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Jul 1988

Volume 59, Issue 7, pp. 1021-1249

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Automated search for supernova explosions

Jordin T. Kare, M. Shane Burns, Frank S. Crawford, Peter G. Friedman, Richard A. Muller, Carlton R. Pennypacker, Saul Perlmutter, Richard Treffers, and Roger Williams

Rev. Sci. Instrum. 59, 1021 (1988); http://dx.doi.org/10.1063/1.1139773 (10 pages) | Cited 1 time

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We describe the design and construction of a new search for supernovae, based on the use of current computer and detector technology. This search uses a computer‐controlled telescope and charge coupled device (CCD) detector to collect images of hundreds of galaxies per night of observation, and a dedicated minicomputer to process these images in real time. The search system has a detection threshold of 17th visual magnitude, discovered its first supernova on 18 May 1986, and at this writing has found three additional supernovae. The system currently is being upgraded with an improved detector and a more powerful computer. At full speed and sensitivity, the system will be able to search 2500 galaxies per night with a limiting magnitude of 19 or fainter.
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95.55.Sh Auxiliary and recording instruments; clocks and frequency standards
85.30.Tv Field effect devices
95.55.Qf Photometric, polarimetric, and spectroscopic instrumentation

Null input current SQUID magnetometer for the measurement of the transition temperature of high‐Tc superconducting samples

S. Barbanera, M. G. Castellano, and V. Foglietti

Rev. Sci. Instrum. 59, 1031 (1988); http://dx.doi.org/10.1063/1.1139774 (4 pages) | Cited 3 times

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In this article we describe a SQUID‐based system used to measure the superconducting transition temperature in the range 4.2–300 K. The apparatus has been tested using a high‐critical‐temperature single crystal of YBa2 Cu3 O7−x (≂ 10−1 mm3 volume). The system is based on mutual inductance variations measurements, performed in a low‐frequency ac magnetic field of 2×10−5 T. A feedback loop is closed on the input circuit in order to null out the current flowing in the pickup coil. This is achieved using an electronic scheme which does not involve any modification of the commercial SQUID electronics. Our experiment is performed using a copper wire pickup coil, but the scheme can also be used with a superconducting input circuit, thus allowing measurements in a dc regime. The obtained sensitivity is 5×10−5/√Hz. This figure can be further improved by optimizing the circuit parameters.
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85.25.Dq Superconducting quantum interference devices (SQUIDs)
74.70.-b Superconducting materials other than cuprates

Compact, high‐stability, ‘‘thimble‐size’’ scanning tunneling microscope

F. Besenbacher, E. Laegsgaard, K. Mortensen, U. Nielsen, and I. Stensgaard

Rev. Sci. Instrum. 59, 1035 (1988); http://dx.doi.org/10.1063/1.1139775 (4 pages) | Cited 24 times

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A new high‐stability scanning tunneling microscope (STM) has been developed. Its key design feature is the application of two, concentrically aligned, piezoelectric ceramic tubes, allowing x–y–z motion of the tungsten tip as well as sample mounting to be cast into a single compact unit. The construction is small, very rigid, and temperature compensated, yielding reduced sensitivity to mechanical and acoustic vibrations and temperature variations. Other advantages of this ‘‘thimble‐size’’ STM include easy sample mounting and, at a later stage, operation under UHV conditions with access to other surface‐analysis (UHV) tools. At present, the microscope is operated in air, and its performance is tested by imaging a highly oriented pyrolytic graphite surface and a Si(111) surface on which a 100‐Å‐thick Au layer has been deposited.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers
07.79.Cz Scanning tunneling microscopes
61.05.-a Techniques for structure determination

Characterization of a cesium surface ionization source with a porous tungsten ionizer. I

G. D. Alton

Rev. Sci. Instrum. 59, 1039 (1988); http://dx.doi.org/10.1063/1.1139776 (6 pages) | Cited 5 times

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A cesium surface ionization source of the type and geometry customarily used in conjunction with sputter‐type negative heavy ion sources has been characterized. Measurements have been made of positive‐ion production and probabilities of ionization as functions of extraction voltage and cesium oven temperature for ionizer porosities of 0.7 and 0.8. The perveance P of the source, when operated in the space‐charge‐limited regime with the ρ=0.7ρ0 ionizer, is found from experiment to be 7.61×10−4 μP, while that for the ρ=0.8ρ0 ionizer is 1.92×10−4 μP. These values are lower by factors of 3.88 and 15.53, respectively, than those predicted by numerical solution to Poisson’s equation for full area emission from the source. Positive‐ion current versus ionizer temperature data are also presented along with mechanical design features of the source.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Aspects of negative‐ion generation and extraction from a refocus geometry cesium sputter negative‐ion source. II

