Electrostatic Collection Efficiency Research Articles

A theoretical approach to the study of saturation phenomena of electrostatic collection efficiency of 218Po

Radon monitors based on electrostatic collection have been widely used in different radon studies. Collection efficiency of this kind of instrument first depends on the cell geometry and electrostatic field intensity. In the process of new instrument development, some researchers found that electrostatic collection efficiency of 218Po was almost saturated when the voltage between the cylindrical vessel and the detector was higher than 1500V. In this paper, we analyze the physical processes of the freshly positively charged 218Po formed from the α decay of 222Rn and the neutralization kinetics for positively charged 218Po cluster. The analytical expressions of the collection probability of any freshly positively charged 218Po cluster and the total collection efficiency in electrostatic collection cell are obtained. The ratio of the relative growth rate of the collection efficiency to the relative growth rate of the voltage is inversely proportional to the voltage. Such an approach is useful to understand the mechanism of the electrostatic collection of 218Po.

Development of scintillating crystal hybrid photon detectors for the KM3NeT ( [formula omitted]-scale) deep-sea neutrino telescope

Scintillating crystal-based hybrid photon detectors have been demonstrated as viable single photon detectors since 1996 in the Lake Baikal neutrino telescope. Prior to this, the Philips XP2600 was developed under the DUMAND program, while more recently, developments at CERN have demonstrated the advantages of a true concentric geometry with a scintillator at the geometric centre of a spherical photocathode, giving almost 100% electrostatic collection efficiency over 3 π solid angle coverage. We have started to develop a new series of quasi-spherical crystal hybrid photon detectors starting at 8 in. and progressing toward the maximum that can be fitting in a standard 17 in. optical pressure sphere for a future large deep-sea neutrino telescope. The thrust of this R&D will be to investigate the industrialisation of these sensors to the point where they represent a significant cost reduction per cubic kilometre of instrumented volume compared to conventional large hemispherical photomultiplier tubes, thereby allowing for extremely large telescope target volumes. Such gains will arise through an all-glass envelope, internal processing of a standard or enhanced bialkali photocathode, and either from cost reductions in the central scintillating crystal or the use of a deposited phosphor viewed by a small photomultiplier tube. Details of the development program and recent progress in the characterisation of prototypes are presented.

Scintillator-based hybrid photon detector development for the KM3NeT ( [formula omitted]-scale) deep sea neutrino telescope

Scintillating crystal-based hybrid photon detectors (X-HPDs) have been demonstrated as viable single photon detectors since 1996 in the Lake Baikal neutrino telescope. Prior to this, the Philips XP2600 was developed under the DUMAND program, while more recently developments at CERN have demonstrated the advantages of a true concentric geometry with a scintillator at the geometric centre of a spherical photocathode, giving almost 100% electrostatic collection efficiency over 3 π solid angle coverage. We have started to develop a new series of quasi-spherical X-HPDs starting at 8 in. and progressing toward the maximum that can be fitted in a standard 17 in. optical pressure sphere for a future large deep sea neutrino telescope. The thrust of this R&D will be to investigate the industrialisation of the X-HPD to the point where it represents a significant cost reduction per cubic kilometre of instrumented volume compared to conventional PMTs, thereby allowing for extremely large telescope target volumes. Such gains will arise through an all-glass envelope, internal processing of a standard or enhanced bialkali photocathode, and either from cost reductions in the central scintillating crystal or from the use of a deposited phosphor viewed by a small PMT. Details of the development program and recent progress in the characterisation of prototypes will be presented.

A Setup for Investigating Radioactive Ion Neutralization Processes in Air

An experimental setup and measurement technique for determining the survival time of radon daughter (218Po) ions is described. This technique is based on the precipitation of radioactive ions on a semiconductor detector surface in an electrostatic field with the subsequent detection of α radiation from 218Po. A dependence of the 218Po ion neutralization probability per path unit on the absolute air humidity was obtained from the experimental results. It is revealed that a change in the air humidity from 3 to 20 g/m3 weakly influences the radon daughter transfer in the air of the measurement chamber in the absence of the electric field. The electrostatic collection efficiency is independent of the volumetric ionization rate at a radon concentration of < 3.0 × 104 Bq/m3. The mean 218Po ion survival time was found to be 2.4 and 0.9 s at a humidity of 0.8 and 14 g/m3, respectively.

Electrostatic Collection Efficiency in Binary Fluidized Beds

Abstract Fluidized beds of binary mixtures have been used to clean air streams containing dust particles in the size range 4.4 to 14 μ. All beds were composed of glass beads and plastic granules mixed at different proportions. The effect on the electrostatic collection efficiency of a number of variables, including type of collecting mixture, bed height, and gas velocity, was examined. To calculate the single collection efficiency from experimental results, an early model proposed by Clift et al. was used. The electrostatic collection efficiency was determined by subtracting the other individual mechanism efficiencies from the single particle collection efficiency.

The nature of unattached RaA (218Po) particles.

Careful measurement of the diffusion coefficient of RaA shows that it is a function of the length; ftowrate ratio of the diffusion tube used (or of age) and leads to the conclusion that there is no single diffusion coefficient for RaA, and to the hypothesis that the diffusivity depends upon the chemical nature of the reaction product formed between RaA and the gaseous environment. In agreement with this hypothesis, the electrostatic collection efficiency of RaA in atmospheres of various gases correlates with the ionization potential of the gases. There is a clear need to investigate further the chemistry of radon daughters in order to understand their dosimetry and deposition in the human lung.