scholarly journals The Drift Velocity of Electrons in Oxygen at 293 K

1973 ◽  
Vol 26 (6) ◽  
pp. 771 ◽  
Author(s):  
RW Crompton ◽  
MT Elford
Keyword(s):  
Drift Velocity ◽  
Drift Tube ◽  
Time Of Flight ◽  
Velocity Measurements ◽  
Time Of Flight Method ◽  
Good Agreement

The drift velocity of electrons in oxygen at 293 K has been measured over the range 0.8 ≤ E/N ≤ 12 Td by the Bradbury–Nielsen time-of-flight method. The factors governing the range over which measurements can be made are discussed and it is shown that long drift tubes should be used for drift velocity measurements in oxygen at low values of E/N. A 50 cm drift tube is described. The error in the present results is estimated to be less than 1 % for 1.8 E/N E/N > 6 Td and at 1.5 Td, 5 % at 1 Td, and 10 % at 0.8 Td. The present data are in good agreement with those of Fleming et al. (1972) and Nelson and Davis (1972) over the E/N range where the sets of data overlap.

scholarly journals A Note on End Effects in Electron Drift Tube Experiments

1973 ◽  
Vol 26 (5) ◽  
pp. 685
Author(s):  
MT Elford ◽  
AG Robertson
Keyword(s):  
Drift Velocity ◽  
Drift Tube ◽  
Time Of Flight ◽  
Drift Chamber ◽  
Electron Drift Velocity ◽  
Electron Drift ◽  
Velocity Measurements ◽  
End Effects ◽  
Time Of Flight Method

Experiments to test the influence of end effects on electron drift velocity measurements by the Bradbury-Nielsen time-of-flight method are described. A comparison of data taken at drift distances of 5, 10, and 50 cm in hydrogen and 5 and 10 cm in helium shows that over the EIN and pressure ranges investigated the results are independent of drift distance and that it is justifiable to consider this distance as that between the mid planes of the grids which terminate the drift chamber.

scholarly journals Momentum Transfer Cross Section for Electrons in Mercury Vapour Derived from Drift Velocity Measurements in Mercury Vapour?Gas Mixtures

1991 ◽  
Vol 44 (6) ◽  
pp. 647 ◽  
Author(s):  
JP England ◽  
MT Elford
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Personal Communication ◽  
Mercury Vapour ◽  
Semi Empirical ◽  
Time Of Flight Method ◽  
Momentum Transfer Cross Section ◽  
Good Agreement

The Bradbury-Nielsen time-of-flight method has been used to measure electron drift velocities at 573 K in pure mercury vapour, a mixture of 46�80% helium-53� 20% mercury vapour and a mixture of 9�37% nitrogen-90� 63% mercury vapour. The E/N and pressure ranges used were O� 2 to 1� 5 Td and 5�4 to 15�2 kPa for pure mercury vapour, 0 �08 to 3�0 Td and 5 �40 to 26�88kPa for the mixture containing helium and 0�06 to 5�0Td and 3�33 to 16�67kPa for the mixture containing nitrogen. It is shown that the use of mixtures significantly reduces the dependence of the measured drift velocity on the pressure, due to the effect of mercury dimers, from that measured in pure mercury vapour. An iterative procedure to derive the momentum transfer cross section for electrons in mercury vapour over the range 0�04 to 4 eV with an uncertainty between �5 and 10% is described. It is concluded that previously published momentum transfer cross sections for mercury vapour derived from drift velocity data are significantly in error, due to diffusion effects and the procedure used to correct for the influence of dimers. The present cross section is in good agreement with the semi-empirical calculations of Walker (personal communication).

scholarly journals The Drift Velocity of Electrons in Mercury Vapour at 573 K

1980 ◽  
Vol 33 (2) ◽  
pp. 239
Author(s):  
MT Elford
Keyword(s):  
Density Dependence ◽  
Drift Velocity ◽  
Time Of Flight ◽  
Mercury Vapour ◽  
Number Density ◽  
Sources Of Error ◽  
Time Of Flight Method

The drift velocity of electrons in mercury vapour at 573 K has been measured using the Bradbury-Nielsen time-of-flight method at vapour number densities ranging from 3�40x 1017 to 1�83x1018 cm-3 and at E/Nvalues from 0�1 to 3�0 Td. The measured drift velocities increase linearly with mercury vapour number density, the magnitude of the dependence being a function of E/ N. This number density dependence has been attributed to the presence of mercury dimers and the drift velocity corresponding to dimer-free mercury vapour has been obtained by extrapolation. Sources-of error are examined and the present results are compared with those of previous workers.

scholarly journals Drift Velocity and DT/m Ratio for Electrons in a 0.5% Hydrogen?Xenon Mixture at 295 K

1994 ◽  
Vol 47 (3) ◽  
pp. 253 ◽  
Author(s):  
MT Elford ◽  
S Sasaki ◽  
KF Ness
Keyword(s):  
Cross Section ◽  
Drift Velocity ◽  
Diffusion Chamber ◽  
Number Density ◽  
Velocity Measurements ◽  
Transverse Diffusion ◽  
Xenon Mixture ◽  
Time Of Flight Method ◽  
Momentum Transfer Cross Section ◽  
Electron Transport Coefficient

