Die Energieaufnahme der Ionen in einem sehr schnellen Theta-Pinch

In a theta pinch with an extremely fast rising magnetic field (dB/dt 10¹¹ G/sec), a strong compression wave is produced in an initially fieldless low-density deuterium plasma. Assuming simple plasma models, a high-energy gain of the ions is expected already during the implosion of the plasma. In agreement with these calculations for a filling pressure of 20 μ D₂, a mean ion energy of 1–2 keV is determined from the first neutron emission at the end of the implosion, only 150 nsec after ignition. Decreasing the initial pressure to 10 μ D₂ does not cause any further increase of the achieved ion energy. This limitation of the ion heating is explained by a strong broadening of the current carrying layer at low densities which is observed by magnetic probe measurements. In the adiabatic compression, the mean ion energy attains values of several keV. During the first part of this phase, the energy distribution function of the ions is found to be essentially anisotropic, and monoenergetic rather than Maxwellian.     

Analysis of average primary gamma-transition intensities and cross sections of the113Cd(n, γ) reaction

A combined analysis of the available data on the primaryγ-ray intensities from the¹¹³Cd(n, γ) reaction atE _n=1.9 and 24.3 keV neutron energies together with the data on¹¹³Cd neutron capture cross sections in theE _n=3–200 keV energy region was carried out. The neutron strength functions were determined asS _n0=(0.260±0.073) 10^?4 and S_n1=(5.06±0.67) 10^?4. No spin-orbit splitting of thep-wave neutron strength function was found. The energy dependence of theE 1 radiative strength function {ie147-01} was fitted by the Kadmenski-Furman model somewhat better than by a standard Lorentzian. TheM 1 giant resonance parameters were obtained as E _G ^{M 1} =8.8±1.6 MeV and Γ _G ^{M 1} = 4.7±2.6 MeV. The neutron capture cross section of¹¹³Cd from its isomeric state ({ie147-02}=11/2^?, E ₁ ^m =263.7 keV) was calculated.     

Multi-state impact parameter approximation for many particle excitations in atomic collisions; Total cross sections for Na-Ne and N-Ne

A multi-state impact parameter treatment of many electron excitations in atomic collisions for the energy rangeE _lab=1 keV–1 MeV is applied to the 3s-3p excitation of Na and to the⁴ S ² D,² P excitations of N by collision with Ne. The Ne-target, for which simultaneous excitations are neglected, is described by a Hartree-Fock frozen-core potential. The calculated cross sections for Na-Ne turn out to be higher by an order of magnitude than the available experiment.     

Computer simulation of atomic mixing during ion bombardment

The atomic mixing in the target under ion bombardment is assumed to result from cascades of atomic collision events. Computer simulations have been applied to collision cascades to estimate the depth resolution of surface analysis with an ion probe. The Monte Carlo method based on a single scattering model has been used mainly in the calculation under the assumptions of random collision process, no diffusion and no target saturation processes. High-energy collisions are characterized by a Lenz-Jensen or a Thomas-Fermi potential, while a Born-Mayer potential is used in the low energy region. The simulations have been performed for the bombardment of Ar ions withE ₀=5 keV and 10 keV at angles of incidence θ=0° and 60° on Si targets. The depth resolutions [the definition of which is explained by (15) in the text] are about 140Å for the Lenz-Jensen cross section and about 80Å for the Thomas-Fermi one for θ=0° atE ₀=5 keV, and decrease by 20–40% at θ=60° and increase by 70–90% forE ₀=10 keV.     

Gamma ray energies and 36Cl level scheme from the reaction 35Cl(n, γ)

The γ-ray spectrum emitted after thermal neutron capture in ³⁵Cl has been studied by use of the crystal and pair spectrometers installed at the ILL high flux reactor. We identified about 400 transitions in this reaction 326 of which were placed into the ³⁶C1 level scheme; several new states were found. The level energies up to 3.5 MeV were measured with a precision of 5–20 eV relative to the 412 keV ¹⁹⁸Au standard, those above 3.5 MeV with a precision of ¹⁰ppm. The neutron binding energy was determined to be E_B = 8579.68(9) keV.     

