In quantum computing, a qubit or quantum bit (sometimes qbit) is the basic unit of quantum information: K

K – Potassium

Potassium is a chemical element with the symbol K (from Neo-Latin kalium) and atomic number 19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmospheric oxygen to form flaky white potassium peroxide in only seconds of exposure. It was first isolated from potash, the ashes of plants, from which its name derives. In the periodic table, potassium is one of the alkali metals, all of which have a single valence electron in the outer electron shell, that is easily removed to create an ion with a positive charge – a cation, that combines with anions to form salts. Potassium in nature occurs only in ionic salts. Elemental potassium reacts vigorously with water, generating sufficient heat to ignite hydrogen emitted in the reaction, and burning with a lilac-colored flame. It is found dissolved in sea water (which is 0.04% potassium by weight), and occurs in many minerals such as orthoclase, a common constituent of granites and other igneous rocks.

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  • 2019 – Maintained high-temperature plasma for 1.5 seconds, Temperature: >100×106 K.
  • 2020, March – Maintained high-temperature plasma for 8 seconds, Temperature: >100×106 K (Mean temperature: >97×106 K)
  • 2020, Nov – Maintained high-temperature plasma for 20 seconds, Temperature: >100×106 K

The KSTAR (or Korea Superconducting Tokamak Advanced Research; Korean: 초전도 핵융합연구장치, literally “superconducting nuclear fusion research device”) is a magnetic fusion device at the National Fusion Research Institute in Daejeon, South Korea. It is intended to study aspects of magnetic fusion energy which will be pertinent to the ITER fusion project as part of that country’s contribution to the ITER effort. The project was approved in 1995 but construction was delayed by the East Asian financial crisis which weakened the South Korean economy considerably; however the construction phase of the project was completed on September 14, 2007. The first plasma was achieved in June 2008.

KSTAR is one of the first research tokamaks in the world to feature fully superconducting magnets, which again will be of great relevance to ITER as this will also use superconducting magnets. The KSTAR magnet system consists of 16 niobium-tin direct current toroidal field magnets, 10 niobium-tin alternating current poloidal field magnets and 4 niobium-titanium alternating current poloidal field magnets. It is planned that the reactor will study plasma pulses of up to 20 seconds duration until 2011, when it will be upgraded to study pulses of up to 300 seconds duration. The reactor vessel will have a major radius of 1.8 m, a minor radius of 0.5 m, a maximum toroidal field of 3.5 Tesla, and a maximum plasma current of 2 megaampere. As with other tokamaks, heating and current drive will be initiated using neutral beam injection, ion cyclotron resonance heating (ICRH), radio frequency heating and electron cyclotron resonance heating (ECRH). Initial heating power will be 8 megawatt from neutral beam injection upgradeable to 24 MW, 6 MW from ICRH upgradeable to 12 MW, and at present undetermined heating power from ECRH and RF heating. The experiment will use both hydrogen and deuterium fuels but not the deuterium-tritium mix which will be studied in ITER.

In December 2016, KSTAR set a world record (longest high-confinement mode) by confining and maintaining a high-temperature hydrogen plasma (about 50 million degrees Celsius) for 70 seconds. The record was broken by China’s Experimental Advanced Superconducting Tokamak (EAST) (101.2 seconds) in July 2017.

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