摘要:

Dielectric measurements are reported on capacitance thermometers based on SrTiO3crystallized from glass at 1100 and 1200°C. Multilayer experimental units, approximately 5×2×1 mm, were fabricated using pilot plant facilities and measured from 1.7 to 300 K. If both the capacitance and loss tangent are measured, the range of the 1100°C crystallized thermometer is from at least 1.7 to 300 K. For capacitance measurement alone, the thermometer range is below 72 K, and in this range the capacitance varies smoothly and monotonically with temperature, becoming linear below 5.2 K. The sensitivity is largest in this linear region and averages 250 pF·K−1for the 1100°C crystallized thermometers. The self‐heating at 4.2 K is about 70 pW (5 kHz, 7 mV) and decreases with decreasing temperature. The effect of a magnetic field on the thermometer was measured in an open Dewar of liquid helium at four frequencies in fields up to 80 kG. The measured changes were ≤±1 mK and are interpreted as fluctuations in the bath temperature rather than an intrinsic magnetocapacitance effect. The response time between 4.2 and 300 K is at least 70 K·sec−1. The main disadvantage of the thermometer is a transient (∼30 min) capacitance instability which is equivalent to a ≤30 mK change before stabilization. Once stabilized, the thermometer repeats to about ±2 mK when compared to a germanium thermometer, and repeats to ±13 mK on cyclically plunging into liquid helium (15 cycles) in the unstabilized case. This instability is apparently due to helium migration into the unencapsulated sensor body. The polar properties of glass crystallized SrTiO3, on which the thermometer is based, are briefly discussed, and comparisons are made with two other capacitance thermometers reported in the literature.

ISSN:0034-6748    

DOI:10.1063/1.1685170

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Capacitance measurements from 0.025 to 2.4 K are reported for capacitance thermometers (made from an SrTiO3glass‐ceramic crystallized at 1100 and 1203°C), two of which were the ones reported in the previous article. It was found that the 1200‐type thermometer has a useful thermometric range down to 0.06 K and a linearC‐Tregion down to 0.5 K. The 1100‐type thermometer has a useful range down to 0.110 K and a linear region down to 1.1 K. The measured data do not appear to be influenced by self‐heating or adiabatic correction effects. Both thermometers display an unexpected increase in capacitance with decreasing temperature below their monotonically decreasing ranges. The 1100‐type thermometer displays the more pronounced increase, withC∝T−1from 0.100 to 0.025 K. It is argued that thisT−1behavior is due to the onset of an ultralow temperature phase transition in the glass crystallized SrTiO3, and the possibility of using this effect to achieve adiabatic depolarization cooling is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1685171

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The effect of an intense magnetic field on an 1100‐type capacitance thermometer (made from an SrTiO3glass‐ceramic crystallized at 1100°C) was accurately measured at five temperatures between 1.5 and 4.2 K. At each manostatically maintained temperature, the capacitance changes were measured five times betweenB=0 andB=14 T, and it was found that these changes did not exceed the measurement uncertainty, ±0.3 pF≅±1 mK. Similar results were obtained on a second 1100‐type thermometer. Some suggestions are made for the use of this type of thermometer in magnetic field experiments.

ISSN:0034-6748    

DOI:10.1063/1.1685172

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Generally it is too costly or otherwise not feasible to conduct performance tests on a radio communication system under conditions of actual atmospheric radio noise because this noise is nonstationary. Accurate simulation of desired conditions solves this difficulty. Magnetic tape recordings were made of atmospheric radio noise from low frequency through high frequency. The recordings were computer analyzed and were used as a model for the design of an atmospheric noise simulator. The simulation is valid and accurate for the limited available data base.

ISSN:0034-6748    

DOI:10.1063/1.1685173

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A method for the determination of the thermal pressure coefficient (∂P/∂T)vor &ggr;vfor molten salts up to 400°C and 400 bars is described. The results, which are considered to be accurate to ±3%, are compared with previous work.

ISSN:0034-6748    

DOI:10.1063/1.1685174

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

A simple and inexpensive refrigerating vapor bath has been developed for the purpose of cooling gas line traps. The cooling medium in the bath is the cold vapor from liquid nitrogen. The temperature regulation range is from −196 to ∼0°C. For a glass‐isolated stainless steel gas trap the liquid nitrogen consumption rate was less than ½ liter/24 h at temperatures between −130 and −196°C.

ISSN:0034-6748    

DOI:10.1063/1.1685175

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Data are presented which describe and compare the behavior of Ta, W, and Pt‐8%W surface ionization detectors for fast potassium atom detection. The potassium atom energy in these experiments covered the range from thermal energy to 500 eV.

ISSN:0034-6748    

DOI:10.1063/1.1685176

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

We have designed and built an arc melter which uses an inexpensive Pyrex pipe cross for a controlled atmosphere chamber. An argon jet has been incorporated into the electrode holder which provides both dynamic flushing and rapid quenching capabilities.

ISSN:0034-6748    

DOI:10.1063/1.1685177

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

Paired comparison measurements of the spectrum of electrostatic potential fluctuations in a steady state turbulent plasma confined in a magnetic mirror geometry have been made with capacitive and floating Langmuir probes over the frequency range from 0.2 to 10.0 MHz. For the experimental conditions investigated (5×107≤ne≤5×108/cm3, 8≤Te≤38 eV, 350≤Ti≤930 eV,Bmax=1.0 T), no significant difference in the relative frequency response was observed below 4.0 MHz. At about this frequency, however, the signal detected by the floating Langmuir probe dropped off relative to that of the capacitive probe. The source resistance of the turbulent fluctuations sensed by the Langmuir probe was about 400 &OHgr;. At higher frequencies (from 7.0 to 10.0 MHz) a signal was detected by the floating Langmuir probe that was not detected by the capacitive probe. This spurious signal may be confused with the turbulent fluctuations of the plasma in the absence of paired comparison tests.

ISSN:0034-6748    

DOI:10.1063/1.1685178

出版商:AIP    

年代:1971

数据来源: AIP

摘要:

The paper presents an outline of the physical mechanism of corona discharge between a highly stressed anode and a large plate cathode as applied to the operation of a new type of anemometer. An operational hypothesis is proposed for the anemometer with reference to its kinematic and electrostatic principles of performance. Experimental results are presented to justify the hypothesis and the calibration of the probe. A discussion of the probe sensitivity to yaw of gas stream is included.

ISSN:0034-6748    

DOI:10.1063/1.1685179

出版商:AIP    

年代:1971

数据来源: AIP