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95-763: The current classification system, the Government Security Classifications Policy , replaced the old Government Protective Marking Scheme in 2014. Since classifications can last for 100 years many documents are still covered by the old scheme. Policy is set by the Cabinet Office . The Security Policy Framework (SPF) superseded the Manual of Protective Security and contains the primary internal protective security policy and guidance on security and risk management for His Majesty's Government (HMG) Departments and associated bodies. It

190-452: A liquid deuterium-fusing device. While fusion bomb detonations were loosely considered for energy production , the possibility of controlled and sustained reactions remained the scientific focus for peaceful fusion power. Research into developing controlled fusion inside fusion reactors has been ongoing since the 1930s, with Los Alamos National Laboratory 's Scylla I device producing the first laboratory thermonuclear fusion in 1958, but

285-465: A risk assessment , and should consider what the aggregated information is, who needs to access it, and how. OFFICIAL includes most public-sector data, including a wide range of information on day-to-day government business. It is not subject to any special risks. Personal data would usually be OFFICIAL. The data should be protected by controls based on commercial best practice instead of expensive, difficult specialist technology and bureaucracy. There

380-449: A supernova can produce enough energy to fuse nuclei into elements heavier than iron. American chemist William Draper Harkins was the first to propose the concept of nuclear fusion in 1915. Then in 1921, Arthur Eddington suggested hydrogen–helium fusion could be the primary source of stellar energy. Quantum tunneling was discovered by Friedrich Hund in 1927, and shortly afterwards Robert Atkinson and Fritz Houtermans used

475-451: A flux of neutrons. Hundreds of neutron generators are produced annually for use in the petroleum industry where they are used in measurement equipment for locating and mapping oil reserves. A number of attempts to recirculate the ions that "miss" collisions have been made over the years. One of the better-known attempts in the 1970s was Migma , which used a unique particle storage ring to capture ions into circular orbits and return them to

570-494: A lab for nuclear fusion power production is completely impractical. Because nuclear reaction rates depend on density as well as temperature and most fusion schemes operate at relatively low densities, those methods are strongly dependent on higher temperatures. The fusion rate as a function of temperature (exp(− E / kT )), leads to the need to achieve temperatures in terrestrial reactors 10–100 times higher than in stellar interiors: T ≈ (0.1–1.0) × 10  K . In artificial fusion,

665-512: A manifestation of the strong interaction , which holds protons and neutrons tightly together in the atomic nucleus ; and the Coulomb force , which causes positively charged protons in the nucleus to repel each other. Lighter nuclei (nuclei smaller than iron and nickel) are sufficiently small and proton-poor to allow the nuclear force to overcome the Coulomb force. This is because the nucleus

760-476: A manner appropriate to its classification level and disposal must be in accordance with the SPF. The act of destruction or disposal is included in the accounting process. Protectively marked material may also be marked with a descriptor, or privacy marking, which identifies sensitivities around distribution and handling. Examples of descriptors include, but are not restricted to: Protectively marked material may bear

855-416: A miniature Voitenko compressor , where a plane diaphragm was driven by the implosion wave into a secondary small spherical cavity that contained pure deuterium gas at one atmosphere. There are also electrostatic confinement fusion devices. These devices confine ions using electrostatic fields. The best known is the fusor . This device has a cathode inside an anode wire cage. Positive ions fly towards

950-639: A nationality caveat , a descriptor defining to which nationality groups it may be released. By default, material in the UK is not caveated by nationality, the classification being sufficient protection. Examples of nationality caveats include, but are not limited to: Dissemination of already protectively marked material may be further limited only to those with a legitimate need to know using compartmentalisation by use of codewords. Examples of compartmented material would include information about nuclear warheads, fusion , and naval nuclear propulsion . In some cases,

1045-450: A nucleus with a diameter of about four nucleons. It is important to keep in mind that nucleons are quantum objects . So, for example, since two neutrons in a nucleus are identical to each other, the goal of distinguishing one from the other, such as which one is in the interior and which is on the surface, is in fact meaningless, and the inclusion of quantum mechanics is therefore necessary for proper calculations. The electrostatic force, on

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1140-505: A process called nucleosynthesis . The Sun is a main-sequence star, and, as such, generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses 620 million metric tons of hydrogen and makes 616 million metric tons of helium each second. The fusion of lighter elements in stars releases energy and the mass that always accompanies it. For example, in the fusion of two hydrogen nuclei to form helium, 0.645% of