G. D. Alton

Rev. Sci. Instrum. 59, 1045 (1988); http://dx.doi.org/10.1063/1.1139777 (8 pages) | Cited 4 times

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The basic parameters of the refocus geometry cesium sputter ion source for the production of negative ions from a low‐sputtering material (carbon) and a high‐sputtering material (copper) have been measured. The question of the influence of sample temperature on the negative‐ion generation process has been addressed. Negative‐ion yields from carbon samples are found to be weakly dependent on temperature over a range from 26° to 400 °C, while those from copper samples are found to be essentially independent of temperature over a range of 26° to 200 °C. The results of these investigations indicate that (1) sample temperature does not strongly influence negative formation in these sources, and (2) the maximum negative‐ion yields for a given sample are dependent on both cesium‐ion energy and positive‐ion current. In addition to these data, the negative‐ion extraction optics of the source are briefly discussed and cursory estimates of the probabilities for negative‐ion formation presented.
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29.25.Lg Ion sources: polarized
29.25.Ni Ion sources: positive and negative
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces

Novel Langmuir probe technique for the real‐time measurement of the electron temperature

R. Van Nieuwenhove and G. Van Oost

Rev. Sci. Instrum. 59, 1053 (1988); http://dx.doi.org/10.1063/1.1139724 (4 pages) | Cited 22 times

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A new method for the evaluation of the electron temperature from the voltage–current characteristic of a single Langmuir probe under the application of an ac signal was developed and tested. This method exploits harmonics in the current spectrum which arise from the nonlinearity of the characteristic; from the amplitude of these harmonics the electron temperature can be deduced. Langmuir probe measurements on the TEXTOR edge plasma show a good agreement of the new method with the conventional one. The advantages of this method over other methods are discussed. Proposals for further improvements are given.
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52.70.Ds Electric and magnetic measurements
07.50.-e Electrical and electronic instruments and components

Measurement of large displacements of the toroidal current centroid using an external coil diagnostic

H. Y. Che, T. H. Ivers, and M. E. Mauel

Rev. Sci. Instrum. 59, 1057 (1988); http://dx.doi.org/10.1063/1.1139725 (6 pages) | Cited 2 times

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Several sinusoidal and saddle coils have been used to measure the toroidal current centroid of discharges produced in a pulsed tokamak experiment. Careful analysis of the external coil measurements and elaborate calibrations made the measurements possible even for large displacements of the plasma current and the noncircular geometry of the diagnostic coils. The calibration techniques and the data analysis formula are described, and examples of the use of the external coils to measure m=1 kinks of unstable toroidal Z‐pinch discharges are presented.
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52.70.Ds Electric and magnetic measurements
07.50.-e Electrical and electronic instruments and components

Real‐time, vibration‐compensated CO2 interferometer operation on the DIII‐D tokamak

T. N. Carlstrom, D. R. Ahlgren, and J. Crosbie

Rev. Sci. Instrum. 59, 1063 (1988); http://dx.doi.org/10.1063/1.1139726 (4 pages) | Cited 42 times

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A multichannel, two‐color, quadrature heterodyne interferometer is used to measure the line density in the DIII‐D tokamak. The unique feature of this real‐time vibration‐compensated interferometer is the combination of high speed (1 MHz), high resolution (2π/256), and wide range (±8193 fringes). Quadrature phase information from a CO2 laser (10.6 μm) and a He–Ne laser (0.63 μm) are digitized with high‐speed (6 MHz) flash digitizers. Zero crossings of the signals are counted with digital circuitry yielding quarter fringe resolution with a 4‐MHz bandwidth. Further fringe resolution of 1/256 is provided at 350 kHz by a PROM which uses the digital signals as input to a look‐up table. Analog line density is presently available at 80 kHz with a system noise equivalent phase shift of ±2/256. Error monitoring is provided for low signal amplitude and exceeding the maximum fringe rate. In addition, a method to prevent coating of in‐vessel mirrors due to plasma and vessel wall cleaning discharges has been developed.
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52.70.Gw Radio-frequency and microwave measurements
07.60.Ly Interferometers

