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Apr 1987

Volume 58, Issue 4, pp. 501-715

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Experimental tests of a toroidal electrostatic analyzer

D. T. Young, A. G. Ghielmetti, E. G. Shelley, J. A. Marshall, J. L. Burch, and T. L. Booker

Rev. Sci. Instrum. 58, 501 (1987); http://dx.doi.org/10.1063/1.1139260 (8 pages) | Cited 8 times

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A toroidal electrostatic analyzer of a design suitable for space plasma instrumentation has been constructed and tested. Experimental results are compared with second‐order ion optical theory and are in good agreement. Verifying the ion optics of the toroid was simplified by use of a position‐sensing microchannel‐plate detector mounted on a positioning system with three translational degrees of freedom located at the toroid exit. The toroidal analyzer described here is the first optical element in a fully toroidal mass spectrograph intended for analysis of kilovolt magnetospheric plasmas.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.75.+h Mass spectrometers
52.70.Nc Particle measurements

Magnetic surface mapping with an emissive filament technique on the Auburn torsatron

R. F. Gandy, M. A. Henderson, J. D. Hanson, G. J. Hartwell, and D. G. Swanson

Rev. Sci. Instrum. 58, 509 (1987); http://dx.doi.org/10.1063/1.1139261 (7 pages) | Cited 15 times

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Torsatron and stellarator plasma confinement devices rely on magnetic surface mapping to determine the critical vacuum magnetic field structure. A recently developed method employing an emissive filament offers some advantages over the traditional technique of mapping with a directed electron beam. On the Auburn torsatron a comparative study between the emissive filament and directed electron beam techniques has been conducted. The parameters varied in the comparative study are filament geometry, emission current, bias voltage, background gas pressure, and magnetic field strength. This comparative study indicates that the emissive filament technique is reliable over a broad and easily accessible range of parameters. We have also measured the spatial distribution of electrons on a given magnetic surface. As an application of the emissive filament technique, the optimization of the magnetic surfaces on the Auburn torsatron is shown.
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52.70.Ds Electric and magnetic measurements
07.50.-e Electrical and electronic instruments and components
07.55.-w Magnetic instruments and components

Heavy ion beam probe energy analyzer for measurements of plasma potential fluctuations

L. Solensten and K. A. Connor

Rev. Sci. Instrum. 58, 516 (1987); http://dx.doi.org/10.1063/1.1139262 (4 pages) | Cited 24 times

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The operation of a Proca and Green type 30° parallel plate electrostatic energy analyzer is modeled in a new manner that permits high‐resolution heavy ion beam probe measurements of fluctuating plasma potential. Systematic calibration procedures permit detection of potential changes smaller than 0.01% of the probing beam energy at frequencies up to a megahertz. Most recent applications of beam probes have made use of this new capability.
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52.70.Nc Particle measurements
52.70.Ds Electric and magnetic measurements
07.78.+s Electron, positron, and ion microscopes; electron diffractometers

High spectral resolution, photon counting detector for Doppler temperature measurements in magnetically confined plasmas

R. D. Benjamin, J. L. Terry, and H. W. Moos

Rev. Sci. Instrum. 58, 520 (1987); http://dx.doi.org/10.1063/1.1139263 (10 pages) | Cited 3 times

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This paper describes the design, construction, and performance of a single‐stage microchannel‐plate image intensifier used as a photon counting detector over the wavelength range from 1150 to ∼2000 Å. The intensifer incorporates three high strip current (∼300 μA) microchannel plates, constructed with 12‐μ‐diam channels and 15‐μ center–center spacing, in a ‘‘Z’’ configuration. The use of high strip current MCPs requires gating the power supply to protect the plates from thermal runaway of the strip current. The output pulses are proximity focused onto a P‐46 phosphor screen, which is fiber‐optically coupled to a linear, self‐scanning photodiode array. Maximum frame rates for the photodiode array are ∼ 125 000 frames/s, with maximum count rates of ∼25 000 photoevents/s. The detector was placed at the focal plane of a 1‐m focal length Ebert–Fastie spectrometer and the performance characteristics of the spectrometer‐detector system were evaluated using a hollow cathode Pt lamp. The linewidths measured during this evaluation demonstrate that the spatial resolution of the detector is better than 50 μ. The spectrometer‐detector system was then used to determine ion temperatures from Doppler broadened impurity lines emitted from plasmas of the Alcator C tokamak. This detector demonstrated more than an order of magnitude increase in sensitivity compared to a photon‐counting photomultiplier tube with a vibrating mirror previously used for these measurements with the same spectrometer. This permitted a determination of the central ion temperature of the Alcator C tokamak using the ‘‘forbidden’’ line of Fe xii at 1354.1 Å which was not detected with the previous system.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Rd Visible and ultraviolet spectrometers

