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Mar 1992

Volume 63, Issue 3, pp. 1859-2105

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High performance automatic alignment and power stabilization system for a multikilowatt CO2 laser

Dale R. Akitt, H. J. J. Seguin, Christopher V. Sellathamby, and H. Reshef

Rev. Sci. Instrum. 63, 1859 (1992); http://dx.doi.org/10.1063/1.1143295 (8 pages) | Cited 2 times

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A beam profile sensor for use in an automatic alignment and power stabilization system for a multikilowatt CO2 laser is described. An inexpensive pyroelectric array is used in conjunction with a diamond machined rotating wand, to provide on‐line samples of the laser beam. Interface circuits utilize the multiple outputs derived from the detector array for precise monitoring and control of the laser’s output radiation. Data from a 5‐kW CO2 laser are presented to characterize the response of this new beam profile sensor to major perturbations in the optical cavity and lasing gas chemistry. The device has demonstrated exceptional performance in the maintenance of both mode quality and optical power level.
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42.60.By Design of specific laser systems
42.60.Da Resonators, cavities, amplifiers, arrays, and rings

Differential optical absorption spectrometer for measuring atmospheric trace gases@fa@f)

John M. C. Plane@f@f and Chia‐Fu Nien

Rev. Sci. Instrum. 63, 1867 (1992); http://dx.doi.org/10.1063/1.1143296 (10 pages) | Cited 21 times

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The construction of a differential optical absorption spectrometer (DOAS) is described. The instrument was designed for making automated measurements, with relatively high detection sensitivities, of important tropospheric trace gases, and with the ability to operate in rugged environments without frequent attention. Major innovative features of the instrument include a retroreflector to fold the light path, a diode array detector, and computer‐controlled operation of the entire instrument package. The advantages of these modifications with respect to previously reported designs are discussed in detail. This DOAS has been employed since 1989 to measure NO3 (1 ppt), NO2 (0.6 ppb), HONO, O3, and CH2O (0.8 ppb), where the mixing ratios in parentheses indicate the detection limits over a 5 km path length and 4 min integration time, for the species where these could be determined.
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07.60.Rd Visible and ultraviolet spectrometers
92.60.Ta Electromagnetic wave propagation
94.80.+g Instrumentation for space plasma physics, ionosphere, and magnetosphere

Robust improvement in the signal‐to‐noise of a laser fluorosensor through selectively averaging signals

H. Wang, T. Hengstermann, R. Reuter, and R. Willkomm

Rev. Sci. Instrum. 63, 1877 (1992); http://dx.doi.org/10.1063/1.1143297 (3 pages) | Cited 1 time

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Signals acquired with a laser fluorosensor are composed of the fluorescence of the object and noises. The average of n signals theoretically has the signal‐to‐noise ratio (S/N) which is √n times higher than the S/N of the single signal, provided that the fluorescence remains constant from signal to signal and that the noises are independent of each other. In practice, the sources of noise in the signals are often correlated with each other, leading to S/N improvement below the theoretical one. In this paper a procedure is proposed and applied in a laser fluorosensor to obtain better S/N. It is shown that the average signal can have better S/N if the signals with the correlated noises are selectively discarded by averaging many signals. This procedure can be advanced for improving S/N of any multi sample averager.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
42.65.-k Nonlinear optics

A new‐type antenna for continuous gravitational radiation

T. Suzuki@f@f, N. Akasaka, Y. Ogawa, N. Kudo, and K. Morimoto@f@f

Rev. Sci. Instrum. 63, 1880 (1992); http://dx.doi.org/10.1063/1.1143298 (4 pages) | Cited 1 time

