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Jul 1982

Volume 53, Issue 7, pp. 939-1104

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Instrument to measure wave numbers of cw and pulsed laser lines: The sigmameter

P. Juncar and J. Pinard

Rev. Sci. Instrum. 53, 939 (1982); http://dx.doi.org/10.1063/1.1137112 (10 pages) | Cited 18 times

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We report the first absolute wave number measurements made using a sophisticated version of the sigmameter. This apparatus is composed of four double Michelson type interferometers with fixed path differences. All path differences are calibrated using four reference lines given by single‐mode lasers stabilized on iodine lines whose absolute wave numbers are known to better than one part in 109. This permits us to make absolute wave number measurements of radiation from a cw laser to a precision of the order of one part in 108 (≊5 MHz) and from a pulsed laser to a precision limited only by its spectral width. As examples, using a cw tunable dye laser, several new measurements of 20Ne lines have been achieved with the expected precision (10−8). Measurement of a pulsed laser frequency has also been done with an accuracy of the order of one part in 106.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
07.60.Ly Interferometers
06.30.Ft Time and frequency

Design and performance characteristics of a cw subsonic HF chemical laser with 120 W power output

Z. Babarogić, I. Belić, I. Mendaš, and M. Trtica

Rev. Sci. Instrum. 53, 949 (1982); http://dx.doi.org/10.1063/1.1137113 (3 pages)

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The design and performance of a transverse flow cw subsonic HF chemical laser are presented. The laser provides up to 46 W (120 W) cw output power with argon (helium) as a diluent gas on a number of Pv(J) lines corresponding to v = 1→v = 0 and v = 2→v = 1 vibrational transitions of hydrogen fluoride. The measured values of electrical efficiency, chemical efficiency, and specific power with argon (helium) were 0.4% (0.8%), 1.2% (3.1%), and 13 J/g (66 J/g), respectively.
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42.55.Ks Chemical lasers

Design, construction, and testing of a nuclear‐pumping facility at the University of Missouri Research Reactor

Michael J. Lecours, Mark A. Prelas, Steven Gunn, Chester Edwards, and Gerald Schlapper

Rev. Sci. Instrum. 53, 952 (1982); http://dx.doi.org/10.1063/1.1137114 (8 pages) | Cited 1 time

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An intense effort to design, construct, and test a nuclear‐pumping facility (NPF) has been completed at the University of Missouri‐Columbia (UMC). The NPF has a flow capability similar to that of the now defunct Brookhaven Chemonuclear In‐Pile Research Loop, plus the optical capability to monitor light output from the irradiation chamber. Both features make the UMC NPF a unique research loop usable for a wide variety of projects including radiation chemistry, fluorescence studies, photochemistry, dual media nuclear‐pumped lasers, and direct nuclear‐pumped lasers. Initial tests of the facility included a demonstration of 40.0 ft3/h flow rates (pump limited), and a spectral scan of N2 and He. The latter test represents a first effort in obtaining nuclear‐pumped gas spectra from a high‐power steady‐state reactor such as the University of Missouri Research Reactor (MURR). Results indicate that observed spontaneous emission mainly comes from the first negative spectral series in N2+ (B2Σ+u →x2Σ+g) and from He∗2 electronic transitions.
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28.52.Av Theory, design, and computerized simulation

Description of an electronic controller used with an autocorrelator to measure a femtosecond pulse duration in real time

A. Kalpaxis, A. G. Doukas, Y. Budansky, D. L. Rosen, A. Katz, and R. R. Alfano

Rev. Sci. Instrum. 53, 960 (1982); http://dx.doi.org/10.1063/1.1137115 (3 pages) | Cited 6 times

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An electronic circuit controller is described which is used with an autocorrelator and an oscilloscope to measure the duration of femtosecond laser pulses in real time. The controller drives both the autocorrelator and the oscilloscope to produce a linear trace display of a pulse autocorrelation function on an oscilloscope. The apparatus has been found very useful for monitoring, aligning, and characterizing the output from cw mode‐locked dye lasers.
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06.60.Jn High-speed techniques (microsecond to femtosecond)

Measurement and control of subangstrom mirror displacement by acousto‐optical technique

C. P. Wang, R. L. Varwig, and P. J. Ackman

Rev. Sci. Instrum. 53, 963 (1982); http://dx.doi.org/10.1063/1.1137116 (4 pages) | Cited 3 times

