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Feb 1991

Volume 62, Issue 2, pp. 279-549

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Local phase detection probes in fluid/fluid two‐phase flows

A. Cartellier and J. L. Achard

Rev. Sci. Instrum. 62, 279 (1991); http://dx.doi.org/10.1063/1.1142117 (25 pages) | Cited 40 times

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Phase detection is of primary importance for both the control and the characterization of fluid/fluid two‐phase flows. Admitting that local probes ideally give access to the indicator function of one of the phases, various theoretical treatments of this information are reviewed. Optical, impedance, thermal and electrochemical techniques are then detailed, both for the associated theory of operation and the practical designs. A qualitative description of probe/interface interactions provides some insight into typical signal evolutions. From experiments performed in well‐controlled conditions, the relation between signal and hydrodynamic phenomena can be partially quantified. Additional difficulties encountered in realistic situations are presented. Usual signal processing techniques are analyzed, as well as calibration procedures. The resulting accuracy of the sensors is then discussed on the basis of volume fraction measurements. Suggestions are given for future improvements.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
07.07.Df Sensors (chemical, optical, electrical, movement, gas, etc.); remote sensing
68.03.-g Gas-liquid and vacuum-liquid interfaces
68.05.-n Liquid-liquid interfaces

Frequency shift of 1.45 MHz for 337‐μm HCN laser beam with a super rotating grating

T. Maekawa, T. Minami, K. Makino, S. Tanaka, S. Kubo, and M. Iguchi

Rev. Sci. Instrum. 62, 304 (1991); http://dx.doi.org/10.1063/1.1142118 (4 pages) | Cited 10 times

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A frequency shift of ω1F/2π=1.45 MHz is obtained for a 337‐μm HCN laser beam by use of a rotating grating fabricated on the top of the rotor of a turbomolecular pump with a high rotating speed of 43200 rpm (super rotating grating). The frequency shift is one order higher than those with usual rotating gratings. Using this as a local beam, heterodyne detection of low‐frequency microturbulence as well as high time resolution interferometry in plasmas becomes possible with a single far‐infrared laser. The frequency‐shifted beam is slightly frequency modulated (modulation index Mf≂1.2) with a period equal to the rotation period of the grating. This frequency modulation does no harm to these diagnostics.
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07.60.Ly Interferometers
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.79.Dj Gratings

A fast cavity dumper for a picosecond glass laser

S. M. Oak, K. S. Bindra, B. S. Narayan, and R. K. Khardekar

Rev. Sci. Instrum. 62, 308 (1991); http://dx.doi.org/10.1063/1.1142119 (5 pages) | Cited 12 times

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A fast cavity dumper for picosecond glass laser has been made. The optical and electrical characterization of the cavity dumper is described. An avalanche transistor Marx bank generator drives the cavity dumper. Up to 5 kV peak amplitude and 1.5 ns fall time negative polarity step pulses are generated by the Marx bank circuit. With a capacitive load like Pockels cell the pulse fall time increases to 4 ns. Optical switching times as fast as 2 ns (10%–90%) are experimentally measured. The contrast ratio of 1000 is obtained after a double pass through an amplifier. Single picosecond pulses are produced with an energy jitter of 10%.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings

A multiple path cell, without mirrors, for far infrared spectroscopy

Ph. Marteau and J. Obriot

Rev. Sci. Instrum. 62, 313 (1991); http://dx.doi.org/10.1063/1.1142120 (5 pages)

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We describe a new type of multiple‐path cell with internal reflections but without mirrors. Its principle is based upon the high reflecting power of some metals. The light beam is directly reflected on the internal walls of the cell in which it goes back and forth before partially and gradually leaving through an exit light hole. The device is particularly well adapted to far infrared spectroscopy at room temperature and even more at lower temperatures. Its main advantages are a reasonable volume and the absence of any optical adjustment. It is shown that the maximum efficiency can be reached only under peculiar geometrical conditions, so as to get a uniform intensity distribution of the light through the cross section of the cylindrical cell. The relation between the experimentally measured quantity and the true absorption coefficient is established. Some spectra obtained with the cell are also shown.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