Development of a beam probing system for measurement of density, temperature, and magnetic field of RFP plasma

Y. Kamada, M. Utsumi, M. Saitoh, J. Morikawa, H. Nihei, Z. Yoshida, and N. Inoue

Rev. Sci. Instrum. 58, 530 (1987); http://dx.doi.org/10.1063/1.1139264 (6 pages) | Cited 2 times

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A hydrogen beam probing system developed for the REPUTE‐1 reversed field pinch device is described. With this system, the plasma ion line density, the central ion temperature, and the magnetic field profile can be measured. Before being applied to the REPUTE‐1 device, the probing system was tested on the TORIUT‐5 tokamak and TORIUT‐6 ultralow‐q (ULQ) devices. The experimental results show the availability of the system. The measured line density agrees well with that measured by the microwave interferometry. The measurable density ranges from 1019 m−3 to 3×1020 m−3. A new method of magnetic field measurement which is effective and important for RFP plasmas is proposed. The resolution and the accuracy of this measurement have been confirmed by experiments on the TORIUT‐5 device. Experimental results agree well with computation.
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52.70.Nc Particle measurements
52.40.Mj Particle beam interactions in plasmas
52.55.Ez Theta pinch

Solid deuterium fiber extruder

J. D. Sethian, K. A. Gerber, and M. O. Sy

Rev. Sci. Instrum. 58, 536 (1987); http://dx.doi.org/10.1063/1.1139265 (3 pages) | Cited 6 times

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A simple fiber extruder has been developed to produce small diameter filaments of frozen deuterium. The extruder is based on a commercially available liquid‐helium‐cooled cryostat, and only the actual deuterium extruder mechanism must be fabricated. The extruder features interchangeable nozzles and fibers ranging in diameter from 40 to 300 μ have been made. All fibers are over 10 cm in length and their physical dimensions remain unchanged for at least 4 min. The neutral gas density outside the fiber is on the order of 1013 and drops off with the inverse of the radius. These fibers are used to provide the plasma for the NRL dense z‐pinch experiment whose objective is to study the fusion application of small, dense plasmas.
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67.80.-s Quantum solids
07.10.-h Mechanical instruments and equipment
07.20.Mc Cryogenics; refrigerators, low-temperature detectors, and other low-temperature equipment
52.50.-b Plasma production and heating

Microwave reflectometry with the extraordinary mode on tokamaks: Determination of the electron density profile of Petula‐B

H. Bottollier‐Curtet and G. Ichtchenko

Rev. Sci. Instrum. 58, 539 (1987); http://dx.doi.org/10.1063/1.1139266 (8 pages) | Cited 39 times

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The use of an ordinary mode reflectometer has already proved to be a good means for determining the density profile of a plasma, but the fact that this mode reflects where its frequency equals the local plasma frequency restricts its use to the region of the density gradient. The extraordinary mode reflectometry investigated here permits the observation of the scrape‐off layer as well as the near‐axis region and in certain conditions also the high magnetic field side of the density profile. It is also shown that this mode requires a range of frequency sweep for measuring a given density profile smaller than the ordinary mode. On the Petula‐B tokamak, the density profile has been measured in 200 μs, its evolution when applying the lower hybrid current drive could be also followed. Since the measurement is particularly sensitive near the reflection point of the wave, it could be used to determine precisely the position of magnetic islands and the fluctuation amplitudes. In addition, the access and place occupied in the vacuum chamber being very small, this diagnostic should be compatible with reactor conditions.
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52.70.Gw Radio-frequency and microwave measurements
52.55.Fa Tokamaks, spherical tokamaks
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)

Cold high‐intensity atomic hydrogen beam source

A. Hershcovitch, A. Kponou, and T. O. Niinikoski

Rev. Sci. Instrum. 58, 547 (1987); http://dx.doi.org/10.1063/1.1139267 (10 pages) | Cited 8 times

