George T. Reynolds

Light at deep-sea hydrothermal vents

Ambient light spectral data were acquired at two deep-sea hydrothermal vents with a temperature of ∼350°C: the Hole-to-Hell site on the East Pacific Rise at 9°N and the Snake-Pit site on the Mid-Atlantic Ridge. Measurements were made with a simple, multi-channel photometer which simultaneously detected light in four 100 nm-wide bands over the wavelength range of 650–1050 nm. Most of the light detected is near-infrared (750–1050 nm), but there is a 19x greater photon flux than expected from thermal radiation alone at shorter wavelengths (650–750 nm) at the Hole-to-Hell vent. At Snake Pit, more light in the 750–850 nm band was observed 10 cm above the orifice where the temperature was 50–100°C than at the 351°C vent opening. These data suggest the presence of non-thermal light sources in the vent environment. Some possible non-thermal mechanisms are identified, but further data will be required to resolve them.

Piezoluminescence from a ferroelectric polymer and quartz

Abstract Piezoluminescence has been observed from polyvinylidene fluoride, a ferroelectric polymer, and from quartz not previously irradiated in the laboratory. The light was imaged using a CCD camera in addition to being recorded by a photomultiplier.

FILAMENT SCINTILLATION COUNTER

As a part of a program to develop a solid scintillation chamber, filaments of plastic scintillator material were prepared and formed into a scintillation counter. The filaments can be prepated in lengths of many feet. Care must be taken to avoid surface crazing. The diameter was chosen between 0.5 and l.0 mm in view of the proposed application. The action of this sort of light pipes is well known, and a large number of diameters is possible. (A.C.)

Slow‐scan silicon‐intensified target‐TV x‐ray detector for quantitative recording of weak x‐ray images

The construction and performance of a two‐dimensional x‐ray detector is described. X‐rays are detected as scintillations in a thin phosphor screen which is fiber‐optically coupled to a cooled SIT vidicon TV camera tube. The x‐ray image is analog integrated on the vidicon target during an exposure period; afterwards, the x‐ray signal is gated off and the target is read via a slow‐scan, low‐noise readout in a 256×256‐pixel raster. Test data are presented on the performance of a detector based on an 80‐mm SIT tube. The device is shown to be a quantitative, quantum‐limited detector suitable for recording x‐ray diffraction patterns over a wide range of x‐ray intensities. The detector is shown to be especially suited for high count‐rate applications. Current applications of the detector are described.

Mechanical stimulation of bioluminescence in the dinoflagellate Gonyaulax polyedra Stein

Abstract Cultures of the marine dinoflagellate Gonyaulax polyedra Stein were exposed to a variety of flow regimes in small tubes, pressure chambers, and vessels in which objects could be rotated. Bioluminescence was mechanically stimulated by changes in shear, acceleration, and pressure, not by constant values of these parameters. In a biological context, such stimuli would be associated with waves and other surface turbulence, with moving objects such as ships or some large marine organisms, or with close or direct contact as would occur if the dinoflagellate is a prey item. The effects of pressure are complicated by the observation that the luminescence response did not occur in the bulk of the fluid in a pressure chamber, but was confined to the liquid boundaries. The importance of luminescence at surfaces was also seen when objects were rotated in suspensions of G. polyedra ; light emissions were restricted to regions with sharp shear gradients. These data were obtained using an image intensifier which made it possible to visualize the spatial pattern of luminescence in the various flow regimes studied. Past results obtained with photo-multipliers are shown to be misleading.

APPLICATION OF PHOTOSENSITIVE DEVICES TO BIOLUMINESCENCE STUDIES

Abstract—A brief review is given of some results obtained by the application of image intensification to studies of bioluminescence. The system consists of an image intensifier placed at the output of a suitable microscope., so that the image from the microscope falls on the intensifier cathode. The photon gain of the intensifier can be varied from a few thousand to one million. The output of the intensifier is recorded either on film or, in most applications to date, by means of a TV vidicon. The TV system permits display on a monitor in real time and simultaneous recording on magnetic tape for subsequent playback and analysis. It also provides time resolution for dynamic studies. Results are summarized for in vivo observations on Noctiluca miliaris, Obelia, Renilla, and Mnemiopsis leidyi. Utilization of the luminescence of aequorin in the presence of Ca2+ has been directed to observations on amoebae and the egg of the Medaka fish.

Present Status of Scintillation Chambers

The advantages of imaging the tracks of high-energy particles in scintillation counters have been noted by nuclear physicists for some years. Recent developments in scintillator techniques and improvements in the image intensifiers required have resulted in usable systems. The basis for the design of these systems, and their specific advantages to high-energy nuclear physics will be discussed. Several experimental proposals will be described quantitatively to illustrate the advantages and limitations of the technique. Accomplishments of various groups working in this field will be summarized.

Variations in ambient light emission from black smokers and flange pools on the Juan De Fuca Ridge

Ambient light emitted by high-temperature black smokers and flange pools on the Juan de Fuca Ridge was imaged using a new spectral imaging camera. Most of the light is emitted at long wavelengths (700–1000 nm) and corresponds well to thermal radiation from a body at the same temperature as the vents/flanges. However, black smokers also emit time-varying radiation in the visible region (400–650 nm) which cannot be explained by a thermal source. This visible radiation is 1–2 orders of magnitude greater than would be expected for purely thermal radiation; it exhibits variation with time, despite relatively constant vent temperatures; and it is not associated with the hottest part of the plume (i.e. the orifice). Flange pools do not exhibit excess visible light over that for a thermal source, suggesting that the light at smokers is caused by mechanisms related to turbulence, mixing, or precipitation.

Mechanoluminescence of plastic scintillation counters

Luminescence has been observed from the mechanical deformation of plastic scintillation materials. The light was recorded by means of a photomultiplier, and observed on a monitor by means of an intensified CCD camera. There is evidence for piezoluminescence as well as triboluminescence.

Sensitivity of an Image Intensifier Film System

Using calibrated light sources, the sensitivities of several commonly used films have been determined in terms of the number of photons incident required to develop one grain of emulsion. By incorporating an image intensifier in the system, the time required to obtain an image of a given quality or information content can be reduced significantly. Criteria are discussed whereby an estimate of the time advantage can be made for various experimental conditions. Noise, quantum fluctuations, spatial resolution, and over-all detection efficiency are discussed.