Electron Temperature Probe Research Articles

Effect of Direction of Magnetic Field and Probe Surface on Measurement of the Electron Density by Electron Density and Temperature Probe

The electron density and temperature probe (EDTP) was proposed by Oyama and others instead of a Langmuir probe that is the conventional measurement tool of an ionosphere measurement. The EDTP is the most reliable instrument to measure the electron density and temperature of ionosphere. The EDTP sweeps high frequencies which were applied to a probe and measures the resonance frequency of a plasma in the electron density measurement. The plasma of ionosphere is influenced by the magnetic field of the Earth. Therefore, the electron density varies by the relationship between the plane of the probe and the directions of the magnetic field. We generated a plasma in the space plasma chamber and changed the magnetic field of the chamber using a Helmholtz coil. In this study, we investigated the effects that are caused by the electron density in the direction of the magnetic field. As a result, we found the electron density become very high when the magnetic field was applied to the direction of the front of the disk probe.

Improvements to the Whoosh Bottle Rocket Car Demonstration

The whoosh bottle rocket car has been redesigned to be more reusable and more robust, making it even easier to use as a demonstration. Enhancements of this demonstration, including the use of heat sensitive ink and electronic temperature probes, enable users to find warmer and cooler regions on the surface of the whoosh bottle.

Electron temperature and density probe for small aeronomy satellites.

A compact and low power consumption instrument for measuring the electron density and temperature in the ionosphere has been developed by modifying the previously developed Electron Temperature Probe (ETP). A circuit block which controls frequency of the sinusoidal signal is added to the ETP so that the instrument can measure both T(e) in low frequency mode and N(e) in high frequency mode from the floating potential shift of the electrode. The floating potential shift shows a minimum at the upper hybrid resonance frequency (f(UHR)). The instrument which is named "TeNeP" can be used for tiny satellites which do not have enough conductive surface area for conventional DC Langmuir probe measurements. The instrument also eliminates the serious problems associated with the contamination of satellite surface as well as the sensor electrode.

Plasma Measurements in the Space Plasma Operation Chamber (SPOC)

Plasma with a temperature and density similar to the ionospheric plasma is produced in the Space Plasma Operation Chamber (SPOC). SPOC, constructed at NCKU in 2009, is a research plasma device designed for the calibration and testing of satellite/rocket-borne instruments and for studying space plasma processes. It is a cylindrical chamber 2 meters in diameter and 3 meters in length. The vacuum pressure inside the SPOC can reach 10^(-8) Torr. The plasma in this large vacuum space is produced by two back-diffusion type plasma sources installed at the center of the chamber side doors. The sources produce ions of controllable drifting energy from a few ten eV to several hundred eV, these ions, together with the thermal electrons emitted from nickel cathodes, collide with neutral molecules at a pressure of 10^(-4) Torr in the chamber and form the plasma environment. The plasma density varies from 10^3 to 10^6 cm^(-3), and the neutral density is ~1012 cm^(-3). The electrons have a Maxwellian distribution with a temperature in the range 1000-3000 K. The ions have two component distributionsP: one is the drift-Maxwellian component with temperature close to the neutral particle temperature (room temperature), and the other is a small ion beam component. We have developed several space instruments for testing in the SPOC. This paper describes the SPOC machine and its capabilities for plasma experiments and space environmental tests. The plasma environment in the SPOC is measured by the Langmuir probe, the retarding potential analyzer, and the electron temperature and density probe. Results measured by different instruments are compared and discussed. The thermal and beam components of the ion energy distributions at different positions and the electron temperature and density spatial distributions are shown and discussed. The SPOC can be used to develop space-borne instruments and plasma thrusters, check the performance of instruments before flight, check whole payload systems in the plasma and vacuum environment, and conduct basic plasma experiments related to space sciences.

