A bhangmeter is a non-imaging radiometer installed on

reconnaissance In military operations, reconnaissance or scouting is the exploration of an area by military forces to obtain information about enemy forces, terrain, and other activities. Examples of reconnaissance include patrolling by troops (skirmisher ...

and

navigation satellite A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pre ...

s to detect atmospheric nuclear detonations and determine the yield of the nuclear weapon. They are also installed on some

armored fighting vehicles An armoured fighting vehicle (AFV) is an armed combat vehicle protected by armour, generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked. Examples of AFVs are tanks, armoured car ...

, in particular NBC reconnaissance vehicles, in order to help detect, localise and analyse tactical nuclear detonations. They are often used alongside pressure and sound sensors in this role in addition to standard radiation sensors. Some nuclear bunkers and military facilities may also be equipped with such sensors alongside seismic event detectors. The bhangmeter was developed at

Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...

by a team led by Herman Hoerlin.

History

The bhangmeter was invented, and the first proof-of-concept device was built, in 1948 to measure the nuclear test detonations of

Operation Sandstone Operation Sandstone was a series of nuclear weapon tests in 1948. It was the third series of American tests, following Trinity in 1945 and Crossroads in 1946, and preceding Ranger. Like the Crossroads tests, the Sandstone tests were carried ou ...

. Prototype and production instruments were later built by

EG&G EG&G, formally known as Edgerton, Germeshausen, and Grier, Inc., was a United States national defense contractor and provider of management and technical services. The company was involved in contracting services to the United States government ...

, and the name "bhangmeter" was coined in 1950 by

Frederick Reines Frederick Reines ( ; March 16, 1918 – August 26, 1998) was an American physicist. He was awarded the 1995 Nobel Prize in Physics for his co-detection of the neutrino with Clyde Cowan in the neutrino experiment. He may be the only scientist i ...

. Bhangmeters became standard instruments used to observe US

nuclear test Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, Nuclear weapon yield, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detona ...

s. A bhangmeter was developed to observe the detonations of Operation Buster-Jangle (1951) and Operation Tumbler-Snapper (1952). These tests lay the groundwork for a large deployment of nationwide North American bhangmeters with the

Bomb Alarm System The Bomb Alarm System (also known as the Bomb Alarm Display System) was a US and UK network of optical bhangmeter sensors intended to confirm the detonation of an enemy nuclear weapon near cities or military installations within the US or at US op ...

(1961-1967). US president

John F. Kennedy John Fitzgerald Kennedy (May 29, 1917 – November 22, 1963), often referred to by his initials JFK and the nickname Jack, was an American politician who served as the 35th president of the United States from 1961 until his assassination ...

and the

First Secretary of the Communist Party of the Soviet Union First or 1st is the ordinal form of the number one (#1). First or 1st may also refer to: *World record, specifically the first instance of a particular achievement Arts and media Music * 1$T, American rapper, singer-songwriter, DJ, and rec ...

Nikita Khrushchev Nikita Sergeyevich Khrushchev (– 11 September 1971) was the First Secretary of the Communist Party of the Soviet Union from 1953 to 1964 and chairman of the country's Council of Ministers from 1958 to 1964. During his rule, Khrushchev s ...

signed the

Partial Test Ban Treaty The Partial Test Ban Treaty (PTBT) is the abbreviated name of the 1963 Treaty Banning Nuclear Weapon Tests in the Atmosphere, in Outer Space and Under Water, which prohibited all test detonations of nuclear weapons except for those conducted ...

on August 5, 1963, under the condition that each party could use its own technical means to monitor the ban on nuclear testing in the atmosphere or in outer space. Bhangmeters were first installed, in 1961, aboard a modified US

KC-135A The Boeing KC-135 Stratotanker is an American military aerial refueling aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It is the predominant variant of the C-135 Stratolifter family of transpo ...

aircraft monitoring the pre-announced Soviet test of

Tsar Bomba The Tsar Bomba () ( code name: ''Ivan'' or ''Vanya''), also known by the alphanumerical designation "AN602", was a thermonuclear aerial bomb, and the most powerful nuclear weapon ever created and tested. Overall, the Soviet physicist Andrei ...

The Vela satellites were the first space-based observation devices jointly developed by the

U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sign ...

and the Atomic Energy Commission. The first generation of Vela satellites were not equipped with bhangmeters but with

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

sensors to detect the intense single pulse of X-rays produced by a nuclear explosion. The first satellites which incorporated bhangmeters were the Advanced Vela satellites. Since 1980, bhangmeters have been included on US

GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...

navigation satellites.

Description

The

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

photodiode sensors are designed to detect the distinctive bright double pulse of visible light that is emitted from

atmospheric nuclear weapons explosion A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, tho ...

s. This signature consists of a short and intense flash lasting around 1 millisecond, followed by a second much more prolonged and less intense emission of light taking a fraction of a second to several seconds to build up. This signature, with a double intensity maximum, is characteristic of atmospheric nuclear explosions and is the result of the Earth's atmosphere becoming opaque to visible light and transparent again as the explosion's shock wave travels through it. The effect occurs because the surface of the early fireball is quickly overtaken by the expanding "case shock", the atmospheric shock wave composed of the ionised plasma of what was once the casing and other matter of the device. Although it emits a considerable amount of light itself, it is opaque and prevents the far brighter fireball from shining through. The net result recorded is a decrease of the light visible from outer space as the shock wave expands, producing the first peak recorded by the bhangmeter. As it expands, the shock wave cools off and becomes less opaque to the visible light produced by the inner fireball. The bhangmeter starts eventually to record an increase in visible light intensity. The expansion of the fireball leads to an increase of its surface area and consequently an increase of the amount of visible light radiated off to space. The fireball continues to cool down so the amount of light eventually starts to decrease, causing the second peak observed by the bhangmeter. The time between the first and second peaks can be used to determine its

nuclear yield The explosive yield of a nuclear weapon is the amount of energy released when that particular nuclear weapon is detonated, usually expressed as a TNT equivalent (the standardized equivalent mass of trinitrotoluene which, if detonated, would produ ...

. The effect is unambiguous for explosions below about altitude, but above this height a more ambiguous single pulse is produced.

Origin of the name

The name of the detector is a

pun A pun, also known as paronomasia, is a form of word play that exploits multiple meanings of a term, or of similar-sounding words, for an intended humorous or rhetorical effect. These ambiguities can arise from the intentional use of homophoni ...

, which was bestowed upon it by Fred Reines, one of the scientists working on the project. The name is derived from the Hindi word "

bhang Bhang (IAST: ''Bhāṅg'') is an edible preparation made from the leaves of the cannabis plant originating from the Indian subcontinent. It has been used in food and drink as early as 1000 BC in ancient India. Bhang is traditionally distribu ...

", a locally grown variety of

cannabis ''Cannabis'' () is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: '' Cannabis sativa'', '' C. indica'', and '' C. ruderalis''. Alternative ...

which is smoked or drunk to induce intoxicating effects, the joke being that one would have to be on drugs to believe the bhangmeter detectors would work properly. This is in contrast to a "bangmeter" one might associate with detection of nuclear explosions.

History

Description

Origin of the name

See also

References

Further reading