Geschwindigkeitsverteilung anisotroper Deuteriumplasmen aus zeitaufgelösten Neutronenspektren

The ion energy in hot deuterium plasmas can be determined by using the Doppler broadening of thed-d-neutron line at 2.45 MeV. A method allowing time resolved measurement of neutron spectra in pulsed discharges is described. It utilizes the known energy dependence of the total neutron cross section of light to medium weight nuclei for energy selection of the neutrons. The neutrons are detected with plastic scintillators which afford both a high detection efficiency and a time resolution in the nanosecond range. The method is applied to a theta pinch for investigating the anisotropy and relaxation of the deuteron velocity distribution. It is shown that, in particular, the ion energy parallel to the magnetic field can readily be measured even at the low neutron yield available at present. Suitable combination of this procedure with known diagnostic methods allows deviation of the velocity distribution from the isotropic Maxwell distribution to be determined with sufficient accuracy. Comparison of the experimental relaxation rate with the theoretical predicted collision relaxation shows that Coulomb collisions are not a sufficient explanation. The short wave-length mirror instabilities also observed probably make a major contribution to the relaxation of the anisotropic velocity distribution.     

Experimental determination of the electron screening potential energy for the d(d, n)3He Reaction in ZrD2 and D2O in the ultralow energy region

This work is devoted to measuring of the values of the astrophysical S-factors and electron screening potential energy for a d(d,n)³He reaction occurring at ultralow energies in zirconium deuteride ZrD₂ (3.5–7.0 keV) and heavy water D₂O (2.2–6.0 keV). The experiment was performed on the Hall pulsed plasma accelerator at the TPU Nuclear Physics Institute (Tomsk) with ZrD₂ and D₂O targets produced by the magnetron sputtering of zirconium in a deuterium environment and heavy water freezing-out on a copper support, respectively. A χ ² analysis of the dependence of the neutron yields and astrophysical S-factors for the dd reaction on the deuteron collision energy E revealed that the upper bounds of the electron screening potential energy for interacting deuterons in ZrD₂ and D₂O and of the astrophysical S-factors at the deuteron collision energy E = 0 were U _e (ZrD₂) < 30 eV, U _e (D₂O) < 25 eV, S(0) = (57.2 ± 3.9) keV · b (ZrD₂), S(0) = (58.6 ± 3.6) keV · b (D₂O) at the 90% confidence level.     

Energy flow in ultra-relativistic nucleus-nucleus collisions and comparison between models

We calculate the cross sections of transverse and neutral energy production in the nucleus-nucleus collisions using the additive quark model (AQM) and the wounded nucleon model (WNM). In the case of α?α collisions, the experimental data of the transverse energy (E _T ) distribution favor the WNM, whereas those of the total neutral energy and the transverse neutral energy distributions favor the AQM. We predict theE _T distributions in the heavy ion collisions using these two models. The AQM and the WNM give the different results.     

Enhancement of DD-Reaction yields from the Pd/PdO:Dx heterostructure by N+ and Ne+ ion beams using the GELIS setup

The results on DD-reaction yield enhancement from the Pd/PdO:D_x heterostructure by N⁺ and Ne⁺ ion beams in the energy range of 10–25 keV are presented. Neutron and proton fluxes were measured using a neutron detector based on He-3 counters and a CR-39 plastic track detector. Measurements showed significant DD-reaction yield enhancement effects. The screening potential for this heterostructure under these experimental conditions was determined as U _e = 897 eV.     

New aspects of the rotational model in25Mg

Spin assignments have been made to the²⁵Mg levels in theE _x=5–6 MeV region fromγ-ray angular distributions measured in the²²Ne(α, n y) reaction atE _α=8.0 and 8.8 MeV and fromp-γ angular correlations measured in the²⁴Mg(d, p γ) reaction atE _d=6 MeV. Unique spin assignments ofJ=7/2, 5/2, 5/2, and 9/2 could be made to the levels atE _x=5005, 5511, 5851, and 5967 keV, respectively. Ambigious assignments have been made to the levels atE _x=5245, 5524, 5785, 6032 keV (J=11/2, 7/2), 5455 keVJ=13/2, 9/2), and 5738 keV (J=3/2, 5/2). The present data confirm previous assignments ofJ=1/2 to the levels atE _x=5108 and 5466 keV, respectively. Lifetime estimates have been obtained, using the Doppler-shift attenuation method, for the levels atE _x=5245 keV (τ=30–60 fs), 5785 keV (τ=50–100 fs), 5967 keV (τ=50–100 fs), and 5455 keV (τ>1ps). All other levels in theE _x=5–6 MeV region haveτ<60 fs. A breakdown of theK-selection rule has been observed in theγ-decay of some high spin states, indicating a deviation from the strong coupling model.     

