"Degaussing Degaussing is the process of decreasing or eliminating a remnant magnetic field. It is named after the gauss, a unit of magnetism, which in turn was named after Carl Friedrich Gauss. Due to magnetic hysteresis, it is generally not possible to reduce a magnetic field completely to zero, so degaussing typically induces a very small ""known"" field referred to as bias. Degaussing was originally applied to reduce ships' magnetic signatures during World War II. Degaussing is also used to reduce magnetic fields in cathode ray tube monitors and to destroy data held on magnetic storage. The term was first"
"used by then-Commander Charles F. Goodeve, RCNVR, during World War II while trying to counter the German magnetic naval mines that were playing havoc with the British fleet. The mines detected the increase in the magnetic field when the steel in a ship concentrated the Earth's magnetic field over it. Admiralty scientists, including Goodeve, developed a number of systems to induce a small ""N-pole up"" field into the ship to offset this effect, meaning that the net field was the same as the background. Since the Germans used the gauss as the unit of the strength of the magnetic field"
"magnetic field around ships which triggered mines; Goodeve coined the term after the gauss unit, used by the Germans during the war to measure magnetic fields which they named after German scientist Carl Friedrich Gauss (1777–1855). He also developed the related technique of ""wiping"". To aid the Dunkirk evacuation, the British ""wiped"" 400 ships in four days. In 1940, Goodeve implemented the British production of the Swiss-designed Oerlikon 20 mm cannon, which was needed as anti-aircraft protection on naval and merchant ships. His group, renamed the Directorate of Miscellaneous Weapons Development (D.M.W.D.), then worked on antisubmarine warfare developing the hedgehog,"
"magnetic field at that particular spot. When a ship passed over it, the mass of the ship caused the magnetic needle inside the mine to move slightly. The movement was enough to detonate the mine and cause an underwater explosion powerful enough to send up huge geysers that would literally lift a ship out of the water and severely damage the ship's infrastructure. In his autobiography ""Magnets, the Education of a Physicist"", he referred to this unique work as ""Degaussing the fleet"". (It is possible that he worked with Francis Crick, who was researching the same problem.) After the war,"
"space for the solution, while the amount of power needed to overcome the magnetic field of a large ship is impractical. Active countermeasures are ways to clear a path through a minefield or remove it completely. This is one of the most important tasks of any mine warfare flotilla. A sweep is either a contact sweep, a wire dragged through the water by one or two ships to cut the mooring wire of floating mines, or a distance sweep that mimics a ship to detonate the mines. The sweeps are dragged by minesweepers, either purpose-built military ships or converted trawlers."
"Magnetic self-protection Magnetic self-protection (MSP), also ""mine protection"" is an active measure to reduce the magnetic signature of a ship. This is needed so that the magnetic ignition mechanism of naval mines or torpedoes are not triggered. The mere demagnetization is to be distinguished from that with which the permanent magnetic orientation of a metal hulk can be lifted with a strong magnetic field for some time. The first magnetic self-protection equipment was developed at the beginning of World War II because of the advent of magnetically detonated mines. This was initially a cable which was placed along the entire"
"minesweeping, only mines that could be cleared by magnetic sweeps were used, and the vast majority of mines laid were programmed either to self-destruct or render themselves inert after a specified period of time. Of course, the U.S. Navy also knew generally where the mines had been laid, although the inherent inaccuracy of aerial minelaying meant that the precise location of each mine was not known. Rear Admiral Brian McCauley became Commander, Mine Warfare Force, and Commander, Task Force 78, in September 1972. Task Force 78 was designated as Mine Countermeasures Force, U.S. Seventh Fleet, and was created for the"
"in their mines' triggers (this was not yet a standard measure), Goodeve referred to the various processes to counter the mines as ""degaussing"". The term became a common word. The original method of degaussing was to install electromagnetic coils into the ships, known simply as coiling. In addition to being able to bias the ship continually, coiling also allowed the bias field to be reversed in the southern hemisphere, where the mines were set to detect ""S-pole down"" fields. British ships, notably cruisers and battleships, were well protected by about 1943. Installing such special equipment was, however, far too expensive"