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A cold atomic hydrogen beam source has been built and tested at BNL. The flow channel of the source, consisting of a discharge tube, a constricting nozzle, a thermal transition section, and an accommodator, was designed to operate in the laminar flow range. A novel feature of this source is a 0.3‐mm gap between the transition Teflon tube which guides the flow and an accommodator which cools the flowing gas; across this gap the wall temperature may step from 100 K in the Teflon to 3 K in the accommodator. A record pulsed H° beam flux of 9.4×1018 H° sr−1 s−1 was obtained at an accommodator temperature of 5.8 K. The gas dynamic analysis of the system is in excellent agreement with the experimental results.
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07.77.-n Atomic, molecular, and charged-particle sources and detectors
29.27.-a Beams in particle accelerators
29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative

One Tesla rare‐earth permanent quadrupole magnet for spin separation of metal clusters

Klaus‐Peter Ziock and W. A. Little

Rev. Sci. Instrum. 58, 557 (1987); http://dx.doi.org/10.1063/1.1139268 (6 pages) | Cited 1 time

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We have constructed a 1.20‐T pole tip field quadrupole magnet which is used to separate electrically neutral metal clusters by their spin magnetic moment. The device is magnetically energized with rare‐earth samarium cobalt magnets. The use of this material allows for both the low cost and the small size of the device.
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07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices
07.55.-w Magnetic instruments and components
07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
07.77.-n Atomic, molecular, and charged-particle sources and detectors

Efficient electro‐optic modulator for optical pumping of Na beams

J. F. Kelly and A. Gallagher

Rev. Sci. Instrum. 58, 563 (1987); http://dx.doi.org/10.1063/1.1139269 (4 pages) | Cited 38 times

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An electro‐optic modulator using LiTaO3 is described which yields 34% of the carrier intensity in each of the first‐order sidebands with rf phase modulation frequencies fm∼1.0 GHz and ≲1.0 W input power. The modulator makes use of a lumped resonator with Q∼200 to obtain efficient production of the sidebands. It is shown that the device can be scaled for operation at ∼2 GHz. Applications of this modulator include optical pumping of the lighter alkali atoms, FM sideband spectroscopy, and laser phase/frequency stabilization using rf modulation techniques.
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42.79.Hp Optical processors, correlators, and modulators
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers

Bimorph‐driven x–y–z translation stage for scanned image microscopy

J. R. Matey, R. S. Crandall, B. Brycki, and G. A. D. Briggs

Rev. Sci. Instrum. 58, 567 (1987); http://dx.doi.org/10.1063/1.1139270 (4 pages) | Cited 10 times

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We have developed an x–y–z scanning stage for mechanically scanned microscopy. The stage is constructed of ‘‘double‐S’’ mode piezoelectric bimorphs. The prototype unit has a deflection sensitivity of 0.3 μm/V and a travel in each of the three axes of ±60 μm. The lowest mechanical resonances of the stage are at 190, 220, and 360 Hz, corresponding to the x, y, and z axes of the stage, respectively. The noise level of the stage, when mounted on an isolation table, is ∼0.1 nm. The performance of the stage can be understood in terms of a simple lumped element model which can be used to optimize such stages for particular applications.
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07.60.Pb Conventional optical microscopes
07.10.-h Mechanical instruments and equipment

Null ellipsometer for the studies of thin films at gas–water interface

Daniel Ducharme, Alain Tessier, and Roger M. Leblanc

Rev. Sci. Instrum. 58, 571 (1987); http://dx.doi.org/10.1063/1.1139271 (8 pages) | Cited 8 times

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Ellipsometry is a sensitive nondestructive optical technique which can be successfully used for determining the thickness of an optically transparent thin film deposited on a dielectric substrate. In this laboratory we have constructed a vertical null‐type ellipsometer which has been used with a homemade aluminum Teflon‐coated Langmuir trough, to study thin films at gas–water interface. Surface pressure, surface potential, and ellipsometric measurements have been performed simultaneously. Ellipsometric measurements have been done directly on the aqueous substrate contained in the trough, with and without the film, with reproducibility (±0.02°) and good signal stability (±0.1 mV) on the 10‐mV scale. The performance of the homemade instrument had been checked against the known ellipsometric properties of spread arachidic acid on acidic water solution. In this paper, details of construction and performance of the ellipsometer as well as characteristics of the trough and ellipsometric study of β‐palmitoyl‐α‐oleoyl‐L‐α‐phosphatidylcholine is presented. Stability of the photometric signal as a function of the structure of the film‐forming molecules is also discussed.
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07.60.Fs Polarimeters and ellipsometers
68.03.-g Gas-liquid and vacuum-liquid interfaces
68.05.-n Liquid-liquid interfaces