Enhancement of DD-reaction yields from the Ti/TiO2:Dx heterostructure by H+ and N+ ion beams using the GELIS setup

The results on DD-reaction yield enhancement from the Ti/TiO₂:D_x heterostructure by H⁺ and N⁺ ion beams in the energy range of 10–25 keV are presented. Neutron and proton fluxes weremeasured using a neutron detector based onHe-3 counters and a CR-39 plastic track detector. Measurements showed significant DD-reaction yield enhancement effects. The screening potential for this heterostructure under these experimental conditions was determined as U _e = 796 eV.     

The gamma decay of analogue states in61Cu

Resonances in the reaction⁶⁰Ni(p, γ)⁶¹Cu have been studied in the proton energy rangesE _p=1840–1880 keV and 2220–2300 keV. Decay schemes and branching ratios have been determined for a number of resonances, three of which are identified as analogue fragments of the 283 keV (1/2^?) and 656 keV (3/2^?) states in⁶¹Ni. The split analogue components of the 283 keV state atE _x≈6.6 MeV are seen to decay significantly to a group of states in the region of excitation 3–4 MeV. Gamma ray angular distributions yield the following resonance spins:E _p=2248 keV,J=3/2;E _p=2263 keV,J=5/2. Also, the⁶¹Cu ground stateβ ⁺ decay to parent levels in⁶¹Ni has been compared to the respective analogue stateM1 gamma decay to the⁶¹Cu ground state.     

Multiparameter study of 1H, 3H and 4He in fast neutron induced fission of 235U

The emission probabilities per fission of α-particles, tritons and protons have been measured in fast neutron induced fission of ²³⁵U. The measurements were carried out at neutron energies of 120, 180, 230 and 550 keV. AΔE-E semiconductor detector telescope was used to identify different light charged particles and the fission fragments were detected with an ionization chamber. The three-parameter data corresponding to the pulse heights from the ΔE-E detectors and the ion-chamber were recorded event by event on magnetic tape and were analyzed off-line by computer. No significant variation in the most probable energy ($\text{E}$) and the standard deviation (σ_E) of the energy spectra of different light charged particles with incident neutron energy was observed, although $\text{E}{}_{\mathrm{\alpha }}$ was seen to have a slightly higher value beyond E_n = 230 keV. The yield of α-particles in fission induced by neutrons of E_n ～ 200 keV was found to be higher by about 20 % than that in thermal neutron induced fission. The yields of tritons and protons were found to increase significantly with neutron energy.     

Study of the angular and energy distributions of Na+ and K+ ions which have passed through thin copper films

The angular and energy distributions of alkaline Na⁺ and K⁺ ions which have passed through thin Cu films in different crystal states are studied. The ion energy E₀ is varied from 10 to 40 keV, and the incidence angle. ranges from 0° to 60°. The angular aperture of the detector is ～0.5°, which allows the form of the angular distribution of ions which have passed through the solid thin films as a function of the energy, the angle of primary-ion beam incidence, and the layer thickness to be studied in detail. It is shown that, in the range E₀ = 10.40 keV, the energy loss ΔE of those ions that have passed increases linearly as the energy of incident ions increases. The energy loss increases with increasing ion mass in the case of singly charged ions. The surface amorphization of single- and polycrystalline films leads to an increase (by 150–200 eV) in the energy loss caused by the diffuse propagation of ions and to loss-peak broadening. It is probable that surface amorphization is accompanied by an increase in the number of atoms experiencing multiple collisions with atoms of the film, which leads to an increase in the average energy loss by ions that have passed through films.     

The level structure of104Rh deduced from the103Rh(n, γ)104Rh reaction

A sensitive, high resolution study of the¹⁰³Rh(n, γ)¹⁰⁴Rh reaction has revealed the presence of 516 transitions in the energy range 3,700 to 7,000 keV. These results have been used to interpret the reaction in terms of a statistical model in which a constant temperature level density is assumed. Previous work which revealed a much simpler level structure is quantitatively explained in terms of resolution and sensitivity. The average reduced radiative width is significantly lower than that reported for nuclides in theA=100 mass region and the width shows an indication of an energy dependence somewhat greater thanE _γ ³ . The neutron separation energy of the reaction is found to be 6,999.0±0.1 keV.     

