Table of Contents
What is the operating principle of phototube?
Operating principles Phototubes operate according to the photoelectric effect: Incoming photons strike a photocathode, knocking electrons out of its surface, which are attracted to an anode. Thus current is dependent on the frequency and intensity of incoming photons.
Is phototube and photomultiplier tube the same?
Photomultiplier Tubes A special form of the phototube is the photomultiplier tube. This contains additional electrodes, with which a high amplification of the photocurrent can be achieved based on secondary electron emission.
What is photocell describe its construction and working?
Photoelectric cell consists of highly evacuated or gas filled glass tube, an emitter and a collector. The light enters through a quartz window and falls on the semicylindrical cathode C coated with photosensitive metal. The anode is in the form of straight wire of platinum or nickel, co-axial with cathode.
What is phototube detector?
Phototubes are photodetectors that feature high sensitivity, superior temperature stability, wide dynamic range, large photosensitive area, and low-voltage operation. They are widely utilized in applications such as chemical and medical analysis and laser measurement.
How does a Dynode work?
In a PMT, dynodes are electrodes in a vacuum tube that serve as an electron multiplier through SEE (see Figure 1). The dynodes are so arranged that the electric fields between them cause the electrons emitted by each dynode to strike the next with an energy of a few hundred eV.
How does a photomultiplier work?
A photomultiplier tube, useful for light detection of very weak signals, is a photoemissive device in which the absorption of a photon results in the emission of an electron. These detectors work by amplifying the electrons generated by a photocathode exposed to a photon flux.
How does a photocell work physics?
Photoelectric cell or photocell or photovoltaic cell is an electronic device which works on the principle of the photoelectric effect and converts light energy into electrical energy. Photocell consists of an evacuated glass tube containing two electrodes emitter (C) and Collector (A).
What do you mean by the term work function?
Definition of work function : the energy that is needed for a particle to come from the interior of a medium and break through the surface —used especially of the photoelectric and thermionic emission of electrons from metals.
What is a dynode in chemistry?
A dynode is an electrode in a vacuum tube that serves as an electron multiplier through secondary emission. The first tube to incorporate a dynode was the dynatron, an ancestor of the magnetron, which used a single dynode.
What is meant by dynode?
dynode in British English (ˈdaɪnəʊd ) noun. an electrode onto which a beam of electrons can fall, causing the emission of a greater number of electrons by secondary emission. They are used in photomultipliers to amplify the signal.
What is photomultiplier in physics?
What is photomultiplier in analytical chemistry?
A photomultiplier tube is commonly used to measure the intensity of ultraviolet and visible radiation. The measurement is based initially on the photoelectric effect and then on the amplification of the signal through a series of dynodes (Figure 1.3C.
What are dynodes made up of?
The dynode is made of a metal plate containing a substance on the surface such as a bialkali compound, which emits secondary electrons upon impact with accelerated electrons. The acceleration of the photoelectrons and the impact of these on the dynode produce multiple secondary electrons.
What is a work function in chemistry?
The work function (or workfunction) is defined as the minimum amount of thermodynamic work (i.e. energy) required to remove an electron from a solid to a point in the vacuum immediately outside the solid surface.
What is the difference between function and work?
As verbs the difference between function and work is that function is to have or carry on a function (i.e. to be in action) while work is to do a specific task by employing physical or mental powers.
What is photodiode explain working principle and structure of avalanche photodiode?
An avalanche photodiode is a silicon-based semiconductor containing a pn junction consisting of a positively doped p region and a negatively doped n region sandwiching an area of neutral charge termed the depletion region.
Why does photodiode work in reverse bias?
Solution : The current in the forward bias is primarily due to major carriers but in reverse bias it is due to minor carriers. As the fractional change in the reverse current due to the photo-effects is more easily measurable than in the forward bias current. So photodiodes are operated in the reverse bias.
What is a phototube?
A phototube or photoelectric cell is a type of gas-filled or vacuum tube that is sensitive to light. Such a tube is more correctly called a ‘photoemissive cell’ to distinguish it from photovoltaic or photoconductive cells. Phototubes were previously more widely used but are now replaced in many applications by solid state photodetectors.
What is a phototube or photelectric cell?
A phototube or photelectric cell is a type of gas-filled or vacuum tube that is sensitive to light. Such a tube is more correctly called a ‘photoemissive cell’ to distinguish it from photovoltaic or photoconductive cells.
What is the photomultiplier tube used for?
The photomultiplier tube is one of the most sensitive light detectors, and is still widely used in physics research. Phototubes operate according to the photoelectric effect: Incoming photons strike a photocathode, knocking electrons out of its surface, which are attracted to an anode.
What are the properties of a good a phototube?
A phototube should possess the following properties if one is to obtain the best performance from the detector: A photocathode of high photon efficiency so that the maximum number of electrons may be produced by the available light-signal.