The Z Pulsed Power Facility, informally known as the Z machine or simply Z, is the largest high frequency
electromagnetic wave
In physics, electromagnetic radiation (EMR) is a self-propagating wave of the electromagnetic field that carries momentum and radiant energy through space. It encompasses a broad spectrum, classified by frequency or its inverse, wavelength, ...
generator in the world, operated by
Sandia National Laboratories
Sandia National Laboratories (SNL), also known as Sandia, is one of three research and development laboratories of the United States Department of Energy's National Nuclear Security Administration (NNSA). Headquartered in Kirtland Air Force B ...
in
Albuquerque, New Mexico
Albuquerque ( ; ), also known as ABQ, Burque, the Duke City, and in the past 'the Q', is the List of municipalities in New Mexico, most populous city in the U.S. state of New Mexico, and the county seat of Bernalillo County, New Mexico, Bernal ...
.
It has primarily been used as an
inertial confinement fusion
Inertial confinement fusion (ICF) is a fusion energy process that initiates nuclear fusion reactions by compressing and heating targets filled with fuel. The targets are small pellets, typically containing deuterium (2H) and tritium (3H).
Typical ...
(ICF) research facility, including the
magnetized liner inertial fusion (MagLIF) approach, and for testing materials in conditions of extreme temperature and pressure.
In particular, it gathers data to aid in
computer modeling
Computer simulation is the running of a mathematical model on a computer, the model being designed to represent the behaviour of, or the outcome of, a real-world or physical system. The reliability of some mathematical models can be determin ...
of
nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission or atomic bomb) or a combination of fission and fusion reactions (thermonuclear weapon), producing a nuclear exp ...
s and eventual
fusion pulsed power plants.
History
The Z machine's origins can be traced to the
Department of Energy
A ministry of energy or department of energy is a government department in some countries that typically oversees the production of fuel and electricity; in the United States, however, it manages nuclear weapons development and conducts energy-rela ...
(DoE) needing to replicate the
fusion reactions of a
thermonuclear bomb
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
in a lab environment to better understand the physics involved.
Since the 1970s, the DoE has also been looking into ways to
generate electricity from fusion reactions.
The first research at Sandia, headed by Gerold Yonas – the particle-beam fusion program – dates back to 1971. This program tried to generate fusion by compressing fuel with beams of charged particles. Electrons were the first particles to be thought of, because the pulsed power accelerators at the time had already concentrated them at high power in small areas. However, shortly thereafter it was realized that electrons can not possibly heat the fusion fuel rapidly enough for the purpose. The program then moved away from electrons in favor of protons. These turned out to be too light to control well enough to concentrate onto a target, and the program moved on to light ions, lithium. The accelerators names reflect the change in emphasis: first
the accelerator's name was EBFA-I (electron beam fusion accelerator), shortly thereafter PBFA-I, which became Saturn. Protons demanded another accelerator, PBFA-II, which became Z.
The November 1978 issue of ''
Scientific American
''Scientific American'', informally abbreviated ''SciAm'' or sometimes ''SA'', is an American popular science magazine. Many scientists, including Albert Einstein and Nikola Tesla, have contributed articles to it, with more than 150 Nobel Pri ...
'' carried Yonas' first general-public article, "Fusion power with particle beams".
In 1985, the PBFA-II was created. Sandia continued to target heavy ion fusion at a slow pace despite the National Academies report.
Meanwhile, defense-related research was also ongoing at Sandia with the Hermes III machine and Saturn (1987), upgraded from PBFA-I, which operated at lower total power than PBFA-II but advanced Sandia's knowledge in high voltage and high current and was therefore a useful predecessor to the Z machine.
Also in 1996, the PBFA-II machine was once again upgraded into PBFA-Z
or simply "Z machine", described for the first time to the general public in August 1998 in ''Scientific American''.
Physics of the Z machine

The Z machine uses the well known principle of
Z-pinch
In fusion power research, the Z-pinch (zeta pinch) is a type of plasma confinement system that uses an electric current in the plasma to generate a magnetic field that compresses it (see pinch). These systems were originally referred to simpl ...
to produce hot short-lived plasmas. The plasma can be used as a source of x-rays, as a surrogate for the inside of a thermonuclear weapon, or as a surrogate for the core of a fusion power plant.
In a Z-pinch, the fast discharge of current through a column of plasma causes it to be compressed towards its axis by the resulting
Lorentz force
In electromagnetism, the Lorentz force is the force exerted on a charged particle by electric and magnetic fields. It determines how charged particles move in electromagnetic environments and underlies many physical phenomena, from the operation ...
s, thus heating it.
Willard Harrison Bennett
Willard Harrison Bennett (June 13, 1903 – September 28, 1987) was an American scientist and inventor, born in Findlay, Ohio. Bennett conducted research into plasma physics, astrophysics, geophysics, surface physics, and physical chemistry. T ...
successfully researched the application of Z-pinches to plasma compression. The Z machine layout is cylindrical. On the outside it houses huge
capacitor
In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...
s discharging through
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 from a low-voltage DC supply. Marx generators are used in high-energy physics experiments, as well as to simul ...
s which generate a one microsecond high-voltage pulse. This pulse is then compressed by a factor of 10 to enable the creation of 100 ns discharges.
