KEYWORDS: Temperature metrology, Raman spectroscopy, Calibration, Signal attenuation, Raman scattering, Temperature sensors, Optical fibers, High temperature raman spectroscopy, Environmental sensing, Scattering
Temperature measurement system has been applied in industrial areas extensively. The fiber optic distributed temperature system is one of the most popular means. Measurement error is relatively large when using the distributed temperature sensors (DTS) based on Raman scattering to measure ambient temperature in harsh environments. In this paper, we propose a novel calibration technique to measure the temperature highly accurately over a wide range of temperatures. We also propose an improved double-ended configuration that is insusceptible to the differential loss change in the fiber. By using the improved double-ended configuration, through the anti-Stokes and Stokes signal intensity comparison, the differential mode signal loss in the temperature measurement can be suppressed in optical fiber. So, the measurement results of automatic calibration are irrespectively with the wastage of optical fiber sensors. The result shows that we can obtain the temperature parameters accuracy in wide temperature range, and temperature measurement system has high robustness in harsh environments, suitable for field use.
A new approach to obtain glow discharge in working mixtures of non-chain HF laser has been brought forward. The
most advantage of the approach is without pre-ionization, so the contamination of pre-ionization will not happen and the
laser equipment is compact and simple. It is found, if the cathode surface is equally rough, we can obtain uniform
volume-discharge in SF6 mixtures without any pre-ionization, and dispense with uniform electric field electrode profile.
The form of Self-Sustained Volume Discharge (SSVD) is a Self-Initiated Volume Discharge (SIVD). We show here the
possibility of obtaining SIVD with a uniform energy deposition in a system of electrodes with non-uniform electric field.
Experiments show that, with rough cathode and even anode, a volume discharge is forming in non-uniform electric-field
without pre-ionization in SF6 and C2H6 mixtures. At the beginning of the discharge, many diffuse channels attached to
bright circular cathode spots, then, diverge towards the anode, with the channels overlapping, form a spatially uniform
glow discharge. SIVD has been performed at a total mixture pressure up to 8kPa and energy deposition up to 200J/l. We
also report measurements of the V-I characteristics of SIVD with SF6 and C2H6 mixtures at pressure up to about 8kPa.
The experimental results indicate that SSVD in SF6 and C2H6 mixtures develops in the form of SIVD is promising for
creation of high energy and pulse-periodic HF laser.
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