1235-422: A significant fraction of the fuel before it has dissipated. To achieve these extreme conditions, the initially cold fuel must be explosively compressed. Inertial confinement is used in the hydrogen bomb , where the driver is x-rays created by a fission bomb. Inertial confinement is also attempted in "controlled" nuclear fusion, where the driver is a laser , ion , or electron beam, or a Z-pinch . Another method

1330-407: A single positive charge. A diproton is not stable, so neutrons must also be involved, ideally in such a way that a helium nucleus, with its extremely tight binding, is one of the products. Using deuterium–tritium fuel, the resulting energy barrier is about 0.1 MeV. In comparison, the energy needed to remove an electron from hydrogen is 13.6 eV. The (intermediate) result of the fusion

1425-572: A small subset of information marked OFFICIAL that require special handling by staff. "Very sensitive information", which might (for example) seriously harm national defence or crime investigations. Data should only be marked as SECRET if the Senior Information Risk Owner (which is a board level position in an organisation) agrees that it is high-impact and that the data must be protected against very capable attackers. Although some specialist technology might be used to protect

1520-645: A species of nuclei is reacting with a nucleus like itself, such as the DD reaction, then the product n 1 n 2 {\displaystyle n_{1}n_{2}} must be replaced by n 2 / 2 {\displaystyle n^{2}/2} . ⟨ σ v ⟩ {\displaystyle \langle \sigma v\rangle } increases from virtually zero at room temperatures up to meaningful magnitudes at temperatures of 10 – 100  keV. At these temperatures, well above typical ionization energies (13.6 eV in

1615-424: A static fuel-infused target, known as beam–target fusion, or by accelerating two streams of ions towards each other, beam–beam fusion. The key problem with accelerator-based fusion (and with cold targets in general) is that fusion cross sections are many orders of magnitude lower than Coulomb interaction cross-sections. Therefore, the vast majority of ions expend their energy emitting bremsstrahlung radiation and

1710-427: Is a reaction in which two or more atomic nuclei , usually deuterium and tritium (hydrogen isotopes ), combine to form one or more different atomic nuclei and subatomic particles ( neutrons or protons ). The difference in mass between the reactants and products is manifested as either the release or absorption of energy . This difference in mass arises due to the difference in nuclear binding energy between

1805-423: Is a technique using particle accelerators to achieve particle kinetic energies sufficient to induce light-ion fusion reactions. Accelerating light ions is relatively easy, and can be done in an efficient manner—requiring only a vacuum tube, a pair of electrodes, and a high-voltage transformer; fusion can be observed with as little as 10 kV between the electrodes. The system can be arranged to accelerate ions into

1900-401: Is an unstable He nucleus, which immediately ejects a neutron with 14.1 MeV. The recoil energy of the remaining He nucleus is 3.5 MeV, so the total energy liberated is 17.6 MeV. This is many times more than what was needed to overcome the energy barrier. The reaction cross section (σ) is a measure of the probability of a fusion reaction as a function of the relative velocity of

1995-508: Is because protons and neutrons are fermions , which according to the Pauli exclusion principle cannot exist in the same nucleus in exactly the same state. Each proton or neutron's energy state in a nucleus can accommodate both a spin up particle and a spin down particle. Helium-4 has an anomalously large binding energy because its nucleus consists of two protons and two neutrons (it is a doubly magic nucleus), so all four of its nucleons can be in

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2090-420: Is completely risk-free. People with routine access to TOP SECRET information should usually have DV clearance . TOP SECRET information is assumed to be exempt from FOIA disclosure. Disclosure of such information is assumed to be above the threshold for Official Secrets Act prosecution. Special handling instructions are additional markings which used in conjunction with a classification marking to indicate

2185-553: Is deliberately omitted from the new model. Government bodies are not expected to automatically remark existing data, so there may be cases where organisations working under the new system still handle some data marked according to the old system. Information Asset Owners continue to be responsible for information. The new policy does not specify particular IT security requirements – IT systems should be built and used in accordance with existing guidance from CESG . Everybody who works with government – including contractors and suppliers –

2280-400: Is greater than the repulsive Coulomb force. The strong force grows rapidly once the nuclei are close enough, and the fusing nucleons can essentially "fall" into each other and the result is fusion; this is an exothermic process . Energy released in most nuclear reactions is much larger than in chemical reactions , because the binding energy that holds a nucleus together is greater than