A simple relative laser power meter

Bojan B. Radak and Branislav B. Radak

Rev. Sci. Instrum. 62, 318 (1991); http://dx.doi.org/10.1063/1.1142121 (3 pages)

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A simple relative laser power meter was designed and built according to the principles of the ‘‘pedestal’’ calorimeter. The principles and specific details of the construction are given. The time response was measured and characterized by the time constants of the heating (‘‘laser on’’) and cooling (‘‘laser off’’) of the receiving element. The time constants were 1.46 s for heating and 1.34 s for cooling.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
07.60.-j Optical instruments and equipment
43.58.+z Acoustical measurements and instrumentation
07.20.Fw Calorimeters

A protection circuit for side window photomultiplier tubes

P. E. Hartley and S. Wagner

Rev. Sci. Instrum. 62, 321 (1991); http://dx.doi.org/10.1063/1.1142122 (2 pages) | Cited 1 time

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A simple circuit to protect side window photomultiplier tubes against damage from accidental exposure to intense light is described. The gain of the tube is reduced by a factor of at least 104 within 20 μs of overload and automatically returns to normal when the over exposure is removed. This is achieved by using high voltage transistor optocouplers to reduce the voltage between the photocathode and the first seven stages of the tube to zero. The circuit may be easily adapted to suit other types of photomultiplier.
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07.50.Ek Circuits and circuit components
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors

Laser‐driven electron ionization for a VUV photoionization time‐of‐flight mass spectrometer

J. G. Boyle, L. D. Pfefferle, E. E. Gulcicek, and S. D. Colson

Rev. Sci. Instrum. 62, 323 (1991); http://dx.doi.org/10.1063/1.1142123 (11 pages) | Cited 14 times

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The modification of a VUV photoionization time‐of‐flight mass spectrometer (TOF‐MS) to accommodate pulsed electron ionization is described. Utilizing a selected wavelength from a UV or VUV laser, structurally important fragment ions can be created for mass analysis. Data are straightforwardly obtained with only minor modifications to the experimental apparatus. The electron energy is continuously adjustable, thereby allowing the extent of fragmentation to be controlled. Observed fragmentation patterns are quantitatively similar to conventional electron ionization. Performance using UV or VUV radiation as the photoelectric driver is adequate to perform pulsed electron ionization on a time scale compatible with TOF‐MS.
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07.75.+h Mass spectrometers
82.50.Bc Processes caused by infrared radiation
82.50.Hp Processes caused by visible and UV light

Automated, differentially pumped, mass‐spectrometer sampling system

Jon C. Little and Lloyd B. Gordon

Rev. Sci. Instrum. 62, 334 (1991); http://dx.doi.org/10.1063/1.1142124 (8 pages)

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The design, construction, and testing of an automated gas sampling system for a quadrupole mass spectrometer on a process chamber with a wide pressure range is described. A set of two parallel stepper‐activated vacuum valves are used to vary the amount of gas admitted into the mass spectrometer chamber. One valve is a standard low‐conductance leak valve to allow the sampling of high pressures (760 down to 10−2 Torr). The other valve is a specially designed high‐conductance valve to allow the sampling of lower pressures (1×10−2 down to 2×10−5 Torr). The computer‐controlled sampling system automatically adjusts the position of the valves to provide the proper leak rate so that the mass spectrometer can continuously monitor a process chamber with a time varying pressure between 760 and 2×10−5 Torr. This provides a constant pressure at the mass spectrometer sensing head, despite the varying process chamber pressure. No commercially available mass spectrometer system was found which was able to automatically monitor the gas composition in a process chamber with such time varying pressures. The principles of operation are presented along with calculations of the gas flow and the control equations.
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07.75.+h Mass spectrometers

