scholarly journals Effect of a magnetic force on the motion of negative ions in a gas

1912 ◽  
Vol 87 (596) ◽  
pp. 357-365 ◽  
Keyword(s):  
Charged Particle ◽  
Atmospheric Pressure ◽  
Magnetic Force ◽  
Large Range ◽  
Negative Ions ◽  
Negative Ion ◽  
Electric Force ◽  
Dry Air ◽  
Low Pressures ◽  
Made In

1. When the velocity of a charged particle in a gas is proportional to the electric force and inversely proportional to the pressure, the size of the particle is unaltered either by changes in the pressure or in the force. For a large range of pressures and forces the mass of an ion is thus shown to be constant, since the velocity is proportional to the ratio X / P. At low pressures when the ratio X / P exceeds a certain value the velocity of the negative ions undergoes large changes when small variations are made in the force or in the pressure. The increase in the mobility may be explained on the hypothesis that the mass associated with the negative ion diminishes. Thus in dry air at a pressure of 29 mm. the velocity of the negative ions is 926 cm. per second, under a force of 2·3 volts per centimetre, whereas if the ion travelled with the same mass that it has at atmospheric pressure the velocity would be about 114 cm. per second.

scholarly journals The effect of small traces of water vapour on the velocities of ions produced by Röntgen rays in air

1910 ◽  
Vol 84 (569) ◽  
pp. 173-181 ◽  
Keyword(s):  
Electric Field ◽  
Water Vapour ◽  
Lateral Diffusion ◽  
Negative Ions ◽  
Complete Removal ◽  
The Other ◽  
Electric Force ◽  
Dry Air ◽  
Positive Ions ◽  
Low Pressures

Some experiments by Prof. J. S. Townsend on the lateral diffusion of a narrow stream of ions moving in an electric field led to the conclusion that negative ions in perfectly dry air are much smaller than those in air containing a small quantity of moisture. It was consequently to be expected that the complete removal of water vapour would cause an increase in the velocity with which negative ions move under the influence of an electric field of force. At his suggestion the following investigation of the velocities of ions in air at low pressures was undertaken, and it was found that, while the complete removal of water vapour had only a small effect on the velocities of positive ions, yet the same cause increased the velocities of the negative ions by a factor varying between 2 and 30 for the range of pressures and electric forces used in the experiments. The method adopted was to let the ions travel between two gauzes under a known electric force for a time t and then to reverse the field. If v is the velocity of the ions and d is the distance between the gauzes, then ions starting from one gauze will reach the other if t ≮ d / v . If t is gradually decreased, it is possible to find, by means of an electrometer, when ions cease to reach the second gauze; when this happens v = d / t .

The Boltzmann relation in electronegative plasmas: When is it permissible to use it?

2000 ◽  
Vol 64 (2) ◽  
pp. 131-153 ◽  
Author(s):  
R. N. FRANKLIN ◽  
J. SNELL
Keyword(s):  
Fluid Model ◽  
Negative Ions ◽  
Ionization Rate ◽  
Negative Ion ◽  
Simple Relationship ◽  
Ion Temperature ◽  
Ion Density ◽  
Positive Ions ◽  
Electronegative Plasmas ◽  
Low Pressures

This paper reports the results of computations to obtain the spatial distributions of the charged particles in a bounded active plasma dominated by negative ions. Using the fluid model with a constant collision frequency for electrons, positive ions and negative ions the cases of both detachment-dominated gases (such as oxygen) and recombination-dominated gases (such as chlorine) are examined. It is concluded that it is valid to use a Boltzmann relation ne = ne0exp(eV/kT) for the electrons of density ne, where the temperature T is approximately the electron temperature Te, and that the density nn of the negative ions at low pressures obeys nn = nn0exp(eV/kTn), where Tn is the negative-ion temperature. However, at high pressure in detachment-dominated gases where the ratio of negative-ion density to electron density is constant and greater than unity, and when the attachment rate is larger than the ionization rate, the negative ions are distributed with the same effective temperature as the electrons. In all other cases there is no simple relationship. Thus to put nn/ne = const, nn = ne0exp(eV/kTe) and nn = nn0exp(eV/kTn) simultaneously is mathematically inconsistent and physically unsound. Accordingly, expressions deduced for ambipolar diffusion coefficients based on these assumptions have no validity. The correct expressions for the situation where nn/ne = const are obtained without invoking a Boltzmann relation for the negative ions.