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A new‐type disk antenna has been developed to search for continuous gravitational waves emitted from millisecond and submillisecond pulsars. The antenna not only has a wide tunable range of the eigenfrequency that covers down to almost half of the original frequency of the quadrupole mode, but also is easily tuned to an objective frequency with an accuracy of 4×10−5 at 4.2 K. The mechanical quality factor has reached 3.0×107 at 4.2 K in an antenna made of Al5056.
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98.80.Es Observational cosmology (including Hubble constant, distance scale, cosmological constant, early Universe, etc)
04.30.-w Gravitational waves
95.85.Sz Gravitational radiation, magnetic fields, and other observations

A general method for determination of Brillouin linewidths by correction for instrumental effects and aperture broadening: Application to high‐pressure diamond anvil cell experiments

W. F. Oliver, C. A. Herbst, S. M. Lindsay, and G. H. Wolf

Rev. Sci. Instrum. 63, 1884 (1992); http://dx.doi.org/10.1063/1.1143299 (12 pages) | Cited 25 times

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A general method for determining true acoustic‐mode linewidths from Brillouin scattering data is presented. The method is specifically applied to diamond anvil cell experiments to obtain accurate hypersonic attenuation data at high pressure. This work was motivated by the noticeable lack of acoustic attenuation data at high pressure in the literature and by our own attempts to obtain relaxation data from Brillouin experiments in the diamond anvil cell. A detailed discussion of both instrumental and finite aperture contributions to the measured acoustic‐mode linewidth is given, as well as specific algorithms for calculating these effects. Fits to Brillouin scattering spectra obtained at high pressures in different organic liquids are shown. Finally, a discussion is given of experimental details for obtaining accurate Brillouin linewidths in high‐pressure diamond anvil cell experiments.
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62.65.+k Acoustical properties of solids
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells

A normal incidence vacuum ultraviolet emission spectrometer

Zizhou Tang, Zengli Xu, and Steve Kevan

Rev. Sci. Instrum. 63, 1896 (1992); http://dx.doi.org/10.1063/1.1143300 (6 pages) | Cited 1 time

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A compact, normal incidence vacuum ultraviolet (VUV) fluorescence spectrometer for use with both electron and photon excitation in the energy range of 15–40 eV was built and tested. This 1‐m concave grating spectrometer is described together with the performance of its microchannel plate‐charge coupled device detector system. Results of the calibration of the system at the SURF‐II synchrotron light source at the National Institute of Standards and Technology are given. Initial results of experiments using both photon and electron excitation are also presented.
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07.60.Rd Visible and ultraviolet spectrometers

Spin‐polarized photoemission spectroscopy of magnetic surfaces using undulator radiation

P. D. Johnson, N. B. Brookes, S. L. Hulbert, R. Klaffky, A. Clarke@f@f, B. Sinković@f@f, N. V. Smith, R. Celotta, M. H. Kelly, D. T. Pierce, M. R. Scheinfein@f@f, B. J. Waclawski, and M. R. Howells

Rev. Sci. Instrum. 63, 1902 (1992); http://dx.doi.org/10.1063/1.1143301 (7 pages) | Cited 36 times

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A beamline has been established at the National Synchrotron Light Source to perform angle‐resolved photoemission experiments on magnetic surfaces with spin sensitivity. The system has two novel features: it uses a miniature electron‐spin polarization analyzer and it also uses synchrotron radiation from an undulator rather than a bending magnet.
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79.60.-i Photoemission and photoelectron spectra
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
29.30.Aj Charged-particle spectrometers: electric and magnetic
29.30.Ep Charged-particle spectroscopy

Improvement of sensitivity of photothermal deflection spectroscopy by a double pass method

Susumu Horita, Eiji Miyagoshi@f@f, Masahiko Ishimaru, and Tomonobu Hata

Rev. Sci. Instrum. 63, 1909 (1992); http://dx.doi.org/10.1063/1.1143302 (5 pages)

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In order to improve the sensitivity of photothermal deflection spectroscopy, we propose a double pass method, in which a pump beam is passed twice through the sample using a total reflector set behind the sample. A one‐dimensional theoretical analysis of this method is developed and is verified by the measurement results of Si and InP wafers. Also, it is shown theoretically and experimentally that this method can determine lower optical absorption coefficients than conventional ones.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
07.60.Rd Visible and ultraviolet spectrometers
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects

Atomic force microscope with integrated optical microscope for biological applications

Constant A. J. Putman@f@f, Kees O. van der Werf, Bart G. de Grooth, Niek F. van Hulst, Frans B. Segerink, and Jan Greve

Rev. Sci. Instrum. 63, 1914 (1992); http://dx.doi.org/10.1063/1.1143303 (4 pages) | Cited 27 times

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Since atomic force microscopy (AFM) is capable of imaging nonconducting surfaces, the technique holds great promises for high‐resolution imaging of biological specimens. A disadvantage of most AFMs is the fact that the relatively large sample surface has to be scanned multiple times to pinpoint a specific biological object of interest. Here an AFM is presented which has an incorporated inverted optical microscope. The optical image from the optical microscope is not obscured by the cantilever. Using a XY stage to move the sample, an object is selected with the optical microscope and an AFM image of the selected object can be obtained. AFM images of chromosomes and K562 cells show the potential of the microscope. The microscope further enables a direct comparison between optically observed features and topological information obtained from AFM images.
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68.37.-d Microscopy of surfaces, interfaces, and thin films
87.80.-y Biophysical techniques (research methods)

Fabrication of ultrasmall tunnel junctions by electron‐beam lithography

S. J. Koester@f@f, G. Bazán, G. H. Bernstein, and W. Porod

Rev. Sci. Instrum. 63, 1918 (1992); http://dx.doi.org/10.1063/1.1143304 (4 pages) | Cited 1 time

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Fabrication of a variety of ultrasmall tunneling structures is presented for possible applications in single electronics. Two main structures are described: (i) arrays of nanometer‐scale metal dots and (ii) single and multiple linear tunnel junctions formed by overlapping lines. Very large, uniform particle arrays were fabricated by electron‐beam lithography (EBL) with particle diameters as small as 25 nm. The advantage of our dot array system is its high degree of uniformity and very small junction size coupled with the use of isolated particles to reduce stray capacitance effects. Single and multiple linear tunnel junctions were fabricated by EBL using single‐layer resist and angled evaporations. Our fabrication technique differs from previous ones in its ability to create very small tunnel junctions without the need for multilayer resist systems or precise knowledge of the angle of evaporation.
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85.40.Hp Lithography, masks and pattern transfer
61.80.Fe Electron and positron radiation effects
81.65.-b Surface treatments

Histogramming data acquisition system for an (e,2e) coincidence experiment

M. A. Bennett@f@f, P. A. Smith, D. K. Waterhouse, M. J. Ford, J. Flexman, and J. F. Williams

Rev. Sci. Instrum. 63, 1922 (1992); http://dx.doi.org/10.1063/1.1143305 (5 pages) | Cited 6 times

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A four‐dimensional histogramming data acquisition system has been developed for use on an 80386 IBM‐compatible computer. The method has a large data storage capacity providing good experimental resolution and system flexibility. A custom‐built analog‐to‐digital board generates a memory address in hardware from the incoming data which permit the use of a simple and elegant histogramming algorithm. The system is used to collect and analyze data from (e,2e) experiments. Results from coplanar symmetric (e,2e) experiments on argon, at an incident energy of 3 keV, are presented to demonstrate the performance of the instrument. The method is applicable to experiments where data from several sources have to be combined and then histogrammed in real time.
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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
07.50.Ek Circuits and circuit components
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

Inexpensive plasma discharge source for molecular emission spectroscopy with application to 15N analysis

D. I. Hoult@f@f and C. M. Preston@f@f

Rev. Sci. Instrum. 63, 1927 (1992); http://dx.doi.org/10.1063/1.1143306 (5 pages) | Cited 3 times

