Energieverlustmessungen in Anthrazen,Terphenyl und Plastikszintillator für Protonen und Deuteronen im Energiebereich von 100 bis 900 keV

Experimental determinations of stopping cross sections of anthracene, terphenyl and plastic scintillator were made for protons and deuterons in the energy range 100 to 900 keV. A semiconductor counter was used to measure the energy loss of the particles in the stopping materials. The thickness of the crystals of anthracene and terphenyl was measured by interferometry. The thickness of the foils of plastic scintillator was obtained by weighing a known area of foil. Range-energy curves for protons and deuterons in anthracene and terphenyl were computed by integration of the energy loss curves.     

Elastische und unelastische Streuung von Deuteronen an Aluminium bei 11,8 MeV

Using the 11.8 MeV deuteron beam of a cyclotron, a study has been made of the angular dependence of the deuteron spectrum from interactions on Al²⁷. Separation of the deuterons from other products of the deuteron reactions was accomplished by recordingdE/dx, measured by a three fold proportional counter, andE, measured by a CsI-counter, on an oscilloscope screen. The experimental inelastic angular distributions have the shape of a direct interaction process. The elastic angular distribution shows pronounced diffraction maxima.     

Diffusion von Protonen (Tritonen) in reinen und dotierten Eis-Einkristallen

The diffusion of tritium in HF doped ice was studied as a function of HF concentration ranging from 10^?5 to 5·10^?3 mol/l. The magnitude of the coefficient of diffusion as well as the activation energy of diffusion were found to be independent of HF concentration within this range. At a temperature of ?10°C an anisotropy in the diffusion coefficientD was observed in undoped monocrystalline ice samples. In the direction perpendicular to thec-axis,D exceeded by 10% the value found in the parallel direction. An interpretation of these observations is based on a mechanism involving only vacancies.     

Strippingreaktionen mit polarisierten Deuteronen

The nucleons liberated in a (d, p)- or (d, n)-stripping-reaction are generally polarized even if unpolarized deuterons are used. In this paper however these reactions are examined for polarized deuterons in order to provide more detailed information concerning the interactions between the reaction products.     

Anwendung der Kernreaktionsmethode zur Untersuchung der Diffusion von Deuteronen in mono- und polykristallinen Nickel-Absorbern

The isothermic diffusion (T=254 K) of implanted deuterons in single- and polycristalline nickel absorbers is studied by means of theD(d,p)T nuclear reaction. At high doses the mobility of the implanted deuterons is drastically reduced, which is connected with the radiation damage caused by the implantation process itself. On the other hand at low doses the deuteron distributions change as predicted by the common diffusion law of Fick. The applied nuclear reaction technique permits the direct observation of ion distributions in an absorber and their changes by diffusion—without any influence of the surface conditions on the evaluation. The method can be applied successfully in the study of slowly changing ion distributions (small diffusion coefficients).     

Elastische und unelastische Streuung von Deuteronen an Sr,Zr, Nb,Pd und Ag bei 11,8 MeV

Continuing previous experiments on the elastic and inelastic scattering of 11·8MeV deuterons on medium weight nuclei, Sr, Zr, Nb, Pd, and Ag targets have been studied. In addition to elastically scattered deuterons, angular distributions of inelastically scattered deuterons have been obtained for one group in Sr, and three groups in Zr and Nb, respectively, between 20° and 165°. The correlation between the diffraction maxima is discussed in terms ofBlair's phase rule. As in our previous results, this rule works poorly in the comparison between elastic and inelastic angular distributions. However the strongly excited inelastic groups which are interpreted as collective vibrational states do follow this rule. In the case of Pd and Ag, energy spectra at several scattering angles have been measured. The integrated differential cross sections of the inelastically scattered deuterons atΘ=90° of all investigated elements are compared with those of previous measurements. They show the influence of closed shells but no systematic decrease or increase with increasing atomic weight.     

Channeling- und Blocking-Effekte bei Transmission von Deuteronen der Energie 16 bis 27,5 MeV durch Lithiumfluorid-Einkristalle

The energy loss of deuterons transmitted through single crystals of LiF has been studied as a function of incidence angle near the (010), (¯110) and (¯120) planes. In the spectrum of transmitted deuterons particles were found with higher and lower energy loss in addition to the deuterons with normal energy loss. The critical angle for channeling was calculated and compared with experimentell results. The yield of blocked deuterons as a function of incidence angle has been explained by a model, which describes the trajectories of blocked particles.     

Asymmetrie des β-Zerfalls und NMR von28Al,38Cl und116In nach dem Einfang polarisierter Neutronen

Polarized²⁸Al,³⁸Cl and¹¹⁶In nuclei have been produced by capture of polarized thermal neutrons. The nuclear magnetic resonance has been observed by measuring the asymmetry of the β-decay. The nuclear magnetic moments were found to be μ(²⁸Al)=2.789(1) nm and μ(³⁸Cl)=2.05(2) nm (uncorrected). The β-decay asymmetry of¹¹⁶In has been observed in superconducting In-metal.     

Erzeugung polarisierter Elektronenstrahlen durch optisches Pumpen

The valence electrons in sodium vapour were aligned by optical pumping to a polarization between 5% and 15%. An electron beam of 10^?12 A current, 10^?2rad divergency and 1 mm diameter has been obtained by ionisation of the sodium vapour with uv-light. This electron beam was polarized up to 2% as measured by Mott scattering.     

Anlage zur Kernpolarisation mittels polarisierter Neutronen

An experimental set-up to be used for nuclear polarisation by means of the absorption of thermal polarized neutrons is described. The set-up consists essentially of a double spectrometer arrangement for polarized neutrons in connection with an arrangement for the detection of the nuclear polarisation by means of the anisotropic β-decay. The described method is especially useful for short-living isotopes which cannot be polarized by other methods.     

Untersuchung ferromagnetischen Materials mit polarisierter γ-Strahlung

Circularly polarized Co⁶⁰ γ-ray quanta have been used to measure the polarization-dependent part of the Compton effect on an iron-cobalt alloy. The asymmetryδ=(N ₊?N _?)/(N ₊+N _?) observed by inversion of the magnetic field direction was investigated as a function of the mean induction¯B between 1 and 23kI ^?. The experimental values of δ do not nearly drop as fast as¯B when going down from saturation to zero.     

Das elektronische Bremsvermögen von Stickstoff und Sauerstoff für niederenergetische Protonen

The electronic stopping power of molecular oxygen and nitrogen for protons with energies between 1 keV and 30 keV has been measured using a differentially pumped stopping cell. Our results give a surprisingly good confirmation of the Lindhard-Scharff statistical theory which predicts a linear velocity dependence of the electronic stopping power at low projectile energies. Moreover our data are in fair agreement with earlier high energy (E ≧ 20 keV) measurements in other laboratories. The combination of the present measurements with theoretically calculated nuclear stopping powers yields an estimate of the atomic stopping power. This estimate leads to substantially lower atomic stopping powers at low energies compared to values derived from range measurements. This result may have interesting implications on auroral hydrogen emissions.     

Experimente zur Herstellung polarisierter Elektronen aus Atomstrahlen

Zeitschrift für Physik A Hadrons and nuclei - We determine the maximal intensity of a polarized electron beam one can extract from an atomic beam with today available light sources. The real...