High pressure measurement with simple piston gauge in static condition

This paper describes the characterization of the newly developed piston gauge pressure standard at the National Physical Laboratory (NPL), with particular reference to its fall rate, engagement length of the piston and the deceleration rate for the measurement of hydraulic hydrostatic pressure up to 60 MPa. The low pressure effective area of the gauge derived from its dimensional measurements when compared with the value obtained by its direct calibration against NPL transfer pressure standard agrees within 0.025%. The pressure gauge is quite stable, reproducible and has a sensitivity of 3 ppm. Though the theoretically calculated value of the pressure coefficient is low as compared to the experimentally observed one in its absolute terms, the pressure dependent effective area agrees within ± 0.025% over whole of the pressure range which is well within the uncertainty statement of the two independent techniques used.     

Quartz as a pressure sensor in the infrared

The pressure dependence of the 795 cm^?1 mode of quartz has been measured in the infrared up to 20 GPa at 300 and 400 K. For the measurements, which are impossible with a laser light, on photo sensitive or biological samples, we propose to use the pressure dependence of this mode as a pressure gauge.     

Direct measurement of subglottic pressure and laryngealresistance in normal subjects and in spasmodic dysphonia

This study tested the accuracy of indirect methods of measurementof laryngeal airway resistance in normal subjects and in spasmodic dysphonia (SD). The indirect method assumes that subglottic air pressure remains constant during the voiced segment of a syllable. In this study subglottic air pressure was directly measured via puncture of the cricothyroid membrane in seven normal subjects and seven subjects with SD. The true laryngeal airway resistance was calculated and compared with airway resistance measured using indirect techniques based on intraoral air pressure. In five of the seven normal subjects, subglottic air pressure did not remain constant during the voiced segment. As a result, the error produced using indirect method of calculating average laryngeal resistance for the normal subjects varied from −44% to +50%. For SD subjects the error ranged from −49% to +22%. In general, the indirect technique over-estimated laryngeal airway resistance in normal subjects and underestimated the resistance in subjects with SD.     

Ruby-spheres as pressure gauge for optically transparent high pressure cells

Abstract

Ruby is widely used as an in siru pressure gauge for optically transparent pressure cells up to the megabar range. Usually ruby chips cut from bulk crystals are used which are ill-characterized and inconvenient to handle and to identify visually. Here we present a systematic study on corundum samples doped with Cr³⁺ ions with concentration from 60 to 23500 ppm to determine the optimal conditions for the use as an accurate pressure marker. The influence of the excitation wavelength on the luminescence spectra was investigated. These studies led to the synthesis of small (1–50 micrometer) ruby spheres with 3000 ppm chromium concentration. After annealing and a heat treatment to avoid internal strains we find reproducible values of the position and the width of the fluorescence lines. These ruby spheres are not only well suited for a reliable and accurate pressure determination in experiments using diamond anvil cells, but can also be used as an in sihr micro-thermometer in high pressure-low temperature studies.     

297 K和0.13～1 GPa压力下菱镁矿的拉曼光谱实验研究

在T=297 K,130 MPa＜P＜967 MPa下用拉曼光谱对菱镁矿1 094 cm-1峰随压力变化关系进行了测量,结果表明随着压力增大,1 094 cm-1峰往高波数方向移动,其波峰位置与压力关系为：ν(cm-1)=0.007 44×P(MPa)+1 093.3。在T=297 K,130 MPa＜P＜967 MPa时,菱镁矿可用作地质压力计。压力与菱镁矿1 094 cm-1峰偏移量关系为：P(MPa)=125.8×(Δν_p)_{1 094}+124.7,(1 094 cm-1＜ν_p＜1 101 cm-1)。在实验的压力范围内未观察到菱镁矿的相变和有机物的生成。     

Exploiting optical properties of nanopolycrystalline diamond in high pressure experiments

ABSTRACT

We investigated the optical properties (absorption, luminescence and Raman spectra) of nanopolycrystalline diamond (NPD) aiming at exploring its capabilities as a pressure sensor and as a pressure-cell anvil for combined X-ray/neutron and optical studies. Notably, we analysed the Raman peak shift and broadening with pressure using a Moissanite Anvil Cell (MAC). The results are compared with those obtained in a DAC, where Raman signals from NPD chips and diamond anvils strongly overlap. Its pressure behaviour in the hydrostatic and non-hydrostatic regimes were investigated. We showed that the nanopolycrystalline structure induces remarkable differences in the peak shift and broadening between NPD and natural type IIa single-crystal diamond, making NPD suitable as pressure gauge for pressure determination and testing hydrostaticity of pressure transmitting medium.     