2375-433: Is how to confine the hot plasma. Due to the high temperature, the plasma cannot be in direct contact with any solid material, so it has to be located in a vacuum . Also, high temperatures imply high pressures. The plasma tends to expand immediately and some force is necessary to act against it. This force can take one of three forms: gravitation in stars, magnetic forces in magnetic confinement fusion reactors, or inertial as

2470-449: Is no requirement to mark every document as "OFFICIAL" – it is understood that this is the default for government documents. Organisations may add "descriptors" to highlight particular types of official data, for instance commercially sensitive information about contracts, or diplomatic data which should not be seen by locally hired embassy staff. These descriptors do not automatically require special controls. "OFFICIAL" will usually include

2565-511: Is not necessary to protect this from an attacker who has the capabilities of a Foreign Intelligence Service or Serious and Organised Crime. Conversely some data with much lower consequences (for example ongoing Police investigations into a criminal group, or intelligence information relating to possible prosecutions) but where the business will not accept compromise from such an attacker could be classified as SECRET. Guidance issued in April 2014 at

2660-630: Is now arguably somewhat reduced as a published standard. Higher classifications still tend to require stricter personnel vetting . The Government Security Classifications Policy was completed and published in December 2012; additional guidance and supporting processes were developed over time. The policy came into effect on 2 April 2014. Government procurement procedures took account of the new policy from 21 October 2023 so that new security requirements could be taken into account in contracts let from that date. Nuclear fusion Nuclear fusion

2755-402: Is responsible for protecting information they work with, regardless of whether it has a protective marking. Aggregation does not automatically trigger an increase in protective marking. For instance, a database with thousands of records which are individually OFFICIAL should not be relabeled as a SECRET database. Instead, information owners are expected to make decisions about controls based on

2850-481: Is subject to separate regulatory requirements, such as the Data Protection Act (personal data) or PCI DSS (card payments). OFFICIAL-SENSITIVE is an additional caveat for OFFICIAL data where it is particularly important to enforce need to know rules. OFFICIAL-SENSITIVE documents should be marked, but they are not necessarily tracked. It is not a classification. ‘Sensitive’ is a handling caveat for

2945-456: Is sufficiently small that all nucleons feel the short-range attractive force at least as strongly as they feel the infinite-range Coulomb repulsion. Building up nuclei from lighter nuclei by fusion releases the extra energy from the net attraction of particles. For larger nuclei , however, no energy is released, because the nuclear force is short-range and cannot act across larger nuclei. Fusion powers stars and produces virtually all elements in

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3040-595: Is the source on which all localised security policies are based. The classification system was formerly included in the Manual of Protective Security (MPS) which specified the impact of release and protection level required for each classification. Departments issued localised versions of the content of the MPS as appropriate to their operational needs. The Cabinet Office issued the Government Security Classifications Policy (GSCP) in 2013; it came into effect in 2014. It replaced

3135-408: Is to merge two FRC's rotating in opposite directions, which is being actively studied by Helion Energy . Because these approaches all have ion energies well beyond the Coulomb barrier , they often suggest the use of alternative fuel cycles like p- B that are too difficult to attempt using conventional approaches. Muon-catalyzed fusion is a fusion process that occurs at ordinary temperatures. It

3230-407: Is to use conventional high explosive material to compress a fuel to fusion conditions. The UTIAS explosive-driven-implosion facility was used to produce stable, centred and focused hemispherical implosions to generate neutrons from D-D reactions. The simplest and most direct method proved to be in a predetonated stoichiometric mixture of deuterium - oxygen . The other successful method was using

3325-409: Is under review too and in most practical contexts have now fallen into disuse. It is therefore no longer strictly the case that the greater the consequences if the data confidentiality were to be compromised, the higher the classification, since data with a high impact (including material which could result in threat to life) may still be classified as OFFICIAL if the relevant business owner believes it

3420-555: The CNO cycle and other processes are more important. As a star uses up a substantial fraction of its hydrogen, it begins to synthesize heavier elements. The heaviest elements are synthesized by fusion that occurs when a more massive star undergoes a violent supernova at the end of its life, a process known as supernova nucleosynthesis . A substantial energy barrier of electrostatic forces must be overcome before fusion can occur. At large distances, two naked nuclei repel one another because of

3515-542: The Lawson criterion , the energy of accidental collisions within the plasma is high enough to overcome the Coulomb barrier and the particles may fuse together. In a deuterium–tritium fusion reaction , for example, the energy necessary to overcome the Coulomb barrier is 0.1  MeV . Converting between energy and temperature shows that the 0.1 MeV barrier would be overcome at a temperature in excess of 1.2 billion kelvin . There are two effects that are needed to lower