Pseudotomographic fitting algorithm for density profile reconstruction from a sparse 1‐D interferometer array

J. A. Casey, E. Sevillano, J. H. Irby, and B. G. Lane

Rev. Sci. Instrum. 59, 1067 (1988); http://dx.doi.org/10.1063/1.1139727 (5 pages) | Cited 2 times

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An algorithm has been developed for fast analysis of a sparse multichord interferometer array, yielding peak density, Gaussian width, radial offset, ellipticity, and instability amplitude and frequency from line‐integrated density measurements. A nonlinear least‐squares fit is performed over many short time intervals, with independent variables reduced to one dimension. Assumptions of plasma rigidity and slowly evolving rotation rate are necessary to trade temporal resolution (on instability timescales) for spatial resolution across the moving plasma column. Results from the Tara tandem mirror experiment are shown.
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52.70.-m Plasma diagnostic techniques and instrumentation
07.60.Ly Interferometers

Microwave multipolar plasmas excited by distributed electron cyclotron resonance: Concept and performance

M. Pichot, A. Durandet, J. Pelletier, Y. Arnal, and L. Vallier

Rev. Sci. Instrum. 59, 1072 (1988); http://dx.doi.org/10.1063/1.1139728 (4 pages) | Cited 65 times

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Distributed electron cyclotron resonance or DECR, a new plasma excitation technique well adapted to microwave multipolar plasmas, is described. The novel reactor concept is based upon the use of several microwave linear applicators working at the ECR mode along the multipolar confinement magnets. At a microwave frequency of 2.45 GHz, large volumes of highly homogeneous plasmas with an electron temperature of the order of 3 eV and ion densities better than 1011 cm−3 are currently being produced in DECR reactors.
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52.50.Gj Plasma heating by particle beams
52.75.-d Plasma devices

X‐ray luminosity time‐of‐flight spectrometer for laser‐produced plasmas

P. A. Naik, P. D. Gupta, and S. R. Kumbhare

Rev. Sci. Instrum. 59, 1076 (1988); http://dx.doi.org/10.1063/1.1139729 (5 pages) | Cited 3 times

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A simple and compact x‐ray luminosity time‐of‐flight spectrometer for measurements of the velocity distribution of highly charged ions in laser‐produced plasmas is presented. The spectrometer is based on making time‐ and space‐resolved measurements of x‐ray line emission from these ions in the expansion zone. Design, operation, and performance of this system are described. The spectrometer is useful in studying processes of interaction between highly charged ions and buffer gases, and nonthermal behavior of laser‐produced plasma expansion.
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52.70.Nc Particle measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.25.Fi Transport properties
07.85.-m X- and γ-ray instruments

Multichannel boxcar‐averaged measurements of plasma parameters made using a digital storage scope

T. E. Sheridan and M. A. Hayes

Rev. Sci. Instrum. 59, 1081 (1988); http://dx.doi.org/10.1063/1.1139730 (4 pages) | Cited 2 times

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We present a technique for rapidly acquiring time‐resolved, ensemble‐averaged Langmuir probe characteristics. Fifty probe characteristics are acquired using a digital storage oscilloscope in the time it would take to acquire a one‐probe characteristic using a single‐channel boxcar averager. A single Langmuir probe is used, and the probe bias is swept quite slowly, so that the probe is always in equilibrium with the plasma. A method for the automatic extraction of electron temperature, electron density, and the plasma potential from the acquired probe characteristics is described. This technique for acquisition and analysis is applied to the study of plasma decay and the effects of rf excitation in a pulsed, strongly magnetized plasma.
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07.50.Ek Circuits and circuit components
52.70.Ds Electric and magnetic measurements
07.50.-e Electrical and electronic instruments and components

Microwave measurement of the mass of frozen hydrogen pellets

V. Talanker and M. Greenwald

Rev. Sci. Instrum. 59, 1085 (1988); http://dx.doi.org/10.1063/1.1139731 (3 pages) | Cited 5 times