A beamline zero‐degree spectrometer for measurements of projectile fragment distributions

G. A. Souliotis, D. J. Morrissey, and B. M. Sherrill

Rev. Sci. Instrum. 62, 342 (1991); http://dx.doi.org/10.1063/1.1142125 (8 pages) | Cited 1 time

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A technique for using a section of a beamline as a zero‐degree spectrometer is described. The beamline magnets of the K1200 cyclotron at NSCL were operated as a zero‐degree medium acceptance spectrometer to measure projectile fragment distributions. Projectile fragments were produced in a fragmentation target at the exit of the cyclotron and detected at the end of the beamline with a detector array consisting of two position‐sensitive detectors and a ΔE−E telescope. Energy loss, position and angle at the focal plane and time of flight were measured for the isotopes produced. A procedure was developed to calculate the reaction angle and the momentum of the isotopes from the measured quantities. Typical examples of momentum and angular distributions of projectile fragments from a 14N beam at 75 MeV/u with Al and Ta targets at and near 0° are shown.
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29.20.dg Cyclotrons
29.30.-h Spectrometers and spectroscopic techniques

A condenser objective lens with asymmetric polepieces to facilitate the extraction of secondary and Auger electrons

A. J. Bleeker and P. Kruit

Rev. Sci. Instrum. 62, 350 (1991); http://dx.doi.org/10.1063/1.1142126 (7 pages) | Cited 2 times

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A new condenser objective lens for a scanning transmission electron microscope especially designed for through‐the‐lens extraction of secondary and Auger electrons is presented. The optimal axial field to extract the secondary and Auger electrons is a field that falls off as 1/z2. This field form has been realized by a new lens design with one sharp polepiece and a second, carefully shaped, polepiece. This polepiece consists of two magnetically separated parts. The bore in this polepiece measures 20 mm while the working distance is 10 mm. The spherical aberration on the condenser side is 2.5 mm for an acceleration voltage of 125 kV while, with the same lens excitation, the projector side spherical and chromatic aberrations are 1.1 and 1.5 mm, respectively. All (Auger) electrons with an energy up to 1000 eV emerging from the specimen can be concentrated in a disk of 4.2 mm and a maximum opening angle of 6° for further energy analysis.
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41.75.Fr Electron and positron beams
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Simple raster generator for use with scanning tunneling microscopes

J. Maps

Rev. Sci. Instrum. 62, 357 (1991); http://dx.doi.org/10.1063/1.1142127 (3 pages) | Cited 2 times

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A simple, inexpensive circuit to generate a two‐dimensional raster pattern for use in a scanning tunneling microscope is presented. The circuit is constructed from common analog and digital integrated circuits. Externally provided dc voltages and the use of analog multipliers allow for easily programmed scan ranges and the system is easily expanded for higher density images. Interfacing to personal computer‐based data acquisition and video frame grabber boards is discussed.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.50.Ek Circuits and circuit components
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Direct imaging of x rays with a CCD using hardware processing

R. Mayer

Rev. Sci. Instrum. 62, 360 (1991); http://dx.doi.org/10.1063/1.1142128 (4 pages) | Cited 1 time

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This study investigated the direct imaging of low intensity x‐rays by a room‐temperature charge coupled device (CCD). Commercial CCD evaluation kits read out the information and provided initial processing of the data. The extraction of the signal from noise was achieved using NIM modules rather than by storing and numerically analyzing the data. Due to the fast processing at standard TV rates, the storage of the data required conversion of the signal from a timing to a pulse height analysis (PHA) spectrum. The tested CCDs were found to have lower efficiency relative to the proportional counter for the range of photon energies (1.5–8.0 keV) studied but had higher spatial resolution than gas‐filled position‐sensitive detectors. Application of CCDs for x‐ray energy dispersive detectors is described.
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07.85.-m X- and γ-ray instruments
29.30.Kv X- and γ-ray spectroscopy
29.40.Gx Tracking and position-sensitive detectors