scholarly journals Mobility of the positive and negative ions in gases at high pressure

1912 ◽  
Vol 86 (584) ◽  
pp. 154-162 ◽  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Mathematical Expression ◽  
Negative Ions ◽  
Negative Ion ◽  
Positive Ions ◽  
Low Pressures ◽  
Positive Ion ◽  
Reduced Pressures

The velocity of ions in gases at reduced pressures was first investigated by Rutherford and by Langevin. Recently the author and others have carried out similar investigations. The results of these investigations show that for the negative ions in air the product of the mobility and the pressure is constant for pressures ranging from 760 mm. to 200 mm. of mercury, but with further reduction the product increases with the reduction of pressure, this increase becoming very great at low pressures. For the positive ions in air the product of the mobility and pressure is constant for pressures investigated between 760 mm. and 3 mm. of mercury. Similar results were obtained for the mobilities of the ions in other gases. The results show that if the ion is an aggregation of molecules, this aggregation becomes, at low pressures, less complex in the ease of the negative ion, while in the ease of the positive ion it persists down to 3 mm. of mercury. The purpose of the present research was the study of the mobilities of both kinds of ions in gases at high pressures. The method of investigation is based on the mathematical expression, developed by Prof. Rutherford, for the current between two plates, assuming that a very intense ionisation exists near the surface of one of the electrodes.

scholarly journals On the conductivity of a gas, between parallel plate electrodes, when the current approaches the maximum value

1911 ◽  
Vol 86 (583) ◽  
pp. 72-77 ◽  
Keyword(s):  
Atmospheric Pressure ◽  
Parallel Plate ◽  
Complete Solution ◽  
Negative Electrode ◽  
Negative Ions ◽  
Saturation Current ◽  
Maximum Value ◽  
The Difference ◽  
Minimum Force ◽  
Made In

The relation connecting the current with the potential difference between parallel plate electrodes when the gas between the plates has been uniformly ionised by Röntgen rays or Becquerel rays has been investigated theoretically by many physicists. In all cases various assumptions are made in order to simplify the calculations, as the problem becomes very complicated when the disturbance of the field due to the separation of the ions is taken into consideration. Perhaps the most complete solution is that given by Mie, in which the only effect that is neglected is that of diffusion. The difference between the velocities of the positive and negative ions is taken into consideration, and the disturbance of the field due to the charge in the gas produced by the excess of ions of one sign in the neighbourhood of the electrodes. The method of analysis, consisting of a series of approximations, is difficult, but the results have been presented in a convenient form, for currents in air at atmospheric pressure that are certain fractions of the saturation current. A curve is given for each current which shows the distribution of force between the plates. The currents investigated ranged between those that were one-fifth and nine-tenths of the saturation current. In the former case the ratio of the electric force at the negative electrode to the minimum force in the filed was found to be 2.7. The ratio diminishes as the force increases, and for the current that is nine-tenths of the saturation current the ratio becomes 1.39.

Negative-ion bombardment increases during low-pressure sputtering deposition and their effects on the crystallinities and piezoelectric properties of scandium aluminum nitride films

2021 ◽  
Author(s):  
Takumi Tominaga ◽  
Shinji Takayanagi ◽  
Takahiko Yanagitani
Keyword(s):  
Acoustic Wave ◽  
Aluminum Nitride ◽  
Piezoelectric Properties ◽  
Negative Ions ◽  
Ion Bombardment ◽  
Low Pressure ◽  
Film Deposition ◽  
Negative Ion ◽  
Sputtering Deposition ◽  
Low Pressures