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A nondestructive method for measuring the mass of high‐speed, frozen hydrogen pellets is described. The measurement technique is an improvement on previous methods based on the perturbation to a resonant cavity caused by a dielectric pellet passing through the cavity. In the new method, an oscillator circuit is formed with a resonant cavity in the positive feedback loop of a microwave power amplifier. An injected pellet perturbs the resonance characteristics of the cavity causing a shift in the operating frequency of the oscillator proportional to the ratio of the pellet volume to the volume of the cavity. Through digital measurement of the frequency shift the size of the pellet is determined automatically. In a ‘‘proof‐of‐principle’’ experiment it was shown that polyethylene pellets, with an average volume of 0.26 mm3 and velocity ≊500 m/s, caused a shift in the operating frequency of the oscillator circuit that was within 10% of the predicted value. The hydrogen pellets (of interest to us) will have 4–10× the volume of the plastic pellets. Thus with a dielectric constant of about 1.26 for frozen hydrogen, the signals in the actual experiment would be 1–2× those described here.
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28.52.-s Fusion reactors
52.70.-m Plasma diagnostic techniques and instrumentation
52.75.-d Plasma devices

Improved control and averaging system for microwave Fourier transform spectroscopy

U. Andresen and B. Kleibömer

Rev. Sci. Instrum. 59, 1088 (1988); http://dx.doi.org/10.1063/1.1139732 (6 pages)

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A control and averaging system for microwave Fourier transform spectroscopy is described, in which data acquisition and accumulation are performed in parallel to obtain a maximum repetition rate of 75 kHz. Details of circuitry as well as examples of performance are given.
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07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
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
84.30.Sk Pulse and digital circuits

Superior free‐standing meshes for use as infrared Fabry–Perot elements made with a new photolithographic technique

C. Jackson Taylor, Howard A. Smith, and Jacqueline Fischer

Rev. Sci. Instrum. 59, 1094 (1988); http://dx.doi.org/10.1063/1.1139733 (4 pages) | Cited 2 times

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A photolithographic technique for fabrication of very smooth and highly uniform metallic, free‐standing, inductive meshes, is described. The fabrication process was developed in order to produce highly reflective, low‐loss Fabry–Perot étalon elements for use in the infrared spectral region. The measured rms smoothness of the grids is typically ≤30 Å. Because of their nickel core, the mechanical strength of the grids is such that they can be easily stretched flat on stainless‐steel rings.
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42.79.Ci Filters, zone plates, and polarizers
42.79.Dj Gratings
07.60.Ly Interferometers

Ultrafast emission spectroscopy in the ultraviolet by time‐gated upconversion

Michael A. Kahlow, Włodzimierz Jarzȩba, Thomas P. DuBruil, and Paul F. Barbara

Rev. Sci. Instrum. 59, 1098 (1988); http://dx.doi.org/10.1063/1.1139734 (12 pages) | Cited 52 times

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We have built a new apparatus to time resolve ultrafast fluorescence following ultraviolet excitation. A synchronously pumped dye laser produces optical pulses of 1‐ps or 70‐fs full‐width half‐maximum, depending upon dyes and optical configuration. These pulses are amplified at a 8.2‐kHz repetition rate using a copper vapor laser‐pumped multipass amplifier. The resulting amplified laser pulses are frequency doubled to obtain ultrafast pulses in the ultraviolet. This ultraviolet light is used to electronically excite a sample; the resulting fluorescence is time resolved using fluorescence upconversion as the optical gating technique. A minimum 300‐fs full‐width half‐maximum instrument response function is obtained. After a brief introduction, we discuss the principles involved in this method of time resolving fluorescence. We review special considerations for femtosecond laser experimentation, and discuss the construction of our apparatus. Finally, as an example, we show how this system can be used to study fundamental physical processes in solution.
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78.47.-p Spectroscopy of solid state dynamics
07.60.Rd Visible and ultraviolet spectrometers

Position and velocity sensing laser interferometer–fringe counter

F. Martin, J. Gauthier, S. Gulick, and F. Laroche

Rev. Sci. Instrum. 59, 1110 (1988); http://dx.doi.org/10.1063/1.1139735 (5 pages)

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A CO2 laser interferometer and fringe counter, made of commercially available equipment, which can resolve displacements of 5 μm and accurately track velocities of up to 50 m/s in either a positive or negative sense, is described. Coupled to a heterodyne interferometer, this simple fringe‐counting circuit does not require exact quadrature to determine the direction of motion, is wideband and capable of high count rates (dc—10 MHz) and will not introduce false fringe counts at phase reversal or due to dithering of the target. A prototype has been built and employed to characterize the operation of a pulsed gas valve.
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47.80.-v Instrumentation and measurement methods in fluid dynamics
07.60.Ly Interferometers
06.30.Gv Velocity, acceleration, and rotation