The effectiveness of domestic cook on inactivation of murine norovirus in experimentally infected Manila clams (Ruditapes philippinarum)

The aim of this work was to evaluate the efficacy of domestic cooking in inactivating Manila clams experimentally infected with murine norovirus (MNV). A cooking pan was modified to enable electronic temperature probes to be positioned to record both flesh and environment temperature. Manila clams were infected with 10(4) TCID 50% ml(-1) of MNV. The infected whole-in-shell clams, divided into three replicates, were cooked on an electric stove, and groups of nine clams were removed from the pan at fixed intervals. Pools of three digestive glands were examined by virus isolation to ascertain residual viral load. Results showed that 10 min of cooking by a traditional domestic method at a temperature close to 100°C, for at least 2 min, can completely devitalize the MNV in infected clams. This is generally the time needed for the majority of valves to open up. At present, it is highly recommended to label all lagoon products as 'requiring cooking before consumption', but no specifications are given on how long and at what temperature they should be cooked. Our results can provide the consumer with useful indications on how to cook clams to prevent any risk of foodborne illness.

Langmuir probe experiments on Korean satellites

We report in this paper the test results of the Langmuir Probes (LPs) that have been used on several Korean low earth orbit (LEO) satellites since 1999. The probes were designed to measure the electrons in the density range of ∼104 to ∼106/cm3 and temperatures less than ∼104 K, which are the typical characteristics of the upper ionosphere. Careful considerations were given to the probe design to reduce many error sources. For example, a 10 Hz fast voltage sweep was applied to the probe to minimize measurement errors caused by probe contaminations. An electron temperature probe was installed in addition to the LP on the KOMPSAT-1, and the electron temperatures measured simultaneously and independently by the two instruments were compared. The results showed good agreement, which confirms the validity of the LP data obtained from these Korean satellites.

Free Flap Monitoring Using Skin Temperature Strip Indicators: Adjunct to Clinical Examination

Sir: Free tissue transfer procedures are performed with high levels of success today. Accurate postoperative flap monitoring is critical for favorable surgical outcome. Serial clinical surveillance by an experienced microsurgeon remains the standard of care for free flap monitoring. Unfortunately, this is neither practical nor always possible; therefore, additional medical caregivers are taught this art. In our practice, we have a dedicated hospital wing with experienced nurses monitoring the flaps in the postoperative setting. In most hospital environments, shift-changing nurses, residents, medical students, nurses’ aides, and even family members are educated about flap monitoring in an abbreviated manner. Morning rounds can be greeted with unpleasant surprises. To make free flap monitoring more reliable, various “technological advances” for flap monitoring have been developed to complement clinical evaluation. Technological tools available include laser Doppler imaging, fluorescein blue mapping, lactic acid elevation, photoplethysmography, differential thermometry, dermofluorometry, radioactive microspheres, electromagnetic flowmetry, and internal Doppler devices.1 Many of these techniques are impractical, unavailable, and expensive. Surface temperature recordings for flap monitoring have been reported to be successful.2,3 Electronic temperature probes are clinically available and require additional leads to be attached to the flap skin island and surrounding skin. Using this cumbersome technique, the patient is soon wrapped in a web of electrocardiographic and temperature probe leads. A simpler solution is the use of anesthesia skin temperature strip indicators (Sharn Anesthesia, Inc., Tampa, Fla.), which can be placed on both the patient’s flap skin island and native skin without much trouble (Fig. 1). These temperature strips detect temperature changes of 2ºC. Medical personnel can use this additional flap monitoring method along with clinical and Doppler examination. Our experience using temperature strips to monitor perforator flaps is similar to that in the 1979 report by Baudet et al. using infrared thermograms to monitor groin (known today as superficial inferior epigastric artery) free flaps.4 It is common to observe a 2ºC to 3ºC difference between flap and control temperatures in the early postoperative setting. However, an acute drop of 3ºC at the center of the skin island is indicative of arterial thrombosis, whereas a 1ºC to 2ºC uniform drop over of the flap is indicative of venous compromise. Temperature strips can detect these changes with effectiveness equal to that of electronic temperature monitoring.Fig. 1.: Temperature strip monitoring after deep inferior epigastric perforator microsurgical breast reconstruction.This adjunctive technique is simple and inexpensive ($1 per strip). We advocate that this technique complement but not replace traditional clinical and handheld Doppler examination. Despite 30 years of greater flap physiology understanding, flap monitoring continues to require competent human clinical judgment. Improved flap monitoring education for all medical personnel makes for restful evenings. Ernest S. Chiu, M.D. Andrew Altman, M.D. Tulane Health Sciences Center New Orleans, La. Robert J. Allen, Jr., B.S. Robert J. Allen, Sr., M.D. Center for Microsurgical Breast Reconstruction Charleston, S.C.

