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In a photomultiplier tube, every photon striking the photocathode initiates an avalanche of electrons that produces a detectable current pulse.
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photomultiplier and tube
Currently available scanners typically use charge-coupled device ( CCD ) or contact image sensor ( CIS ) as the image sensor, whereas older drum scanners use a photomultiplier tube as the image sensor.
On November 12, 2001, about 6, 600 of the photomultiplier tubes ( costing about $ 3000 each ) in the Super-Kamiokande detector imploded, apparently in a chain reaction or cascade failure, as the shock wave from the concussion of each imploding tube cracked its neighbours.
Although wide bandwidth sources typically suffer from low spectral power per unit frequency, the photomultiplier tube offers high gain ( about ) amplification of photon shot noise, making it advantageous over other lower gain noise sources.
After passing a pinhole, the light intensity is detected by a photodetection device ( usually a photomultiplier tube ( PMT ) or avalanche photodiode ), transforming the light signal into an electrical one that is recorded by a computer.
From there, a fiber optic will transfer the light out of the microscope where it will be separated by a monochromator and then detected with a photomultiplier tube.
The primary advantages to the electron microscope based technique is the ability to resolve features down to 1 nanometer, the ability to measure an entire spectrum at each point ( hyperspectral imaging ) if the photomultiplier tube is replaced with a CCD camera, and the ability to perform nanosecond-to picosecond-level time-resolved measurements if the electron beam can be " chopped " into nano-or pico-second pulses.
The detector is typically a photomultiplier tube, a photodiode, a photodiode array or a charge-coupled device ( CCD ).
UV-visible spectroscopy of microscopic samples is done by integrating an optical microscope with UV-visible optics, white light sources, a monochromator, and a sensitive detector such as a charge-coupled device ( CCD ) or photomultiplier tube ( PMT ).
The invention of the photomultiplier is predicated upon two prior achievements, the discoveries of the photoelectric effect and the secondary emission ( i. e., the ability of electrons in a vacuum tube to cause the emission of additional electrons by striking an electrode ).
The ingredients for inventing the photomultiplier were coming together during the 1920s as the pace of vacuum tube technologies accelerated.
By October 1935, Vladimir Zworykin, George Ashmun Morton, and Louis Malter of RCA in Camden, NJ submitted their manuscript describing the first comprehensive experimental and theoretical analysis of a multiple dynode tube — the device later called a photomultiplier — to Proc.
There are two common photomultiplier orientations, the head-on or end-on ( transmission mode ) design, as shown above, where light enters the flat, circular top of the tube and passes the photocathode, and the side-on design ( reflection mode ), where light enters at a particular spot on the side of the tube, and impacts on an opaque photocathode.
After fifty years, during which solid-state electronic components have largely displaced the vacuum tube, the photomultiplier remains a unique and important optoelectronic component.
Behind this grid system, an image dissector tube ( photomultiplier type detector ) with a sensitive field of view of about 38 arc-sec diameter converted the modulated light into a sequence of photon counts ( with a sampling frequency of 1200 Hz ) from which the phase of the entire pulse train from a star could be derived.
Other hardware components were supplied as follows: the beam-combining mirror from REOSC at Saint Pierre du Perray ; the spherical, folding and relay mirrors from Carl Zeiss AG in Oberkochen ; the external straylight baffles from CASA in Madrid ; the modulating grid from CSEM in Neuchatel ; the mechanism control system and the thermal control electronics from Dornier Satellite Systems in Friedrichshafen ; optical filters, the experiment structures and the attitude and orbit control system from Matra Marconi Space in Velizy ; instrument switching mechanisms from Oerlikon-Contraves in Zurich ; the image dissector tube and photomultiplier detectors assembled by the Dutch Space Research Organisation, SRON in The Netherlands ; the refocusing assembly mechanism designed by TNO-TPD in Delft ; the electrical power subsystem from British Aerospace in Bristol ; the structure and reaction control system from Daimler-Benz Aerospace in Bremen ; the solar arrays and thermal control system from Fokker Space System in Leiden ; the data handling and telecommunications system from Saab Ericsson Space in Gothenburg ; and the apogee boost motor from SEP in France.
A sensitive photomultiplier tube ( PMT ) measures the light from the crystal, and the output signal is fed to an electronic amplifier and other electronic equipment to count and possibly quantify the amplitude of the signals produced by the photomultiplier.
The industrial contamination monitoring detector, consisting of a scintillator and photomultiplier tube, finds wide application in the field of radioactive contamination monitoring of personnel and the environment.
The spectrometer consists of a suitable scintillator crystal, a photomultiplier tube, and a circuit for measuring the height of the pulses produced by the photomultiplier.