Four‐hundred‐picosecond single‐photon timing with commercially available avalanche photodiodes

A. Lacaita, S. Cova, and M. Ghioni

Rev. Sci. Instrum. 59, 1115 (1988); http://dx.doi.org/10.1063/1.1139736 (7 pages) | Cited 14 times

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Avalanche photodiodes biased above the breakdown voltage are an interesting alternative to photomultiplier tubes in time‐correlated single‐photon counting. The characteristics and performance of a commercially available device (RCA C30921S) have been investigated. The time resolution is found to improve as the excess bias above the breakdown voltage is increased. Full width at half‐maximum values down to 400 ps have been measured with the detector cooled at −40 °C, and down to 460 ps at room temperature. The best results were obtained with an active quenching circuit, suitable for operation with excess bias voltage up to 40 V; at room temperature, fast gated operation was used for attaining optimum performance. Experimental data on the statistical behavior of the avalanche current pulses in these devices are reported and discussed.
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85.60.Dw Photodiodes; phototransistors; photoresistors
85.60.Gz Photodetectors (including infrared and CCD detectors)

Two‐dimensional photon counter for x‐ray imaging

Brian Collett and Richard J. Podolsky

Rev. Sci. Instrum. 59, 1122 (1988); http://dx.doi.org/10.1063/1.1139737 (5 pages) | Cited 1 time

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This paper characterizes an imaging x‐ray detector formed by coupling a gadolinium oxysulphide phosphor to the input of an optical imaging photon detector. The device is small, light, easy to use, and features a direct digital readout. It exhibits fairly high efficiency (40%–80%) and high resolution (160 μm‐width point spread function) near the center of its 40‐mm active area. There is a small amount of pincushion distortion which seems to be associated with a loss in resolution toward the edge of the active area. The device has very low noise and can be used at x‐ray fluxes down to about 0.1 x‐ray/mm2/s without loss of accuracy but it is count rate limited at 105 x rays/s over the active area and so is not usable in high‐flux situations such as are often found at synchrotrons. We have used the device to record good diffraction patterns from striated rabbit muscle in 30 min on a rotating anode x‐ray generator: less than one tenth the time needed under similar conditions when using film.
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87.57.Q- Computed tomography
87.59.B- Radiography
07.85.-m X- and γ-ray instruments
85.60.Gz Photodetectors (including infrared and CCD detectors)

Double‐crystal spectrometer for laboratory EXAFS spectroscopy

Kazuyuki Tohji, Yasuo Udagawa, Tsutomu Kawasaki, and Kimitoshi Mieno

Rev. Sci. Instrum. 59, 1127 (1988); http://dx.doi.org/10.1063/1.1139738 (5 pages) | Cited 9 times

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A double‐crystal x‐ray spectrometer designed for in‐laboratory EXAFS (extended x‐ray absorption fine structure) study is described. By the use of two curved crystals with different structure factors such as Ge(220) and Ge(111), reflections other than the desired order are virtually eliminated and monochromatic as well as intense x‐ray flux can be obtained by applying higher voltage to the x‐ray generator. As a result, data of very high quality can be collected in a short period by measuring the incident and the transmitted beam intensity simultaneously. It can cover a wide spectral range (7–26 keV) and is especially useful in the high‐energy region, where the laboratory EXAFS system previously reported has some difficulties.
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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.

Parallel detection for high‐resolution electron energy loss studies in the scanning transmission electron microscope

P. E. Batson

Rev. Sci. Instrum. 59, 1132 (1988); http://dx.doi.org/10.1063/1.1139739 (7 pages) | Cited 28 times

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A parallel detection system has been added to the Wien Filter electron spectrometer on the dedicated scanning transmission electron microscope at IBM. The system uses an intensified diode array that is optically coupled to a single‐crystal YAG screen by a vacuum window and an f/1.4–22 camera lens. The YAG screen shares the spectrometer image plane with energy selecting slits used for bright field STEM images and for single‐channel energy loss analysis. Energy calibration to ±0.05 eV for scans over arbitrary energy ranges is accomplished by combining many parallel spectra having different energy centers. This process can remove channel gain variations, background variations, and nonlinear energy scale effects.
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07.78.+s Electron, positron, and ion microscopes; electron diffractometers