"Coercivity In electrical engineering and materials science, the coercivity, also called the magnetic coercivity, coercive field or coercive force, is a measure of the ability of a ferromagnetic material to withstand an external magnetic field without becoming demagnetized. An analogous property, electric coercivity, is the ability of a ferroelectric material to withstand an external electric field without becoming depolarized. For ferromagnetic material the coercivity is the intensity of the applied magnetic field required to reduce the magnetization of that material to zero ""after"" the magnetization of the sample has been driven to saturation. Thus coercivity measures the resistance of a"
"the electromagnetic field around submarine cables carrying alternating current, and he investigated underwater explosions and the stability of torpedoes. In 1939, he was a ""Principal Scientific Officer"" at the Admiralty Research Laboratory in the Admiralty's Scientific Research and Experiment Department. During World War II, he investigated both magnetic mines and the degaussing of ships (as a means of protecting them from magnetic mines). He was a first-rate applied mathematician. He often solved problems that others had regarded as insoluble. For his successes, he employed judicious approximations, penetrating physical insight, ingenious experiments, and skilful use of models. He was a quiet"
"in effect. From May 1964 to the early 1970s the USA participated in Operation CHASE, a United States Department of Defense program that aimed to dispose of chemical weapons by sinking ships laden with the weapons in the deep Atlantic. After the Marine Protection, Research, and Sanctuaries Act of 1972, Operation Chase was scrapped and safer disposal methods for chemical weapons were researched, with the U.S. destroying several thousand tons of mustard gas by incineration at the Rocky Mountain Arsenal, and nearly 4,200 tons of nerve agent by chemical neutralisation at Tooele Army Depot. The U.S. ratified the Geneva Protocol"
"French naval officer Jacques Yves Cousteau's Undersea Research Group was once involved in mine-hunting operations: They removed or detonated a variety of German mines, but one particularly defusion-resistant batch—equipped with acutely sensitive pressure, magnetic, and acoustic sensors and wired together so that one explosion would trigger the rest—was simply left undisturbed for years until corrosion would (hopefully) disable the mines. A more drastic method is simply to run a ship through the minefield, letting other ships safely follow the same path. An early example of this was Farragut's actions at Mobile Bay during the American Civil War. However, as mine"
"1939, a bomb disposal team under Lieutenant Commander J. G. D. Ouvry recovered an intact aerial mine from a mudflat at Shoeburyness, and the threat was revealed to be a magnetic mine. In December 1939, Massey joined a group at the Admiralty Research Laboratory in Teddington led by Stephen Butterworth. They were soon joined by a number of other physicists, including Bates, Buckingham, Francis Crick and John Gunn. Together, they came up with a series of countermeasures that enable the Navy to successfully sweep the mines. With this in hand, Massey became Deputy Chief Scientist to the Scientific Section of"
"Minesweeping Minesweeping is the practice of the removal of explosive naval mines, usually by a specially designed ship called a minesweeper using various measures to either capture or detonate the mines, but sometimes also with an aircraft made for that purpose. Minesweeping has been practiced since the advent of naval mining in 1855 in the Crimean War. The first minesweepers date to that war and consisted of British rowboats trailing grapnels to snag the mines. A sweep is either a contact sweep, a wire dragged through the water by one or two ships to cut the mooring wire of floating"
"the army and a base with men and workshops was at hand. Experts were dispatched from HMS Vernon to investigate the mine. The Royal Navy knew that mines could use magnetic sensors, Britain having developed magnetic mines in World war I, so everyone removed all metal, including their buttons, and made tools of non-magnetic brass. They disarmed the mine and rushed it to the labs at HMS Vernon, where scientists discovered that the mine had a magnetic arming mechanism. A large ferrous object passing through the Earth's magnetic field will concentrate the field through it; the mine's detector was designed"
"Magnetic separation Magnetic Separation is which separating components of mixtures by using magnets to attract magnetically susceptible materials. This separation technique can be useful in mining iron as it is attracted to a magnet. In mines where wolframite was mixed with cassiterite, such as South Crofty and East Pool mine in Cornwall or with bismuth such as at the Shepherd and Murphy mine in Moina, Tasmania, magnetic separation is used to separate the ores. At these mines, a device called a Wetherill's Magnetic Separator (invented by John Price Wetherill, 1844–1906) was used. In this machine, the raw ore, after calcination"
