Doublet of cosmic-ray events with primary energies >1020 eV

The Telescope Array Collaboration has observed a cosmic-ray event with estimated primary energy of 1.38 × 10²⁰ eV whose arrival direction coincides [T. Abu-Zayyad et al. (Telescope Array Collaboration), arXiv:1205.5984], given the angular resolution of 1.5°, with that of an event with estimated primary energy of 1.23 × 10²⁰ eV observed by the Pierre Auger Observatory. The total number of events with energies >10²⁰ eV published by both experiments is six. I estimate the statistical significance of the doublet, which is rather weak, and point out that the arrival directions of events in the doublet coincide with the Galactic X-ray source Aql X-1.     

The GZK horizon and constraints on the cosmic ray source spectrum from observations in the GZK regime

We discuss the GZK horizon of protons and present a method to constrain the injection spectrum of ultrahigh energy cosmic rays (UHECRs) from supposedly identified extragalactic sources. This method can be applied even when only one or two events per source are observed and is based on the analysis of the probability for a given source to populate different energy bins, depending on the actual cosmic ray injection spectral index. In particular, we show that for a typical source density of 4 × 10⁻⁵ Mpc⁻³, a data set of 100 events above 6 × 10¹⁹ eV allows one in 97% of all cases to distinguish a source spectrum dN/dE ∝ E ^−1.1 from one with E ^–2.7 at 95% confidence level. The article is published in the original.     

The radio structure of BL Lac object S5 2007+777

BL Lac object S5 2007+777 has been classified as a HYMOR (Hybrid Morphology radio source) for its hybrid FR I and FR II radio morphology. It is one of four BL Lac objects with a kpc scale extended X-ray jet. In this paper, we searched the unpublished European VLBI Network (EVN) archived high resolution data for this source, and present the high resolution radio structure. The EVN images all show a core-jet structure in 1.6, 5 and 8 GHz. In combination with the VLA data in the literature, we found position angle differences (ΔPA) of about 10°–20° between pc and kpc scale jet structures. The brightness temperature estimated from multi-band EVN images are around 10^11.2–10^11.8 K, from which the Doppler factor ranges from 3.2 to 12.0. We found significant flux variations of the radio core in 1.6 and 5 GHz, from which we derived the variability in brightness temperature T _var to be 10^13.6 K and 10^14.0 K, corresponding to the Doppler factors of 9.3 and 12.4, respectively.

     

Operation of the CSNS Penning surface H− ion source

The accelerator complex of the China Spallation Neutron Source (CSNS) consists of a H⁻ linear accelerator (linac) and a rapid cycling synchrotron (RCS). The linac contains a Penning surface H⁻ ion source. The designed energy and the beam current of the source are 50 keV and 20 mA respectively, with a normalized root mean square (norm. rms.) emittance of 0.2π mm mrad. The manufactures and tests of the discharge chamber are in great progress. The construction of H⁻ ion source test stand has been completed, and the operation of the source is also in progress. Stable H⁻ ion beams with energy of 50 keV and current up to 50 mA are attained. Emittance measurement for the H⁻ beam is being prepared.

     

A study of radiation damage by elastic scattering experiments

Abstract

Chaneling measurements are used to study the structure and configuration of defects produced in CdS under irradiation by 50–150 KeV Na⁺ ions at room temperature with a current density of 1 μA/cm² and irradiation dose 3.10¹⁵ ion/cm².

The results of studies of 1.8 MeV He⁺ ion dechaneling along the <1120> and <0001> axes are probably indicative of the defect structure extended along the <0001> axis.

For the dependence of the dechaneling cross-section on the ⁴He energy in the energy range 1.2 to 2.4 MeV we found E^?1, which characterizes the produced defects as randomly distributed complexes of interstitial atoms straining the crystal lattice.

The fact that the defects are mostly located along the <0001> direction can possibly be explained by strong anisotropy of CdS therefore the defects form the region of elastic stresses in the crystal which are maximum along the <0001> axis.     

