Coincidence circuit
Encyclopedia
In physics
, a coincidence circuit is an electronic device with one output
and two (or more) inputs. The output is activated only when signals are received within a time window accepted as at the same time and in parallel at both inputs. Coincidence circuits are widely used in particle physics experiments
and in other areas of science and technology.
Walther Bothe
shared the Nobel Prize for Physics
in 1954 "for his discovery of the method of coincidence and the discoveries subsequently made by it". Bruno Rossi
invented the electronic coincidence circuit for implementing the coincidence method.
in 1924. The experiment was aimed to check whether Compton scattering produces a recoil electron simultaneously with the scattered gamma ray
. Bothe used two point discharge counters connected to separate fibre electrometer
s and recorded the fibre deflections on a moving photographic film. On the film record he could discern coincident discharges with a time resolution of approximately 1 millisecond
.
published the description of a coincidence experiment with tubular discharge counters invented in 1928 by Hans Geiger and Wilhelm Müller
. The Bothe-Kohlhörster experiment demonstrated the presence of penetrating charged particles in cosmic ray
s. They used the same mechanical-photographic method for recording simultaneous discharges which, in this experiment, signalled the passage of a charged cosmic ray particle through both counters and through the thick wall of lead and iron with which they had surrounded the counters. Their paper, entitled "Das Wesen der Höhenstrahlung", was published in the Zeitschrift für Physik
v.56, p.751 (1929).
when he read the Bothe-Kohlhörster paper. It inspired him to begin his own research on cosmic rays. He fabricated Geiger tubes according to the published recipe, and he invented the first practical electronic coincident circuit. It employed several triode
vacuum tube
s, and was capable of registering coincident pulses from any number of counters with a tenfold improvement in time resolution over the mechanical method of Bothe. Rossi described his invention in a paper entitled "Method of Registering Multiple Simultaneous Impulses of Several Geiger Counters", published in Nature
v.125, p.636 (1930). The Rossi coincidence circuit was rapidly adopted by experimenters around the world. It was the first practical AND
circuit, precursor of the AND logic circuits of electronic computers.
To detect the voltage pulse produced by the coincidence circuit when a coincidence event occurred, Rossi first used earphones and counted the ‘clicks’, and soon an electro-mechanical register to count the coincidence pulses automatically. Rossi used a triple-coincidence version of his circuit with various configurations of Geiger counters in a series of experiments during the period from 1930 to 1943 that laid an essential part of the foundations of cosmic-ray and particle physics.
About the same time and independently of Rossi, Bothe devised a less practical electronic coincidence device. It employed a single pentode
vacuum tube and could register only twofold coincidences.
, that the detected pulse is actually a noise pulse. But if two detectors detect the signal pulse simultaneously, the probability that it is a noise pulse in the detectors is 
. Suppose 
. Then 
. Thus the chance of a false detection is reduced by the use of coincidence detection.
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
, a coincidence circuit is an electronic device with one output
Output
Output is the term denoting either an exit or changes which exit a system and which activate/modify a process. It is an abstract concept, used in the modeling, system design and system exploitation.-In control theory:...
and two (or more) inputs. The output is activated only when signals are received within a time window accepted as at the same time and in parallel at both inputs. Coincidence circuits are widely used in particle physics experiments
Particle physics experiments
Particle physics experiments briefly discusses a number of past, present, and proposed experiments with particle accelerators, throughout the world. In addition, some important accelerator interactions are discussed...
and in other areas of science and technology.
Walther Bothe
Walther Bothe
Walther Wilhelm Georg Bothe was a German nuclear physicist, who shared the Nobel Prize in Physics in 1954 with Max Born....
shared the Nobel Prize for Physics
Nobel Prize in Physics
The Nobel Prize in Physics is awarded once a year by the Royal Swedish Academy of Sciences. It is one of the five Nobel Prizes established by the will of Alfred Nobel in 1895 and awarded since 1901; the others are the Nobel Prize in Chemistry, Nobel Prize in Literature, Nobel Peace Prize, and...
in 1954 "for his discovery of the method of coincidence and the discoveries subsequently made by it". Bruno Rossi
Bruno Rossi
Bruno Benedetto Rossi was a leading Italian-American experimental physicist. He made major contributions to cosmic ray and particle physics from 1930 through the 1950s, and pioneered X-ray astronomy and space plasma physics in the 1960s.-Biography:Rossi was born in Venice, Italy...
invented the electronic coincidence circuit for implementing the coincidence method.