An electronic Cranz–Schardin camera

B. Bretthauer, G. E. A. Meier, and B. Stasicki

Rev. Sci. Instrum. 62, 364 (1991); http://dx.doi.org/10.1063/1.1142129 (5 pages) | Cited 10 times

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An electronic high‐speed multiple‐image camera based on the Cranz–Schardin principle has been developed. High‐power LEDs are used as a light source. Frames are recorded by a system of eight CCDs and an eight channel image processor enabling a series of eight subsequent images at full‐frame (512× 512) resolution or more images (up to 80) at a lower resolution. The maximum framing frequency is 10 MHz. The advantages upon the classical spark illumination and photographic techniques are mainly the precise electronic control, the immediate access to the frames, the on‐line image processing and the low cost of the system. Examples of gas‐ and two‐phase flow visualization are presented.
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07.68.+m Photography, photographic instruments; xerography

A plasma shutter to generate a synchronized subnanosecond pulse for optical probing of laser‐produced plasmas

L. J. Dhareshwar, P. A. Naik, and D. D. Bhawalkar

Rev. Sci. Instrum. 62, 369 (1991); http://dx.doi.org/10.1063/1.1142130 (7 pages) | Cited 5 times

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A simple and reliable technique to temporally shorten a multinanosecond Nd:glass laser pulse to less than nanosecond duration at the second harmonic wavelength is described in this article. Using this technique a short probe pulse synchronized with the main laser was generated for optical probing of laser‐produced plasmas. Experiments reported were conducted with a Nd:glass laser of wavelength 1.06 μm and of 20 ns duration to yield a temporally shortened pulse of duration less than a nanosecond at a wavelength of 0.53 μm. This technique would be particularly useful and give better results for shorter wavelength lasers (UV and VUV) for which the conventional techniques of pulse slicing are sophisticated as well as add to the expense and complexity of the laser system.
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42.60.Fc Modulation, tuning, and mode locking
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.75.-d Plasma devices

Experiments with high‐voltage insulators in the presence of tritium

L. R. Grisham, H. Falter, R. Causey, W. Chrisman, T. Stevenson, and K. Wright

Rev. Sci. Instrum. 62, 376 (1991); http://dx.doi.org/10.1063/1.1142131 (5 pages) | Cited 2 times

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During the final deuterium‐tritium phases of the TFTR and JET tokamaks half of the neutral injectors will be used to produce tritium neutral beams to maintain an equal mix of deuterium and tritium in the core plasma, and such requirements may also occur in future devices. This will require that the voltage hold off capabilities of the high voltage insulators in the accelerators be unimpaired by any charge buildups associated with the beta decay of adsorbed layers. We report tests in which we measured the drain currents under high dc voltage of TFTR and JET accelerator insulators while they were successively exposed to vacuum, deuterium and tritium. There did not appear to be any substantial reduction in hold‐off capability with tritium, although at some voltages there was a small increase in the leakage current. We also compared the breakdown properties of a plastic tubing filled with deuterium and then tritium at varying pressures, since such tubing has been considered as a high‐voltage break in the gas feed system for TFTR, and the presence of large numbers of electron‐ion pairs might lead to enhanced Paschen breakdown. We found no significant differences in the behavior for the geometry used.
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52.55.Fa Tokamaks, spherical tokamaks
52.75.Di Ion and plasma propulsion

High UV (λ≥2200 Å), visible, and near infrared (λ≤0.8 μm) transmissive liquid coolant for high power microwave (2.45 GHz) plasma tubes

L. A. Schlie, R. D. Rathge, and E. A. Dunkle

Rev. Sci. Instrum. 62, 381 (1991); http://dx.doi.org/10.1063/1.1142132 (11 pages) | Cited 6 times

