A novel gas pressure sensor is designed and demonstrated experimentally, which is composed of a Fabry–Perot cavity based on a quartz capillary filled with polydimethylsiloxane (PDMS). The PDMS has excellent elasticity and is an ideal material for gas pressure sensing. The experimental results show that the sensor has a high sensitivity as the gas pressure increases (or decreases). When the gas pressure rises, the maximum sensitivity reaches the -15.95 nm/MPa. When the gas pressure drops, the maximum sensitivity reaches -23.1 nm/MPa. Experimental results show that there are large differences in the sensor sensitivity when the gas pressure rises or decreases, which may be related to the characteristics of the PDMS. The designed sensors have the advantages of simple and compact structure, low cost and high sensitivity, and have certain application prospects in engineering practice.
A novel gas pressure sensor based on Fabry-Perot interferometer is proposed and experimentally demonstrated. The sensor is fabricated by splicing the single-mode fiber onto a short length quartz capillary and coating a Polyimide film on the end-face of the quartz capillary. The total length of the sensor head is less than 60μm, compact structure which can be used flexibly in limited space and harsh environment. The experimental results show that the proposed sensor can detect the environment gas pressure by demodulating the wavelength drift of the reflection spectrum of the sensor. The maximum gas pressure sensitivity is 5.357nm/MPa, the linearity is 98.48% and the gas pressure measurement range is 0~0.3MPa. The sensor has the temperature sensitivity at low temperature, and it is insensitive to high temperature. Thus, the temperature cross-sensitivity can be ignored under the high-temperature conditions. The proposed sensor shows some advantages of compact size, high sensitivity, fast response time and low temperature cross-sensitivity, and it has a certain practical application value in industrial production and daily life.
Micro-hollow cathode discharge (MHCD), as a high-pressure glow discharge, has many applications in industry. Theclosed-MHCD is investigated experimentally in argon in the paper. The relations between breakdown voltages of glow discharge and gas pressure in argon are measured. Minimum breakdown voltages obtained, are about 520V at 200Torr argon. The differential resistivity of the voltage-current characteristics for all of the pressure studied is positive. Strong optical emission from the closed-MHCD is also observed. Measurement of electron temperature is carried out by optical emission spectroscopy. The electron temperature was about 1eV at the pressure from 200Torr to 760Torr and at the discharge current from 0.5mA to 10mA. An increase in pressure of the working gas leads to a slight decrease in electron temperature. The electron number density and gas temperature of closed-MHCD was investigated by diode laser atomic absorption spectroscopy. The gas temperature and the electron number density were evaluated from the analysis of the absorption line profiles, taking into account significant Stark broadening mechanisms. The gas temperature was found to increase with pressure from 1100K to 2100K. The electron number density was calculated from Stark broadening and shift, and it ranges from 7×1014 to 1.5×1015cm-3. Thus, the closed-MHCD is similar to MHCD, which has the non-equilibrium character with the advantage of high-pressure. And it can also be used for non-thermal plasma processing e.g. surface treatment, plasma chemistry and generation of UV and VUV radiation.
The new discharge system for RF-excited lasers is discussed in this paper, in which symmetric, homogeneous helical glow discharge by RF excitation can be got. The theoretical model based on the discharge system has been set up. The distributions of the electrical field and electron density inside the discharge tube are calculated. The advantages of the discharge system are consistent with the experimental results well.
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