The momentum transfer cross section for electrons in xenon, am, has been studied using electron transport coefficient measurements for a dilute hydrogen-xenon mixture (0�47% H2- 99 �53% Xe). Drift velocity measurements were made using the Bradbury-Nielsen time-of-flight method at E/N values from 0 �12 to 2�50 Td, pressures from 10�3 to 94�0 kPa and a temperature of 295 K (E is the electric field strength and N the gas number density; 1 Td == 10-17 Vcm2). The ratio DT/f.t (where DT is the transverse diffusion coefficient and {� the electron mobility) was measured using a Townsend-Huxley diffusion chamber at E/N values from 0�035 to 1� 70 Td, pressures from 13�4 to 40�3 kPa, and a temperature of 294 K. Three recently published Urn values for xenon have been tested and shown to be incompatible with both the present drift velocity and DT / f.t measurements.

scholarly journals The Dependence of Measured Drift Velocity on Shutter Open Time in the Four Gauze Time-of-Flight Method

1986 ◽  
Vol 39 (2) ◽  
pp. 225 ◽  
Author(s):  
OM Williams ◽  
MT Elford
Keyword(s):  
Transit Time ◽  
Drift Velocity ◽  
Time Of Flight ◽  
Combined Effects ◽  
Drift Space ◽  
Open Time ◽  
The Asymmetry ◽  
Time Of Flight Method ◽  
Experimental Scatter

Measurements of ion transit time by the four gauze time-of-f1ight method have been shown previously to have a small dependence on the shutter open time. This effect has been investigated for the case of Kr + ions in Kr and found to be due to the combined effects of diffusion and the injection of asymmetric ion pulses into the drift space. The cause of the asymmetry and procedures for checking for the presence of an error from this source are discussed. It is estimated that the error incurred can be reduced to within the experimental scatter of the measured mobility; that is, to less than �0�15%.

scholarly journals Comparison of Quantitative Texture Analysis Results From Time-of-Flight and Conventional Neutron Diffraction

1980 ◽  
Vol 4 (1) ◽  
pp. 1-11 ◽  
Author(s):  
K. Feldmann ◽  
M. Betzl ◽  
A. Andreeff ◽  
K. Hennig ◽  
K. Kleinstück ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Texture Analysis ◽  
Steel Wire ◽  
Time Of Flight ◽  
Multiphase Materials ◽  
Neutron Time ◽  
Time Of Flight Method ◽  
Low Symmetry ◽  
Good Agreement

The adaptability of time-of-flight neutron diffraction for quantitative texture analysis is demonstrated. Measurements with this technique on drawn steel wire show good agreement with the results from conventional neutron diffraction experiments. A short description of the neutron time-of-flight method is given. Its application for texture investigations especially on low-symmetry crystalline systems, multiphase materials and for in situ studies is discussed.

Laser ion time-of-flight (LITOF) velocity measurements using N2(+) tracers

1994 ◽  
Author(s):  
James Ress ◽  
Gabriel Laufer ◽  
Roland Krauss
Keyword(s):  
Time Of Flight ◽  
Velocity Measurements

scholarly journals Optimization of the flow conditions in the spawning ground of the Chinese sturgeon (Acipenser sinensis) through Gezhouba Dam generating units

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Anyang Huang ◽  
Jinzhong Yao ◽  
Jiazhi Zhu ◽  
Xingchen Gao ◽  
Wei Jiang
Keyword(s):  
Spawning Ground ◽  
Chinese Sturgeon ◽  
Flow Conditions ◽  
Velocity Measurements ◽  
Acipenser Sinensis ◽  
Critically Endangered Species ◽  
Gezhouba Dam ◽  
Opening Mode ◽  
Suitable Area ◽  
Good Agreement

AbstractChinese sturgeon (Acipenser sinensis) is a critically endangered species, and waters downstream from Gezhouba Dam are the only known spawning ground. To optimize the velocity conditions in the spawning ground by controlling the opening mode of Gezhouba Dam generator units, a mathematical model of Chinese sturgeon spawning ground was established in FLOW-3D. The model was evaluated with velocity measurements, and the results were determined to be in good agreement. By inverting the 2016–2019 field monitoring results, the model shows that the preferred velocity range for Chinese sturgeon spawning is 0.6–1.5 m/s. Velocity fields of different opening modes of the generator units were simulated with identical discharge. The suitable-velocity area was maximal when all units of Dajiang Plant of Gezhouba Dam were open. For discharges below 12,000 m3/s, most of the area was suitable; for discharges above 12,000 m3/s, the suitable area rapidly decreased with increasing discharge. A comparison of suitable areas under high-flow showed that at discharges of 12,000–15,000 m3/s, opening 11–13 units on the left side was optimal. For discharges above 15,000 m3/s, all units should be open. We used these results to recommend a new operation scheme to support the conservation of Chinese sturgeon.

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