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Control of laser mirror spacing and angular orientation is important for laser frequency and mode stability. A wave front sensor that employs acousto‐optic modulation and optical heterodyning has been applied in conjunction with a servo‐control loop to control mirror motion. The measurement and control of subangstrom mirror displacements are possible using this system. Experimental results are presented that indicate closed‐loop control of mirror displacement to within 0.06 nm.
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42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Simple switching circuit to improve vidicon (OMA2) linearity

Horace E. Cascio, Paul D. Smith, and Gerard W. Liesegang

Rev. Sci. Instrum. 53, 967 (1982); http://dx.doi.org/10.1063/1.1137117 (2 pages) | Cited 2 times

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A simple switching circuit which allows a change of the target scan voltage to a new value at the end of the preparation frames in OMA2 vidicon detectors is described. This voltage change reduces lag significantly and leads to a linear response of the vidicon to pulsed illumination. The circuit is readily incorporated into OMA2 detectors.
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07.50.-e Electrical and electronic instruments and components

Fast polarization modulated ellipsometer using a microprocessor system for digital Fourier analysis

B. Drevillon, J. Perrin, R. Marbot, A. Violet, and J. L. Dalby

Rev. Sci. Instrum. 53, 969 (1982); http://dx.doi.org/10.1063/1.1137118 (9 pages) | Cited 86 times

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A new type of spectroscopic automatic ellipsometer using a piezobirefringent element for polarization modulation at 50 kHz is described. Instead of lock‐in amplifiers the data‐acquisition system consists of a 12.8‐MHz digital sampling of the detected signal with a high word rate 8‐bit ADC, followed by on line Fourier transformation of the accumulated data with a short instruction cycle (∼200 ns) microprocessor, driven by a commercial microcomputer. The absolute minimum time required for measuring one set of Fourier coefficients is thus reduced to the modulation period of 20 μs. For digital error reduction purposes and signal‐to‐noise ratio improvement a basic 5 ms sequence of 256 accumulated periods per point is chosen. At this data‐acquisition rate a precision of 5×10−4 is obtained. Further accumulation over 10 s leads to 10−5 precision capability. A detailed analysis of various sources of inaccuracy leads to an estimate of 0.5° maximum systematic error on the ellipsometric angles and ψ and Δ. Applications to the in situ study of a‐Si:H plasma deposited films are also presented.
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07.60.Fs Polarimeters and ellipsometers
07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

Pyroelectric‐vidicon‐aided infrared spectrometer for balloon experiments

A. Matsuzaki, Y. Nakamura, and T. Itoh

Rev. Sci. Instrum. 53, 978 (1982); http://dx.doi.org/10.1063/1.1137119 (6 pages)

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A new type of IR spectrometer has been developed for balloon experiments on spectral measurement in the 2–5‐μm region with a solar occultation method. The spectrometer is based on multichannel spectroscopy using a pyroelectric vidicon as the detecting sensor. In order to improve the spectral resolution and the dynamic range of the signal, the spectrum is divided into three spectra which are focused in parallel to each other on the target of the vidicon. The present spectrometer turns out to be applicable to a spacecraft‐borne IR spectrometer.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques

High‐power radio frequency irradiation system with automatic tuning

Leslie G. Butler, Carl Reiner, and Theodore L. Brown

Rev. Sci. Instrum. 53, 984 (1982); http://dx.doi.org/10.1063/1.1137120 (5 pages) | Cited 2 times

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A high‐power radio frequency irradiation system that can be tuned automatically is described. A rf magnetic field, H1, of up to 1.8 mT can be maintained over the frequency interval from 0.01 to 6.4 MHz with low harmonic distortion. The system is useful in a nuclear quadrupole double resonance spectrometer, and in other nuclear resonance experiments involving frequency sweeps.
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84.30.-r Electronic circuits

Frequency‐scanning marginal oscillator for ion cyclotron resonance spectroscopy

Paul R. Kemper and Michael T. Bowers

Rev. Sci. Instrum. 53, 989 (1982); http://dx.doi.org/10.1063/1.1137121 (8 pages) | Cited 7 times

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A number of ion cyclotron resonance applications have arisen in the past few years which require a frequency‐scanned detection system. Since the traditional marginal oscillator detector has always been a fixed‐frequency detector, alternative detection techniques such as bridge circuit detectors have become widely used. In this paper we present an alternative to the bridge detector, namely, a frequency‐scanning marginal oscillator. Requirements and modifications necessary to convert a marginal oscillator to frequency scanning operation are discussed in detail and the necessary circuit diagrams presented. Finally, a theoretical comparison is made between bridge circuit and marginal oscillator sensitivities.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques

Point‐contact electron tunneling spectrometer

V. Leo

Rev. Sci. Instrum. 53, 997 (1982); http://dx.doi.org/10.1063/1.1137122 (4 pages) | Cited 4 times

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In this paper we present the description of a point contact spectrometer which allows us to realize tunnel junctions (sample/Al oxide/Al) by mechanically approaching the sample (mounted as a moving electrode) to an oxidized Al counterelectrode. Due to the design, the careful choice of materials, and the use of a very accurate driving system (with an approach detecting feedback) this spectrometer is extremely efficient over a wide temperature range. The particular geometry makes possible the study of tunnel characteristics on single crystals of compounds that do not stand vacuum evaporation, usually involved in standard thin‐film tunnel technique.
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73.40.Gk Tunneling

Simple microcomputer‐based apparatus for combined DLTS–C‐V measurement

Kunihiro Asada and Takuo Sugano

Rev. Sci. Instrum. 53, 1001 (1982); http://dx.doi.org/10.1063/1.1137098 (6 pages) | Cited 7 times

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A very simple high‐performance microcomputer‐based apparatus for the combination of DLTS and C‐V curve measurements is reported here. This apparatus has an A/D converter instead of gated boxcar integrators and a D/A converter instead of a pulse generator, both of which are controlled by an eight‐bit microcomputer. An analog feedback loop for CCDLTS is replaced by a digital control loop which does not appear in hardware. This has been done by developing an adaptive feedback gain control algorithm for the control program of the microcomputer. All data required for DLTS analyses such as the determination of energy levels, thermal emission rates, and in‐depth profiles of deep traps can be obtained in a single temperature scan using the multipoint measurements of the capacitance transient (DLTS mode) performed repetitively with different filling pulse voltages. The acquisition capacity of this apparatus in a single temperature scan is about 50 times higher than that of a conventional one, which uses double boxcar integrators. In addition, C‐V curve measurements (C‐V mode) can be done in DLTS mode in 20 K intervals.
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07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation

Versatile and user‐friendly computer system for the CAMECA IMS‐300 secondary ion mass spectrometer

M. Van Craen, P. Van Espen, and F. Adams

Rev. Sci. Instrum. 53, 1007 (1982); http://dx.doi.org/10.1063/1.1137099 (5 pages) | Cited 4 times

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A microcomputer using CAMAC as an interface was implemented on the CAMECA IMS‐300 ion analyzer. The development of hardware and software resulted in a versatile system, allowing higher precision and accuracy of the ion intensity measurements, very accurate mass calibration, larger dynamic intensity range, and considerable improvement of detection limits compared with the original system. The hardware and software components used are described and examples of the advantages of the computer system over the analog recording mode are presented.
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07.05.Hd Data acquisition: hardware and software
07.05.Kf Data analysis: algorithms and implementation; data management
07.05.Rm Data presentation and visualization: algorithms and implementation
07.75.+h Mass spectrometers

Birefringence measurements of crystalline polymers using a far‐infrared interferometer

Stellan Jacobsson and Sverker Hård

Rev. Sci. Instrum. 53, 1012 (1982); http://dx.doi.org/10.1063/1.1137100 (2 pages) | Cited 3 times

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It is demonstrated that far‐infrared interferometry can be used successfully to measure birefringence of crystalline polymer samples thick enough to be opaque at visible wavelengths. The use of a strong, optically‐pumped laser as a source of radiation allows absorbing plastics to be measured. An injection molded, high‐density polyethylene specimen showed a birefringence of about 2%, whereas a compression‐molded sample of the same material showed no measurable birefringence.
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78.20.Fm Birefringence
07.60.Ly Interferometers

Low‐noise rf capacitance bridge transducer

Paul S. Linsay and David H. Shoemaker

Rev. Sci. Instrum. 53, 1014 (1982); http://dx.doi.org/10.1063/1.1137101 (6 pages) | Cited 8 times

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We have designed a low‐noise servo system to both damp the motion of a high Q pendulum as well as measure the ground noise that drives it. The servo is based on a high‐frequency low‐noise capacitance bridge which is used as a displacement transducer for sensing the position of the pendulum. The bridge itself is servoed to minimize the need to adjust its components because of slow mechanical thermal drifts. Used as a displacement transducer we have achieved a position sensitivity of 4×10−11 cm/√Hz.
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06.30.Ft Time and frequency

Time and position‐sensitive detector for dissociative processes in fast beams

D. P. de Bruijn and J. Los

Rev. Sci. Instrum. 53, 1020 (1982); http://dx.doi.org/10.1063/1.1137102 (7 pages) | Cited 129 times