Third‐order correlator for point processes

L. Basano and P. Ottonello

Rev. Sci. Instrum. 58, 579 (1987); http://dx.doi.org/10.1063/1.1139219 (5 pages) | Cited 3 times

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We present a triple correlator for point processes in which a long batch of pulses is first recorded by direct memory access (DMA) and subsequently analyzed by a microcomputer. Provision is also made for the retrieval of the second‐order correlation function. Applications to the statistical analysis of level crossings by random noise are briefly outlined.
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42.79.Vb Optical storage systems, optical disks
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
42.30.-d Imaging and optical processing
42.79.Bh Lenses, prisms and mirrors
42.79.Fm Reflectors, beam splitters, and deflectors

Fourier transform infrared spectrometer for a single aerosol particle

Gideon Sageev Grader, Richard C. Flagan, John H. Seinfeld, and Stephen Arnold

Rev. Sci. Instrum. 58, 584 (1987); http://dx.doi.org/10.1063/1.1139220 (4 pages) | Cited 7 times

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A spectrometer is reported here for obtaining the infrared spectrum of a single aqueous aerosol particle by a Fourier transform technique. The particle is held in an electrodynamic balance and irradiated simultaneously by the infrared output from a Michelson interferometer and the visible light from a dye laser. The size of the particle is modulated by chopping the IR beam, and the resulting visible scattered light fluctuation is detected at 90° with a photomultiplier tube. The amplitude of the scattered light fluctuation is measured with a lock‐in amplifier at each interferometer mirror position. The electronic circuitry for stepping the interferometer mirror is presented and discussed. Inverting the lock‐in signal by a discrete fast Fourier transform routine (FFT) yields the particle absorption spectrum. The resulting spectrum for an (NH4)2SO4 droplet is presented.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.30.-j Infrared and Raman spectra

Variable Rowland radius laboratory EXAFS system

Y. Yacoby, M. Brettschneider, and M. Bezalel

Rev. Sci. Instrum. 58, 588 (1987); http://dx.doi.org/10.1063/1.1139221 (5 pages) | Cited 6 times

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We report here on a new EXAFS laboratory facility. It features a variable Rowland radius with a source to bent crystal distance that can vary from 250 to 750 mm. It has a sample carrying table which is mechanically detached from the monochromator and can carry more than 50 lb with no effect on the monochromator. The system is completely computer controlled in such a way that the operator can control every part of the system separately as well as perform complete automatic runs. The data‐analysis programs had been divided into a general package which performs the bookkeeping of files experimental parameters and program parameters and a specific package for the analysis of the EXAFS data. The monochromator is shown to have almost theoretical resolution. We present experimental results of EXAFS on copper. The Fourier transform of these spectra agree very well with the Fourier transform of EXAFS spectra measured on a synchrotron. It is shown that the resolution of 4.5 eV of these data does not present a limitation on the quality of the data. The signal‐to‐noise ratio is, on the other hand, quite critical.
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07.85.-m X- and γ-ray instruments
61.05.cf X-ray scattering (including small-angle scattering)
61.05.cj X-ray absorption spectroscopy: EXAFS, NEXAFS, XANES, etc.
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
07.05.Bx Computer systems: hardware, operating systems, computer languages, and utilities

Device to measure friction coefficients and contact resistance inside a scanning Auger microscope

T. G. McDonald, D. E. Peebles, L. E. Pope, and H. C. Peebles

Rev. Sci. Instrum. 58, 593 (1987); http://dx.doi.org/10.1063/1.1139650 (5 pages) | Cited 3 times

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A device is described for in situ, rotary pin‐on‐disk wear studies in a commercial scanning Auger microscope. This device is mounted on a single 8‐in. vacuum flange and can be installed in place of the normal sample mounting manipulator. The device allows simultaneous measurement of contact resistance and friction coefficient under controlled atmospheric conditions as wear progresses. The surface composition and topography of the wear track are measured without exposure of the surface to contaminating environments or removal of the pin from the wear track. Modifications made to the vacuum system to facilitate atmospheric control are also described.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
06.60.Sx Positioning and alignment; manipulating, remote handling
73.40.Cg Contact resistance, contact potential

Test pattern for fluorescence microscopy

G. C. A. M. Janssen, B. A. C. Rousseeuw, and H. T. M. van der Voort

Rev. Sci. Instrum. 58, 598 (1987); http://dx.doi.org/10.1063/1.1139222 (2 pages) | Cited 1 time

