The Tokamak Physics Experiment (TPX) was a

plasma physics Plasma ()πλάσμα
, Henry George Liddell, R ...

experiment that was designed but not built. It was designed by an inter-organizational team in the USA led by

Princeton Plasma Physics Laboratory Princeton Plasma Physics Laboratory (PPPL) is a United States Department of Energy national laboratory for plasma physics and nuclear fusion science. Its primary mission is research into and development of fusion as an energy source. It is known ...

. The experiment was designed to test theories about how

Tokamaks A tokamak (; russian: токамáк; otk, 𐱃𐰸𐰢𐰴, Toḳamaḳ) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being ...

would behave in a high-performance, steady-state regime.

Goals

TPX was to be the successor to the

Tokamak Fusion Test Reactor The Tokamak Fusion Test Reactor (TFTR) was an experimental tokamak built at Princeton Plasma Physics Laboratory (PPPL) circa 1980 and entering service in 1982. TFTR was designed with the explicit goal of reaching scientific breakeven, the point wh ...

(TFTR). While TFTR was designed to achieve Q>1 (more fusion power produced by the plasma than injected into the plasma), TFTR only operated for short pulses, and did not provide data from and experience with plasmas behave like those of an economic

Fusion power Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion, nuclear fusion reactions. In a fusion process, two lighter atomic nucleus, atomic nuclei combine to form a heavier nucleus, whi ...

reactor. Specifically, TPX was designed to fill this need. TPX was designed to test theories which suggested ways of making a future

fusion power Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion, nuclear fusion reactions. In a fusion process, two lighter atomic nucleus, atomic nuclei combine to form a heavier nucleus, whi ...

reactor compact, economic, and reliable. Specifically, TPX was designed to be near steady state, with pulse lengths of 1,000 seconds (more than 15 minutes). It was designed to operate at high

Bootstrap current In a toroidal fusion power device, a plasma is confined within a donut-shaped cylinder. If the gas pressure of the plasma varies across the radius of the cylinder, a self-generated current will spontaneously arise within the plasma, due to collisi ...

, meaning that less power would have to be expended driving toroidal current. It was designed to operate at high values of

Beta Beta (, ; uppercase , lowercase , or cursive ; grc, βῆτα, bē̂ta or ell, βήτα, víta) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Modern Greek, it represents the voiced labiod ...

, meaning that it would be able to store more plasma pressure for a given magnetic field. It was designed to operate with a high level of confinement, meaning that less auxiliary heating would be required.

History

After the cancellation of the

Compact Ignition Tokamak The Compact Ignition Tokamak (CIT) was a plasma physics experiment that was designed but not built. It was designed by an inter-organizational team in the USA led by Princeton Plasma Physics Laboratory. The experiment was designed to achieve a self- ...

in 1991, the

United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...

directed the US fusion program to find ways to improve the

tokamak A tokamak (; russian: токамáк; otk, 𐱃𐰸𐰢𐰴, Toḳamaḳ) is a device which uses a powerful magnetic field to confine plasma in the shape of a torus. The tokamak is one of several types of magnetic confinement devices being d ...

. In 1993, a conceptual design review was held for TPX in 1993, finalizing the conceptual design. The design team was managed by

and included members from other US institutions. The program was canceled in 1995, as the proposed cost was too high. The proposed cost was $539 Million in 1993 dollars.

Legacy

The

KSTAR The KSTAR (or Korea Superconducting Tokamak Advanced Research; ko, 초전도 핵융합연구장치, literally "superconducting nuclear fusion research device") is a magnetic fusion device at the Korea Institute of Fusion Energy in Daejeon, So ...

tokamak built

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

is based on the TPX design. KSTAR uses Hydrogen, not

Deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two Stable isotope ratio, stable isotopes of hydrogen (the other being Hydrogen atom, protium, or hydrogen-1). The atomic nucleus, nucleus of a deuterium ato ...

as TPX was designed to, so neutron activation of components is not as large a problem. Because of this, the titanium vacuum vessel of the TPX design was replaced with a stainless steel vessel in KSTAR, and the remote maintenance system was removed from the design.

Description

Because TPX was designed to be steady-state (or at least long-pulse, with 1,000 seconds duration), the electromagnetic coils which provide the magnetic field were to be

superconducting Superconductivity is a set of physical properties observed in certain materials where Electrical resistance and conductance, electrical resistance vanishes and magnetic field, magnetic flux fields are expelled from the material. Any material e ...

. They were to be made of

Niobium–tin Niobium–tin is an intermetallic compound of niobium (Nb) and tin (Sn), used industrially as a type II superconductor. This intermetallic compound has a simple structure: A3B. It is more expensive than niobium–titanium (NbTi), but remains su ...

superconducting cables. The toroidal magnetic field strength at the center of the plasma was to be 4.0 Tesla. TPX was designed to have its toroidal electric current be 100% non-inductively driven. Because of this, it was to have three current drive systems: An 8 MW neutral beam injector system, an 8 MW ion cyclotron resonance system, and a 1.5 MW lower hybrid wave system. The toroidal current carried by the plasma was to be up to 2.0 MA. Because TPX was designed to test at least six different high-performance scenarios, its poloidal field coils and current drive systems were designed for flexibility. Some examples of possible scenarios are: one inspired by the ARIES-I reactor design which had an aggressive

, one inspired by the

Supershot regime, and one with a profile which produced an internal transport barrier for enhanced confinement.

References

{{fusion experiments Tokamaks