Avalanche-type process

In a strong electric field, a free electron acquires enough kinetic energy to cause an impact ionization i.e., an electron impacting on a neutral molecule causes an emission of a new electron, leading to the formation of new electron-ion pair. The new free electron is, in turn, accelerated to a velocity sufficient to cause further ionization. This leads to an avalanche-type generation of free electrons and ions. The electric field provides the necessary energy in such a way that the process can continue without the external radiation which was necessary for the onset of the process. 

The authors of paper [14] used fractal analysis methods for the description of the glass transition process of crosslinked polymers. For this purpose they used the expression for the estimation of beginning time T. of the accumulation of avalanche-type defects obtained in paper [15] ... 

Pus] Pustov, Y.A., Baldokhin, Y.V., Labutin, V.Y., Nefedov, V.I., Kolotyikin, P.Y., Ovcharov, V.P, Kislogubov, LA., Avalanche-Type Relaxation Processes in Fe-Cr-B System Alloys at Isothermal Annealing at Different Partial Oxygen Pressure (in Russian), Dokl. Akad. Nauk SSSR, 311(3), 654-658 (1990) (Experimental, Kinetics, 2)... 

Systematic studies of the influence of border pressure on the kinetics of foam column destruction and foam lifetime have been performed in [18,24,41,64-71], Foams were produced from solution of various surfactants, including proteins, to which electrolytes were added (NaCI and KC1). The latter provide the formation of foams with different types of foam films (thin, common black and Newton black). The apparatus and measuring cells used are given in Fig. 1.4. The rates of foam column destruction as a function of pressure drop are plotted in Fig. 6.11 [68]. Increased pressure drop accelerates the rate of foam destruction and considerably shortens its lifetime. Furthermore, the increase in Ap boosts the tendency to avalanche-like destruction of the foam column as a whole and the process itself begins at higher values of foam dispersity. This means that at high pressure drops the foam lifetime is determined mainly by its induction period of existence, i.e. the time interval before the onset of its avalanche-like destruction. This time proves to be an appropriate and precise characteristic of foam column destruction. 

The noise spectral density is l/f type in the frequency band 10 mHz to 300 Hz in normal and reverse operation mode. Noise spectral density is a quadratic function of the current, when the electric field strength in isolating layer is so low that avalanche process caimot occur. Measurement performed at very low frequency band 10 mHz to 1 Hz reveals that for some samples noise is l/f type, but it was observed some time instability, which is probably related to the self-healing process. 

The topics included here are limited to the usual types of noise in the common types of infrared photon detectors. Noise in thermal detectors, such as temperature noise in bolometers, is not included. Noise associated with the avalanche process is omitted. The detailed noise theory of phototransistors, an extension of shot noise in photodiodes, is not included. Modulation noise, an example of which arises from conductivity modulation by means of carrier trapping in slow surface states, is not included. Pattern noise, due to the... 

Fig. 1 Schematic representation of the three main types of processes causing upconversion in rare earth doped materials (a) excited state absorption (b) energy transfer upconversion (c) photon avalanche. The dotted lines refer to photon excitation, dashed lines to non-radiative energy transfer, and full arrows to emissive processes, respectively...

The second type of detection system uses the delay wire technique (61), and a schematic diagram of this detector is shown in Figure 2. The beta radiation (fast electrons) emitted from the radioactivity source on the plate ionizes the counting gas, which has been specifically chosen so that this process can freely take place. This is the primary mode of ionization and the resultant charged particles, free electrons and positive ions, are then accelerated towards the anode wire and cathode, respectively. In this primary mode of ionization, the free electrons are accelerated to such an extent that they themselves cause ionization of the counting gas, producing further free electrons and ions. This is the secondary ionization mode. This continues causing an avalanche of ionization from the primary point of ionization towards the anode wire. 

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