"hull temporarily cancelled the ships' magnetic signature sufficiently to nullify the threat. This started in late 1939, and by 1940 merchant vessels and the smaller British warships were largely immune for a few months at a time until they once again built up a field. Many of the boats that sailed to Dunkirk were degaussed in a marathon four-day effort by degaussing stations. The Allies and Germany deployed acoustic mines in WW II, against which even wooden-hulled ships (in particular minesweepers) remained vulnerable. Japan developed sonic generators to sweep these; the gear was not ready by war's end. The primary"
"a way of attaching a magnetic needle at right-angles to the dip needle in order to measure the intensity of force (by seeing the extent to which the right-angle needle deflected the dip-needle). By World War I the most advanced dip circles were being made. With the development of electronic systems dip circles became obsolete. Dip circle Dip circles (also ""dip needles"") are used to measure the angle between the horizon and the Earth's magnetic field (the dip angle). They were used in surveying, mining and prospecting as well as for the demonstration and study of magnetism. Georg Hartmann first"
"to trigger as a ship passed over, when its magnetic field was concentrated as measured by the mine. The mechanism had an adjustable sensitivity, calibrated in milligauss. (As it turned out, the German firing mechanism was overly sensitive, making sweeping easier.) The U.S. began adding delay counters to their magnetic mines in June 1945. From this data, known methods were used to clear these mines. Early methods included the use of large electromagnets dragged behind ships or below low-flying aircraft (a number of older bombers like the Vickers Wellington were used for this). Both of these methods had the disadvantage"
"the wire instead of towards the ship by its wake. More recently, heavy-lift helicopters have dragged minesweeping sleds, as in the 1991 Persian Gulf War. The distance sweep mimics the sound and magnetism of a ship and is pulled behind the sweeper. It has floating coils and large underwater ""drums"". It is the only sweep effective against bottom mines. During the Second World War, RAF Coastal Command used Vickers Wellington bombers Wellington DW.Mk I fitted with degaussing coils to trigger magnetic mines. Modern influence mines are designed to discriminate against false inputs and are therefore much harder to sweep. They"
"length to the hull of the vessel and the application of direct current produced a magnetic field that counteracted the magnetic field of the steel mass of the vessel. During the second world war these methods of mine protection were standard for all large battle ships. A simple magnetic coil, however, was no longer capable of adequately compensating for the increasingly sophisticated magneto ignition, for the non-uniform magnetic field of a ship and for the variable effects of the Earth's magnetic field in different regions of the world. Modern MSP systems consist of a plurality of electromagnetic coils which suppress"
"Low magnetic electric motor A low magnetic electric motor (or non magnetic electric motor) is an AC or DC motor with a reduced magnetic stray field signature. Low magnetic or nonmagnetic electric motors are used on board mine countermeasures vessels, minehunters, minesweepers and specific types of submarines. For about a hundred years sea mines or naval mines have been an established element in naval warfare. Modern naval mines nowadays react on magnetic, acoustic and pressure signals. By far the most important step in their development was the invention of the magnetic influence firing principle, which utilizes the magnetic interference field"
"vessel in various operating states and for different measured latitudes. Magnetic self-protection Magnetic self-protection (MSP), also ""mine protection"" is an active measure to reduce the magnetic signature of a ship. This is needed so that the magnetic ignition mechanism of naval mines or torpedoes are not triggered. The mere demagnetization is to be distinguished from that with which the permanent magnetic orientation of a metal hulk can be lifted with a strong magnetic field for some time. The first magnetic self-protection equipment was developed at the beginning of World War II because of the advent of magnetically detonated mines. This"
"more serious problem was later realized: as a ship travels through Earth's magnetic field, it will slowly pick up that field, counteracting the effects of the degaussing. From then on captains were instructed to change direction as often as possible to avoid this problem. Nevertheless, the bias did wear off eventually, and ships had to be degaussed on a schedule. Smaller ships continued to use wiping through the war. To aid the Dunkirk evacuation, the British ""wiped"" 400 ships in four days. During World War II, the United States Navy commissioned a specialized class of degaussing ships that were capable"
"and is the best source of information on the past Earth's field. Magnetization formed by phase change, chemical action or growth of crystals at low temperature is called chemical remanent magnetization. Sediments acquire a ""depositional remanent magnetization"" during their formation or a ""post-depositional remanent magnetization"" afterwards. Some kinds of remanence are undesirable and must be removed before the useful remanence is measured. One is isothermal remanent magnetization (IRM), which as a component of NRM induced through exposing a particle to a large magnetic field, causing the field to flip its lower coercivity magnetic moments to a field-favored direction. A commonly"
