lower level at 2539 keV. The experimental level scheme is compared with calculations according to nuclear models.     

Untersuchung der Elektronenkomponente von Einzellawinen mit dem Photomultiplier

With a photomultiplier single electron avalanches of 10³ carriers can be observed in nitrogen. 2.5% of all photons (in the range 3000≦λ≦7000 Å) of an avalanche produce a photoelectron at the cathode of the photomultiplier. The influence of the variable solid angle on the photomultiplier pulse is given. Trouble by noise is calculated and it is shown that the information depends on the number of photoelectrons only. The electron components of avalanches in methane, nitrogen, and mixtures have an exponential rise and the measured rise time constant τ_beob is in accordance with the theoretical value 1/αυ_. For carrier numbers >10⁶ space charge influence is observed, as given by theory. The quantum efficiencyQ per ionizing impact is found to beQ～10^?3 in vapours andQ～1 in gases. Values of the electron drift velocity in mixtures of N₂ and CH₄ are given.     

Messung der Zirkularpolarisation der 478 keV-Gammaquanten aus der Reaktion Li6(d,p)Li7 mit 2 MeV-Deuteronen

The circular polarizationP _γ of 478 keVγ quanta from the reaction Li⁶(d, pγ) Li⁷ with 2 MeV deuterons was measured by forward Compton scattering from magnetized iron. The protons were observed at 25° lab angle. The fast neutron background in theγ detector was suppressed by pulse shape discrimination. The resultP _γ=+ 0.022 ± 0.17 with the Basel sign convention confines the ratio of the reduced widthsΘ _± for the capture of the neutron withj=1±1/2 to the regions ?2.36≦Θ ₊/Θ _?≦?0.74 or ?0.06≦Θ ₊/Θ _?≦+0.61.     

Tritiumausbeute der Reaktion He4 (γ,p) H3 mit 44 und 54 MeV-Bremsstrahlung

The photo disintegration of the α-particle was investigated by counting the tritium accumulated during irradiation with a low-level gas counting system. The measured yield is compared with values calculated from published cross-section data.     

Die Reaktion54Xe(n, α)52Te mit Neutronen der Energie 12,5 bis 18,0 MeV

The reaction₅₄Xe(n, α)₅₂Te was investigated in the neutron energy range 12.5 to 18.0 MeV. A high pressure gas scintillator filled either with pure xenon of natural isotopic abundance or with a mixture of xenon and helium was used as a target and as a detector simultaneously. The helium served as a monitor, (n, α)-spectra were measured and analyzed by evaporation theory. Large components of direct processes were found. The level density parameter of⁵²Te was determined as (17.0±1.7) MeV^?1. The cross section excitation function is given as well as the branching ratios for evaporation and direct processes as a function of neutron energy.     

Zur Untersuchung von Versetzungen mit Hilfe der magnetischen Kernresonanz

The line width of the nmr signal is obtained for a statistical distribution of distances and orientations of dislocations as a function of the dislocation density. The quadrupolar part of the line width increases proportional to the root of the dislocation density in the case of first order distortion but is proportional to the dislocation density itself in the case of second order distortion. The total line width passes through a maximum within the range of first order distortion and approaches the value of the undistorted central line which arises from magnetic dipole interaction when the dislocation density becomes sufficiently large. The intensity decay of the nmr signal connected with this line width behaviour will also be presented. In the range of second order distortion the total line width is determined by the constant dipole interaction and the quadrupole interaction of the central line which depends on the dislocation density. Under the assumption of a Gaussian distribution for the line shape a simple expression for this width can be obtained. The calculations are checked for the case of first order distortion by measurements on the Na²³ and Cl³⁵ nmr signals of NaCl single crystals and for the case of second order distortion by measurements on the J¹²⁷ signal of KJ single crystals.     

Untersuchung der Strahlungsreduktiön von Metallionen durch γ-Resonanzmessungen

The mechanism of the reduction of metal ions by mercury light and X-rays in the solid state is examined for the case of the potassium- and ammonium iron oxalates. From the dependence of the reduction yield on temperature and on the wavelength of the reducing radiation, it follows that the primary process is a charge transfer from the ligand system to the metal ion. The new charge state is stabilized by destruction of the complex. Several chemical reactions following this event give products which can be identified by theirγ-resonance spectra. One of them shows an unexpected large quadrupole splitting which is compared with the calculations of Ingalls. The results of experiments on iron and some rare earths suggest that no unusual charge state is produced in this way.     