** Photodiode, photoresistor, phototransistor, photomultiplier tube – converts changing light levels into electrical signals
photomultiplier and every
The drawback, however, is that not every photon incident on the primary surface is counted either because of less-than-perfect efficiency of the photomultiplier, or because a second photon can arrive at the photomultiplier during the " dead time " associated with a first photon and never be noticed.
photomultiplier and photon
When a single photon is sent through an interferometer, it passes through both paths, interfering with itself, as waves do, yet is detected by a photomultiplier or other sensitive detector only once.
Photomultiplier-amplified photocurrents can be electronically amplified by a high-input-impedance electronic amplifier ( in the signal path, subsequent to the photomultiplier ), thus producing appreciable voltages even for nearly infinitesimally small photon fluxes.
For smaller photon fluxes, the photomultiplier can be operated in photon counting or Geiger mode ( see also: single-photon avalanche diode ).
In Geiger mode the photomultiplier gain is set so high ( using high voltage ) that a single photo-electron resulting from a single photon incident on the primary surface generates a very large current at the output circuit.
The light sensing element in photon counting devices in NIR, visible and ultraviolet wavelengths is a photomultiplier to achieve sufficient sensitivity.
photomultiplier and photocathode
directed at the photomultiplier tube's photocathode which is connected to the negative of a high voltage source.
In a photomultiplier tube, one or more electrons are emitted from a photocathode and accelerated towards a polished metal electrode ( called a dynode ).
A photocathode is a negatively charged electrode in a light detection device such as a photomultiplier or phototube that is coated with a photosensitive compound.
Since Ag-O-Cs has a higher dark current than more modern materials photomultiplier tubes with this photocathode material are nowadays used only in the infrared region with cooling.
photomultiplier and avalanche
These are detected when they reach a scintillator in the scanning device, creating a burst of light which is detected by photomultiplier tubes or silicon avalanche photodiodes ( Si APD ).
This light is collected by the same objective and, because it is red-shifted with respect to the excitation light it passes the dichroic mirror reaching a detector, typically a photomultiplier tube or avalanche photodiode detector.
photomultiplier and electrons
This light then passed through an exit slit into photomultiplier tubes that produced pulses or " sprays " of electrons.
The secondary electrons are first collected by attracting them towards an electrically biased grid at about + 400 V, and then further accelerated towards a phosphor or scintillator positively biased to about + 2, 000 V. The accelerated secondary electrons are now sufficiently energetic to cause the scintillator to emit flashes of light ( cathodoluminescence ), which are conducted to a photomultiplier outside the SEM column via a light pipe and a window in the wall of the specimen chamber.
photomultiplier and current
A photomultiplier will produce a small current even without incident photons ; this is called the dark current.
Unlike photomultiplier tubes, no amplification takes place, so the current that flows through the device is typically of the order of a few microamperes.
photomultiplier and pulse
This assumption is based on two requirements: ( 1 ) that the light output of the scintillator is proportional to the energy of the incident radiation ; ( 2 ) that the electrical pulse produced by the photomultiplier tube is proportional to the emitted scintillation light.
The voltage pulse produced by the detector ( or by the photomultiplier in a scintillation detector ) is shaped by a multichannel analyzer ( MCA ).
photomultiplier and .
The fluorescence signal is captured by a photomultiplier a known distance downstream of the de Laval nozzle.
The amplified electrical signal output by the photomultiplier is displayed as a two-dimensional intensity distribution that can be viewed and photographed on an analogue video display, or subjected to analog-to-digital conversion and displayed and saved as a digital image.
The heavy water was viewed by approximately 9, 600 photomultiplier tubes ( PMTs ) mounted on a geodesic sphere at a radius of about.
Mounted on the superstructure are 11, 146 photomultiplier tubes ( PMT ) in diameter that face the ID and 1, 885 PMTs that face the OD.
The detector, named KamiokaNDE for Kamioka Nucleon Decay Experiment, was a tank in height and in width, containing 3, 048 metric tons ( 3, 000 tons ) of pure water and about 1, 000 photomultiplier tubes ( PMTs ) attached to its inner surface.
The scanner had a single photomultiplier detector, and operated on the Translate / Rotate principle.
This machine had 30 photomultiplier tubes as detectors and completed a scan in only 9 translate / rotate cycles, much faster than the EMI-scanner.
The detection of these photons has been made possible ( and easier ) by the development of more sensitive photomultiplier tubes and associated electronic equipment.
Single photodiode detectors and photomultiplier tubes are used with scanning monochromators, which filter the light so that only light of a single wavelength reaches the detector at one time.
In wavelength dispersive analysis, the single-wavelength radiation produced by the monochromator is passed into a photomultiplier, a detector similar to a Geiger counter, which counts individual photons as they pass through.
Elements of photomultiplier technology, when integrated differently, are the basis of night vision devices.