低压载人试验舱复压系统的气动特性计算和声学设计

随着我国高山医学和航空航天生物学研究的发展，低压舱的设计与建造已提到了议事日程。低压载人试验舱要为科学家提供合适的低压条件，同时又要为乘员创造必要的工作生活环境包括声学环境，本文介绍低压舱舱内气动状态的计算方法和复压系统的声学设计，并给出计算实例。     

Elastic distortions in simple piston-cylinder units at pressures up to 100 MPa

Abstract

The study of elastic distortions in piston-cylinder units of primary standards piston gauges is of importance for the improvement of pressure measurement accuracy. Preliminary work (GF. Molinar et al., 1989) on distortion calculations was carried out on a tungsten carbide (t.c.) piston-cylinder of 0.2 cm² nominal effective area in the 100 MPa pressure range. The same calculations are now applied in the study of a similar piston-cylinder unit of hard steel (h.s.). The distortions on the outer surface of the cylinder are measured with strain gages and with a capacitance sensor. The calculated distortions, which can be also derived with other methods (G. Klingenberg 1989, R. Wisniewski et al. 1989), are compared with the experimental results obtained on the outer surface of the cylinder. The present two piston-cylinder units of h.s. and of t.c. were cross-floated up to 100 MPa and the ratio R = f(P) = Ae_h.s./Ae_t.c. obtained experimentally is compared with the calculated.     

Polarization maintaining index-guided photonic crystal fiber sensor for slowly varying pressure measurement

The paper presents an experimental investigation of slowly varying pressure measurement using the polarization maintaining photonic crystal fiber (PCF) sensor. Versatility of the sensor has been proved by analyzing its response for various types of time varying pressure profiles viz. exponentially decaying, sinusoidally varying and linearly increasing pressure. Temporal behavior of the sensor has been fully characterised. Dependence on temperature has been explored and it is found that the sensor is an attractive choice for applications in harsh environments.     

Generation of very high pressure pulses at the surface of a sandwiched piezoelectric material

New clinical concepts in lithotripsy demand small shock heads. Reducing the size of piezoelectric shock heads will only be possible if the pressure generated at the surface of each transducer can be increased so that the total pressure at the focus remains very high. We propose for the first time to increase the pressure without increasing the transducer voltage by using sandwiched transducers, which are a combination of several stacked transducers. When excited at appropriate time intervals, the pressure waves generated by each one reinforce when they reach the load. This new technique has been successfully tested. A pressure of 2.5 MPa was generated with two stacked, 5 mm-thick 1-3 piezocomposite transducers operating at an excitation voltage of 8 kV. No transducer damage was detected after 10(6) shocks, which corresponds approximately to the treatment of 500 patients.     

29 ℃和0～1.0 GPa压力下丙三醇的拉曼光谱研究

利用氧化锆压腔在0～1.0 GPa和29 ℃条件下对液态丙三醇进行了拉曼光谱测量。实验结果表明,丙三醇的拉曼位移在2 800～3 000 cm-1范围内的CH和CH₂的伸缩振动谱峰随着压力的增大均连续向高波数位移,其拉曼位移与压力的关系可以表示为：ν_(CH)=0.009 2P+2 886.67和ν_(CH2)=0.009 4P+2 948.53。另一方面处理实验结果时发现,在0～1.0 GPa下丙三醇的ν_(CH2)拉曼位移可以进行压力标定,给出了以丙三醇作为压力标定计时的压力标定方程：P=106.4ν-3.14×105。     

Effect of liquid phase on the triple point pressure of argon

We report here a systematic data analysis of the vapour pressure of argon at different amounts of the liquid phase to understand the thermodynamic behaviour of this inert gas around triple point. At the triple point plateau, the applied heat pulse melts a certain phase of solid argon into liquid and increases vapour pressure. It is observed that this vapour pressure attains the thermodynamic equilibrium pressure after a certain time interval. The expoential decay of the vapour pressure as a function of time at different fractions of the liquid phase shows two different features. In one region, the relexation time constant (τ) is low and is not varying with the liquid phase, while in the other region the value ofτ increases with the amount of the liquid phase. Further, the peak pressure from the equilibrium pressure (ΔP _h), obtained from the fitting parameters, shows a dip at around 50% of the liquid phase. A qualitative physical interpretation has been given to explain these results.     

