Z machine
Encyclopedia
Sandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....
, it gathers data to aid in computer modeling of nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
s. The Z machine is located at Sandia's main site in Albuquerque
Albuquerque, New Mexico
Albuquerque is the largest city in the state of New Mexico, United States. It is the county seat of Bernalillo County and is situated in the central part of the state, straddling the Rio Grande. The city population was 545,852 as of the 2010 Census and ranks as the 32nd-largest city in the U.S. As...
, New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...
.
Operation overview
The Z machine fires a very powerful electrical discharge (several tens of millions of ampereAmpere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
s for less than 100 nanoseconds
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
) into an array of thin, parallel tungsten
Tungsten
Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...
wires called a liner (pictured here). The high electrical current vaporizes the wires, which are transformed into a cylindrical plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
curtain. Simultaneously, the current density
Current density
Current density is a measure of the density of flow of a conserved charge. Usually the charge is the electric charge, in which case the associated current density is the electric current per unit area of cross section, but the term current density can also be applied to other conserved...
induces a powerful magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
, and their combination creates Lorentz force
Lorentz force
In physics, the Lorentz force is the force on a point charge due to electromagnetic fields. It is given by the following equation in terms of the electric and magnetic fields:...
s that radially compress the plasma into a z-pinch
Z-pinch
In fusion power research, the Z-pinch, also known as zeta pinch or Bennett pinch , is a type of plasma confinement system that uses an electrical current in the plasma to generate a magnetic field that compresses it...
process. The imploding plasma produces a high temperature and an X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
pulse that can create a shock wave
Shock wave
A shock wave is a type of propagating disturbance. Like an ordinary wave, it carries energy and can propagate through a medium or in some cases in the absence of a material medium, through a field such as the electromagnetic field...
in a target structure. The target structure is placed in a cavity inside the wires called a hohlraum
Hohlraum
In radiation thermodynamics, a hohlraum is a cavity whose walls are in radiative equilibrium with the radiant energy within the cavity. This idealized cavity can be approximated in practice by making a small perforation in the wall of a hollow container of any opaque material...
. The powerful fluctuation in the magnetic field (an "electromagnetic pulse
Electromagnetic pulse
An electromagnetic pulse is a burst of electromagnetic radiation. The abrupt pulse of electromagnetic radiation usually results from certain types of high energy explosions, especially a nuclear explosion, or from a suddenly fluctuating magnetic field...
") also generates electric current in all of the metallic objects in the room (see picture at upper right). The vertical cylinder's axis is conventionally termed the z-axis, hence the name "Z machine".
Originally designed to supply 50 terawatts of power in one fast pulse, technological advances resulted in an increased output of 290 terawatts, enough to study nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
. Z releases 80 times the world's electrical power output for about seventy nanoseconds; however, only a moderate amount of energy is consumed in each test (roughly twelve megajoules)—the efficiency from wall current to X-ray output is about 15%. Marx generator
Marx generator
A Marx generator is an electrical circuit first described by Erwin Otto Marx in 1924. Its purpose is to generate a high-voltage pulse. Marx generators are often used to simulate the effects of lightning on power line gear and aviation equipment....
s are slowly charged with energy prior to firing.
Sandia announced the fusing of deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
in the Z machine on April 7, 2003. This application could result in an efficient method to ignite a nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
reaction starting from a small capsule of deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
. Unfortunately many technical difficulties—for instance the small quantity of deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
that can be contained in the hohlraum and the practical impossibility of transferring the compressed capsule to a larger nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...
reservoir—prevent the machine from being used this way.
Besides being used as an X-ray generator, the Z machine propelled small plates at 34 kilometres a second, faster than the 30 kilometres per second that Earth travels in its orbit around the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, and three times Earth's escape velocity
Escape velocity
In physics, escape velocity is the speed at which the kinetic energy plus the gravitational potential energy of an object is zero gravitational potential energy is negative since gravity is an attractive force and the potential is defined to be zero at infinity...
. It also successfully created a special, hyperdense "hot ice" known as ice VII
Ice VII
Ice VII is a cubic crystalline form of ice. It has a triple point with liquid water and Ice VI at 355 K and 2.216 GPa, with the melt line extending to at least 715 K and 10 GPa. It can also be reached in the solid state by increasing the pressure on ice VI at ambient temperature. Like the majority...
, by quickly compressing water to pressures of 70,000 to 120,000 atmospheres
Atmosphere (unit)
The standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of pressure. For practical purposes it has been replaced by the bar which is 105 Pa...
(7 to 12 GPa).
At the beginning of 2006, the Z machine produced plasmas with announced temperatures in excess of 2 billion kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
s (2 GK, 2×109 K) or 3.6 billion °F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
, even reaching a peak at 3.7 GK or 6.6 billion °F.
It was achieved in part by replacing the tungsten wires with thicker steel wires. This temperature, which enables a 10% to 15% efficiency in converting electrical energy to soft x-rays, was much higher than anticipated (3 to 4 times the kinetic energy
Kinetic energy
The kinetic energy of an object is the energy which it possesses due to its motion.It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes...
of the incoming wires on axis). The Guinness Book Of Records
Guinness World Records
Guinness World Records, known until 2000 as The Guinness Book of Records , is a reference book published annually, containing a collection of world records, both human achievements and the extremes of the natural world...
listed it as the highest human-achieved temperature,, which has, however, been exceeded by the Relativistic Heavy Ion Collider
Relativistic Heavy Ion Collider
The Relativistic Heavy Ion Collider is one of two existing heavy-ion colliders, and the only spin-polarized proton collider in the world. It is located at Brookhaven National Laboratory in Upton, New York and operated by an international team of researchers...
at Brookhaven National Laboratory
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...