3610-479: The Polywell , MIX POPS and Marble concepts. At the temperatures and densities in stellar cores, the rates of fusion reactions are notoriously slow. For example, at solar core temperature ( T ≈ 15 MK) and density (160 g/cm ), the energy release rate is only 276 μW/cm —about a quarter of the volumetric rate at which a resting human body generates heat. Thus, reproduction of stellar core conditions in

3705-419: The annihilatory collision of matter and antimatter , is more energetic per unit of mass than nuclear fusion. (The complete conversion of one gram of matter would release 9 × 10  joules of energy.) An important fusion process is the stellar nucleosynthesis that powers stars , including the Sun. In the 20th century, it was recognized that the energy released from nuclear fusion reactions accounts for

3800-415: The nickel isotope , Ni , is more stable, the iron isotope Fe is an order of magnitude more common. This is due to the fact that there is no easy way for stars to create Ni through the alpha process . An exception to this general trend is the helium-4 nucleus, whose binding energy is higher than that of lithium , the next heavier element. This

3895-465: The Coulomb barrier completely. If they have nearly enough energy, they can tunnel through the remaining barrier. For these reasons fuel at lower temperatures will still undergo fusion events, at a lower rate. Thermonuclear fusion is one of the methods being researched in the attempts to produce fusion power . If thermonuclear fusion becomes favorable to use, it would significantly reduce the world's carbon footprint . Accelerator-based light-ion fusion

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3990-632: The Protective Marking Scheme still exist and need correct handling. After 100 years all the classifications will have run out but the procedures may still be of interest to historians. Access to protectively marked material is defined according to a vetting level which the individual has achieved. Vetting is intended to assure the department that the individual has not been involved in espionage, terrorism, sabotage or actions intended to overthrow or undermine Parliamentary democracy by political, industrial or violent means. It also assures

4085-568: The Stars . At that time, the source of stellar energy was unknown; Eddington correctly speculated that the source was fusion of hydrogen into helium, liberating enormous energy according to Einstein's equation E = mc . This was a particularly remarkable development since at that time fusion and thermonuclear energy had not yet been discovered, nor even that stars are largely composed of hydrogen (see metallicity ). Eddington's paper reasoned that: All of these speculations were proven correct in

4180-530: The UK EYES ONLY national caveat are not sent overseas. As per the previous GPMS model, the choice of classification relates only to the data's confidentiality. Unlike the old model it replaces however, the GSCP does not consider the consequence of a compromise as the primary factor, but instead is based on the capability and motivation of potential threat actors (attackers) and the acceptability of that risk to

4275-556: The UK as the originating country and that the British Government should be consulted before any possible disclosure. National caveats follow the security classification. Unless explicitly named, information bearing a national caveat is not sent to foreign governments, overseas contractors, international organisations or released to any foreign nationals. Example With the exception of British Embassies and Diplomatic Missions or Service units or establishments, assets bearing

4370-441: The UK; it divides data into UNCLASSIFIED, PROTECT, RESTRICTED, CONFIDENTIAL, SECRET and TOP SECRET. This system was designed for paper-based records; it is not easily adapted to modern government work and is not widely understood. The GSCP uses three levels of classification: OFFICIAL, SECRET and TOP SECRET. This is simpler than the old model and there is no direct relationship between the old and new classifications. "Unclassified"

4465-456: The actual temperature. One is the fact that temperature is the average kinetic energy, implying that some nuclei at this temperature would actually have much higher energy than 0.1 MeV, while others would be much lower. It is the nuclei in the high-energy tail of the velocity distribution that account for most of the fusion reactions. The other effect is quantum tunnelling . The nuclei do not actually have to have enough energy to overcome

4560-646: The amount needed to heat plasma to the required temperatures are in development (see ITER ). The ITER facility is expected to finish its construction phase in 2025. It will start commissioning the reactor that same year and initiate plasma experiments in 2025, but is not expected to begin full deuterium–tritium fusion until 2035. Private companies pursuing the commercialization of nuclear fusion received $ 2.6 billion in private funding in 2021 alone, going to many notable startups including but not limited to Commonwealth Fusion Systems , Helion Energy Inc ., General Fusion , TAE Technologies Inc. and Zap Energy Inc. One of

4655-433: The atom is small enough), but primarily to its immediate neighbors due to the short range of the force. The nucleons in the interior of a nucleus have more neighboring nucleons than those on the surface. Since smaller nuclei have a larger surface-area-to-volume ratio, the binding energy per nucleon due to the nuclear force generally increases with the size of the nucleus but approaches a limiting value corresponding to that of