The effect of external electric field on mass attenuation coefficients of some semiconductor

In this study, we measured the mass attenuation coefficient of n-type GaAs, p-type GaAs, n-type Si and Au/n-Si/n⁺Si/Al samples with and without external electric field. Samples were set in perpendicular direction to the 100?mCi ²⁴¹Am radioactive source and counts were made with a NaI(Tl) detector. It was observed that when an external electric field was applied onto the samples, mass attenuation coefficients were increased. Results showed that this study is consistent with previous studies.     

Zusammenhänge Zwischen Radonanomalien und Schwarm-Erdbeben im Oberen Vogtland

Abstract

The results of continuous radon measurements in soil air and the water of a mineral spring at Bad Brambach are presented. They are discussed in connection with meteorological, hydrological parameters, and seismic events with magnitudes <3. The atmospheric pressure (especially pressure gradient), the temperature, and the groundwater level gradient have a significant influence onto radon activity of soil air.

The gamma-activity in spring water is influenced by the water flow rate only.

The results show that the soil air (mean Rn activity 130 Bq · l^?1) and especially the water of the Radonquelle of Bad Brambach (mean Rn activity 25 kBq · l^?1) react upon micro earthquakes with small epicentral distances. Frequently there are precursor effects, that means radon maxima due to the building up of tectonic stress/strain.

About 60% of the seismic events had been attended by radon anomalies during the registration period.

The long term measurements will be continued to investigate possible influences of earthquakes with higher epicentral distances and magnitudes >5 onto the radon regime of the bad Brambach area.     

Neutrino-Oscillation Searches in the Short-Baseline Gallium Experiment BEST-2 with a 65Zn Source

The possibility of employing a ⁶⁵Zn source in the gallium experiment BEST-2 with the aim of constraining the region of allowed oscillation parameters is examined. The source activity required for the BEST-2 experiment is calculated, and the size of the source and its effect on the results of oscillation measurements are discussed along with the possibilities for producing such a source. Various schemes for implementing respective measurements are considered.

     

Diagnostics of interplanetary and flaring plasmas in impulsive solar energetic particle events

Using instruments onboard the ACE and Wind spacecrafts, we study temporal evolution, spectra, and ionization states of Fe in the impulsive solar energetic particle (SEP) events of September 6, 1998 and May 1, 2000. Proton and electron intensities and anisotropies were used to constrain the particle mean free path in interplanetary space. The derived values were used to explain the observed energy and charge spectra of heavy ions. It is concluded that the sharp increase in the average charge of Fe ions in the range from 200 to 600 keV per nucleon observed in both events cannot be explained within the framework of the model of single-temperature source even if the effects of interplanetary propagation are taken into account. At least two acceleration regions with temperatures ～10⁶ and 10⁷ K should exist in the source.     

Multiparameter study of the long-range α-particles emitted in the thermal neutron induced fission of 235U

The correlations between the various parameters in the thermal neutron induced fission of ²³⁵U accompanied by long-range α-particles (LRA) have been measured employing a back-to-back gridded ionization chamber. Semiconductor detectors were placed symmetrically along the electric field direction of the chamber behind the thin windows of the collector plates for the measurement of the LRA energies. A distinguishing feature of the present method is that the angle between the fission fragments and the electric field direction (hence the direction of α-particle emission) is also determined electronically by the analysis of the coincident collector and grid pulses of the ionization chamber. About 5 × 10⁵ LRA-accompanied fission events and about 2 × 10⁶ binary fission events were recorded and analyzed to obtain a number of correlations of interest between the fragment mass, total kinetic energy, LRA energy and fragment-LRA angle. These experimental results are presented and discussed with regard to the emission mechanism of the LRA.     

Ion implantation in III–V compounds

In this work we studied the effect of electron and proton irradiation on the depth distribution of sodium in commercial soda-lime glasses. Samples have been irradiated at different energies and fluences.