Energies of Cu1+ ions sputtered from Cu by very low energy (50 eV < E < 1 keV) Inert gas ions

He⁺, Ne⁺ and Ar⁺ ions with energies E₁ between 50 and 1000 eV were used to bombard a polycrystalline Cu target at an angle of 45°. The energies, E₂, of the Cu₁⁺ ions sputtered at 90° to the primary beam were investigated using a UHV magnetic sector mass spectrometer. The maxima of the energy distributions as measured by the instrument, were at values of E₂ of about 4 eV (±1 eV), nearly independent of e₁ and primary ion mass. Plots of log N(E₂) versus log E₂ displayed limited linear portions over which the functional dependence of N(E₂) is proportional to E₂^?0.5. Plots of the average secondary ion energy, ē₂, versus the energy transferred by the primary ion to a Cu atom in a direct collision $\text{([}\text{4m}{}_1\text{m}{}_2\text{(m}{}_1\text{+ m}{}_2\text{)}{}^2\text{]E}{}_1\text{)}$, indicate that ē₂ increases linearly with transfer energy up to a transferred energy of about 200 eV, independent of primary ion mass. Above about 200 eV transferred energy, ē₂ asymptotically approaches values which depend upon primary ion mass. At transferred energies below about 200 eV, the collision kinematics in the fust few collisions appears to dominate the emission process.     

Low energy resonances in21Ne(p,γ)22Na examined with a high energy resolution ion beam

TheE _R=126, 272 and 291 keV resonances in the²¹Ne(p, γ)²²Na reaction have been investigated with a high-energy-resolution ion beam. TheE _R=272 keV resonance was found to consist of two states separated by (888+5) eV, where the lower (higher) energy member is a high-spin (low-spin) state. All four resonances have widths less than a few eV, which is an improvement of nearly two orders of magnitude below previously reported limits. The influence of atomic effects on the determination of the correct value for the resonance energy is examined.     

Stellar reaction rate of26Mg(p, γ)27Al

The reaction²⁶Mg(p, γ)²⁷Al has been investigated atE _p (lab)=80–355 keV. The existence of the resonances atE _p =292 and 338 keV has been verified and new resonances were found atE _p =227 and 275 keV. Information on branching and mixing ratios,ωγ values, total widths, andJ ^π assignments for the observed resonances is given. Upper limits on theωγ strengths for expected resonances in the energy range covered are presented. The astrophysical aspects of the data are discussed in the light of the²⁶Mg(²⁶Al) isotopic anomaly.     

Some detailed investigations of optically detected Ē(2 E) →4 A 2 cross relaxation in ruby

Cross relaxation betweenē(² E) and⁴ A ₂ states of Cr³⁺ in ruby at an applied external magnetic field ofH=5336 Oe was measured by monitoring the ¦? 1/2〉_ex→ ¦? 3/2〉_g optical transition in the temperature region of 1.6 to 4.2 °K. The chromium concentration varied from 2.9· 10^?4 to 4 · 10^?6 Cr³⁺/Al³⁺. With a concentration greater than 2 · 10^?5, the light intensity of the observed transition increases when cross relaxation takes place, while below this value it decreases. By measurement of the fluorescent intensity of one transition and simultaneously inducing EPR ground state transitions, we monitored the effect of trapping. Taking the value for trapping from fluorescence decay time measurements, we have used rate equations for calculating the actual change of excited state population when cross relaxation occurs. With this phenomenological model we are able to explain our experimental data. Finally some calculations for the effective spin temperature in theē(² E) state as a function of Cr³⁺ concentration as well as for various applied magnetic fields have been done.     

Nuclear resonance fluorescence in94Mo,95Mo and96Mo

Using gaseous sources of Tc₂O₇ containing the radioactive isotopes⁹⁴Tc,⁹⁵Tc and⁹⁶Tc, levels at 871.0keV (⁹⁴Mo), 765.8, 820.6, 947.8, 1074.0keV (⁹⁵Mo) and 778.3keV (⁹⁶Mo) have been excited. From the effective cross sections for nuclear resonance scattering and from the lifetimes of the 947.8, 1074.0 and 778.3keV levels known from Coulomb excitation experiments the profiles of theγ-lines have been determined. A broadening of theγ-lines due to Coulomb explosion of the molecules has been observed. Making use of the line profiles, lifetimes ofΤ=(6.4±1.0) ps andΤ=(0.90 ± 0.20) ps have been determined for the 765.8 and 820.6keV levels, respectively. The angular distribution of the resonantly scattered radiation yields an amplitude ratioδ for the mixed M1 E2 765.8keV transition ofδ=0.14 _?0.009 ^+0.08 . TheB(E2) from a Coulomb excitation experiment and the lifetimeΤ from the present experiment yield ¦δ¦=0.07±0.01 for the 820.6keV transition.