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Commercially available dimethyl polysiloxane is shown to be an excellent liquid coolant for the containing walls of high power plasmas (≥300 W/cm3) excited with 2.45‐GHz microwaves. This stable, nontoxic, and nonflammable fluid has very low microwave absorption (tan δ=ϵ″/ϵ′=3.5×10−4) at this frequency. Fortuitously, it also has excellent ultraviolet, visible, and near infrared (λ≤0.8 μm) transmission. The UV transmission over 1 cm shows 2% transmission at 2000 Å, a 30% transmission at 2200 Å, 80% at 2400 Å, and 100% for λ≳2500 Å. These features plus its good physical (viscosity, thermal conductivity, specific heat capacity, heat of vaporization, and density) and electrical (resistivity and breakdown) properties make it very unique as a liquid coolant of UV emitting microwave plasma lamps. The clear coolant’s infrared absorption for λ≥1.0 μm reduces the radiative (heat) emission from the plasma. In addition, dimethyl polysiloxane has a very wide operating temperature range, −73 °C≤T≤260 °C. Particular procedures required to assure its excellent ultraviolet transmission are described along with different geometrical combinations of liquid cooled plasma lamps and reflector housings. This liquid may also be used to cool microwave excited laser tubes.
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07.90.+c Other topics in instruments, apparatus, and components common to several branches of physics and astronomy (restricted to new topics in section 07)
52.80.Pi High-frequency and RF discharges
84.40.Fe Microwave tubes (e.g., klystrons, magnetrons, traveling-wave, backward-wave tubes, etc.)
78.40.Dw Liquids

Noncontact temperature measurement. I. Interpolation based techniques

Mansoor A. Khan, Charly Allemand, and Thomas W. Eagar

Rev. Sci. Instrum. 62, 392 (1991); http://dx.doi.org/10.1063/1.1142133 (11 pages) | Cited 24 times

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Various ratio pyrometry techniques (two, three, and four color) are analyzed and shown to possess hitherto unknown sources of error under certain conditions. These conditions are shown to arise quite frequently. The ratio method is shown to be better suited to the shorter wavelengths. It has been shown, for various emissivities, that the predicted temperature has an asymptote at some wavelength. Ratio pyrometry methods are shown to be very sensitive to measurement noise and this sensitivity grows quickly with the number of terms in the ratio. The effect of a reference temperature in the system is examined and it is shown that under certain conditions this reference temperature can be used to make accurate predictions regarding the temperature elsewhere in the system even if the emissivity changes.
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07.20.Ka High-temperature instrumentation; pyrometers

Noncontact temperature measurement. II. Least squares based techniques

Mansoor A. Khan, Charly Allemand, and Thomas W. Eagar

Rev. Sci. Instrum. 62, 403 (1991); http://dx.doi.org/10.1063/1.1142134 (7 pages) | Cited 21 times

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A technique for the noncontact measurement of temperatures is described. The technique is based on the measurement of the emitted intensity at multiple wavelengths and the simultaneous calculation of emissivity and temperature through the use of least squares curve fitting techniques. The technique is shown to make no assumptions regarding the emissivity of the target except that it be possible to model it with an analytic function. A theory is developed to predict the errors in the estimation of temperatures based on both linear and nonlinear least‐squares techniques. It is shown that the maximum error in the predicted temperature is related to the noise in the measured intensities in a quantifiable manner. It is shown using computer simulations that the theory and algorithms developed here can predict both the temperatures and the uncertainty associated with each temperature prediction with a very high accuracy. An instrument was developed to test this theory. This instrument, referred to as the MITTMA, was used to measure absolute temperatures of various sources from 900 °C to 2300 °C with an average accuracy of approximately 0.5%.
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07.20.Ka High-temperature instrumentation; pyrometers

A sensitive resistivity probe of high temperature phase transformations

J. C. Holzer, G. Summers, E. H. Majzoub, and K. F. Kelton

Rev. Sci. Instrum. 62, 410 (1991); http://dx.doi.org/10.1063/1.1142135 (5 pages)