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The assaying of nitrogen isotope abundance using emission spectroscopy commonly requires a plasma discharge in a sample of N2 gas at low pressure (∼0.5 kPa) in a sealed glass tube. Expensive high‐power (≳20 W) radio‐frequency or microwave amplifiers are often used for this purpose. However, with correct design, a simple and inexpensive, single transistor, 100 MHz, 1 W oscillator can be used to produce a bright plasma discharge in a low‐pressure sample of nitrogen in a 6 mm diameter by 10 cm tube. The device utilizes optimal impedance matching to minimize the power requirements. The principles and limitations of the matching are outlined, and a simple feedback circuit is also described which, with the aid of a phototransistor, enables the emission intensity to be controlled. Ignition of discharge by friction or with the help of a simple piezoelectric gas lighter is also described, and construction details are given.
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52.80.Yr Discharges for spectral sources (including inductively coupled plasma)
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

Performance characteristics of a microwave plasma source using an axial mirror and multipole magnetic fields

H. Nihei, J. Morikawa, D. Nagahara, H. Enomoto, and N. Inoue

Rev. Sci. Instrum. 63, 1932 (1992); http://dx.doi.org/10.1063/1.1143307 (7 pages) | Cited 5 times

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The performance characteristics of a microwave plasma source are presented. The plasma source consists of two chambers: chamber 1 generates a high‐density plasma over which a magnetic field is applied at electron cyclotron resonance condition or greater, and chamber 2 makes the plasma uniform in its lower region by surrounding the peripheral region with magnetic multipole line‐cusp fields. Plasma parameters were measured with a movable Langmuir probe located 1 cm above a plasma grid which is attached at the bottom of chamber 2. The dependence of plasma parameters on the magnetic field configuration, gas pressure and microwave power were examined, and radial distributions were measured. Uniform high‐density plasmas over a 9‐cm‐diam area were produced on the plasma grid in a suitable magnetic field configuration, and uniformity was maintained over a wide pressure range. The uniform density region was determined by the magnetic multipole fields existing in chamber 2’s peripheral region. The ion beam current density evaluated from the extracted ion beam correlated well with the ion saturation current density estimated from the plasma parameters.
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52.50.Dg Plasma sources
52.50.Gj Plasma heating by particle beams

E‐plane horn excitation of slow wave structures for obtaining high‐density electron cyclotron resonance plasmas

R. Baskaran@f@f, S. K. Jain, and S. S. Ramamurthi

Rev. Sci. Instrum. 63, 1939 (1992); http://dx.doi.org/10.1063/1.1143308 (6 pages) | Cited 4 times

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This paper describes a new method of exciting slow wave structures (SWS) for obtaining high‐density electron cyclotron resonance plasmas. The electric field component corresponding to the slow wave mode (SWM) of SWS is excited by an E‐plane horn antenna. The special features of the microwave transmission line are the stable tuning for a given antenna and no requirement for water cooling on any of the components. Two types of SWS, a helical coil and a slotted line antenna, are studied, and the experiments are carried out in nitrogen and argon. The plasma producing capability is examined for these systems in the region wce,wpe≳wrf, where wce, wpe, and wrf correspond to electron cyclotron, plasma, and microwave frequencies, respectively. A high‐density, large‐diameter plasma (n0∼5×1011 cm−3; diameter ∼8.0 cm) could be obtained and the plasma could be maintained in the region 1≤wce/wrf≤2.
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52.50.Gj Plasma heating by particle beams
52.40.Fd Plasma interactions with antennas; plasma-filled waveguides

In situ calibration of neutron detectors on TEXTOR

F. Hoenen, H. Euringer, H. S. Bosch, A. V. Alevra, H. Klein, and T. Delvigne

Rev. Sci. Instrum. 63, 1945 (1992); http://dx.doi.org/10.1063/1.1143309 (8 pages) | Cited 4 times

