Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge,in which streamers start from a diffuse spark channel having a curved sh...Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge,in which streamers start from a diffuse spark channel having a curved shape at a high repetition rate of voltage pulse.In this work,to estimate the electron concentration in the plasma forming the apokamp a digital holographic laser scanning method is applied for the first time.The method is based on a comparison of the phases of two optical wavefronts,registered at different time instants in the form of digital holograms.The result of the phase comparison between the wavefronts is presented in the form of a numerically calculated map of the phase difference of the reconstructed wavefronts.A gas-discharge plasma is a phase(transparent)object,and the interference fringes are formed as a result of the change in the refractive index introduced by the plasma with respect to the original unperturbed medium.The obtained value of the refractive index allows estimation of the concentration of electrons in the spark channel plasma.It is shown that at as the voltage pulse repetition rate increases from 5 to 50 kHz the concentration of electrons in the plasma forming the apokamp decreases by an estimated four times.展开更多
In this paper,we propose a dual-wavelength digital holographic interferometry method based on a compact dual vertical-cavity surface-emitting laser(VCSEL)source.The source simultaneously emits light from two highly st...In this paper,we propose a dual-wavelength digital holographic interferometry method based on a compact dual vertical-cavity surface-emitting laser(VCSEL)source.The source simultaneously emits light from two highly stabilized coherent light sources with slightly different wavelengths.A highly stabilized and adjustable current source enables the application of digital holographic dual-wavelength techniques to measure the shape of an object with height steps of a few millimeters.The wavelength drift over 12 h over the entire measurement range,which was evaluated using a wavemeter,was smaller than 1 pm.In addition to the low measurement uncertainty at large height jumps,the dual-wavelength digital holographic system distinguishes itself by its robustness to environmental disturbances such as air turbulence,heat load,and/or mechanical vibrations.This is enabled via a fiber-based almost common-path single-shot digital holographic acquisition of the information of the two different wavelengths using angular multiplexing.The experimental setup and data evaluation are discussed,and we present measurements of non-cooperative objects with specular reflective and/or diffuse reflective surfaces having different colors.展开更多
基金performed in accordance with the support of the Russian Science Foundation(RSF)(No.23-79-00023)。
文摘Streamer discharges that do not transition to a spark channel are now being widely investigated.One of these discharges is the apokamp discharge,in which streamers start from a diffuse spark channel having a curved shape at a high repetition rate of voltage pulse.In this work,to estimate the electron concentration in the plasma forming the apokamp a digital holographic laser scanning method is applied for the first time.The method is based on a comparison of the phases of two optical wavefronts,registered at different time instants in the form of digital holograms.The result of the phase comparison between the wavefronts is presented in the form of a numerically calculated map of the phase difference of the reconstructed wavefronts.A gas-discharge plasma is a phase(transparent)object,and the interference fringes are formed as a result of the change in the refractive index introduced by the plasma with respect to the original unperturbed medium.The obtained value of the refractive index allows estimation of the concentration of electrons in the spark channel plasma.It is shown that at as the voltage pulse repetition rate increases from 5 to 50 kHz the concentration of electrons in the plasma forming the apokamp decreases by an estimated four times.
文摘In this paper,we propose a dual-wavelength digital holographic interferometry method based on a compact dual vertical-cavity surface-emitting laser(VCSEL)source.The source simultaneously emits light from two highly stabilized coherent light sources with slightly different wavelengths.A highly stabilized and adjustable current source enables the application of digital holographic dual-wavelength techniques to measure the shape of an object with height steps of a few millimeters.The wavelength drift over 12 h over the entire measurement range,which was evaluated using a wavemeter,was smaller than 1 pm.In addition to the low measurement uncertainty at large height jumps,the dual-wavelength digital holographic system distinguishes itself by its robustness to environmental disturbances such as air turbulence,heat load,and/or mechanical vibrations.This is enabled via a fiber-based almost common-path single-shot digital holographic acquisition of the information of the two different wavelengths using angular multiplexing.The experimental setup and data evaluation are discussed,and we present measurements of non-cooperative objects with specular reflective and/or diffuse reflective surfaces having different colors.