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A new apparatus for making in situ measurements of changes in the electrical resistivity accompanying phase transformations in metallic alloys is presented. Measurements can be made in vacuum or inert gas at annealing temperatures as high as 1500 K. The long‐term thermal stability is better than ±0.3 K. The measurement circuit is stable to better than 0.01% over any time scale. This apparatus provides a relatively simple and inexpensive means for obtaining high temperature resistivity measurements on very brittle samples.
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07.20.Ka High-temperature instrumentation; pyrometers
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

An ac calorimeter for measuring heat capacity of free‐standing liquid‐crystal films

R. Geer, T. Stoebe, T. Pitchford, and C. C. Huang

Rev. Sci. Instrum. 62, 415 (1991); http://dx.doi.org/10.1063/1.1142136 (7 pages) | Cited 36 times

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A unique ac calorimeter for measuring the heat capacity of free‐standing liquid‐crystal films has been developed. A theory of the measurement method used is presented and the experimental setup is discussed. The calorimeter has been used to study the nature of the smectic‐A‐hexatic‐B transition of several liquid‐crystal compounds. The evolution of the heat‐capacity anomaly associated with this transition has been studied for films ranging from three to a few thousand smectic layers in thickness.
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07.20.Fw Calorimeters
61.30.-v Liquid crystals
65.20.-w Thermal properties of liquids

Thickness‐direction coefficient of thermal expansion measurement of thin polymer films

H. M. Tong, H. K. D. Hsuen, K. L. Saenger, and G. W. Su

Rev. Sci. Instrum. 62, 422 (1991); http://dx.doi.org/10.1063/1.1142137 (9 pages) | Cited 12 times

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A highly sensitive capacitance‐change technique, suitable for thin polymer films, has been developed for the measurement of the coefficient of thermal expansion (CTE) in the film‐thickness direction. Using this technique, we have determined the thickness‐direction CTE of Kapton polyimide to be about 81±4 ppm/°C, averaged over the temperature range 50–150 °C. This polymer was chosen because it is widely used in the electronics industry for the fabrication of flexible printed circuits. Two other techniques, a Fabry–Perot laser interferometric technique, and the more conventional but less sensitive thermomechanical analysis, were also investigated. The thickness‐direction CTEs obtained from the three techniques were at least a factor of 2.4 greater than the in‐plane CTE of about 34±2 ppm/°C. The in‐plane CTE, found here via simple length measurements, was in good agreement with literature values. It is speculated that the CTE anisotropy observed might be due to the in‐plane molecular orientation of the polymer chains.
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07.20.Dt Thermometers
68.90.+g Other topics in structure, and nonelectronic properties of surfaces and interfaces; thin films and low-dimensional structures (restricted to new topics in section 68)
07.50.-e Electrical and electronic instruments and components

Influence of the propellant flow on the performance of diaphragm operated gas guns

M. de Icaza, C. Renero, and F. E. Prieto

Rev. Sci. Instrum. 62, 431 (1991); http://dx.doi.org/10.1063/1.1142138 (6 pages)

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Many different properties of matter under shock wave loading can be studied through the use of gas‐gun accelerated projectiles. Knowledge of the motion of the projectile, and in particular of its velocity, is thus of prime importance. This motion depends upon the sudden release of a compressed gas confined in a breech. The corresponding firing mechanism is a geometrical restriction to the flow of the accelerating gas behind the projectile. In this article a theoretical expression is obtained to take into account this restriction, and is applied to the case of the diaphragm type of firing mechanism. Two conditions are imposed to the one dimensional and isentropic flow at the diaphragm zone: the continuity of the fluid flow (density times velocity times cross section) and the continuity of force (pressure times cross section). The theoretical expression obtained can be expressed in term of upper and lower bounds. A comparison with experimental results, obtained in our laboratory, is carried out, showing that they systematically fall around the upper bound. The reasons for this behavior are discussed and a useful rule to design the firing mechanism is suggested.
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47.40.-x Compressible flows; shock waves
47.60.-i Flow phenomena in quasi-one-dimensional systems
47.80.-v Instrumentation and measurement methods in fluid dynamics