Study on plasma discharge parameters in double-glow plasma surface alloying furnace

Double Langmuir probe technique was used for plasma diagnostics of discharge process in double-glow plasma alloying furnace. Investigated that the effect of changes of voltage of the source pole and air pressure on plasma parameters. Results show that plasma density increases, electron temperature decreases and potential of the probe decreases, with the rise of voltage of the source pole under condition of fixed cathode potential and fixed air pressure. During increasing of air pressure in furnace, electron temperature decreases and probe potential increases. The change of probe potential is smart at start of the measuring and probe potential goes to stabilization only when degas process goes to finishing.

Ion loss on Mars caused by the Kelvin–Helmholtz instability

Mars Global Surveyor detected cold electrons above the Martian ionopause, which can be interpreted as detached ionospheric plasma clouds. Similar observations by the Pioneer Venus Orbiter electron temperature probe showed also extreme spatial irregularities of electrons in the form of plasma clouds on Venus, which were explained by the occurrence of the Kelvin–Helmholtz instability. Therefore, we suggest that the Kelvin–Helmholtz instability may also detach ionospheric plasma clouds on Mars. We investigate the instability growth rate at the Martian ionopause resulting from the flow of the solar wind for the case where the interplanetary magnetic field is oriented normal to the flow direction. Since the velocity shear near the subsolar point is very small, this area is stable with respect to the Kelvin–Helmholtz instability. We found that the highest flow velocities are reached at the equatorial flanks near the terminator plane, while the maximum plasma density in the terminator plane appears at the polar areas. By comparing the instability growth rate with the magnetic barrier formation time, we found that the instability can evolve into a non-linear stage at the whole terminator plane but preferably at the equatorial flanks. Escape rates of O + ions due to detached plasma clouds in the order of about 2 × 10 23 – 3 × 10 24 s - 1 are found. Thus, atmospheric loss caused by the Kelvin–Helmholtz instability should be comparable with other non-thermal loss processes. Further, we discuss our results in view of the expected observations of heavy ion loss rates by ASPERA-3 on board of Mars Express.

Plasma erosion in the Venus nightside ionosphere

Pioneer Venus Orbiter (PVO) data from the orbiter electron temperature probe (OETP) measurements show that near the midnight plane the electron density profiles in the upper ionosphere are different from those obtained throughout most of the nightside hemisphere. The density profiles near the midnight plane have a near constant density plateau that extends from very low (∼200 km) altitudes located near the PVO trajectory periapsis up to the ionopause crossing that may reach high (∼2300 km) altitudes. Such profiles are interpreted in terms of ionospheric plasma that has been dragged by the solar wind that streams over the nightside ionopause and also within the polar plasma channels. The latter features are produced by the solar wind that carves out the upper ionospheric plasma near the magnetic polar regions and can account for the presence of the ionospheric holes detected in the nightside hemisphere. The solar wind-directed displacement of the ionospheric plasma in the vicinity of the plasma channels results from the transfer of the momentum of the solar wind that moves within them. Data compatible with the view that the PVO moved within a plasma channel before entering the ionosphere (ionosheath–channel–ionosphere transit) are also examined. It is shown that the orientation and intensity of the magnetic field within the channels is similar to the values observed in the ionospheric holes and it is argued that these conditions are set by the magnetic field that accumulates within the channels in response to the thermal pressure made by the solar wind on the polar upper ionosphere. The temperature of the hot electron component in the holes (channels) is much smaller than that in the ionosheath flow because a large fraction of the latter thermal energy density may be replaced by the magnetic energy density of the (∼30 nT) magnetic field that accumulates within the channels and that is measured within the holes.