4750-510: The atomic nuclei before and after the reaction. Nuclear fusion is the process that powers active or main-sequence stars and other high-magnitude stars, where large amounts of energy are released . A nuclear fusion process that produces atomic nuclei lighter than iron-56 or nickel-62 will generally release energy. These elements have a relatively small mass and a relatively large binding energy per nucleon . Fusion of nuclei lighter than these releases energy (an exothermic process), while

4845-443: The business. Where a capable and motivated attacker such as a Foreign Intelligence Service, or Serious and Organised Crime are considered to be in scope of the data to be classified, the business must implicitly accept this risk to classify the data as OFFICIAL. If they do not or cannot accept this risk they must at least initially consider the data to be SECRET, though it may be reduced to OFFICIAL or increased to TOP SECRET later when

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4940-462: The cage, by generating the field using a non-neutral cloud. These include a plasma oscillating device, a Penning trap and the polywell . The technology is relatively immature, however, and many scientific and engineering questions remain. The most well known Inertial electrostatic confinement approach is the fusor . Starting in 1999, a number of amateurs have been able to do amateur fusion using these homemade devices. Other IEC devices include:

5035-586: The confidentiality of the data under classification. It is often incorrectly assumed that the OFFICIAL classification replaces the GPMS markings of PROTECT, RESTRICTED and CONFIDENTIAL, however this is not the case, since the criteria on which GPMS markings were applied bear no relationship to the criteria used for GSCP classifications. It is quite possible, and not uncommon, for data within an OFFICIAL classification to have serious impacts including serious injury in

5130-605: The consequences of a compromise are also considered. The implication of this approach and the binary nature of determining if a risk from capable and motivated attackers is acceptable or not, means that data cannot easily progress through the GSCP in a linear fashion as it did through GPMS. This is a complexity often lost on Information Asset Owners previously used to the strictly hierarchical tiered rising structure of GPMS (e.g. UNCLASSIFIED, PROTECT, RESTRICTED, CONFIDENTIAL, SECRET, TOP SECRET). By contrast GSCP data starts either with an OFFICIAL OR SECRET classification depending on

5225-449: The current advanced technical state. Thermonuclear fusion is the process of atomic nuclei combining or "fusing" using high temperatures to drive them close enough together for this to become possible. Such temperatures cause the matter to become a plasma and, if confined, fusion reactions may occur due to collisions with extreme thermal kinetic energies of the particles. There are two forms of thermonuclear fusion: uncontrolled , in which

5320-473: The data is deemed sensitive, how it must be held, processed and transferred. The older system used five levels of classification, supplemented with caveat keywords. The keyword was placed in all capital letters in the centre of the top and bottom of each page of a classified document and described the foreseeable consequence of an unauthorised release of the data (a ‘breach of confidentiality’). In descending order of secrecy, these are: Documents classified under

5415-806: The data, there is still strong emphasis on reuse of commercial security tools. SECRET is a big step up from OFFICIAL; government bodies are warned against being overcautious and applying much stricter rules when OFFICIAL would be sufficient. People with routine access to SECRET information should usually have SC clearance . SECRET data may often be exempt from FOIA disclosure. Data with exceptionally high impact levels; compromise would have very serious impacts – for instance, many deaths. This requires an extremely high level of protection, and controls are expected to be similar to those used on existing "Top Secret" data, including CESG-approved products. Very little risk can be tolerated in TOP SECRET, although no activity

5510-451: The department that the individual has not been a member of, or associated with, any organisation which has advocated such activities or has demonstrated a lack of reliability through dishonesty, lack of integrity or behaviour. Finally, the process assures the department that the individual will not be subject to pressure or improper influence through past behaviour or personal circumstances. Protectively marked material must be accounted for in

5605-472: The early 1940s as part of the Manhattan Project . The first artificial thermonuclear fusion reaction occurred during the 1951 Greenhouse Item test of the first boosted fission weapon , which uses a small amount of deuterium–tritium gas to enhance the fission yield. The first thermonuclear weapon detonation, where the vast majority of the yield comes from fusion, was the 1952 Ivy Mike test of

5700-449: The elements iron and nickel , and then decreases for heavier nuclei. Eventually, the binding energy becomes negative and very heavy nuclei (all with more than 208 nucleons, corresponding to a diameter of about 6 nucleons) are not stable. The four most tightly bound nuclei, in decreasing order of binding energy per nucleon, are Ni , Fe , Fe , and Ni . Even though