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A microchannel‐plate detector has been developed to detect the time and position of two particles simultaneously. High resolution in position and timing is achieved with 100 μm FWHM and 0.5 ns FWHM, respectively. The detector is designed to measure dissociative processes of molecules in fast beams. The released kinetic energy and the direction of the associated momentum with respect to the beam direction in the center of mass can be determined directly. This method offers big advantages over the determination by means of a mass spectrometer which is common practice in the field of ’’translational spectroscopy.’’ The efficiency is increased by a factor of 103–105 with comparable energy resolution. Measurements are performed on the dissociative charge exchange of H+2 with Mg atoms. In the range of 7.2–10.2 eV 17 discrete energies are observed due to the predissociation of the c3πu state in H2 and presumably also the c1πu state.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors

Novel directional ion energy analyzer

R. L. Stenzel, R. Williams, R. Agüero, K. Kitazaki, A. Ling, T. McDonald, and J. Spitzer

Rev. Sci. Instrum. 53, 1027 (1982); http://dx.doi.org/10.1063/1.1137103 (5 pages) | Cited 36 times

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A new ion energy analyzer with high angular resolution (⩽3×10−4 sr) is described. It consists of a microchannel plate followed by a retarding‐grid type analyzer. The microchannel plate is not used for charge multiplication but as a geometric filter with narrow angular passband (ϑ≃0.6°) yet high transparency (T≃60%). The energy analyzer is used to measure the true velocity space distribution of low‐energy ion beams (Eb = 10–100 eV) in a double plasma device. Its superior performance over the conventional gridded energy analyzer is demonstrated. Applications to the study of beam wakes are shown.
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07.75.+h Mass spectrometers

New electron energy analyzer for magnetized plasmas

D. N. Arion and R. F. Ellis

Rev. Sci. Instrum. 53, 1032 (1982); http://dx.doi.org/10.1063/1.1137104 (6 pages) | Cited 5 times

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A single selecting electrode device for the measurement of electron energy distributions parallel to a strong magnetic field in a plasma is described. A series of parallel plates eliminates ion entry into the analyzer and selectively retards electrons for energy analysis. The device was tested in a hot cathode discharge in the University of Maryland Mirror Machine. Results compare favorably with data taken with a conventional four‐grid energy analyzer.
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52.70.Nc Particle measurements
07.75.+h Mass spectrometers

Reduction of gas flow into a hollow cathode ion source for a neutral beam injector

Shigeru Tanaka, Masato Akiba, Yoshihiro Arakawa, Hiroshi Horiike, and Junji Sakuraba

Rev. Sci. Instrum. 53, 1038 (1982); http://dx.doi.org/10.1063/1.1137105 (11 pages) | Cited 3 times

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Experimental studies have been made on the reduction of the gas flow rate into ion sources which utilize a hollow cathode. The electron emitter of the hollow cathode was a barium oxide impregnated porous tungsten tube. The hollow cathode was mounted to a circular or a rectangular bucket source and the following results were obtained. There was a tendency for the minimum gas flow rate for the stable source operation to decrease with increasing orifice diameter of the hollow cathode up to 10 mm. A molybdenum button with an appropriate diameter set in front of the orifice reduced the minimum gas flow rate to one half of that without button. An external magnetic field applied antiparallel to the field generated by the heater current stabilized the discharges and reduced the minimum gas flow rate to one half of that without field. Combination of the button and the antiparallel field reduced the minimum gas flow rate from the initial value (9.5 Torr 1/s) to 2.4 Torr 1/s. The reason for these effects was discussed on the basis of the theory for arc starvation.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative

New technique for direct measurement of electron temperature

Nobuyuki Kaya

Rev. Sci. Instrum. 53, 1049 (1982); http://dx.doi.org/10.1063/1.1137106 (4 pages) | Cited 1 time

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The Langmuir probe is frequently used as a conventional method in laboratories and space observations to measure an electron temperature. However, the method needs a complicated analysis to determine the electron temperature. A new technique which automatically determines the electron temperature is proposed in this paper. Its principle is: two potentials at which a preset electron current is collected by the probe are automatically measured and the difference of the two potentials is simply proportional to the electron temperature. Merits of this technique are high accuracy, quick response, direct display of an electron temperature independent of electron density, and diagnostic simplicity. Results of experiments of electron temperature measurements on a sounding rocket and in a space chamber proved the usefulness of this technique.
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07.50.-e Electrical and electronic instruments and components