Plasma distribution at Venus and Ionospheric magnetic fields: Implication for Mars

[1] Magnetometer measurements on the Pioneer Venus Orbiter, (PVO), have shown the presence of large-scale steady horizontal magnetic fields in the dayside ionosphere of Venus during episodes of high solar wind dynamic pressure, Psw. These horizontal magnetic fields are expected to inhibit plasma diffusion and modify the plasma distribution from a diffusive equilibrium type profile to a “depressed” type profile. We have analyzed electron and ion density profiles measured by the electron temperature probe and ion mass spectrometer for several orbits having large scale horizontal magnetic fields. We find that the observed density profiles are nearly similar to those expected under diffusive equilibrium, thereby suggesting that these fields perhaps do not inhibit diffusion. This observation has a major consequence for Mars ionosphere where the observed electron density profiles are of “depressed” type and have been explained on the basis of horizontal magnetic fields measured by the MAG/ER experiment on Mars Global Surveyor, spacecraft.

Spacecraft Charging for Microsatellite KITSAT-3

Floating potentials for a microsatellite KITSAT-3 are measured with an electron temperature probe. The orbit of the satellite is 730-km altitude, sun-synchronous, with a fixed local time of descending node near 1200 hrs local time. The dimension of the satellite in stowed configuration is approximately 495 × × 614 × 852 mm 3 . The weight of the satellite is 112 kg. In the dayside, a series of attitude maneuvering is performed to rotate the satellite. Significant correlation between the currents generated from the solar arrays and the floating potentials is found. The initial floating potentials that are largely negative (<−10 V) when the solar arrays are directed toward the sun are found to increase up to ∼ ∼− 3V as the rotation of the spacecraft brings the solar arrays nearly perpendicular to the sunlight. The result of the potential variation is verified by a numerical simulation with NASCAP/LEO. The present investigation finds that the floating potentials for a microsatellite KITSAT-3 are determined by the negative charging of the satellite due to the presence of solar arrays. Nomenclature AC = conductive area of the satellite body, m 2 AS = surface area of the satellite, m 2 AW = conductive area of interconnectors, m 2 B = magnetic field, nT e = electron charge, 1.60 × 10 −19 C I = current, A ISC = current collected in the ram direction by the orbital motion of the satellite, A ITH = current collected due to the satellite potential, A k = Boltzmann constant q= charge, C Vp = satellite potential, V Vpp = peak-to-peak voltage, V Vsc = orbital speed of satellite, m/s α = angle between the orbital velocity and the normal vector of the conductive surface �� = potential difference between the solar cells, V θ = angle of satellite orientation relative to the orbital velocity, deg

Electronic ventilator temperature sensors as a potential source of respiratory tract colonization withStenotrophomonas maltophilia

Stenotrophomonas maltophilia (S. maltophilia) is an important cause of nosocomial infection among ventilated and immunocompromised patients, and among patients receiving broad-spectrum antimicrobials. We report a cluster of patients in a surgical intensive care unit who were colonized or infected with S. maltophilia. An epidemiological investigation was initiated after surveillance data revealed that eight patients were culture-positive from sputum for S. maltophilia in the preceding month. Review of respiratory care procedures revealed that when mechanical ventilators were serviced between patients, the electronic temperature probes used with servo-controlled humidifiers were wiped with inadequate disinfection. We collected cultures of case-patient room surfaces, sinks and ventilator equipment. S. maltophilia was recovered from room surfaces, ventilator expiratory circuits and a temperature sensor which had been kept in ambient air after disinfection. Patients and environmental isolates were examined by RAPD-PCR. Three clinical isolates and one environmental isolate had the same profile, which suggests cross-contamination or common source exposure. The outbreak was controlled by adequate disinfection of the temperature sensors. No single epidemic strain was identified but several observations support the conclusion that the temperature probes contributed to the outbreak.

Electron temperature probe onboard Japan’s Mars orbiter

Japan’ s first Mars spacecraft PLANET-B was successfully launched on 4th of July, 1998 and was named “NO-ZOMI” after the launch. One of the scientific instruments is a unique electron temperature probe which was developed in Japan and has been used for more than 20 years on sounding rockets as well as on scientific satellites (Oyama, 1991). The electron temperature probe dubbed PET (Probe for Electron Temperature measurements) consists of two planar electrodes, 150 mm in diameter, placed at the edges of the two solar cell panels of the “NOZOMI” spacecraft. Electron temperatures can be measured in plasmas with densities exceeding 1000 cm−3 with sufficient accuracy. The maximum sampling rate of 8 data points per satellite spin for each probe allows high resolution measurements (i.e., an angular resolution around the spin axis of 23 degrees). Additionally, the probe can measure the anisotropy of the electron temperature, if it exists. It is also possible to infer the existence of nonthermal electrons.

