| 1. |
- Alm, Ove, et al.
(författare)
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A multiple coaxial wire for pressure calibration
- 1974
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 45:4, s. 594-595
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Tidskriftsartikel (refereegranskat)abstract
- A single wire containing several metals suitable for pressure calibration has been produced by extrusion. Coaxial combinations of Ce-Bi-TI and Ce-Bi-Ba have been prepared by the procedure described.
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| 2. |
- Andersson, Per, et al.
(författare)
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Electrical resistance of Evanohm under pressure
- 1975
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 46:9, s. 1292-1293
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Tidskriftsartikel (refereegranskat)abstract
- The electrical resistance of Evanohm wire has been determined as a function of hydrostatic pressure. A Teflon cell with a novel type of electrical feedthrough was used to contain the fluid medium. The resistance was found to decrease approximately linearly by 0.3% up to 27 kilobar. The remarkably small variation of its resistance with temperature and pressure makes Evanohm a suitable material for strain measurements under pressure.
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| 3. |
- Andersson, Per, et al.
(författare)
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Thermal conductivity of solids under pressure by the transient hot wire method
- 1976
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 47:2, s. 205-209
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Tidskriftsartikel (refereegranskat)abstract
- An electronic circuit has been constructed which delivers constant power to a nickel wire also functioning as a resistance thermometer. The temperature increase versus time, t, is linear in ln t, and the coefficient of slope directly yields the thermal conductivity of the medium surrounding the wire. Systematic errors due to finite time, wire length, and lateral extension of the medium and due to plastic deformation of the wire are analyzed. Temperatures are sampled automatically, and the digital data are reduced by means of an on-line desk calculator. The thermal conductivities of AgCl and polytetrafluoroethylene have been measured up to 10 kilobar.
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| 4. |
- Bäckström, Gunnar
(författare)
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Circuitry for ac thermometry and dc heating in measurements of thermal properties
- 1978
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 49:6, s. 864-865
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Tidskriftsartikel (refereegranskat)abstract
- An instrument is described in which the resistance of a metal wire thermometer is measured by an ac bridge and sampled at a fixed rate. A superimposed dc pulse heats the wire during a selectable time interval. The temperature may be recorded before heating, during heating, and during cooling.
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| 5. |
- Cedergren, Magnus, et al.
(författare)
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Strain gauge measurements of volume changes in polymorphic transitions under pressure
- 1972
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 43:4, s. 686-688
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Tidskriftsartikel (refereegranskat)abstract
- A strain gauge wire was wound around a sample of cylindrical shape. One part of the wire was wound around the belly, the other in a plane going through the axis. For a certain choice of the turn ratio and the length-to-diameter ratio the strain could be made proportional to ΔV. From tests performed on Bi, it appears that ΔV / Vo approximately 2 x 10-4 may be detected with the present method. No volume discontinuity corresponding to the phase transition at 43 kilobar reported by Bridgman was observed.
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| 6. |
- Loriers-Susse, C., et al.
(författare)
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Specific heat measured at high pressures by a pulse method
- 1973
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 44:9, s. 1344-1349
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Tidskriftsartikel (refereegranskat)abstract
- The classical electric pulse technique has been adapted to measurements of specific heat at high pressure. A wire specimen is heated by a 100 μsec pulse, stabilized at I = 50 A. The resulting temperature rise is extracted from the voltage drop U over the sample by means of a bridge circuit. The specific heat isobtained from the formula cp = C (T, P) UI/m de/dt, where C (T, P) is a function to be experimentally determined for a given sample, m the mass of the sample, and de/dt the time derivative of the bridge output voltage. A procedure has been developed for in situ corrections of de/dt for heat loss to the medium surrounding the wire. Digital techniques are used for the pulse analysis. The method has been used to ascertain the pressure dependence of cp for Cu up to 100 kilobars at room temperature. The relative change in cp was found to be 2.8 X 10-4/kilobar.
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| 7. |
- Lundberg, Bo, et al.
(författare)
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Hall voltage and magnetoresistance of Bi measured by a sum frequency method in a belt apparatus
- 1972
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics (AIP). - 0034-6748 .- 1089-7623. ; 43:6, s. 872-875
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Tidskriftsartikel (refereegranskat)abstract
- An alternating magnetic field, 1.4 kG in amplitude at 5 Hz, was obtained in a belt type of high pressure apparatus by the use of conical pistons made of hardened high speed tool steel, permitting operation up to 50 kilobar. A frequency of 12 Hz was used for the current through the sample, and the Hall voltage was synchronously detected at 17 Hz. A signal yielding the coefficient of magnetoresistance was extracted at 22 Hz, using another lock‐in amplifier. The Ohmic resistance may also be measured in the same experiment, and, by making certain assumptions, the variation of the carrier density and the hole and electron mobilities of a semimetal may be determined. Data for polycrystalline Bi at room temperature are given.
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| 8. |
- Sundqvist, Bertil, et al.
(författare)
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Low noise and drift by parallel amplifiers
- 1975
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics. - 0034-6748 .- 1089-7623. ; 46:7, s. 928-929
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Tidskriftsartikel (refereegranskat)abstract
- A low noise and low drift amplifier has been constructed using several monolithic operational amplifiers in parallel. It is shown that each amplifier may be connected by only three resistors. An input noise of 0.15 µV (p–p) in the band 0.1–10 Hz was obtained with six amplifiers, and the noise is expected to decrease as N−1/2 as the number of units is increased.
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| 9. |
- Sundqvist, Bertil, et al.
(författare)
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Thermal conduction of metals under pressure
- 1976
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Ingår i: Review of Scientific Instruments. - : American Institute of Physics. - 0034-6748 .- 1089-7623. ; 47:2, s. 177-182
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Tidskriftsartikel (refereegranskat)abstract
- It is shown that the original Ångström method of determining the thermal diffusivity of metals is not valid in the case of a specimen surrounded by a solid medium, and an appropriate modification is described. Several simplifications of this method are also presented and criteria for their validity given. An electronic system has been developed for automatic sampling and analysis of the temperature data. The new method has been applied to Cu under pressure, and the results show that the thermal conductivity rises by 6.4% up to 2.5 GPa (25 kilobar).
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