Magnetic field evolution and measurement of fast rise‐time electron beams

Dushan Mitrovich

Rev. Sci. Instrum. 59, 1139 (1988); http://dx.doi.org/10.1063/1.1139740 (5 pages) | Cited 1 time

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In charged particle beam experiments, the electromagnetic signal produced at the beam injection point (conducting foil or aperture) by a fast‐rise beam will reflect off conducting boundaries (pipe walls) to produce constructive and destructive interference. B‐dot loop diagnostics can, in that case, give rather complicated signal histories that are difficult to interpret. An idealized, cylindrical model of a sudden rise beam on axis is solved analytically and shows, in the relativistic limit, how the interference is manifested. Results of the model corroborate and provide interpretation of corresponding PIC simulation results. B‐dot loop diagnostics of fast‐rise charged particle beams are most easily interpreted when the loops are close to the beam axis, or far downstream from the injection plane, and when frequency filtering of the signal is performed.
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41.75.Fr Electron and positron beams
41.75.Ht Relativistic electron and positron beams
41.60.-m Radiation by moving charges

On‐line gas electron diffraction identification of gas chromatography effluents (GC‐GED)

John D. Ewbank, David W. Paul, Lothar Schäfer, Khamis Siam, David L. Monts, and Walter L. Faust

Rev. Sci. Instrum. 59, 1144 (1988); http://dx.doi.org/10.1063/1.1139741 (4 pages) | Cited 2 times

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Experiments are described which document the utility of gas electron diffraction (GED) as a means of detecting analytes emerging from the column of a gas chromatograph (GC). In these experiments electron diffraction patterns from GC effluents are made visible on a phosphor screen, and the intensities of each GC peak are recorded on line by a 1024‐channel linear photodiode array detector. The technique not only indicates the presence of elutants but also provides auxiliary information on their molecular structures under favorable conditions. Minimum sample sizes of about 1 μl per component are currently required for GC‐GED, but indications are that further detector enhancements will allow the recording of electron intensities from smaller samples.
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82.80.Bg Chromatography
07.77.-n Atomic, molecular, and charged-particle sources and detectors
37.20.+j Atomic and molecular beam sources and techniques

Performance comparison of a single‐photon avalanche diode with a microchannel‐plate photomultiplier in time‐correlated single‐photon counting

T. Louis, G. H. Schatz, P. Klein‐Bölting, A. R. Holzwarth, G. Ripamonti, and S. Cova

Rev. Sci. Instrum. 59, 1148 (1988); http://dx.doi.org/10.1063/1.1140258 (5 pages) | Cited 20 times

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A silicon single‐photon avalanche diode (SPAD) detector and a proximity‐focus‐type microchannel‐plate photomultiplier tube (MCP‐PMT) are compared with respect to their performance in time‐correlated single‐photon counting (TCSPC) applications. A solution of pinacyanol (1,1′‐diethyl–2,2′‐carbocyanine) in ethanol, which is used as a test substance with short‐lived fluorescence, is excited at 620 nm with a synchronously pumped, cavity‐dumped rhodamine 6G dye laser. Deconvolution analysis of the fluorescence decay with a biexponential decay model gives excellent fits to the experimental data recorded with any one of the detectors. The fluorescence lifetimes for the dominating decay component are 13±2 and 11±2 ps as measured at 635 nm with the SPAD detector and the MCP‐PMT, respectively. The excellent agreement of these values and the quality of the fits show that the SPAD detector as well as the MCP‐PMT can resolve fluorescence decay time constants of the order of 10 ps. This is significantly better than what had been expected on the basis of the instrumental response widths of 70 ps (FWHM) with the SPAD detector and 50 ps (FWHM) with the MCP‐PMT.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.60.Dw Photodiodes; phototransistors; photoresistors

Simple laser refractometer for liquids

A. A. Zaidi

Rev. Sci. Instrum. 59, 1153 (1988); http://dx.doi.org/10.1063/1.1139742 (3 pages) | Cited 5 times

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A method for the determination of the refractive index of liquids using a He–Ne laser is presented. The experimental setup is simple and utilizes equipment which is normally available in most optics laboratories. Measurements carried out on water and several organic liquids are reported. The values of the refractive indices obtained by this method are in good agreement with those given in literature. The accuracy of results is of the order of ±5×10−3 and can be improved by the use of a scale of higher precision.
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07.60.Hv Refractometers and reflectometers
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
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