. The origin of this extra energy still remains unexplained, but it has been theorized that small-scale MHD
Magnetohydrodynamics
Magnetohydrodynamics is an academic discipline which studies the dynamics of electrically conducting fluids. Examples of such fluids include plasmas, liquid metals, and salt water or electrolytes...
turbulence and viscous damping would convert magnetic energy into thermal energy of the ions, which then would transfer their energy to the electrons through collisions.
Prospects
Marx generator
A Marx generator is an electrical circuit first described by Erwin Otto Marx in 1924. Its purpose is to generate a high-voltage pulse. Marx generators are often used to simulate the effects of lightning on power line gear and aviation equipment....
s. The de-ionized water section of the machine has been reduced to about half the previous size while the oil section has been expanded significantly in order to house larger intermediate storage lines (i-stores) and new laser towers, which used to sit in the water section. The refurbishment was completed in October 2007.
The newer Z machine can now shoot 27 million amperes (instead of 18 million amperes previously) in 95 nanoseconds.
The radiated power has been raised to 350 terawatts and the X-ray energy output to 2.7 megajoules. However the maximum temperature the new version may reach with the same record holder stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
wire-array liner used in 2005 is not yet known.
Sandia's roadmap includes another Z machine version called ZN (Z Neutron) to test higher yields in fusion power and automation systems. ZN is planned to give between 20 and 30 MJ of hydrogen fusion power with a shot per hour using a Russian Linear Transformer Driver
Linear Transformer Driver
The linear transformer driver is a low-voltage variant of the inductive-voltage-adder technology first applied at Arzamas-16 , Russia and later at the Institute for high-current electronics in Tomsk, Russia. The Hermes III gamma-ray simulator at Sandia National Laboratories is another example of...
(LTD) replacing the current Marx generators. After 8 to 10 years of operation, ZN would become a transmutation pilot plant capable of a fusion shot every 100 seconds.
The next step planned would be the Z-IFE (Z-inertial fusion energy) test facility, the first true z-pinch driven prototype fusion power plant. It is suggested it would integrate Sandia's latest designs using LTDs. Sandia labs recently proposed a conceptual 1 petawatt (1015 watts) LTD Z-pinch power plant, where the electric discharge would reach 70 million amperes.
One should however note all these announced fusion systems make use of the X-ray radiation to heat a hohlraum in order to indirectly ignite fusion reaction of isotopes of hydrogen
Isotopes of hydrogen
Hydrogen has three naturally occurring isotopes, sometimes denoted 1H, 2H, and 3H. Other, highly unstable nuclei have been synthesized in the laboratory but not observed in nature. The most stable radioisotope is tritium, with a half-life of 12.32 years...
. The unexpected ultra high temperature achieved recently is not taken into account yet for any possible use of direct aneutronic fusion reactions (p
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
–7Li
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
or p–11B
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
) which, if proven practicable, would imply reconsidering some proposed designs.
The ultra-high temperatures reached in 2006 (2.66 to 3.7 billion kelvins) are much higher than those required for the classical hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
, deuterium and tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
fusion previously considered. They could allow, in theory if not in practice, the fusion of light hydrogen atoms with heavier atoms such as lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
or boron
Boron
Boron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
. These two possible fusion reactions do not produce neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s, and thus no radioactivity
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
or nuclear waste
Radioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
, so they open for the first time the possibility of human-made clean aneutronic fusion
Aneutronic fusion
Aneutronic fusion is any form of fusion power where neutrons carry no more than 1% of the total released energy. The most-studied fusion reactions release up to 80% of their energy in neutrons...
.
Z-Pinch Inertial Fusion Energy program
The Sandia LaboratoriesSandia National Laboratories
The Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....
Z-IFE project aims to solve the practical difficulties in harnessing fusion power. Major problems include producing energy in a single Z-pinch shot, and quickly reloading the reactor after each shot. By their early estimates, an implosion of a fuel capsule every 10 seconds could economically produce 300 MW of fusion energy.
See also
- Sandia National LaboratoriesSandia National LaboratoriesThe Sandia National Laboratories, managed and operated by the Sandia Corporation , are two major United States Department of Energy research and development national laboratories....
- Fusion powerFusion powerFusion power is the power generated by nuclear fusion processes. In fusion reactions two light atomic nuclei fuse together to form a heavier nucleus . In doing so they release a comparatively large amount of energy arising from the binding energy due to the strong nuclear force which is manifested...
- Stockpile stewardshipStockpile stewardshipStockpile stewardship refers to the United States program of reliability testing and maintenance of its nuclear weapons without the use of nuclear testing....
- Pulsed powerPulsed powerPulsed power is the term used to describe the science and technology of accumulating energy over a relatively long period of time and releasing it very quickly thus increasing the instantaneous power.-Overview:...
- Inertial fusion power plantInertial fusion power plantAn inertial fusion power plant is intended to produce electric power by use of inertial confinement fusion techniques on an industrial scale. This type of power plant is still in a research phase....
External links
- Z Machine Home Page
- "A machine called Z", an article from The Observer
- Physics News Update, February 28, 2006