Bothe, 1924
In his Nobel Prize lecture, Bothe described how he had implemented the coincidence method in an experiment on Compton scatteringCompton scattering
In physics, Compton scattering is a type of scattering that X-rays and gamma rays undergo in matter. The inelastic scattering of photons in matter results in a decrease in energy of an X-ray or gamma ray photon, called the Compton effect...
in 1924. The experiment was aimed to check whether Compton scattering produces a recoil electron simultaneously with the scattered gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
. Bothe used two point discharge counters connected to separate fibre electrometer
Electrometer
An electrometer is an electrical instrument for measuring electric charge or electrical potential difference. There are many different types, ranging from historical hand-made mechanical instruments to high-precision electronic devices...
s and recorded the fibre deflections on a moving photographic film. On the film record he could discern coincident discharges with a time resolution of approximately 1 millisecond
Millisecond
A millisecond is a thousandth of a second.10 milliseconds are called a centisecond....
.
Bothe and Kohlhörster, 1929
In 1929, Walther Bothe and Werner KolhörsterWerner Kolhörster
Werner Heinrich Gustav Kolhörster was a German physicist and a pioneer of research into cosmic rays.Kolhörster was born in Schwiebus , Province of Brandenburg...
published the description of a coincidence experiment with tubular discharge counters invented in 1928 by Hans Geiger and Wilhelm Müller
Wilhelm Müller
Wilhelm Müller was a German lyric poet.-Life:Wilhelm Müller was born at Dessau, the son of a tailor. He was educated at the gymnasium of his native town and at the university of Berlin, where he devoted himself to philological and historical studies...
. The Bothe-Kohlhörster experiment demonstrated the presence of penetrating charged particles in cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s. They used the same mechanical-photographic method for recording simultaneous discharges which, in this experiment, signalled the passage of a charged cosmic ray particle through both counters and through the thick wall of lead and iron with which they had surrounded the counters. Their paper, entitled "Das Wesen der Höhenstrahlung", was published in the Zeitschrift für Physik
Zeitschrift für Physik
The European Physical Journal is a joint publication of EDP Sciences, Springer Science+Business Media, and the Società Italiana di Fisica...
v.56, p.751 (1929).
Rossi, 1930
Bruno Rossi, at the age of 24, was in his first job as assistant in the Physics Institute of the University of FlorenceUniversity of Florence
The University of Florence is a higher study institute in Florence, central Italy. One of the largest and oldest universities in the country, it consists of 12 faculties...
when he read the Bothe-Kohlhörster paper. It inspired him to begin his own research on cosmic rays. He fabricated Geiger tubes according to the published recipe, and he invented the first practical electronic coincident circuit. It employed several triode
Triode
A triode is an electronic amplification device having three active electrodes. The term most commonly applies to a vacuum tube with three elements: the filament or cathode, the grid, and the plate or anode. The triode vacuum tube was the first electronic amplification device...
vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
s, and was capable of registering coincident pulses from any number of counters with a tenfold improvement in time resolution over the mechanical method of Bothe. Rossi described his invention in a paper entitled "Method of Registering Multiple Simultaneous Impulses of Several Geiger Counters", published in Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
v.125, p.636 (1930). The Rossi coincidence circuit was rapidly adopted by experimenters around the world. It was the first practical AND
Logical conjunction
In logic and mathematics, a two-place logical operator and, also known as logical conjunction, results in true if both of its operands are true, otherwise the value of false....
circuit, precursor of the AND logic circuits of electronic computers.
To detect the voltage pulse produced by the coincidence circuit when a coincidence event occurred, Rossi first used earphones and counted the ‘clicks’, and soon an electro-mechanical register to count the coincidence pulses automatically. Rossi used a triple-coincidence version of his circuit with various configurations of Geiger counters in a series of experiments during the period from 1930 to 1943 that laid an essential part of the foundations of cosmic-ray and particle physics.
About the same time and independently of Rossi, Bothe devised a less practical electronic coincidence device. It employed a single pentode
Pentode
A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid vacuum tube , which was invented by the Dutchman Bernhard D.H. Tellegen in 1926...
vacuum tube and could register only twofold coincidences.
Probability
The main idea of 'coincidence detection' in signal processing is that if a detector detects a signal pulse in the midst of random noise pulses inherent in the detector, there is a certain probability,, that the detected pulse is actually a noise pulse. But if two detectors detect the signal pulse simultaneously, the probability that it is a noise pulse in the detectors is . Suppose . Then . Thus the chance of a false detection is reduced by the use of coincidence detection.