"and difficult to service all ships that would need it, so the navy developed an alternative called wiping, which Goodeve also devised, and which is now also called deperming. This procedure simply dragged a large electrical cable along the side of the ship with a pulse of about 2000 amperes flowing through it. This induced the proper field into the ship in the form of a slight bias. It was originally thought that the pounding of the sea and the ship's engines would slowly randomize this field, but in testing, this was found not to be a real problem. A"
"interaction with Earth's magnetic field. It also picks up the magnetic orientation of the earth's magnetic field where it is built. This signature can be exploited by magnetic mines or facilitate the detection of a submarine by ships or aircraft with magnetic anomaly detection (MAD) equipment. Navies use the deperming procedure, in conjunction with degaussing, as a countermeasure against this. Specialized deperming facilities, such as the United States Navy's Lambert's Point Deperming Station at Naval Station Norfolk, or Pacific Fleet Submarine Drive-In Magnetic Silencing Facility (MSF) at Joint Base Pearl Harbor–Hickam, are used to perform the procedure. During a closed-wrap"
"or ROVs (remote controlled unmanned mini-submarines). It is slow, but also the most reliable way to remove mines. Minehunting started during the Second World War, but it was only after the war that it became truly effective. Sea mammals (mainly the Bottlenose Dolphin) have been trained to hunt and mark mines, most famously by the U.S. Navy Marine Mammal Program. Mine-clearance dolphins were deployed in the Persian Gulf during the Iraq War in 2003. The US Navy claims that these dolphins were effective in helping to clear more than 100 antiship mines and underwater booby traps from Umm Qasr Port."
"steel) as it is an unwanted contamination, for example a magnetization remaining in an electromagnet after the current in the coil is turned off. Where it is unwanted, it can be removed by degaussing. Sometimes the term retentivity is used for remanence measured in units of magnetic flux density. The default definition of magnetic remanence is the magnetization remaining in zero field after a large magnetic field is applied (enough to achieve saturation). The effect of a magnetic hysteresis loop is measured using instruments such as a vibrating sample magnetometer; and the zero-field intercept is a measure of the remanence."
"a ship's metal hull and explode beneath its keel. Mayer described the principle of the fuze and suggested that it could be defended against by generating a suitable magnetic field. The second type was deployed by the Germans as a mine. The Allies defeated it by degaussing their ships so that the mine could no longer detect them. The Allies were also able to sweep the mines by generating a suitable magnetic field to trip the mine. The final section of the report described how mechanical fuzes for artillery shells were being discontinued in favour of electrical fuzes and mentioned"
"Magnetic levitation Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields. Magnetic force is used to counteract the effects of the gravitational acceleration and any other accelerations. The two primary issues involved in magnetic levitation are ""lifting forces"": providing an upward force sufficient to counteract gravity, and ""stability"": ensuring that the system does not spontaneously slide or flip into a configuration where the lift is neutralized. Magnetic levitation is used for maglev trains, contactless melting, magnetic bearings and for product display purposes. Magnetic materials and systems are"
"Demining Demining or mine clearance is the process of removing land mines from an area, while minesweeping describes the act of detecting mines. There are two distinct types of mine detection and removal: military and humanitarian. Minesweepers use many tools in order to accomplish their task. Tools have historically included many trained animals, including dogs and rats, but most often in the modern world minesweepers rely on metal detectors or vehicles with a wide variety of mechanical tools attached to them. Other methods have been developed to detect mines, including the use of trained marine mammals, bacteria, acoustics, and other"
"Magnetic trap (atoms) A magnetic trap is an apparatus which uses a magnetic field gradient to trap neutral particles with magnetic moments. Although such traps have been employed for many purposes in physics research, they are best known as the last stage in cooling atoms to achieve Bose–Einstein condensation. The magnetic trap (as a way of trapping very cold atoms) was first proposed by David E. Pritchard. Many atoms have a magnetic moment; their energy shifts in a magnetic field according to the formula According to the principles of quantum mechanics the magnetic moment of an atom will be quantized;"