A comparison of solar EUV flux from Langmuir probe photoelectron measurements on the Pioneer Venus Orbiter with other solar activity indicators

The electron temperature probe acted as a photo-diode on the Pioneer Venus Orbiter (PVO) and measured the integrated solar EUV flux (I pe) over a 13 year period from January 1979 to December 1991, thus covering the declining phase of solar cycle 21 and the rising phase of solar cycle 22. Gross features in the solar activity variations of this flux during the 13 year period have earlier been studied by Brace et al. (1988) and Hoegy et al. (1993). In this paper, we study the fine features by translating the observed I pe to the solar longitude of Earth (to be called as EI pe) and comparing it with other solar activity indicators like F 10.7, Lyman alpha and the solar magnetic field. We find that while the daily values of EI pe are highly correlated with F10.7 (correlation coefficient 0.87), there is a large scatter in EI pe for any value of this earth based index. Comparison of EI pe with SME and UARS-SOLSTICE Lyman-alpha measurements taken during the same period indicates that EI pe tracks Lyman-alpha quite faithfully. Similar comparison with the solar magnetic field (B s) shows that EI pe correlates better with B s than with F10.7.

Plasma waves and field‐aligned currents in the Venus plasma mantle

Plasma waves, observed above the dayside Venus ionosphere by the Pioneer Venus Orbiter (PVO) plasma wave instrument, have been attributed to whistler mode waves, lower hybrid waves, or ion acoustic waves. In order to clarify the nature of the waves, we have performed both case study and statistical analyses of the plasma wave and magnetic field data. We find that the plasma wave data are well ordered by altitude with respect to the location where the PVO Langmuir probe, or orbiter electron temperature probe (OETP), measures a density of 100 cm−3, known as the OETP ionopause. The dominant signature in the wave data appears to be a change in the instrument noise level because of changes in the plasma Debye length. However, there is a burst of wave activity near the OETP ionopause. Also, we find that there is a rotation in the magnetic field at or near this location. By casting the magnetic field data into a coordinate system ordered by the presumed magnetosheath flow, we find that the rotation of the field tends to orient the field in a more flow‐aligned direction at lower altitudes. We attribute this to mass loading at lower altitudes. We further suggest that the field‐aligned current associated with the field rotation corresponds to a shear Alfvén wave standing in the magnetosheath flow. The field‐aligned currents are present because of boundary conditions imposed on the flow, and it is not clear if the waves are actually associated with the field‐aligned currents or are simply coincidental. Since the waves are observed at the OETP ionopause, further progress in understanding these waves will be made though determining what underlying plasma structure, if any, is related to the OETP ionopause, which is defined by a specific instrument threshold. Nevertheless, our study confirms that the wave activity, field‐aligned currents, and OETP ionopause all occur within the plasma mantle above the ionosphere. As such, the plasma waves are not an energy source for the dayside ionosphere.

Response of Venus ions to solar wind dynamic pressure

Orbiter ion mass spectrometer measurements, as available in the UADS data files are used to study the response of dayside Venus ions at various altitudes to solar wind dynamic pressure, Psw. Ion densities below about 200 km are not affected by changes in Psw. At altitudes above 200 km the ions get abruptly depleted with increase in Psw, and this abrupt depletion occurs at lower altitudes when Psw is high. At lower Psw, the depletion occurs at higher altitudes. The effect is similar for all ions. These results are also compared with the empirical relationship observed by Brace et al. (1980) between the ionopause altitude and Psw from electron density measurements on orbiter electron temperature probe.

