Thermodynamics of supersaturated vapor nucleation on molecular condensation nuclei

Katelevsky²,

Valyukhov

et al. 2014

SPIE Proceedings

The principal foundations, specific features and application fields of the advanced highly sensitive method of gas impurities detection -molecular condensation nuclei (MCN) method are discussed. MCN method is based on the conversion of impurity molecules to condensation nuclei of much larger size followed by the nuclei enlargement in the supersaturated vapor of specially selected low-volatile organic substances and detection of produced aerosol particles using an optical (nephelometric) method. The light scattering properties of the aerosol particles and air in the photometer of an MCN detector as well as sensitivity of the photometer's photodetector are investigated. We have determined that the light scattering by aerosol particles is interferometric by nature and is comparable within an order of magnitude with light scattering by the air inside a photometer. The threshold sensitivity of fotointegrator was reduced a level where the detection limit for the gas analyzer target component is determined by the background level of spontaneous condensation and not by the sensitivity of the detector's photoreceiver.Keywords: Molecular condensation nuclei (MCN), light scattering by aerosol particles and air, nephelometric method, threshold sensitivity of fotointegrator, condensation nuclei detector, gas analyzers based on the molecular condensation nuclei method, aerosol photometer, calibration gas analyzer by air scattering.

Section: A Compromise Light Scattering Anglementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Light scattering by aerosol particles and air in the molecular condensation nuclei (MCN) detector

Katelevsky²,

Valyukhov

et al. 2014

SPIE Proceedings

“…[6,7]. The problem of creation energy and equilibrium concentration of clusters was investigated in [6].…”

Section: Introductionmentioning

confidence: 99%

“…[6,7]. The problem of creation energy and equilibrium concentration of clusters was investigated in [6]. The equation connecting the energy required to transfer MCN from the gas phase into a homogeneous cluster with the energy required to break individual bonds was derived.…”

Section: Introductionmentioning

confidence: 99%

A photointegrator of the molecular condensation nuclei detector

St. Petersburg Polytechnical University Journal: Physics and Ma

Valyukhov

2015

The problem of calculating the threshold sensitivity of an integrating photoreceiver (photocurrent integrator) is investigated. A noise model of a photointegrator is used to develop equivalent noise circuits and to calculate the RMS value of the voltage across the output of the photoreceiver. Among all the models of the real photointegrator it is conceivable that the approximation by an ideal photointegrator may be used. The threshold sensitivity of a photointegrator is defined as the power at the input of a photointegrator at which the root mean squared (RMS) voltage across its output is equal to the RMS voltage of total noise i.e. the signal-to-noise ratio is equal to one. A photomultiplier tube (PMT) can be used to increase the sensitivity. Formulas for calculating the sensitivity of a PMT-based photointegrator are given. The increase in sensitivity due to the use of PMT can be up to 18-30 times.An experimental study of a photometer of a molecular condensation nuclei (MCN) detector that forms a base of highly sensitive MCN gas analyzers was conducted. The measured sensitivity differed from the calculated by 10%. However, at femtowatt power levels it is very difficult to get rid of parasitic optical signals that are responsible for a small decrease in sensitivity compared to the theoretical prediction. In many practical applications, for example, for the X-ray absorption method of mineral extraction using position-sensitive photodiode X-ray receivers, an approximation of a real photointegrator must be used.

Rain attenuation in millimeter wave, centimeter wave and visible light ranges

IOP Conf. Ser.: Mater. Sci. Eng.

Ivanov

Федотов

et al. 2021

The paper presents the results of theoretical simulation of mmWave, cmWave and visible light attenuation in rain based on the Mie scattering theory. Specific rain attenuation has been estimated from the gamma drop size distribution for a spherical drop. Rain attenuation of electromagnetic waves in the visible range, used by video cameras and lidars of «smart» city vehicles, and at the beginning of the millimeter wave range used by radars and positioning systems, have similar values averaging 3-5 dB/km. The attenuation levels of electromagnetic waves in mmWave, cmWave and Visible light ranges must be taken into account when calculating the energy budget of vehicle communications.