Electron-Hole Pair-Creation Energy in Si02

The temperature dependence of the energy loss of 624-keV electrons in ferroelectric barium titanate (${\mathrm{BaTiO}}_{3}$) and triglycine sulfate [(${\mathrm{CH}}_{2}$${\mathrm{NH}}_{2}$COOH${)}_{3}$ ${\mathrm{H}}_{2}$${\mathrm{SO}}_{4}$] has been studied with the use of a single-gap magnetic spectrometer. The present measurements confirm the anomalous increase in energy loss of electrons near the Curie temperature ${T}_{C}$ and indicate its dependence on (a) the magnitude of the dielectric anomaly at ${T}_{C}$, (b) the effect of a dc electric field larger than the coercive field, and (c) the application of an alternating electric field. Probable mechanisms for the origin of the observed phenomenon are discussed.

Gamma-ray interaction in Ge: A Monte Carlo simulation

Starting with the equation of motion for the density matrix operator of an electron gas in second quantization, a system of matrix equations is derived for matrix elements connecting states with various numbers of electron-hole pairs. Allowing up to $n$ electron-hole pairs and neglecting all states with more than $n$ pairs yields a set of ${(n+1)}^{2}$ coupled equations for the various amplitudes in close analogy to the $n\mathrm{th}$ order Tamm-Dancoff approximation. The starting point of this approximation, in which all matrix elements connecting the Fermi vacuum with any pair states are neglected (zero-order Tamm-Dancoff approximation), is an equation for the self-consistent field rather than for free particles as in the usual Tamm-Dancoff method. Correlation effects are therefore automatically taken into account when pair states are included. In a certain sense the approximation scheme given here can be thought of as being an expansion in the deviation of the Fermi surface from the sharp edge of the free-particle ground state, the deviation being caused by the Coulomb interaction among the particles. In this paper, we present calculations based on the first Tamm-Dancoff approximation (taking into account only one electron-hole pair). An expression for the dielectric constant will be derived and applied to a determination of the effects of correlations on the wavelength dependence of plasma oscillations. The theory will be compared with the experiments by Watanabe on the energy loss of fast electrons in metal foils and it will be seen that the agreement with experiment is good considering the inherent simplicity of the theory.

Reflectance data are presented for Si, Ge, GaP, GaAs, InAs, and InSb in the range of photon energies between 1.5 and 25 eV. The real and imaginary parts of the dielectric constant and the function describing the energy loss of fast electrons traversing the materials are deduced from the Kramers-Kronig relations. The results can be described in terms of interband transitions and plasma oscillations. A theory based on the frequency-dependent dielectric constant in the random phase approximation is presented and used to analyze these data above 12 eV, where the oscillator strengths coupling the valence and conduction bands are practically exhausted. The theory predicts and the experiments confirm essentially free electron-like behavior before the onset of $d$-band excitations and a plasma frequency modified from that of free electrons due to oscillator strength coupling between valence and $d$ bands and $d$-band screening effects. These complications are absent in Si. The energy loss functions obtained from optical and characteristic energy loss experiments are also found to be in good agreement. Arguments for interpreting structure in the reflectance curves above 16 eV in terms of $d$-band excitations are given.

During the interaction of a short-pulse high-intensity laser with the preplasma produced by the pulse's pedestal in front of a high-Z metal solid target, high-energy electrons are produced, which in turn create an X-ray source by interacting with the atoms of the converter target. The current brought by the hot electrons is almost completely neutralized by a return current j→ driven by the background electrons of the conductive target, and the force exerted on the hot electrons by the electric field E→ which induces Ohmic heating j→.E→, produced by the background electrons, reduces the energy of the hot electrons and thus lowers the X-ray emission and photon dose. This effect is analyzed here by means of a simple 1-D temperature model which contains the most significant terms of the relativistic Fokker-Planck equation with electron multiple scattering, and the energy equations of ions, hot, and cold electrons are then solved numerically. This Ohmic heating energy loss fraction τOh is introduced as a corrective term in an improved photon dose model. For instance, for a ps laser pulse with 10 μm spot size, the dose obtained with a tantalum target is reduced by less than about 10% to 40% by the Ohmic heating, depending upon the plasma scale length, target thickness, laser parameters, and in particular its spot size. The laser and plasma parameters may be optimized to limit the effect of Ohmic heating, for instance at a small plasma scale length or small laser spot size. Conversely, others regimes not suitable for dose production are identified. For instance, the resistive heating is enhanced in a foam target or at a long plasma scale length and high laser spot size and intensity, as the mean emission angle θ0 of the incident hot electron bunch given by the ponderomotive force is small; thus, the dose produced by a laser interacting in a gas jet may be inhibited under these circumstances. The resistive heating may also be maximized in order to reduce the X-ray emission to lower the radiation level for instance in a safety radiological goal.

A numerical model is developed to describe the electron–hole pair (EHP) creation energy in amorphous selenium (a-Se) for high energy photon excitation by solving the three dimensional coupled continuity equations of electrons and holes considering carrier drift, diffusion and bimolecular recombination between non-geminate electrons and holes. The numerical model is fitted with the published experimental results on widely varying X-ray energy, electric field and temperature. The model shows a good agreement. The results of this paper indicate that the columnar recombination model is capable of describing the electric field, temperature, and photon energy dependent EHP creation energy in a-Se for high energy photons.