5795-687: The energy that holds electrons to a nucleus. For example, the ionization energy gained by adding an electron to a hydrogen nucleus is 13.6  eV —less than one-millionth of the 17.6  MeV released in the deuterium – tritium (D–T) reaction shown in the adjacent diagram. Fusion reactions have an energy density many times greater than nuclear fission ; the reactions produce far greater energy per unit of mass even though individual fission reactions are generally much more energetic than individual fusion ones, which are themselves millions of times more energetic than chemical reactions. Only direct conversion of mass into energy , such as that caused by

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5890-560: The event of unauthorised disclosure. This is one of the characteristics of the GSCP which differs significantly from the Protective Marking Scheme which it replaced. At the OFFICIAL classification there is a general presumption that data may be shared across Government, however where a need to know principle is identified data may be marked as "OFFICIAL-SENSITIVE"; "OFFICIAL-SENSITIVE COMMERCIAL"; "OFFICIAL-SENSITIVE LOCSEN" or "OFFICIAL-SENSITIVE PERSONAL". All OFFICIAL-SENSITIVE data must be marked and contain handling instructions identifying why

5985-573: The existence of a compartment identified by a codeword is itself classified. Examples of codewords include, but are not limited to: Government Security Classifications Policy The Government Security Classifications Policy (GSCP) is a system for classifying sensitive government data in the United Kingdom . Historically, the Government Protective Marking Scheme was used by government bodies in

6080-449: The following decades. The primary source of solar energy, and that of similar size stars, is the fusion of hydrogen to form helium (the proton–proton chain reaction), which occurs at a solar-core temperature of 14 million kelvin. The net result is the fusion of four protons into one alpha particle , with the release of two positrons and two neutrinos (which changes two of the protons into neutrons), and energy. In heavier stars,

6175-434: The fusion of heavier nuclei results in energy retained by the product nucleons, and the resulting reaction is endothermic . The opposite is true for the reverse process, called nuclear fission . Nuclear fusion uses lighter elements, such as hydrogen and helium , which are in general more fusible; while the heavier elements, such as uranium , thorium and plutonium , are more fissionable. The extreme astrophysical event of

6270-516: The fusion reaction may occur before the plasma starts to expand, so the plasma's inertia is keeping the material together. One force capable of confining the fuel well enough to satisfy the Lawson criterion is gravity . The mass needed, however, is so great that gravitational confinement is only found in stars —the least massive stars capable of sustained fusion are red dwarfs , while brown dwarfs are able to fuse deuterium and lithium if they are of sufficient mass. In stars heavy enough , after

6365-400: The ground state. Any additional nucleons would have to go into higher energy states. Indeed, the helium-4 nucleus is so tightly bound that it is commonly treated as a single quantum mechanical particle in nuclear physics, namely, the alpha particle . The situation is similar if two nuclei are brought together. As they approach each other, all the protons in one nucleus repel all the protons in

6460-458: The hydrogen case), the fusion reactants exist in a plasma state. The significance of ⟨ σ v ⟩ {\displaystyle \langle \sigma v\rangle } as a function of temperature in a device with a particular energy confinement time is found by considering the Lawson criterion . This is an extremely challenging barrier to overcome on Earth, which explains why fusion research has taken many years to reach

6555-644: The implementation of the GSCP and still available on Gov.UK sources suggested that UK Government information systems would continue to be accredited much as before, normally using CESG Information Assurance Standard 1 & 2 . This has however been progressively discarded through GDS and NCSC blog statements since May 2014 and the IS1 & 2 standard itself is no longer maintained or mandated. Accreditation has also been largely replaced by alternative models of assurance aligned to various commercial practices. The NAO report "Protecting Information across Government" (Sep 2016)

6650-403: The ionization of atoms of the target. Devices referred to as sealed-tube neutron generators are particularly relevant to this discussion. These small devices are miniature particle accelerators filled with deuterium and tritium gas in an arrangement that allows ions of those nuclei to be accelerated against hydride targets, also containing deuterium and tritium, where fusion takes place, releasing

6745-735: The kinds of data that were previously UNCLASSIFIED, RESTRICTED, or CONFIDENTIAL; but this may vary. The threat model for OFFICIAL data is similar to typical large private-sector organisations; it anticipates that individual hackers, pressure groups, criminals, and investigative journalists might attempt to get information. The threat model does not guarantee protection against very persistent and skilled attacks, for instance by organised crime groups or by foreign governments; these are possible, but normal controls would make them more difficult, and much stronger controls would be disproportionate. People with routine access to OFFICIAL information should be subject to BPSS screening. OFFICIAL may include data which

