Influence Of Secondary Emission Research Articles

Suppression of secondary emission of electrons from end plate in expander of open trap

The influence of secondary emission from the end plate in the expander divertor on the energy confinement in linear plasma devices was considered. A numerical model was developed to calculate a distribution of the electric potential along a magnetic field line in the expander divertor. The model assumes weak collisions and the absence of cross-field losses of both ions and electrons. The potential profiles in the case of both no and strong secondary emission are presented. It was shown that expansion of the magnetic field in the divertor can effectively suppress the influence of cold electrons on energy confinement even if the secondary emission coefficient is more than unity. The dependence of energy lost per one ion leaving the mirror on the secondary emission coefficient was studied. The influence of partial energy recuperation by cold electrons on the total energy balance was discussed. It has been shown that the energy loss per one ion is not sensitive to the recirculation of cold electrons if the secondary emission coefficient is not too large.

An improved inventory of polychlorinated biphenyls in China: A case study on PCB-153

Emission inventory of pollutants is essential for the environmental fate study and management of the pollutant. To construct a reasonable PCB (polychlorinated biphenyls) inventory in China, this study estimates PCB usage and emission using power generating capacity, installed capacity of power plants and transformer substations, population density and GDP as surrogates. Inventory of representative PCB (PCB-153) with a resolution of 1/4° latitude × 1/4° longitude in China from 1952 to 2005 was generated and assessed as an example. Totally, about 20.3 kt PCBs were applied in China, of which 179 t were PCB-153. By the end of 2005, most of them (56.4%) were emitted into the soil, 2.7% entered the air, and about 20.8% was sealed in storage site or still in service. Historical emissions exhibited increasing trends after 1968, 1984 and 1994, which were mainly associated with usage or disposal processes. Although primary emission has been declined since 2005, the influence of secondary emission from soils, unintentionally produced PCBs (UP-PCB), and reemission from storage sites could be a long-lasting issue in the future. This new emission inventory improves previous PCB emission inventory significantly, which underestimated PCB emission in China considerably.

Influence of the secondary electron emission on the characteristics of radio frequency plasmas

In this paper the influence of secondary emission on the characteristics of RF plasmas has been studied. An asymmetrical dual-frequency capacitively coupled plasma reactor has been modeled with one dimensional PIC/MCC (Particle in Cell with Implemented Monte Carlo Collisions) code. The main feature of the modeling code represents the realistic model of the ion-induced secondary electron emission. Secondary emission of electrons is one of the important processes that effects the characteristics of rf plasmas. For modeling the secondary yield per ion, we have used equations proposed by Phelps and Petrovic (Plasma Sources Sci. Technol. 8 (1999) R21-R44) for differently treated metal surfaces. In the model, the energy dependence of the yields per ion for differently treated metal surfaces has been implemented. Results are compared for yields for the so called ?dirty? and ?clean? surfaces, and the spatial profiles of charged particles and ion energy distributions were observed. The simulation results indicate that the plasma characteristics are greatly affected by the ion-induced secondary emission, changing the overall parameters of dual-frequency capacitively coupled plasma reactors especially in applications as etching devices. Conclusion is that an exact model of the secondary electron emission should be included, as to ensure better agreement between simulation and experiment.

142. Influence of secondary emission on the potential of a metallic body in the electron radiation zones around the earth: T Ya Ryabova and K A Trukhanov, Izv Akad Nauk SSSR Ser Fiz, 35 (5), 1971, 1075–1079 ( in Russian).

142. Influence of secondary emission on the potential of a metallic body in the electron radiation zones around the earth: T Ya Ryabova and K A Trukhanov, Izv Akad Nauk SSSR Ser Fiz, 35 (5), 1971, 1075–1079 ( in Russian).

Studies in the development of high-power klystrons

A survey is given of the experience gained during the development of high-power klystron amplifiers, with reference to design principles, the application of getter pumps inside sealed-off valves, wide-band tuning mechanism, output windows, influence of secondary emission on tube performance, etc. Also, further experiments on broadbanding of multi-cavity amplifier systems are discussed.

Test of langmuir's three halves power law, deviations due to β2-factor and secondary emission

According to theory a small correction (the so called β2-factor) should be applied to Langmuir's law for the electron current in a cylindrical high vacuum diode. To test this, a method was developed for eliminating the potential drop along the hot cathode filament. The accuracy thus obtained disclosed an unexpectedly large deviation of the coefficient in Langmuir's formula from its theoretical value. This discrepancy is most probably due to the influence of secondary emission of the anode. It is possible to correct for this influence in a simple way by introducing an “effective reflection coefficient” of the anode. For anode voltages in the range of 1–30 V, values of this coefficient of 14% for tantalum and of 5.5% for aquadag give a good description of the experimental results. In a similar way the well known (ζ, η)-tables of Langmuir should be corrected if they are to represent the real situation.

Surface conditions and stability of characteristics in screened-grid tubes

The characteristics of screened-grid tubes are discussed and the influence of secondary emission is emphasized. The marked change in secondary emission with surface contamination causes instability of characteristics. Experiments with carefully evacuated ′24 tubes indicate that the evaporation of active material from the cathode considerably increases the secondary emission from the plate and that the liberation of “getter” in a completed tube limits the stability attainable.