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Neutron yield measurements are performed at the Jülich Tokamak experiment TEXTOR with different detectors located around the Tokamak and on center axis above the shielding roof. Due to the large structure of the machine and the extended diagnostic equipment, both virgin and scattered neutrons are detected. To prepare a Bonner sphere of appropriate response, the shape of the degraded neutron spectrum was determined with a spherical ionization chamber in situ. These investigations have been enlarged under quasi‐real conditions at the accelerator facility of the Physikalisch‐Technische Bundesanstalt in Braunschweig with a set of Bonner spheres used as a spectrometer. For the calibration the plasma neutron source is simulated by two point sources, 238Pu/B and 252Cf. The sources are moved around the TEXTOR vessel along the position of the magnetic axis.
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52.70.Nc Particle measurements
52.55.Fa Tokamaks, spherical tokamaks
29.30.Hs Neutron spectroscopy
52.25.Tx Emission, absorption, and scattering of particles

A low‐energy reactive‐ion gun using an ECR ion source and acceleration‐deceleration system

Tohru Tanaka, Tesuya Maruo, Yasuhiro Higashi, and Yoshikazu Homma

Rev. Sci. Instrum. 63, 1953 (1992); http://dx.doi.org/10.1063/1.1143310 (5 pages)

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A low‐energy reactive‐ion gun has been developed as a sputtering gun for high‐depth‐resolution analysis. It consists of an electron cyclotron resonance ion source and an acceleration‐deceleration system. The current density, the energy distribution, and the amount of impurity particles were measured to characterize the ion gun. The current density was estimated by measuring the ion current and the beam diameter for various ion beams. The maximum ion current density at 100 eV is 8.42 μA/cm2, and this means that it takes 19 s to sputter atoms on the monolayer of 1015 atoms/cm2 assuming that each ion sputters an atom. The energy width calculated from the full width at half maximum of the energy distribution was very narrow, 2 eV for the 15‐eV beam. The neutralization efficiencies evaluated by measuring secondary‐ion emission under bombardment by only neutral particles were 2.9, 0.5, and 0.33 for 1000‐eV Ar+, O2+, and BF2+, respectively. This order corresponds to the decreasing ionization potentials of the ion species.
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81.15.Cd Deposition by sputtering
29.25.Ni Ion sources: positive and negative

Negative‐ion formation from positive ion by two‐electron transfer from an alkali‐metal target

S. Hayakawa, A. Matsumoto, M. Yoshioka@f@f, and T. Sugiura

Rev. Sci. Instrum. 63, 1958 (1992); http://dx.doi.org/10.1063/1.1143311 (8 pages) | Cited 11 times

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To examine two‐electron transfer producing negative ions from positive ions, an apparatus using an alkali‐metal target has been developed. Positive ions formed by electron impact in an ion source collided with alkali‐metal vapor in a target chamber. Negative ions formed by two‐electron transfer have been analyzed with a single‐focusing mass spectrometer. Precursor positive ions and product negative ions have been identified from the apparent masses in the negative‐ion spectra. Using the target density dependence of the negative‐ion intensity, the processes of negative‐ion formation were determined to be double‐electron transfer in one collision or successive single‐electron transfer in two collisions. The cross section of these processes has been estimated from the peak area of positive‐ and negative‐ion spectra and the target density evaluated using the vapor‐pressure curve as a function of the temperature of the alkali‐metal cell. A cross section for He−‐ion formation in the Cs target with successive single‐electron transfer have been evaluated to be 1.40×10−30±0.2 cm4 at a collision energy of 2.0 keV, which showed the fair agreement with the values reported by Donnally and Thoeming [Phys. Rev. 159, 87 (1967)]. The double‐electron transfer cross section for C2−‐ion formation from a C2+ ion with a Cs target has been evaluated as 7.03×10−18±0.1 cm2 at 3.0 keV. For O−‐ion formation from O2+ ions, four broad peaks were observed due to the kinetic energy releases at dissociation which were 7.3, 3.4, 1.1, and 0.014 eV at full width at half maximum. Since the kinetic energy releases of the broad peaks corresponded with those by Peterson and Bae [Phys. Rev. A 30, 2807 (1984)], the peak extents have been explained as the dissociations of the excited neutral formed from exothermic neutralization. This two‐electron transfer from an alkali‐metal target offers a good advantage for the determination of the dissociation mechanism for excited neutral particles by means of the negative‐ion detection method.
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34.80.Dp Atomic excitation and ionization
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
34.80.-i Electron and positron scattering
29.25.Ni Ion sources: positive and negative