高压下正己醇的拉曼光谱研究

利用碳化硅压腔在25 ℃和163.4～793.4 MPa条件下对正己醇进行了拉曼光谱研究。发现在163.4～767.6 MPa压力下正己醇性质稳定,没有相变发生。在此压力条件下,CH对称伸缩振动和反对称伸缩振动的波峰都随着压力的增大而向高波数偏移,拉曼位移与压力的关系分别为ν_{2 876}=0.009 1P+2 875.1和ν_{2 931}=0.005 7P+2 930.5。到793.4 MPa压力条件下出现了结冰现象。在前人资料的基础上,对甲醇、乙醇和正己醇等醇类的高压性质进行了对比,发现CH对称伸缩振动的波峰偏移与压力的关系不受CC键的影响,即与碳原子数无关。     

Adiabat-reduced isotherms at 100 GPa pressures

The method of deriving shock wave reduced isotherms (SWRIs) as pressure standards up to 150 GPa in a diamond anvil cell (DAC) is discussed. This method is applicable to any adiabatic compression. Hugoniots and isentropes can both be used as reference curves in this analysis. While only Hugoniots have been used to date, isentropes will probably be used in future to develop standards above ～ 200 GPa. Accuracies of SWRIs of Al, Cu, Ta, W, Au, Mo, and Pt are discussed. Hugoniots of diamond and MgO are in excellent agreement with their respective isotherms measured in DAC up to 140 and 55 GPa, respectively. The equation of state of a weakly compressible material is sensitive to pressure and weakly sensitive to temperature. Thus, strong crystals, such as diamond, MgO, and BN, can be used as pressure standards and temperature can be measured independently. Future experiments to improve accuracies of static-pressure standards are suggested.     

The measurement of differential EXAFS modulated by high pressure

Differential EXAFS (DiffEXAFS) is able to detect subtle atomic perturbations in the local area of the absorbing atom. Here a new method of performing DiffEXAFS experiments under the modulation of high pressure has been developed. Periodic pressure was achieved in the gasket with the help of a dynamic diamond anvil cell, and the measurements were conducted in common energy‐scanning mode. This technique has been utilized on ZnSe at 4.8 GPa. The present results have demonstrated a good agreement with the equation of state of ZnSe, and revealed sensitivity to atomic displacements of one order higher in magnitude than that of conventional EXAFS.     

新型压差式吸附式制冷机的设计

设计了一种以太阳能为驱动力,利用渗透压将水分从蒸发器端传输到冷凝器端的压差式吸附制冷机.水分先在蒸发器端被吸附板吸收,再通过渗透压自动运输到最后环节段,并被膨胀物质间歇式地挤压出吸水材料,进入冷凝器,从而保证水分不断从蒸发器抽出,产生制冷效果.通过改变太阳能制冷系统的四通换向阀的开启方向,实现吸附式制冷系统的连续制冷.     

A simple technique for laser-induced ablation pressure measurement

A simple method for measuring laser-induced ablation pressure is described. The technique utilizes the well-known double foil concept. In the present experiment the impact times were estimated by monitoring the reflectivity of the impact foil rear. The measurements were performed using a glass laser (1·06 μm wavelength) in the 10¹¹−10¹³ W/cm² irradiance range. Experimental results showed good agreement with those obtained using other techniques as also those with the self-regulating ablation model prediction.     

HL-2A装置偏滤器室中性气体压强的初步研究

HL-2A装置上首次实现了偏滤器位形放电。采用专门研制的可在强磁场和强噪声环境下工作的快响应真空电离规对偏滤器室内的中性气体压强进行了测量,给出了HL-2A装置偏滤器有关结构的基础数据。初步研究了偏滤器位形和孔栏位形放电期间偏滤器室中性气体压强的特性。     

Accurate measurement of pressure differences and the effect of baffle on pressure distribution in vacuum chamber during dynamic gas flow

The need to know the pressure in relatively large vacuum chambers arises at different measurements (calibration of vacuum gauges, outgassing measurements, etc.) and investigating the ways to minimize these pressure differences are of equal importance in such industrial as well as research applications. The experimental determination of the pressure differences between various gauge positions in a chamber of cylindrical shape and the effect of a baffle on pressure distribution are described in the paper. The pressure in the chamber was generated dynamically in the pressure range 0.1–133 Pa through adjustable gas flow into the chamber. Five identical capacitance diaphragm gauges (CDGs) were used in which one CDG remained fixed at the central position of the chamber while the other four (in two pairs) were mutually interchanged. The differences on the order of several percent between positions at different levels were calculated and the effect of the baffle was investigated which are specific for this chamber.     

Principle of temperature,velocity and pressure of upper atmospheric wind measurement for the Voigt profile

Using the accurate expression of the Fourier transform of the pure Voigt spectral line profile, we present the principle of the passive optical method to measure temperature, velocity, and pressure of atmospheric wind for the Voigt profile. Through discussion, from the Gaussian, Lorentzian and Voigt profiles, we find that velocity will not be affected, pressure can be derived for Lorentzian and Voigt profiles, and temperature will be affected greatly. By simulation and comparison, we find that temperature derived from the Voigt profile is greater than that from the Gaussian profile, and it is less than that from the Lorentzian profile. This discussion will be significant in accurate upper atmospheric wind measurement.