Sample holder for measurement of small magnetic moments using SQUID magnetometers

Apurba Roy, D. Scott Buchanan, D. M. Ginsberg, and P. R. Roach

Rev. Sci. Instrum. 53, 1053 (1982); http://dx.doi.org/10.1063/1.1137086 (5 pages) | Cited 5 times

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A self‐compensating sample holder, suitable for making precise measurements of the magnetic moments of very small samples in SQUID magnetometers, has been developed. The design calculations for this holder are outlined, and its observed performance is described. The compensated holder exhibits a signal whch is only 1.5% of the signal from a noncompensated holder.
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07.55.-w Magnetic instruments and components

Differential reflectometer for studies of adsorption on stepped crystal surfaces

L. Wolterbeek, M. H. J. Hottenhuis, and F. G. Kuper

Rev. Sci. Instrum. 53, 1058 (1982); http://dx.doi.org/10.1063/1.1137087 (3 pages)

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A differential reflectometer is described which is capable of measuring reflectivity variations down to 0.05% of those very small fractions (10−2–10−3) of the illuminated surface that are of interest, i.e., atomically stepped parts of rough or curved surfaces that have a certain orientation and reflect light into a certain direction. The intensities of the incident beam and the light reflected over a certain angle, differing by several orders, are equalized at the point of detection by optical means in order to meet the requirements of accurately determining their ratio. Apart from the glass fiber bundle, which picks up the reflected light, the same optics are present in incident as well as reflected beam paths according to the reflectometer principle. The experimental setup has been tested by measuring the adsorption speed of oxygen on rough cleaved silicon surfaces which consist of parts with varying densities of monoatomic steps.
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07.60.Hv Refractometers and reflectometers

Temperature‐compensated, differential tensimeter for measuring gas adsorption by low surface area solids

Isao Suzuki

Rev. Sci. Instrum. 53, 1061 (1982); http://dx.doi.org/10.1063/1.1137088 (6 pages) | Cited 6 times

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An apparatus is described which permits convenient determination of gas adsorption of solids having lower adsorption capacity at subatmospheric pressures. The apparatus consists of a differential micromanometer whose two arms are connected to a pair of sample and reference burets of nearly equal volume for dosing gas into sample and reference cells also of nearly equal volume. When the two cells are immersed in the same temperature bath this design greatly reduces measurement uncertainties due to fluctuations in temperature. Surface areas as small as 1000 cm2 can be measured through volumetric measurements of nitrogen uptake at overall pressures between 3 and 30 KPa at liquid nitrogen temperature.
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07.30.Hd Vacuum testing methods; leak detectors

Technique of range modulation for a clinical pi‐meson beam

Gabriel K. Y. Lam

Rev. Sci. Instrum. 53, 1067 (1982); http://dx.doi.org/10.1063/1.1137089 (5 pages) | Cited 4 times

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A simple, versatile technique of range modulation has been developed based on the mathematical technique of linear programming for linear addition of depth dose curves. This technique enables the use of discrete step range shifting, and hence results in substantial simplification in the design and operation of range modulators. A prototype using only eight steps has been constructed for the TRIUMF biomedical π− channel for cancer radiotherapy. This system has been shown to be capable of producing depth dose profiles of various characteristics required for biomedical experimentation. Its operation under computer control is also simple, accurate, and immune to large fluctuations in the output of the TRIUMF accelerator.
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87.53.-j Effects of ionizing radiation on biological systems

Adaptation of an electrochemical system for measurement and regulation of oxygen partial pressure to a symmetrical thermogravimetric analysis system developed using a Cahn 1000 electrobalance

A. Caneiro, P. Bavdaz, J. Fouletier, and J.P. Abriata

Rev. Sci. Instrum. 53, 1072 (1982); http://dx.doi.org/10.1063/1.1137090 (4 pages) | Cited 35 times

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We report equipment consisting of the coupling of an electrochemical system for measurement and regulation of oxygen partial pressure (PO2) to a symmetrical thermogravimetric analysis system built on the basis of a Cahn 1000 electrobalance. The electrochemical system allows the measurement and regulation of PO2 within a few percent, and has the additional advantage that it can be checked against systematic errors in an absolute way by means of the ’’Faraday’s law test.’’ The performance of the whole experimental setup is demonstrated by the resolution of a narrow hysteresis loop shown by PO2 as a function of composition in the U3O8 phase of the uranium–oxygen system.
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07.20.Ka High-temperature instrumentation; pyrometers
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