Monte Carlo method for simulating γ-ray interaction with materials: A case study on Si

The integro-differential equation describing the energy distribution of very fast electrons (with negligible collision loss of energy) is reduced to a Volterra integral equation of the second kind. A rigorous solution, for an arbitrarily prescribed boundary condition, is given in terms of a convergent expansion of the Liouville-Neumann type. This method is applicable for transition probabilities of a form which is much more general than the form permitting a successful application of the Mellin transform. Since the reduction of the emission probability for Bremsstrahlung to the latter form involves an approximation in a certain region, the present method may be used in order to obtain a higher accuracy in that region.

Energy loss of fast electrons and positrons in a plasma

The energy distribution, the most probable and the average energy loss of electrons passing through matter were measured with a 180° focusing spectrometer of approximately 0.7% resolution, using K conversion lines of 606, 1414 and 1761 KeV γ-rays of RsC' as homogeneous electron source and the various thicknesses of Al, Cu. In and Pb as stopping materials. The observed value of the most probable energy loss was in accord with Landau's theory within the limits of our experiment. That of the average energy loss, however, was not in accord with his theory but with Bloch's formula. The width of the energy distribution curve obtained was considerably greater than predicted by Landau. However, on the high energy side of the peak, the shape of the curve predicted by Landau's theory was surely better than that of White and Millington's.

<p>We consider the high energy Earth skimming tau neutrinos converting to taus following by tau propagation through rock. The difficulty in predict the final tau flux comes from the theoretical uncertainties in the tau electromagnetic energy loss and the neutrino-nucleon cross section. The first part of the thesis focuses on deriving the dipole cross section from a theoretical parametrization of the electromagnetic structure function, then uses said cross section to compute the tau's energy loss at high energies during Earth propagation. We find the extracted dipole cross section agrees well with other derivation and dipole models. In the second part, we use different approaches to the structure function $F_2$ and the dipole model to evaluate the corresponding energy loss and cross section. We keep consistent the same approach through both calculations of energy loss and neutrino cross section, and find the emerging tau fluxes match well. We also present the results from our Monte Carlo simulation and our analytic evaluation, and we find that they are in agreement. Finally, we briefly discuss the relevence to several experiments that are looking for skimming astrophysical taus, such as the Pierre Auger Observatory, HAWC, and ASHRA. As a quick demonstration, we show our approximation of the aperture at the Pierre Auger using the energy losses and cross sections calculated from the considered approaches.</p>

Although some authors have claimed that the effect is not detectable, we show experimentally for the first time that as the quantum parameter chi grows beyond 1, an increasingly large part of the hard radiation emitted arises from the spin of the electron. Results for the energy loss of electrons in the energy range 35-243 GeV incident on a W single crystal are presented. Close to the axial direction the strong electromagnetic fields induce a radiative energy loss which is significantly enhanced compared to incidence on an amorphous target. In such continuously strong fields, the radiation process is highly nonperturbative for ultrarelativistic particles and a full quantum description is needed. The remarkable effect of spin flips and the energy loss is connected to the presence of a field comparable in magnitude to the Schwinger critical field, E0 = m(2)c(3)/ePlanck's over 2pi, in the rest frame of the emitting electron.

The X-ray sensitivity is one of the most important parameters for X-ray photoconductors; it is usually described in terms of the electron-hole pair creation energy W± – the average energy required to generate a single detectable pair of electron and hole. This parameter accounts only for the detected carriers, reflecting that only a fraction of the X-ray–generated charges are collected, while the rest are lost through the recombination processes. The charge recombination results in an effective W± that is not a material parameter but rather a characteristic of the detection system, which remains larger than its theoretical value 𝑊± ⁰ and depends on the applied electric field F, X-ray energy E and exposure X. In this work, we characterize the X-ray sensitivity of amorphous lead oxide (a-PbO) photoconductor, which is considered as one of the most promising replacements for amorphous selenium (a-Se) for radiographic, fluoroscopic, and tomosynthesis applications, and examine the underlying mechanisms responsible for charge recombination. W± was measured in a wide range of electric fields (1–20 V/μm), X-ray exposures (0.02–2 R) and energies (29–51 keV). W± decreases with both the electric field and X-ray energy, saturating at 18–32 eV/ehp depending on the energy. W± increases with radiation exposure, especially at lower fields and higher energies. The particular dependencies of W± on these parameters, especially X-ray energy-dependent W±, conclude that the columnar recombination mechanism dominates in the a-PbO photoconductor with a secondary contribution of the bulk recombination.

At present commonly used distribution network loss calculation theory method, the not fully consider load curve changes. Thus, the theory energy loss too small, and the management energy loss too large. On this issue, the article puts forward an improved Newtons method for distribution network theory energy loss calculation. According to the current transformer substation of 24h a distribution network power records, the trend of the model results show that the total distribution network energy loss. The experimental results show that, compared with traditional methods, improved Newtons method to calculate the result more close to the energy loss calculation theory statistical energy loss.

Energy loss of pions and electrons of 1– [formula omitted] in drift chambers operated with Xe,CO 2(15%)