Untersuchung des Zinkverhaltens bei der Eisenerzagglomeration mit Hilfe von Radioisotopen

Der Sintermischung warden bestimmte Portionen einer mit ⁶⁵ZnO markierten Mischung zugegeben und danach eine Bilanz dieses Zinks dutch Messen der Radioaktivität von an verschiedenen Stellen der gesinterten Schicht entnomnenen Proben aufgestellt.

Es wurde festgestellt, daß das Zink bei normalem Sinterbetrieb nicht aus der gesinterlen Schicht entweicht. Das markierte Material verbleibt im Agglomerat an der Stelle, an die es bei der Zugabe gelangte, und verbreitet sich infolge der Reaktion mit benachbartem inaktivem Gemisch nur geringfügig.

Die Erhöhung des Koksgrusanteils bis 30% bei gleichzeitiger Verringerung der Sinterluftmenge führt in der Sinterschicht zu reduzierenden Bedingungen, die den Umsatz des ZnO zu metallischem Zink nnd damit seine Entfernung aus dem Sintergemisch begünstigen. Es wurde nachgewiesen, daß man unter solchen Bedingungen elwa 90% des Zinks aus dem Gemisch entfernen kann.     

Die Polarisation der Neutronen aus der Reaktion13C(α,n)16O

The angular distribution of the polarization of neutrons from the reaction¹³C(α,n)¹⁶O has been determined between 1.38 and 2.26 MeV energy of the α-particles by left-right asymmetry induced by elastic scattering from⁴He. The neutrons were detected by a time-of-flight method between a helium gas scintillation counter and two plastic scintillation counters. From Simon and Welton theory analysis a set of spectroscopic data has been obtained for seven states of the compound nucleus¹⁷O.     

Proton-Gamma-Winkelverteilungen an der Reaktion19F(p, α γ)16O

The angular distributions of the 6.13 MeV γ₁ transition in the reaction¹⁹F(p, α γ)¹⁶O have been measured with improved accuracy at proton energies of 873 keV and 1,374 keV using a Ge(Li) detector. The results can be fitted by Legendre polynom series witha ₂=?0,018±0.008;a ₄=0.000±0.008 atE _p =873 keV anda ₂=?0.130±0.005;a ₄=+0.004±0.004 atE _p =1,374 keV. From the measured Legendre coefficients α₁-angular momentum mixing ratios are extracted and compared with the results from (p, α₁) and (α₁, γ₁) correlations.     

Ein Plattenzählerteleskop zur Untersuchung von (n, α)-Reaktionen

The characteristic features of a parallel plate counter telescope are described. Using twodE/dx parallel plate avalanche counters, a silicon detector and a third parallel plate avalanche counter in front of the target operating in anticoincidence the counter telescope has a coincidence resolution time of 20 nsec and it is suitable to study (n, α)-reactions especially for large backward angles.     

Untersuchung der Elektronenlawine mit der Nebelkammer

Zeitschrift für Physik A Hadrons and nuclei - Mit einer Nebelkammer, für die Untersuchung der Stoßionisierungsvorgänge der Elektronen im elektrischen Feld besonders geeignet,...     

Untersuchung der Zustandsdichte und der charakteristischen Energieverluste von Ir,Rh, Pt und Pd mit Isochromatenmessungen

X-ray isochromats of the above metals measured with high resolution are presented. Assuming a rigid band model for the four metals they give — with some usual approximations — the qualitative form of the density of states. It turns out that the densities of statesZ(ε) at the Fermi limits decrease in the succession Ir, Rh, Pt, Pd. This is in contradiction to low temperature measurements of the electronic specific heatc _e which for the same succession give an appreciable raising inZ(ε). It is assumed that this discrepancy is caused by a special coupling of the electrons to the transverse phonons. In consequence of this,Z(ε) of the renormalized electron system measured byc _e can be very different from that of the bare electrons measured by the isochromats. Assuming that the transition temperature of elemental superconductors is related according to BCS-theory to the latter density of states the absence of superconductivity of Rh, Pt and Pd can be understood. In addition the isochromats give values for the characteristic energy losses of the four metals.