6840-465: The longevity of stellar heat and light. The fusion of nuclei in a star, starting from its initial hydrogen and helium abundance, provides that energy and synthesizes new nuclei. Different reaction chains are involved, depending on the mass of the star (and therefore the pressure and temperature in its core). Around 1920, Arthur Eddington anticipated the discovery and mechanism of nuclear fusion processes in stars, in his paper The Internal Constitution of

6935-400: The mass is carried away in the form of kinetic energy of an alpha particle or other forms of energy, such as electromagnetic radiation. It takes considerable energy to force nuclei to fuse, even those of the lightest element, hydrogen . When accelerated to high enough speeds, nuclei can overcome this electrostatic repulsion and be brought close enough such that the attractive nuclear force

7030-486: The measured masses of light elements to demonstrate that large amounts of energy could be released by fusing small nuclei. Building on the early experiments in artificial nuclear transmutation by Patrick Blackett , laboratory fusion of hydrogen isotopes was accomplished by Mark Oliphant in 1932. In the remainder of that decade, the theory of the main cycle of nuclear fusion in stars was worked out by Hans Bethe . Research into fusion for military purposes began in

7125-464: The most recent breakthroughs to date in maintaining a sustained fusion reaction occurred in France's WEST fusion reactor. It maintained a 90 million degree plasma for a record time of six minutes. This is a tokamak style reactor which is the same style as the upcoming ITER reactor. The release of energy with the fusion of light elements is due to the interplay of two opposing forces: the nuclear force ,

7220-578: The nature of threat and its acceptability to the business, and thereafter moves up or down accordingly based on consequence of compromise. OFFICIAL data may therefore rise to TOP SECRET, but cannot be SECRET unless the risk previously accepted for a capable attacker is revised. SECRET data may be reduced to OFFICIAL where no serious consequences can be identified from a potential breach, or SECRET can also rise to TOP SECRET if serious consequences could arise. Impact levels also consider integrity and availability, but CESG's system of Business Impact Levels (BIL)

7315-411: The nature or source of its content, limit access to designated groups, and / or to signify the need for enhanced handling measures. In addition to a paragraph near the start of the document special handling instructions include Descriptors, Codewords, Prefixes and national caveats. A DESCRIPTOR is used with the security classification to identify certain categories of sensitive information and indicates

7410-556: The need for common sense precautions to limit access. The normal descriptors are 'COMMERCIAL’, 'LOCSEN’ and 'PERSONAL’. A Codeword is a single word expressed in CAPITAL letters that follows the security classification to providing security cover for a particular asset or event. They are usually only applied to SECRET and TOP SECRET assets. The UK prefix is added to the security classification of all assets sent to foreign governments or international organisations. This prefix designates

7505-417: The negative inner cage, and are heated by the electric field in the process. If they miss the inner cage they can collide and fuse. Ions typically hit the cathode, however, creating prohibitory high conduction losses. Also, fusion rates in fusors are very low due to competing physical effects, such as energy loss in the form of light radiation. Designs have been proposed to avoid the problems associated with

7600-399: The old Government Protective Marking Scheme (GPMS). Classifications must be capitalised and centrally noted at top and bottom of each document page, save at OFFICIAL where the document marking is optional. All material produced by a public body in the UK must be presumed to be OFFICIAL unless it is otherwise marked. Like the GPMS, which it superseded, the GSCP classifications are applied only to

7695-446: The other hand, is an inverse-square force , so a proton added to a nucleus will feel an electrostatic repulsion from all the other protons in the nucleus. The electrostatic energy per nucleon due to the electrostatic force thus increases without limit as nuclei atomic number grows. The net result of the opposing electrostatic and strong nuclear forces is that the binding energy per nucleon generally increases with increasing size, up to

7790-459: The other. Not until the two nuclei actually come close enough for long enough so the strong attractive nuclear force can take over and overcome the repulsive electrostatic force. This can also be described as the nuclei overcoming the so-called Coulomb barrier . The kinetic energy to achieve this can be lower than the barrier itself because of quantum tunneling. The Coulomb barrier is smallest for isotopes of hydrogen, as their nuclei contain only

7885-410: The outer parts of the stars over long periods of time, by absorbing energy from fusion in the inside of the star, by absorbing neutrons that are emitted from the fusion process. All of the elements heavier than iron have some potential energy to release, in theory. At the extremely heavy end of element production, these heavier elements can produce energy in the process of being split again back toward