An extension of the VIRA electron temperature and density models to include solar cycle variations

The original VIRA ionosphere model was based primarily on the Pioneer Venus Orbiter (PVO) data obtained at solar maximum (F10.7∼200) in 1979 and 1980 when periapsis was being maintained deep in the Venusian ionosphere. In situ measurements provided data on temperature, composition, density, and drift velocity, while the radio occultation method provided height profiles of electron density, N e. The solar cycle variation was deduced by comparison with the Venera 9 and 10 occultation data from the previous solar minimum. No data were available on the solar cycle variations of other ionospheric parameters, because periapsis had already risen out of the ionosphere by the time solar activity began to decline early in 1983. During the Entry period in the Fall of 1992, however, PVO got a brief glimpse of the nightside ionosphere at lower solar activity (F10.7∼120). During the intervening decade important in situ data were obtained on the upper nightside ionosphere that extends far down stream from the planet. This region was found to be highly sensitive to solar wind interactions and solar activity. In this paper, we discuss ways in which the later PVO data can be used to extend the VIRA model to higher altitudes and to include the solar cycle variations. As an example, we present some pre-entry Orbiter Electron Temperature Probe measurements that provide new clues as to the dayside T e behavior at low solar activity.

The nightward ion flow scenario at Venus revisited

In this paper, we indicate how existing Pioneer Venus Orbiter (PVO) data might be used to gain a better understanding of nightward ion flow in the Venusian ionosphere. Calculations based on PVO measurements made at solar maximum suggest that the global nightward flow of O + may be significantly greater than is required to maintain the observed nightside ionosphere densities. The validity of this conclusion depends upon (1) the accuracy with which the flow can be determined from the PVO ion density and velocity measurements and (2) the validity of the ionosphere theory used to estimate the required downward O + flux on the night side. If the measurements and theory are assumed to be accurate, the excess nightward flow implies a significant rate of ion escape from the planet, particularly at times of low solar wind dynamic pressure, Psw, when the ionopause rises to allow increased nightward flow. To illustrate a potentially important mechanism for ion escape from Venus, we present Orbiter Electron Temperature Probe (OETP) observations of plasma clouds and scavenged ionospheric plasma observed above the ionopause. We then employ OETP and Orbiter Retarding Potential Analyzer (ORPA) data to reexamine the global ion flow for average Psw conditions, and we find the net flow to be in agreement with previous estimates. We also find that the net transterminator flow at average Psw approaches the limiting upward ion flow available from the dayside ionosphere, a limit which is imposed by O + collisions with O 2 +. OETP measurements in the terminator ionosphere show that N e declines at times of low Psw. This suggests that the dayside ionosphere is unable to supply the increased demand when the ionopause rises above its average height, thus requiring an upward diversion of some of the nightward flow to populate the overlying, newly-created ionosphere. We predict that the ion velocities will also be found to decrease at times of low Psw, in part due to the source-limited flow, and in part because the expansion of the ionosphere diminishes the “nozzle effect” that has been identified as a source of nightward ion acceleration. Collectively, these effects act to limit the increase in the net nightward ion flow at times of low Psw. Since O +-O 2 + collisions will impart an upward velocity to the O 2 + ions, the O + diffusion limit may be a soft one, so the nightward flow can continue to increase somewhat as Psw declines. The collision process should also enhance the O 2 + concentration in the dayside upper ionosphere and, to the extent that the O 2 + participates in the nightward flow, should produce O 2 + enhancements on the night side as well. These expectations could be verified by an examination of the orbit-to-orbit changes in ion composition and velocity in response to Psw variations.

Observations of the nightside Venus ionosphere: Final encounter of the Pioneer Venus Orbiter Ion Mass Spectrometer

During the last orbital sequences of the Pioneer‐Venus spacecraft prior to final encounter and atmospheric entry, data were obtained by the Orbiter Ion Mass Spectrometer (OIMS) at the lowest periapsis altitudes of the mission. These data verified OIMS observations of the nightside ionospheric peak reported earlier in the mission, and revealed additional details related to composition, energetics and maintenance of the nightside ionosphere. OIMS observations of the ion peak during the final encounter sequence are compared with radio occultation data and OIMS peak observations obtained earlier. OIMS ion density and Orbiter Electron Temperature Probe (OETP) electron density are found to correlate near the peak. Coupling of mass channels 30 and 32 during nightside passes is observed and its interpretation considered. Changes in high altitude composition of the nightside ionosphere, especially the relative changes in O+ and H+, are described.