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A fluorescent test pattern with submicron dimensions has been produced. With this test pattern the optical characteristics of a confocal scanning laser microscope can be determined. The fabrication procedure of the test pattern and the raw data obtained in a measurement of the transfer function of the confocal scanning laser microscope are presented.
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42.87.-d Optical testing techniques
07.60.Pb Conventional optical microscopes
06.20.F- Units and standards

Soft x‐ray imaging by a commercial solid‐state television camera

Isao Matsushima, Kazuyoshi Koyama, Mitsumori Tanimoto, and Masaaki Yano

Rev. Sci. Instrum. 58, 600 (1987); http://dx.doi.org/10.1063/1.1139223 (4 pages) | Cited 2 times

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A commerical, solid‐state television camera has been used to record images of soft x radiation (0.8–12 keV). The performance of the camera is theoretically analyzed and experimentally evaluated compared with an x‐ray photographic film (Kodak direct exposure film). In the application, the camera has been used to provide image patterns of x rays from laser‐produced plasmas. It is demonstrated that the camera has several advantages over x‐ray photographic film.
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07.85.-m X- and γ-ray instruments
07.68.+m Photography, photographic instruments; xerography
52.70.La X-ray and γ-ray measurements

New apparatus for measuring steady‐state diffusion

Nabil Mikati

Rev. Sci. Instrum. 58, 604 (1987); http://dx.doi.org/10.1063/1.1139224 (5 pages)

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A steady concentration gradient is maintained in a narrow vertical diffusion channel making it possible to determine the concentration dependence of the diffusion coefficient in one single experiment. The gradient is sustained by a simple transport system and is observed interferometrically. The apparatus is tested using calcium chloride and sugar. The method is rapid and the results agree fairly well with those reported in the literature. Analyses of the flow velocity and the time to reach the steady state are given.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
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)
66.10.C- Diffusion and thermal diffusion
66.20.-d Viscosity of liquids; diffusive momentum transport

Polarized neutron reflectometer: A new instrument to measure magnetic depth profiles

G. P. Felcher, R. O. Hilleke, R. K. Crawford, J. Haumann, R. Kleb, and G. Ostrowski

Rev. Sci. Instrum. 58, 609 (1987); http://dx.doi.org/10.1063/1.1139225 (11 pages) | Cited 105 times

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A description is given of the prototype polarized neutron reflectometer installed at the intense pulsed neutron source. This instrument is designed for determining the magnetic depth profiles near the surfaces of ferromagnets and superconductors, by measuring the spin‐dependent reflectivities of a well‐collimated (0.01°) beam of cold neutrons from surfaces of a few cm2. Magnetic profiles can be determined with the spatial resolution of 40 Å, over thicknesses up to 5000 Å. Variations of the magnetic flux of the order of 10−5 G cm2 can be detected.
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07.55.-w Magnetic instruments and components
61.05.fm Neutron diffraction

Measurement of the spin‐wave instability threshold hcrit in microwave ferrites

Y. T. Zhang, C. E. Patton, G. Srinivasan, G. O. White, C. J. Brower, and C. A. Edmondson

Rev. Sci. Instrum. 58, 620 (1987); http://dx.doi.org/10.1063/1.1139226 (4 pages) | Cited 3 times

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Several improvements for a previously described semiautomated system for spin‐wave instability threshold measurement in microwave ferrites are described. The effects of sample size, sample position in the microwave cavity, and method of data interpretation on the threshold field hcrit are also reported. The data were obtained by the parallel pumping technique at 8.92 GHz. Sphere‐shaped samples of polycrystalline yttrium iron garnet were used for the measurements. The results show that the initial, ‘‘exact’’ instability onset, the ‘‘extrapolated’’ onset from the loss increase above threshold, and the ‘‘visual’’ onset estimate from the above threshold response can vary by more than 0.5 Oe for hcrit values of 3 Oe or so. Large samples, above 1 mm in diameter, lead to an overestimation of hcrit due to errors in the microwave cavity perturbation theory analysis which forms the basis of the measurement. The amount of overestimation is about 0.1 Oe for a diameter of 2 mm and 0.2 Oe at 3 mm. Sample position relative to the cavity end wall does not appear to be critical. Imaging effects are small for hcrit measurements in the YIG‐like materials of interest here.
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07.55.-w Magnetic instruments and components
75.30.Ds Spin waves
75.50.Bb Fe and its alloys