Abstract Scandium aluminum nitride (ScAlN) films are being actively researched to explore their potential for use in bulk acoustic wave (BAW) and surface acoustic wave (SAW) resonators because of their good piezoelectric properties. Sputtering is commonly used in ScAlN film deposition. Unfortunately, it has been reported that film quality metrics such as the crystallinity and piezoelectric properties can deteriorate before the Sc concentration reaches 43% without an isostructural phase transition. One reason for this is bombardment with negative ions generated from carbon and oxygen impurities in the Sc ingots. Because the number of negative ions increases during low-pressure sputtering deposition, their effect on film quality may be considerable. In this study, we investigated negative-ion bombardment of the substrate during sputtering deposition and its effects on ScAlN crystallinity and piezoelectric properties. Negative-ion energy distribution measurements indicated that many more negative ions collide with the substrate during ScAlN film deposition than during AlN deposition. In addition, decreasing the sputtering pressure further increased the number of negative ions and their energies. It is well known that film quality improves at low pressures because increasing the mean free path reduces thermalization and scattering of sputtered particles. Although, AlN crystallinity and piezoelectric properties improved at low pressures, the properties of ScAlN films deteriorated dramatically. Therefore, the results indicated that ion bombardment increase at low pressure adversely effects ScAlN crystal growth, deteriorating crystallinity and piezoelectric properties. ScAlN films may be improved further by suppressing negative-ion bombardment of the substrate.

scholarly journals The charges on positive and negative ions in gases

1908 ◽  
Vol 80 (537) ◽  
pp. 207-211 ◽  
Keyword(s):  
Negative Ions ◽  
Liquid Electrolyte ◽  
Negative Ion ◽  
Electric Force ◽  
Positive Ions ◽  
Standard Pressure ◽  
Monovalent Ion ◽  
Coefficient Of Diffusion

In a paper on the Diffusion of Ions in Gases, I described a method of comparing the charges on the ions generated in gases with the charge on an ion in a liquid electrolyte. If N be the number of molecules in a cubic centimetre of a gas at standard pressure and temperature, and e the charge on an ion, then N . e = 3∙10 8 . U / K, where U is the velocity of an ion in a field of unit electric force and K the coefficient of diffusion. Thus from separate determinations of the quantities U and K, the product N . e can be obtained. If E is the charge on a monovalent ion in a liquid electrolyte, N . E = 1∙23 x 10 10 , so that a comparison of the various charges may be made, and the calculations have shown that the charge on a positive or negative ion in a gas is nearly equal to the charge E. There were, however, considerable discrepancies, particularly with positive ions, which gave values of N . e as great as 1∙66 x 10 10 in some cases.

scholarly journals On the velocity of the positive ions the Crookes dark space

1923 ◽  
Vol 104 (728) ◽  
pp. 565-571 ◽  
Keyword(s):  
Electric Fields ◽  
Atmospheric Pressure ◽  
Electric Force ◽  
Thermal Agitation ◽  
Great Volume ◽  
Positive Ions ◽  
Dark Space ◽  
The Mean ◽  
The One ◽  
Low Pressures

Notwithstanding the great volume of published investigations on the electric discharge in gases, the nature of the negative glow and the mechanism by which the current is carried across the Crookes dark space at moderately low pressures are still matters of speculation. Some years ago, in describing investigations on the latter phenomenon, I drew attention to the outstanding difficulties in the way of formulating a workable theory. One of these difficulties was an apparently hopeless discrepancy between two values for the velocities of the positive ions at the surface of the cathode, the one calculated from their measured space charge and the total current passing through the tube, the other obtained by extra-polation from the mobility measured at higher pressures. On reconsideration of the problem, I now recognise that the latter value was definitely wrong, and in this paper will show that if instead the velocity is calculated from more reasonable assumptions the discrepancy is almost entirely removed. The mean drift velocity of positive ions in a gas under an electric force varies directly with the electric force and inversely with the pressure of the gas. A linear relation has been shown experimentally to hold from atmospheric pressure down to pressures of the order of 1 mm. of mercury, so long as the electric fields are so small that the mean drift of the ions is insignificant compared with their velocity of thermal agitation. In the particular circumstances now under consideration we are concerned with the movements,of positive ions near the surface of the cathode in the Crookes dark space, where the electric field may be as high as 1000 volts per cm. in gas at pressures of the order of 0·1 mm. of mercury. Under these conditions the velocity of thermal agitation becomes negligible compared with that acquired by the ion between successive collisions, so that a linear extrapolation is quite unjustifiable.

