Low-energy Part Of Spectrum Research Articles

Novel wide spectrum light absorber heterostructures based on hBN/In(Ga)Te

Two-dimensional group III monochalcogenides have recently attracted quite attention for their wide spectrum of optical and electric properties, being promising candidates for optoelectronic and novel electrical applications. However, in their pristine form they are extremely sensitive and vulnerable to oxygen in air and need good mechanical protection and passivization. In this work we modeled and studied two newly designed van der Waals (vdW) heterostructures based on layer of hexagonal boron nitride (hBN) and GaTe or InTe monolayer. Using density functional theory, we investigate electronic and optical properties of those structures. Their moderate band gap and excellent absorption coefficient makes them ideal candidate for broad spectrum absorbers, covering all from part of IR to far UV spectrum, with particularly good absorption of UV light. The hBN layer, which can be beneficial for protection of sensitive GaTe and InTe, does not only preserve their optical properties but also enhances it by changing the band gap width and enhancing absorption in low-energy part of spectrum. Calculated binding energies prove that all three stacking types are possible to obtain experimentally, with H-top as the preferable stacking position. Moreover, it is shown that type of stacking does not affect any relevant properties and bandstructure does not reveal any significant change for each stacking type.

Requirements for fast particle measurements on ITER and candidate measurement techniques

Recent JET and JT-60U results, have underlined the need to look into the measurement requirements of fast particles diagnostics in ITER. Not only alpha particles but all fast ions (He4,p,D,T,He3) present in the plasma should be diagnosed. Furthermore, the electron diagnostics, monitoring the deviations from a Maxwellian distribution function, play a central role in the electron cyclotron heating and current drive. In the present ITER measurement requirements only alpha particles and He ions are mentioned: space resolution is δr = a/10 (a is the minor radius), time resolution is δτ = 100 ms and accuracy 10–30%. The new proposed measurement requirements for fast particles are spatial resolution ∼a/20 (10 cm on ITER), time resolution (minimum) ∼100 τA (∼100 µs for ITER), density of fast ions: the minority ions could be 4–10% of the plasma density. The candidate diagnostic techniques considered for ITER are amongst others γ-ray spectroscopy, fast ion collective Thomson scattering (CTS) and charge exchange recombination spectroscopy (CXRS). γ-ray spectroscopy detects ions in the energy range 1 < E < 5 MeV and R&D is needed to demonstrate the feasibility of these measurements in the presence of a neutron background. Techniques using ultraviolet spectroscopy of ions such as Krypton are being tested, for the low energy part of spectrum of fast particles. A design study of CTS shows that the requirements are closely met; the system includes a high power gyrotron operating in a region not yet tested in current applications (i.e. using a gyrotron at a frequency below the first ECE harmonic). For CXRS the spatial resolution and accuracy are not achievable for r/a < 0.3 and R&D is needed to assess the minimum figures in terms of accuracy possible for measurements close to the centre. The measurement requirements deduced from the need for detecting the effects of interaction of fast particles with MHD instabilities put forward important new objectives to the candidate diagnostic systems. In particular diagnostics for fast particles in the energy region 200 < E < 1300 keV and diagnostics for escaping fast particles need urgent development.

Analysis of intermediate energy proton-induced spallation reactions by an improved quantum molecular dynamics plus statistical decay model

Intermediate energy proton-induced spallation reactions with various targets are studied by the improved quantum molecular dynamics (ImQMD05) model incorporated with the statistical decay model. The influences of the different Skyrme interactions on the mechanism of spallation reaction and the double differential cross sections of emitted neutrons are studied. It is found that the different Skyrme interactions influence the low energy part of spectrum of emitted neutrons. This effect decreases as incident energy becomes higher. The double differential cross sections of emitted neutrons are found to be in good agreement with experimental data when the Skyrme parameter set SkP is adopted.

Revealing low-energy part of the beta spectra

An effective method is proposed to separate electronic noise from the beta-particle spectra revealing lower energy part of the spectra. The available methods for reducing the noise problem cut the noise along with the low-energy part of the beta spectra by using a discriminator. Our setup eliminates this undesirable effect by shifting the noise toward the lowest energy scale leaving the low-energy part of spectra undisturbed. We achieved this noise-pulse-separation by treating the noise as a pulse so that we can exploit the application of the pulse-shape analyzer equipment used for pulse shape identification of particles and rejection of defective pulses. To the best of our knowledge this method of the noise separation is a novel approach.

Raman scattering in ferromagnetic TDAE-C 60 compared to TDAE-C 70

The Raman scattering at 1.16 eV laser excitation has been studied in ferromagnetic TDAE-C 60 and compared to that in paramagnetic TDAE-C 70. The shift of H g and A g modes in TDAE-C 60 indicates transfer of one electron to C 60 while the broadening of H g modes is quite similar to metallic K 3C 60 meaning significant electron-phonon coupling of this Jahn - Teller vibrations. In TDAE-C 70 the lines are narrow sugesting suppresed electron - phonon interaction and hence smaller polaronic effects. Below T c of magnetic ordering the two-magnon excitations are not seen clearly however the low energy part of spectra shows somewhat increased intensity. Upon air-exposure of TDAE-C 60 all H g and A g Raman modes disappear while a new band appears at 1848 cm −1.

The low energy part of spectra delayed neutrons from precursors of87Br

Abstract The low energy part of spectra delayed neutrons and the group's energies from precursor's of 87Br of the thermal fission 235U are presented.

A pitfall in the use of polyethylene vials in liquid scintillation counting

It has been shown that there is a migration of toluene through the walls of polyethylene vials, which are frequently used in liquid scintillation counting (1,2). It seems reasonable to assume that scintillators migrate in a similar way. Mueller (3) reported a continuous drift of the external standard channel ratio when using polyethylene vials. It is proposed in the present study that this drift is due to the migration of the scintillators into the walls of the vials. All the chemicals used were of reagent or scintillation grade. Samples were counted in a Nuclear-Chicago Mark II or a Packard 3375 liquid scintillation counter at 4°C. The pulse-height spectra of the external standards (133Ba and 226Ra + 241Am, respectively) were obtained at the recommended gains for 3H and l*C by stepwise manual movement of a narrow channel, which was 5% of the maximum energy range used. W ith glass vials there were no changes in the spectra obtained from the external st.andards during a 5 day period. W ith polyethylene vials, however, there was an increase of the count rate in the low-energy part of the spectrum when using the recommended 14C gain (Fig. 1). When the 3H gain was used, the additional counts appeared in the low-energy half of the spectrum. After the vials were emptied and washed once with toluene, they still yielded counts in the low-energy part of the spectrum. “Old” scintillator solution transferred into “new” vials showed a normal spectrum. “New” scintillator solution in “old” vials showed an increased count rate in the low-energy part of the spectrum. The count rate in the low-energy part of the spectrum (‘“C gain) gradually increased after the scintillator solution was added to the vial (Fig. 2). The count rate in the integral channel increased by about 1% during a 5 hr period. This increase was fairly similar to that found in the low-energy part of spectrum. Similar results were obtained in both liquid scintillation counters used and with the two scintillator solutions used and also with polyethylene vials of different quality.

Über den Einfluß der Oberflächen dünner Schichten auf die Energieverluste schneller Elektronen in Al

The characteristic energy losses of electrons traversing thin Al-films were measured with high resolution. Especially their dependence on film thickness was investigated. To interpret satisfactory the observed dispersion of surface plasma loss retardation effects had to be taken into account. Furthermore, energy losses in the low energy part of spectrum, e.g. the intraband energy loss of Al, are shown to be surface losses in terms of the dielectric theory.