The ²³Na (ρ, α) ²⁰Ne nuclear reaction has been used to determine the sodium profiles. No detectable changes in the sodium concentration profiles have been introduced during the measurements, the proton fluences and doses needed in this type of analysis being very low.

The obtained results support the hypothesis that the driving force for Na diffusion is mainly connected to the build-up of an electric field whose direction is determined by the projectile charge, while Na mobility changes because of the local temperature increase due to the beam power dissipation.     

Ferrihydrite modification by boron doping

Application of the electrostatic ion storage ring ELISA to studies of clusters and biomolecules is discussed. Ions injected from a plasma source or a sputter source are hot, and at short times the yield of neutrals is usually dominated by decay of metastable ions. We have demonstrated that the decay function is close to a 1/t dependence when the internal energy of the ions is conserved, i.e., when photon emission can be ignored. Deviations from a 1/t distribution therefore gives information about the radiative lifetime or, for larger systems, about the intensity of the emitted radiation. Systematic measurements have been carried out for fullerene anions C _N ^?, for even values of N from 36 to 96, to test a classical dielectric model. Recently we have installed an electrospray ion source with a Paul trap for bunching, which can be used to inject biomolecular ions from solution, and the first experiments on laser spectroscopy of biomolecules have been carried out. Also lifetimes of excited states have been measured for stored biomolecular ions excited by a laser pulse.

     

Two- and three-point energy correlations in Hadronice + e − annihilation

Correlations between the energies incident on two or three detectors arounde ⁺ e ^? annihilation events are considered as a probe of the QCD structure of the events. Practical methods for deducing two-detector energy correlations (which give the mean product of energies incident on two detectors as a function of their angular separation) from measured events are devised. Analytical formulae for energy correlations from QCD perturbation theory are given, but it is found that large corrections from hadron formation obscure these symptotic predictions at available energies. Correlations between the final state and the incominge ^± beam direction are discussed, and observables are presented which measure the angular distributions of planes of final particles with respect to the beam axis (but do not require explicit determination of the planes). Finally, three-detector energy correlatons and their moments are treated, and methods for investigating planar structures ine ⁺ e ^? annihilation events are devised.     

Poisson Cohomology of SU (2)-Covariant “Necklace” Poisson Structures on S 2

Abstract

We compute the Poisson cohomology of the one-parameter family of SU(2)-covariant Poisson structures on the homogeneous space S ²=?P ¹=SU(2)/U(1), where SU(2) is endowed with its standard Poisson–Lie group structure, thus extending the result of Ginzburg [2] on the Bruhat–Poisson structure which is a member of this family. In particular, we compute several invariants of these structures, such as the modular class and the Liouville class. As a corollary of our computation, we deduce that these structures are nontrivial deformations of each other in the direction of the standard rotation-invariant symplectic structure on S ²; another corollary is that these structures do not admit smooth rescaling.     

The influence of incidence angle on disorder production in Cl and Ar ion implanted Si

Abstract

Cl and Ar ions have been implanted, at 30 keV and at various incidence angles, into Si substrates maintained at room temperature during implantation. Implantation induced Si disorder was measured using RBS channelling. The effects upon disorder of various incidence angles were studied over a fluence range of 10¹²-6·10¹⁵ ions·cm^?2

The results show that, at low fluences Cl and Ar ion implantations generate a bimodal disorder-depth profile, whilst at higher fluences measurements of amorphised layer thickness as a function of ion incidence angle allow values of the standard deviation of the disorder profile parallel and transverse to the ion beam direction for each ion to be obtained with good agreement to theoretical predictions. The disorder-fluence behaviour under these conditions is ion species independent.     