A versatile substrate heater for use in highly oxidizing atmospheres

R. C. Estler, N. S. Nogar, R. E. Muenchausen, X. D. Wu, S. Foltyn, and A. R. Garcia

Rev. Sci. Instrum. 62, 437 (1991); http://dx.doi.org/10.1063/1.1142139 (4 pages) | Cited 12 times

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We report the design, construction and performance of a versatile substrate heater that meets the severe design constraints of heating substrates to high temperatures (≤900 °C) in relatively high pressures (hundreds of Torr) of oxidizing gases. The heater has been used to heat substrates by both thermal conduction via a conductive high temperature cement and by direct radiation. In particular, the production of high‐quality YBa2Cu3O7−δ thin films grown on radiatively heated LaAlO3 substrates is demonstrated using the pulsed laser deposition (PLD) technique.
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07.20.Ka High-temperature instrumentation; pyrometers
74.70.-b Superconducting materials other than cuprates
74.78.-w Superconducting films and low-dimensional structures
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Displacement sensor for a gravitational redshift experiment with 67Zn Mössbauer resonance

E. Ikonen, H. Seppä, W. Potzel, and C. Schäfer

Rev. Sci. Instrum. 62, 441 (1991); http://dx.doi.org/10.1063/1.1142140 (9 pages) | Cited 3 times

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A displacement sensor was constructed to monitor the motion of a piezoelectric Doppler velocity transducer in a gravitational redshift experiment with 67Zn Mössbauer resonance. The sensor uses a dc superconducting quantum interference device (SQUID) to detect small displacements of a permanent magnet. To meet the stringent requirements of the redshift experiment, the magnetic flux gradient and the pickup coil of the sensor are designed in such a way that the SQUID flux noise of 7 × 10−6 Φ0/√Hz corresponds to a displacement resolution of 6 × 10−14 m/√Hz. However, resolution up to 3 × 10−15 m/√Hz in the frequency band of 20–20 000 Hz is demonstrated. The linearity of the displacement sensor and the piezoelectric transducer are considered in detail and the resulting uncertainties associated with the Doppler modulation in the Mössbauer experiment are evaluated.
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06.30.Bp Spatial dimensions (e.g., position, lengths, volume, angles, and displacements)
04.80.-y Experimental studies of gravity
76.80.+y Mössbauer effect; other γ-ray spectroscopy

Time domain reflectometry to study the dielectric properties of liquids: Some problems and solutions

D. Bertolini, M. Cassettari, G. Salvetti, E. Tombari, and S. Veronesi

Rev. Sci. Instrum. 62, 450 (1991); http://dx.doi.org/10.1063/1.1142141 (7 pages) | Cited 6 times

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After a brief introduction we review the fundamental mathematical relations necessary to discuss the main aspects of the time domain dielectrometry performed with total reflection from an open cell. Experimental problems due to the presence of resonances in the sample cell, spurious reflections, and fringing fields are considered and possible solutions are suggested. An experimental apparatus realized to study liquids with dielectric constant values up to those of water and water solutions from 10 MHz up to 10 GHz in the temperatures range −45 °C+70 °C is also presented. The performances of some different experimental cells for liquids are compared and representative results obtained with different procedures are reported. The use of the numerical solution of a transcendental equation that takes into account for wave propagation allows us to measure the complex dielectric constant without the use of reference liquids, once the electrical parameters of the sample cell are known. In this case an accuracy better than 2% both in the real and in the imaginary parts of the dielectric constant can be obtained up to 7 GHz, as tested with chloroform. Calibration procedures using liquids of known permittivity can remove the contributions of spurious effects, so allowing us to perform measurements with the same accuracy up to 10 GHz and more on highly polar liquids too.
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07.60.Hv Refractometers and reflectometers
77.22.Gm Dielectric loss and relaxation
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