7980-424: The primary fuel is not constrained to be protons and higher temperatures can be used, so reactions with larger cross-sections are chosen. Another concern is the production of neutrons, which activate the reactor structure radiologically, but also have the advantages of allowing volumetric extraction of the fusion energy and tritium breeding. Reactions that release no neutrons are referred to as aneutronic . To be

8075-431: The reaction area. Theoretical calculations made during funding reviews pointed out that the system would have significant difficulty scaling up to contain enough fusion fuel to be relevant as a power source. In the 1990s, a new arrangement using a field-reversed configuration (FRC) as the storage system was proposed by Norman Rostoker and continues to be studied by TAE Technologies as of 2021 . A closely related approach

8170-408: The repulsive electrostatic force between their positively charged protons. If two nuclei can be brought close enough together, however, the electrostatic repulsion can be overcome by the quantum effect in which nuclei can tunnel through coulomb forces. When a nucleon such as a proton or neutron is added to a nucleus, the nuclear force attracts it to all the other nucleons of the nucleus (if

8265-465: The resulting energy is released in an uncontrolled manner, as it is in thermonuclear weapons ("hydrogen bombs") and in most stars ; and controlled , where the fusion reactions take place in an environment allowing some or all of the energy released to be harnessed for constructive purposes. Temperature is a measure of the average kinetic energy of particles, so by heating the material it will gain energy. After reaching sufficient temperature, given by

8360-421: The size of iron, in the process of nuclear fission . Nuclear fission thus releases energy that has been stored, sometimes billions of years before, during stellar nucleosynthesis . Electrically charged particles (such as fuel ions) will follow magnetic field lines (see Guiding centre ). The fusion fuel can therefore be trapped using a strong magnetic field. A variety of magnetic configurations exist, including

8455-608: The supply of hydrogen is exhausted in their cores, their cores (or a shell around the core) start fusing helium to carbon . In the most massive stars (at least 8–11 solar masses ), the process is continued until some of their energy is produced by fusing lighter elements to iron . As iron has one of the highest binding energies , reactions producing heavier elements are generally endothermic . Therefore, significant amounts of heavier elements are not formed during stable periods of massive star evolution, but are formed in supernova explosions . Some lighter stars also form these elements in

8550-430: The target, resulting in 3.15 MJ of fusion energy output." Prior to this breakthrough, controlled fusion reactions had been unable to produce break-even (self-sustaining) controlled fusion. The two most advanced approaches for it are magnetic confinement (toroid designs) and inertial confinement (laser designs). Workable designs for a toroidal reactor that theoretically will deliver ten times more fusion energy than

8645-653: The technology is still in its developmental phase. The US National Ignition Facility , which uses laser-driven inertial confinement fusion , was designed with a goal of break-even fusion; the first large-scale laser target experiments were performed in June 2009 and ignition experiments began in early 2011. On 13 December 2022, the United States Department of Energy announced that on 5 December 2022, they had successfully accomplished break-even fusion, "delivering 2.05 megajoules (MJ) of energy to

8740-410: The toroidal geometries of tokamaks and stellarators and open-ended mirror confinement systems. A third confinement principle is to apply a rapid pulse of energy to a large part of the surface of a pellet of fusion fuel, causing it to simultaneously "implode" and heat to very high pressure and temperature. If the fuel is dense enough and hot enough, the fusion reaction rate will be high enough to burn

8835-420: The two reactant nuclei. If the reactants have a distribution of velocities, e.g. a thermal distribution, then it is useful to perform an average over the distributions of the product of cross-section and velocity. This average is called the 'reactivity', denoted ⟨ σv ⟩ . The reaction rate (fusions per volume per time) is ⟨ σv ⟩ times the product of the reactant number densities: If

8930-436: Was somewhat critical of the move to this model and the adoption of GSCP overall Existing published guidance continues to suggest that storage media which hold UK government data should still be destroyed or purged according to HMG IA Policy No. 5 , however terminology in this guidance and other material has not been updated fully to reflect the changes from GPMS protective markings to GSCP classifications and as such its value

9025-430: Was studied in detail by Steven Jones in the early 1980s. Net energy production from this reaction has been unsuccessful because of the high energy required to create muons , their short 2.2 μs half-life , and the high chance that a muon will bind to the new alpha particle and thus stop catalyzing fusion. Some other confinement principles have been investigated. The key problem in achieving thermonuclear fusion

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