Chain effect for fast recoils

A strong effect of the regular arrangement of the target atoms on the fast recoil flux formation was found.     

Nuclear dealignment in multiply ionized fast fluorine atoms recoiling in gases

The dealignment of the 5/2 ₁ ⁺ excited nuclear state of¹⁹F (E _x=197keV) has been determined for foil-excited fluorine ions of energies 3 and 6 MeV recoiling in He, N₂ and Ar gases using backscatter-coincidence excitation with He⁺⁺ and the recoil-distance technique. The observed decay of nuclear alignment with increasing gas pressure was interpreted in a microscopic collision model using theories of statistically perturbed angular correlations. The strong velocity dependence of the dealignment cross section indicates the dominance of charge exchange, e.g. capture, processes in producing the ionic states of strong hyperfine interaction.Work supported in part by Bundesministerium für Forschung und Technologie.     

Stimulated Brillouin effect in weakly ionized plasma

The stimulated Brillouin effect in gaseous plasma is investigated by means of classical coupledmode analysis. This process is described as interaction between an ion-acoustic plasma wave and two light waves. The threshold power levels calculated are achievable in giant-pulse lasers. However, the Brillouin effect may possibly be observable in the dense plasma or in the far infrared region of the electromagnetic spectrum.     

Energy deposition of fast α particles in a fully ionized deuterium-tritium plasma

An α particle transport equation has been solved analytically in one-dimensional spherical geometry when the plasma properties are uniform in space and time. The results agree well with earlier results.     

Dependence of nuclear deorientation on nuclear spin for recoils in vacuum

Time-integral measurements have been made of the vacuum deorientation of the 2⁺ and 4⁺ states in ¹⁵⁰Sm and the 6⁺ and 8⁺ states in ¹⁵⁶Gd Coulomb-excited by 133 MeV ³⁵Cl ions. The ¹⁵⁰Sm results were deduced from γ-ray angular distributions measured in coincidence with backscattered ³⁵Cl ions. In the ¹⁵⁶Gd measurements, a fixed counter array and a sandwich target were used to measure directly the differences between the γ-ray angular distributions from nuclei recoiling in vacuum and the unperturbed γ-ray angular distributions from nuclei stopped in a thick ¹⁵⁶Gd target. The measured deorientation time constants in ps are τ₂(2⁺) = 27±4; τ₂(4⁺) = 14±4; τ₂(6⁺) = 24±3; τ₂(8⁺) = 23⁺¹⁰_?6; τ₄(2⁺) = 12±2; τ₄(4⁺) = 5±3; τ₄(6⁺) = 7.6±2.5. The 8⁺ data were analyzed assuming τ₂/τ₄ = $\text{10}\text{3}$ as predicted by the Abragam-Pound theory for $\text{I ≧ 4}$ essentially independently of the degree of quadrupole admixture. The other results are consistent with this except for the 2⁺ level which shows some quadrupole effect. The present results, which show strong deorientation of high spin levels, are in contrast to earlier work on neutron deficient Er isotopes. In light of our findings we suggest that the failure to observe deorientation in the high spin states in Er is primarily due to anomalously low g-factors associated with the backbending observed in these nuclei.     

Calculated yield of isomer depletion due to NEEC for 93m Mo recoils

In the present work, quantitative calculations were carried out for production and depletion of the ^93m Mo isomer in a relatively simple experiment using ⁹¹Zr beam ions. Such studies could be arranged at existing and operating accelerator facilities, e.g. at GSI or in JINR. The ^93m Mo nuclei produced in a He gas target due to the ⁴He(⁹¹Zr, 2n) reaction will recoil into a gas stopper with a high velocity, being then depleted due to NEEC in highly-ionized species.     

Guiding of intense laser beams in highly ionized plasma columns generated by a fast capillary discharge

We have demonstrated the guiding of laser pulses with peak intensities up to 2.2 x 10(17) W/cm(2) in a 5.5 cm long plasma column containing highly charged Ar ions generated by a fast capillary discharge. A rapid discharge-driven hydrodynamic compression guides progressively lower order modes through a plasma with increasing density and degree of ionization, until the guide collapses on axis. The lowest order mode (FWHM approximately 50 microm) is guided with 75% transmission efficiency shortly before the plasma reaches the conditions for lasing in Ne-like Ar. The subsequent rapid plasma expansion forms a significantly leakier and more absorbent guide.     

