High temperature, wireless seismometer sensor for Venus
Space agency mission plans state the need to measure the seismic activity on Venus. Because of the high temperature on Venus (462°C average surface temperature) and the difficulty in placing and wiring multiple sensors using robots, a high temperature, wireless sensor using a wide bandgap semiconductor is an attractive option. This paper presents the description and proof of concept measurements of a high temperature, wireless seismometer sensor for Venus. A variation in inductance of a coil caused by the movement of an aluminum probe held in the coil and attached to a balanced leaf-spring seismometer causes a variation of 700 Hz in the transmitted signal from the oscillator/sensor system at 426°C. This result indicates that the concept may be used on Venus.
The leaf-spring seismometer: Design and performance
abstract A small vertical seismometer whose inertial mass is supported by a leaf spring has been developed as a replacement for conventional long-period (LP) seismometers. The mechanical sensor has a virtually infinite natural period and is operated in a force-balance feedback configuration with an overall response identical to that of a 20-sec LP seismometer. Main considerations in the design were economic production and efficient shielding against environmental disturbances. The sensor is thermally coupled to the ground and protected from atmospheric pressure variations by a vacuum bell. This allows increasing the useful gain at very long periods by two orders of magnitude compared to a standard LP seismograph. The instruments resolve ground noise at least from a 0.3- to 300-sec period (typically, from about 0.1 to 3000 sec) and have a dynamic range of 140 dB. Leaf-spring seismometers have been tested since 1976 as part of wideband, LP, and very LP seismographs. Matching horizontal sensors are also available. This paper discusses the design principles and the initial calibration, and presents test results and typical seismograms.
Changes in Quartz During Heating and the Possible Effects on Si Production
In Si and FeSi production, the main Si source is SiO2, in the form of quartz. Reactions with SiO2 generate SiO gas that further reacts with SiC to Si. During heating, quartz will transform to other SiO2 modifications with cristobalite as the stable high-temperature phase. Transformation to cristobalite is a slow process. Its rate has been investigated for several industrial quartz sources and has been shown to vary considerably among the different quartz types. Other differences in behavior during heating between these quartz sources, such as softening temperature and volume expansion, have also been studied. The quartz-cristobalite ratio will affect the rate of reactions involving SiO2. The industrial consequences and other implications of the observed difference between quartz types are discussed. Initial studies of industrial quartz were published by Ringdalen et al. In the current work, a new experimental method has been developed, and an investigation of several new quartz sources has confirmed the earlier observed large variation between different sources. The repeatability of the data has been studied and the effect of gas atmosphere investigated. The results from the earlier work are included as a basis for the discussion.