Deformation method for the investigation of infinite-dimensional optimization problems

Translated from Matematicheskie Zametki, Vol. 53, No. 2, pp. 175–176, February, 1993.     

Dynamics of an RF Discharge in a Magnetic Field under Strong Initial Preionization

We demonstrate experimentally the possibility to create and sustain a strongly ionized plasma at low gas pressures by the electromagnetic radiation of the intensity which is below the conventional breakdown level. The conditions of ignition and sustaining the plasma are found, and the plasma parameters are measured. The necessary condition for the discharge formation is strong preliminary ionization of an initial gas. Significant electron heating in the RF field, which ensures the effective gas ionization takes place due to Coulomb collisions with protoplasma ions. Such collisions are much more frequent than the electron-neutral collisions. We propose a qualitative analytical model of the discharge evolution, which describes the effects observed.     

Retrieval of vertical stratosphere temperature profile from ground-based measurements of atmospheric self-radiation spectrum in millimeter-range lines of molecular oxygen

The retrieval technique of the vertical stratosphere temperature profile from ground-based measurements of the atmospheric self-radiation spectrum in a millimeter-wave range is proposed. This technique is based on the Bayesian approach to solving an inverse problem and includes assumptions on the measurement noise, as well as some prior information about the retrieved profile. The possibility of temperature retrieval in the range of 20–55 km with 10 K accuracy is demonstrated.     

Short-pulse ECR: A source of multiply charged ions

Extensive investigation is now under way in CERN (European Organization for Nuclear Research) in the framework of the Beta Beam project with the aim of gaining insight into neutrino oscillations. It is suggested that the decay of ⁶He nuclei produce neutrino beams accelerated to an energy on the order of 100 GeV/nucleon. To this end, it is necessary to generate short-pulse (30–100 μs) beams of multiply charged ions of this isotope. Conventional ECR-based ion sources seem to be inappropriate for this purpose, since the plasma density grows slowly (for more than a millisecond) in this case compared with the desired pulse duration. A design concept of a short-pulse ECR-based source of multiply charged ions is proposed. In experiments with pumping at frequencies of 37.5 and 75.0 GHz, pulses as short as ∼50 μs were obtained. Good agreement between theory and experiments is demonstrated.     

Microwave spectroradiometer complex for remote study of the stratosphere thermal structure

We describe a microwave spectroradiometer for thermal sensing of the stratosphere in the molecular oxygen lines located on the slope of a 5-mm band. An uncooled low-noise high-frequency amplifier ensures the device noise temperature 1400 K. The frequency resolution of the used filtering analyzer varies from 0.5 MHz at the center of the line to 15 MHz at its boundary. The through calibration of the spectroradiometer is performed by an electrically controlled noise generator on the basis of the Schottky-barrier diode. The accuracy of the temperature recovery in the altitude range 20–55 km is estimated from the results of surface measurements of the atmospheric emission in the line with a central frequency of 53.0669 GHz. Model calculations based on the Bayesian approach show that the temperature-recovery accuracy no worse than 10 K for the confidence interval 95% can be achieved during an observation period of about half an hour.     

Bayesian approach to recovery of the vertical profile of the stratosphere temperature from the ground-based measurements of solar radiation in millimeter absorption lines of molecular oxygen

We propose a method for recovery of the altitude profile of the stratosphere temperature using ground-based radiometric measurements. The method is based on the Bayesian approach to solving inverse problems and involves determining the probability distribution for the temperature in the entire range of the sounded altitudes. In this case, we use some assumptions on noise in the experimental data and available a priori information about the recovered profile. Using the proposed approach, we compare the recovery results for two methods of approximation and regularization of the recovered profile. It is shown that using the ground-based observations of solar radiation in the oxygen absorption line 27_, it is possible to recover the temperature profile in the altitude range 20–55 km.