Source for excited states of alkali atoms and clusters using diffusion through a thin graphite foil

Leif Holmlid, Jan B. C. Pettersson, Carina Åman, Benny Lönn, and Kenneth Möller

Rev. Sci. Instrum. 63, 1966 (1992); http://dx.doi.org/10.1063/1.1143312 (3 pages) | Cited 9 times

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A molecular beam source used for the production of excited and ionized clusters of Cs and other materials is described. This source is closed, with the emitting graphite foil as an integral part of the source enclosure. The foil is kept at 1100–1500 K by radiation heating. From the foil, excited clusters (Cs)∗n with broad distributions of n, and excited Rydberg atoms Cs∗ are emitted. These highly excited states can be field ionized at field strengths of less than 400 V/cm. At a Cs reservoir temperature of 400 K, total field ionized flux densities up to 1015 ions cm−2 s−1 (3×10−4 A cm−2) are found.  
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36.40.-c Atomic and molecular clusters
07.78.+s Electron, positron, and ion microscopes; electron diffractometers
29.25.Ni Ion sources: positive and negative

An ion detector for imaging two‐dimensional velocity distributions

D. Corr and D. C. Jacobs

Rev. Sci. Instrum. 63, 1969 (1992); http://dx.doi.org/10.1063/1.1143313 (4 pages) | Cited 10 times

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The design and performance of a novel ion detector is described. The detector produces a two‐dimensional image which displays the time‐of‐flight distribution of a pulsed packet of ions. Pulse sequencing within the detector allows for simultaneous mass and velocity resolution of the detected ions. The image capturing hardware combines long‐term signal integration with single‐ion detection in order to provide a wide dynamic range in ion sensitivity.
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07.75.+h Mass spectrometers
06.30.Gv Velocity, acceleration, and rotation

Compact ion/electron analyzer for spaceflight or laboratory use

J. O. McGarity, A. Huber, J. Pantazis, M. R. Oberhardt, D. A. Hardy, and W. E. Slutter

Rev. Sci. Instrum. 63, 1973 (1992); http://dx.doi.org/10.1063/1.1143314 (5 pages) | Cited 3 times

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A space qualified 260° spherical plate electrostatic analyzer has been developed as a plasma diagnostic tool. The use of nested spheres and unusually shaped microchannel plates has resulted in a sensor capable of measuring simultaneously the three‐dimensional populations of ions and electrons in a plasma. High‐current microchannel plates and a new packaging of a hybrid preamplifier discriminator are combined with an uncommon high‐voltage circuit. The combination of these features yields an analyzer that is compact and lightweight, efficient in its power consumption, and has a broad dynamic range.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
52.70.Nc Particle measurements

A mass‐selective neutral particle energy analyzer with background rejection

A. A. E. van Blokland, T. W. M. Grimbergen@f@f, and H. W. van der Ven

Rev. Sci. Instrum. 63, 1978 (1992); http://dx.doi.org/10.1063/1.1143315 (10 pages) | Cited 3 times