scholarly journals The diffusion of ions into gases at low pressure

1912 ◽  
Vol 87 (596) ◽  
pp. 350-357 ◽  
Keyword(s):  
Water Vapour ◽  
Royal Society ◽  
Ultra Violet ◽  
Negative Ions ◽  
Large Change ◽  
Electric Force ◽  
Aluminium Foil ◽  
Ultra Violet Light ◽  
Violet Light ◽  
Low Pressures

1. In papers published in the ‘Proceedings’ of the Royal Society, the charges on ions produced by the action of Rontgen rays and radium on air were determined by a method depending on the diffusion of the ions, and in the course of the investigations it was observed that the removal of water- vapour from the gas produced a large change in the motion of negative ions. In this paper the results are given of some accurate experiments on the ions produced by radium, and experiments at low pressures on the motion of the ions produced by ultra-violet light are described. In the latter case, effects similar to those observed by Prof. Townsend when the gas was ionised by Rontgen rays have been found, and some interesting results at pressures lower than those previously employed have been obtained. 2. The arrangement of the apparatus is here reproduced (fig. 1). The ions are generated in the field A by radium placed in shallow horizontal grooves f , covered with aluminium foil, in brass blocks F. They pass under the action of the electric force through the grating g and the aperture h into the field B, which was kept constant by means of the brass rings G maintained at definite potentials. Here they diffuse and the ratio R of the charge received by the disc D to the charge received by the disc and the ring S together is measured. This ratio is a known function of c = N e Z/P, where e is the charge on an ion, N the number of molecules in a cubic centimetre of air at pressure P at the temperature of the laboratory, and Z the electric force in the field B.

scholarly journals I. Notices of some conclusions derived from the photographic records of the Kew declinometer, in the years 1858,1859, 1860, and 1861

1862 ◽  
Vol 11 ◽  
pp. 585-590
Keyword(s):  
Relative Frequency ◽  
Magnetic Force ◽  
Total Force ◽  
Magnetic Disturbances ◽  
Different Parts ◽  
Made In ◽  
Photographic Records

The discussion of the magnetic observations which have been made in different parts of the globe may now be considered to have established the three following important conclusions in regard to the magnetic disturbances: viz., 1. That these phenomena, whether of the declination, inclination, or total force, are subject in their mean effects to periodical laws, which determine their relative frequency and amount at different hours of the day and night. 2. That the disturbances which occasion westerly and those which occasion easterly deflections of the compass-needle, those which increase and those which decrease the inclination, and those which increase and those which decrease the magnetic force have all distinct and generally different periodical laws.

scholarly journals Directional Dark Matter Searches with CYGNO

Particles ◽  
2021 ◽  
Vol 4 (3) ◽  
pp. 343-353
Author(s):  
Fernando Domingues Amaro ◽  
Elisabetta Baracchini ◽  
Luigi Benussi ◽  
Stefano Bianco ◽  
Cesidio Capoccia ◽  
...  
Keyword(s):  
Dark Matter ◽  
Atmospheric Pressure ◽  
Time Projection Chamber ◽  
Negative Ion ◽  
Cmos Camera ◽  
Resolution Time ◽  
3D Tracking ◽  
Ion Drift ◽  
Optical Readout ◽  
Time Projection

The CYGNO project aims at developing a high resolution Time Projection Chamber with optical readout for directional dark matter searches and solar neutrino spectroscopy. Peculiar CYGNO’s features are the 3D tracking capability provided by the combination of photomultipliers and scientific CMOS camera signals, combined with a helium-fluorine-based gas mixture at atmospheric pressure amplified by gas electron multipliers structures. In this paper, the performances achieved with CYGNO prototypes and the prospects for the upcoming underground installation at Laboratori Nazionali del Gran Sasso of a 50-L detector in fall 2021 will be discussed, together with the plans for a 1-m3 experiment. The synergy with the ERC consolidator, grant project INITIUM, aimed at realising negative ion drift operation within the CYGNO 3D optical approach, will be further illustrated.

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