Method for measuring complex permeability at radio frequencies

Ronald B. Goldfarb and Howard E. Bussey

Rev. Sci. Instrum. 58, 624 (1987); http://dx.doi.org/10.1063/1.1139227 (4 pages) | Cited 7 times

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An established method for measuring complex rf magnetic permeability is based on the change in inductance and resistance of a coaxial transmission line upon insertion of a sample toroid. It is not necessary to wind coils on the toroid or correct for geometric demagnetization factors. The use of modern commercial impedance analyzers, as described in this paper, makes measurements from 1 kHz to 1 GHz particularly easy, fast, and accurate.
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07.55.-w Magnetic instruments and components
75.30.Cr Saturation moments and magnetic susceptibilities
78.70.Gq Microwave and radio-frequency interactions
07.55.Db Generation of magnetic fields; magnets
85.70.-w Magnetic devices

High field nuclear magnetometer

April Dutta and C. N. Archie

Rev. Sci. Instrum. 58, 628 (1987); http://dx.doi.org/10.1063/1.1139228 (4 pages) | Cited 2 times

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A magnetometer capable of measuring changes in the nuclear magnetism of 3He in the presence of an 8‐T magnetic field is described. A key component is a type II superconducting shield (NbTi) which stabilizes the external field. Short‐term sensitivity is equivalent to detecting magnetic field changes of a few parts in 1010. In applications involving large pressure changes and 3He liquid–solid phase changes, additional problems arise. Sensitivity to physical distortion of the device in some applications can generally be corrected for or exploited for pressure detection.
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07.55.-w Magnetic instruments and components
67.30.-n 3He
67.80.-s Quantum solids

Gas‐solution microcalorimeter for determining heat binding curves

Gary A. Bishop, Antonio Parody‐Morreale, Charles H. Robert, and Stanley J. Gill

Rev. Sci. Instrum. 58, 632 (1987); http://dx.doi.org/10.1063/1.1139229 (7 pages) | Cited 1 time

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A gas‐solution reaction microcalorimeter has been developed for measuring the heat produced from a macromolecule in solution when the partial pressure of a reacting ligand is changed. The accumulated result of such stepwise heat processes enables the construction of a heat binding curve: namely the enthalpy per mole of reaction site versus the logarithm of the ligand activity [Gill, Richey, Bishop, and Wyman, Biophys. Chem. 21, 1 (1985)]. The high sensitivity (1 μcal) of the calorimeter is achieved by careful twinning and closed‐loop proportional control achieved through continuous computer monitoring. A 15‐μl liquid sample, for example 5‐mM heme hemoglobin, is held in the form of a thin layer by means of a filter paper membrane. This configuration facilitates rapid equilibrium with exposed gases and allows for the completion of a given heat process within the range of 10 min. Gas partial pressures are accurately produced by means of a precision dilution valve incorporated into the calorimeter. The automatic determination of the heat binding curve is controlled by a small microcomputer programmed to change the gas partial pressure and to measure the heat that results from the change in the gas activity. An entire binding curve can be obtained on a sample of hemoglobin with as little as 20 nmol of oxygen binding sites.
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07.20.Fw Calorimeters
82.60.Cx Enthalpies of combustion, reaction, and formation
82.60.Lf Thermodynamics of solutions
82.80.-d Chemical analysis and related physical methods of analysis

‘‘Tray’’ type calorimeter for the 15–300 K temperature range: Copper as a specific heat standard in this range

Douglas L. Martin

Rev. Sci. Instrum. 58, 639 (1987); http://dx.doi.org/10.1063/1.1139230 (8 pages) | Cited 33 times

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A calorimeter is described in which thermal contact with the sample is made via a grease film. Radiation shields built into the calorimeter minimize the effect of temperature gradients. Used in an adiabatic shield system the apparatus gives results of high precision and accuracy. The new design permits easy sample changing but there is a small specific heat anomaly owing to melting of the grease film. An all‐metal water triple point cell can be installed in place of the sample to check the temperature measuring equipment. The adiabatic shield system used had four independently controlled elements. Experiment showed that a single controlled element is sufficient for discontinuous heating calorimetry. The apparatus could be run in both continuous and discontinuous heating modes. There was no significant difference in results. Measurements on pure copper are reported and the use of this material as a specific heat standard up to 300 K is discussed.
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07.20.Fw Calorimeters
65.40.-b Thermal properties of crystalline solids
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
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