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A mass‐discriminating neutral particle spectrometer has been developed for the Rutherford scattering diagnostic at the TEXTOR tokamak. The analyzer is equipped with a momentum preselector and a triple‐coincidence time‐of‐flight detection system providing a rejection capability for background events. Entering neutral particles are stripped by means of a thin carbon foil. Electrons emitted from a second carbon foil are used to give the time‐zero signal. Calibration has been performed for hydrogen and helium particles in the energy range from 10 to 90 keV. The energy loss inside the carbon foils, the absolute efficiency, and the resolution of the analyzer have been investigated. The momentum preselector has a bandwidth of ±12.5% with respect to its adjustable central momentum. For both hydrogen and helium, the energy resolution is 2.5% for energies above 30 keV. Calculations show that the analyzer can still operate in the highly radiative environments of nuclear fusion devices.
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52.70.Nc Particle measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Tx Emission, absorption, and scattering of particles

A high‐efficiency focusing Cherenkov radiation detector

Katina–Pilar Lewis@f@f, Michael J. Moran, James Hall, and Michael Graser

Rev. Sci. Instrum. 63, 1988 (1992); http://dx.doi.org/10.1063/1.1143316 (3 pages) | Cited 2 times

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A new design uses advanced technology to produce an efficient, high‐bandwidth Cherenkov detector for relativistic charged particles. The detector consists of a diamond‐lathe machined ultraviolet‐grade Lucite radiator, a parabolic focusing mirror, and a photodiode with an S‐20 cathode. This article discusses some details of the detector design and describes preliminary measurements of its response characteristics. The data show the detector to have an overall gain of ≊76 signal electrons per incident electron and a photodiode‐limited response time of ≊450 ps.
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29.40.Ka Cherenkov detectors

System to phase lock a self‐scanning photodiode array to an external signal

K. C. Harvey, Patrick W. Lea, and J. E. Morris

Rev. Sci. Instrum. 63, 1991 (1992); http://dx.doi.org/10.1063/1.1143317 (8 pages)

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We describe an external control circuit for a commercial, real‐time, self‐scanning photodiode array system. It had a phase‐locked loop that synchronized the scan of the photodiode array to an external reference frequency. The signal from the photodiode array had, in principle, an infinite signal‐to‐noise ratio at the reference frequency. The circuit allowed independent adjustment of the integration time of the array and was simple and inexpensive to build. It was useful in measuring periodic or pulsed spectra such as occurs in laser or communications experiments.
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85.60.Dw Photodiodes; phototransistors; photoresistors

Microcomputer‐based Peltier thermostat for precision optical radiation measurements

Xiaosong Zhu, Eike Krochmann, and Jiashu Chen

Rev. Sci. Instrum. 63, 1999 (1992); http://dx.doi.org/10.1063/1.1143838 (5 pages) | Cited 4 times

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We have developed a microcomputer‐based thermostat for a light measuring head in precision optical radiation measurements. This thermostat consists of a single‐chip microcomputer, a digital‐to‐analog converter, a liquid crystal display, a power operational amplifier, and a Peltier element (thermoelectric cooler). The Peltier element keeps the temperature of the photometer head at 20±0.1 °C in the ambient temperature range from −20 to 60 °C. A control algorithm which combines the ‘‘Bang‐Bang’’ mode and proportional‐plus‐integral‐plus‐derivative mode is used to achieve fast and smooth thermostatic performance. This thermostat is effective, inexpensive, and easy to adjust. Several applications of the Peltier thermostat are mentioned.
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07.20.Dt Thermometers
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

Temperature rise and thermal rise‐time measurements of a semiconductor laser diode

H. I. Abdelkader, H. H. Hausien, and J. D. Martin

Rev. Sci. Instrum. 63, 2004 (1992); http://dx.doi.org/10.1063/1.1143318 (4 pages) | Cited 17 times

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A novel method is presented for measurement of the rise in temperature and thermal rise time of a semiconductor laser diode (LD) under pulsed operation. The technique employs the shift in LD threshold current which occurs with a rise in junction temperature. Practical results are given, showing a rise time of about 10 ns.
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42.55.Px Semiconductor lasers; laser diodes
42.60.Da Resonators, cavities, amplifiers, arrays, and rings
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