Oscillator strengths for singly ionized oxygen

The electric dipole oscillator strengths for multiplet and individual lines between some doublet and quartet levels have been calculated using the weakest bound electron potential model theory (WBEPMT) in singly ionized oxygen. We employed both numerical Coulomb approximation (NCA) wave functions and numerical non-relativistic Hartree-Fock (NRHF) wave functions for expectation values of radii in determination of parameters. The calculated oscillator strengths have been compared with available theoretical and experimental results. A good agreement with results in literature has been obtained. Moreover, oscillator strengths not existing in the literature for some highly excited levels have been obtained using this method. Electronic supplementary material  Supplementary Online Material     

Perturbed alpha-gamma angular correlation studies of radon recoils into aluminium

The quadrupole interaction of ²²²Rn and ²²⁰Rn implanted by α-particle-decay in Al metal and Al-oxide has been investigated. The experimental results indicate an electrical interaction in cubic Al metal not in agreement with earlier measurements using isotope implanted sources.     

Excited level lifetime measurements following very low energy nuclear recoils

Using high resolution gamma spectroscopy it is possible to observe Doppler broadening of gamma transitions from excited states which have themselves been populated after emission of gamma photons or other low energy nuclear radiation. This allows the determination of the lifetimes of these intermediate states, providing the time dependence of the recoil velocities is known. Conversely, if the lifetime is well known, this technique may be used to study the recoil process itself (and hence the atomic interaction) at energies of only a few times the lattice binding energy.     

Chapman-Enskog method for a relativistic ionized gas

A linearized transport equation is derived for a multicomponent ionized gas. The magnetic field is treated as a zeroth-order, the electric field as a first-order effect.     

Measurements of scintillation efficiency and pulse shape for low energy recoils in liquid xenon

Results of observations of low energy nuclear and electron recoil events in liquid xenon scintillator detectors are given. The relative scintillation efficiency for nuclear recoils is 0.22±0.01 in the recoil energy range 40–70 keV. Under the assumption of a single dominant decay component to the scintillation pulse shape the log-normal mean parameter T₀ of the maximum likelihood estimator of the decay time constant for 6 keV <E_ee<30 keV nuclear recoil events is equal to 21.0±0.5 ns. It is observed that for electron recoils T₀ rises slowly with energy, having a value ∼30 ns at E_ee∼15 keV. Electron and nuclear recoil pulse shapes are found to be well fitted by single exponential functions although some evidence is found for a double exponential form for the nuclear recoil pulse shape.     

Kerr effect caused by an electric current in a weakly ionized gas

The anisotropy of the velocity distribution caused by an electric current in a fluid leads to a molecular alignment via the non-spherical interaction. This alignment implies a birefringence proportional to the square of the applied electric field just as the ordinary Kerr effect. The kinetic theory of this phenomenon is presented for a lorentzian mixture, viz. a gas of few light charged linear molecules and of many heavy optically isotropic particles. The current-induced contribution to the Kerr effect turns out to be much larger than the contribution which stems from the usually considered orienting influence of the electric field on anisotropic molecules.     

Multicomponent transport algorithms for partially ionized mixtures

We investigate iterative methods for solving linear systems arising from the kinetic theory of gases and providing multicomponent transport coefficients of partially ionized plasmas. We consider the situations of weak and strong magnetic fields as well as electron temperature nonequilibrium and the linear systems are investigated in their natural constrained singular symmetric form. Stationary iterative techniques are considered with new more singular formulations of the transport linear systems as well as orthogonal residuals algorithms. The new formulations are derived by considering generalized inverses with nullspaces of increasing dimension. Numerical tests are performed with high temperature air and iterative techniques lead to fast and accurate evaluation of the transport coefficients for all ionization levels and magnetic field intensities.     

Towards measurement of recoils below 4 keV with the ROSEBUD experiment

An experiment to look for light WIMPs with sapphire bolometers is to be installed in the Canfranc Underground Laboratory (at 2450 m.w.e) in the Spanish Pyrenees. In the first stage two small 25g bolometers with NTD-Ge sensors, operating at 25mK, with an energy threshold of 300eV and FWHM energy resolution of 120eV at 1.5keV will perform a background test experiment. The features of the bolometers, the radioactivity measurements of the components and the set-up and status of the experiment are reported.