Mössbauer studies of after-effects of auger ionization following electron capture in cobalt complexe

Abstract

The electron-capture decay of a cobalt-57 atom triggers an Auger event resulting in the loss of several electrons from the molecule in which it is incorporated. The 14.4 keV Mössbauer emission conveys information regarding the chemical forms in which the daughter iron-57 is ‘stabilized’ within 10^?7 sec following electron capture. During this time the electronic relaxation occurs completely and several tens of electron volt energy is deposited in the molecule as a result of neutralization. We find that the ethylenediamine tetra-acetate, bis-salicylaldehyde tri-ethylenetetramine, acetylacetone, and indenyl chelates fragment in a large majority of events, resulting in the formation of degraded ionic Fe²⁺ and Fe³⁺ in the former cases and C₉H₇Fe⁺ in the latter. On the other hand, highly conjugated compounds such as cobalt phthalocyanine and Vitamin B₁₂ escape fragmentation in 100 per cent of the Auger events. Tris-dipyridyl Co(III) perchlorate also escapes fragmentation in a majority of events. Apparently, the large amount of excitation energy deposited in the molecule as a consequence of charge neutralization is very rapidly (in less than 10^?13sec) and efficiently dispersed through neighboring molecules. It is a novel phenomenon.

When the dipyridyl chelate molecules are dispersed in a foreign matrix, the dissipation of charge and energy is no longer rapid and efficient and the probability of fragmentation is considerably enhanced.

We also find that part of the coordinated parent species, in the case of labeled dipyridyl chelate, arises through fragmentation followed by interaction of the electronically excited degraded iron species with a neighboring chelate molecule resulting in replacement of cobalt with an iron atom. This finding was made possible by using the chelate doped with ‘carrier-free’ ⁵⁷Co citrate.

Emission spectroscopy yields values for the isomer shifts and quadrupole splittings which differ somewhat from those obtained by absorption spectroscopy. The apparent disparities are attributed to the dissimilarities of the matrices in which the Mössbauer emitter or absorber is situated.     

Measurements of hall-effect and sheet resistivity as a function of temperature on hot,phosphorous implants in silicon

Abstract

Results of Hall-effect measurements as a function of temperature on a layer formed by hot, phosphorous (P³¹) implant in Si at 400 keV energy in a random direction are presented; the dose used was 10¹⁵ ions cm^?2. The electrical behaviour of the layer as a function of isochronal annealing was examined.

A detailed analysis of the measured quantities n _8eff, the effective surface density of free carriers, and μ_eff, the effective mobility, down to 4.2°K is presented using the integral equations:

$graphics$

These formulae were solved numerically, the input data viz: the distribution of donor centres and compensating damage centres being assumed from the current literature.

Results from this analysis indicate a rather complicated distribution of current flow in the layer as a function of temperature, indicating that the traditional interpretation of Hall measurements based on a homogeneous distribution model is of questionable validity.     

Monocrystalline on seed diamond growth into HP/HT lpe autoautoclaves

Abstract

In the paper Authors analyse the possible ways of phase nucleation and the mechanisms of crystal growth, which suggest that, if we use as sp³ orbitals organized carbon source, diamond nucleation and growth by the way of spiondal decomposition and volumetic coalescence may take place. Such a process may be analysed as semihydrothermal-metalotheric coalescence may take place. Such a process may be analysed as semihydrothermal-metalothermal high pressure liquid phase epitaxy (MHPLPE) in separated autoautoclaves.     

Electron scattering on disordered double-barrier GaAs–AlxGa1−xAs heterostructures

We present a novel model to calculate vertical transport properties such as conductance and current in unintentionally disordered double-barrier GaAs–Al_xGa_1−xAs heterostructures. The source of disorder comes from interface roughness at the heterojunctions (lateral disorder) as well as spatial inhomogeneities of the Al mole fraction in the barriers (compositional disorder). Both lateral and compositional disorder break translational symmetry along the lateral direction and therefore electrons can be scattered off the growth direction. The model correctly describes channel mixing due to these elastic scattering events. In particular, for realistic degree of disorder, we have found that the effects of compositional disorder on transport properties are negligible as compared to the effects due to lateral disorder.