Most experiments on the Z machine run the current discharge through a conductive tube (called a ''liner'') filled with gas. This approach is known as
magnetized liner inertial fusion, or MagLIF. The compression of a MagLIF Z-pinch is limited because the current flow is highly unstable and rotates along the cylinder which causes twisting of the imploding tube therefore decreasing the quality of the compression.
The Z machine has also conducted experiments with arrays of tungsten wires rather than liners. The space inside the wire array was filled with polystyrene, which helps homogenize the X-ray flux. By removing the polystyrene core, Sandia was able to obtain a thin 1.5 mm plasma cord in which 10 million amperes flowed with 90 megabars of pressure.
Early operation 1996–2006
The key attributes of Sandia's Z machine are its 18 million amperes of current and a discharge time of less than 100
nanoseconds
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, of a second, or seconds.
The term combines the SI prefix ''nano-'' indicating a 1 billionth submultiple of an SI unit (e ...
. This current discharge was initially run through an array of
tungsten
Tungsten (also called wolfram) is a chemical element; it has symbol W and atomic number 74. It is a metal found naturally on Earth almost exclusively in compounds with other elements. It was identified as a distinct element in 1781 and first ...
wires. In 1999, Sandia tested the idea of nested wire arrays; the second array, out of phase with the first, compensates for
Rayleigh-Taylor instabilities. In 2001, Sandia introduced the Z-Beamlet laser (from surplus equipment of the
National Ignition Facility
The National Ignition Facility (NIF) is a laser-based inertial confinement fusion (ICF) research device, located at Lawrence Livermore National Laboratory in Livermore, California, United States. NIF's mission is to achieve fusion ignition wit ...
) as a tool to better image the compressing pellet. This confirmed the shaping uniformity of pellets compressed by the Z machine.
In 1999, Sandia started the Z-inertial fusion energy (Z-IFE) project, which aimed to solve the practical difficulties in harnessing fusion power. Major problems included 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.
Sandia announced the fusing of small amounts of
deuterium
Deuterium (hydrogen-2, symbol H or D, also known as heavy hydrogen) is one of two stable isotopes of hydrogen; the other is protium, or hydrogen-1, H. The deuterium nucleus (deuteron) contains one proton and one neutron, whereas the far more c ...
in the Z machine on April 7, 2003.
Besides being used as an X-ray generator, the Z machine propelled small plates at 34 kilometers a second, faster than the 30 kilometers per second that Earth travels in its orbit around the
Sun
The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, and four times
Earth's escape velocity (3 times it at sea level). It also successfully created a special, hyperdense "hot ice" known as
ice VII
Variations in pressure and temperature give rise to different phases of ice, which have varying properties and molecular geometries. Currently, twenty-one phases, including both crystalline and amorphous ices have been observed. In modern histor ...
, by quickly compressing water to pressures of 70,000 to 120,000
atmospheres (7 to 12
GPa
Grading in education is the application of standardized measurements to evaluate different levels of student achievement in a course. Grades can be expressed as letters (usually A to F), as a range (for example, 1 to 6), percentages, or as num ...
). Mechanical shock from impacting Z-machine accelerated projectiles is able to melt diamonds.
During this period the power of X-ray produced jumped from 10 to 300 TW. In order to target the next milestone of fusion breakeven, another upgrade was then necessary
After refurbishment (2007–)
A $60 million (raised to $90 million) retrofit program called ZR (Z Refurbished) was announced in 2004 to increase its power by 50%. The Z machine was dismantled in July 2006 for this upgrade, including the installation of newly designed hardware and components and more powerful
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 from a low-voltage DC supply. Marx generators are used in high-energy physics experiments, as well as to simul ...
s. The deionized 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 around 26 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
megajoule
The joule ( , or ; symbol: J) is the unit of energy in the International System of Units (SI). In terms of SI base units, one joule corresponds to one kilogram- metre squared per second squared One joule is equal to the amount of work don ...
s. In 2006 wire array experiments reached ultra-high temperatures of 2.66 to 3.7 billion kelvins.
Sandia's roadmap for the future 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 A linear transformer driver (LTD) within physics and energy, is an annular Series and parallel circuits#Parallel circuits, parallel connection of switches and capacitors. The driver is designed to deliver rapid high Power (physics), power pulses. Th ...
(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-inertial fusion energy (Z-IFE) 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 (10
15 W) LTD Z-pinch power plant, where the electric discharge would reach 70 million amperes. As of 2012, fusion shot simulations at 60 to 70 million amperes are showing a 100- to 1000-fold return on input energy. Tests at the Z machine's current design maximum of 26-27 million amperes were set to begin in 2013.
In 2023, the Z machine was used to study the effects of X-rays on simulated asteroid material as part of a planetary defense effort. The experiment was done to assess the feasibility of using a nuclear weapon's X-rays for diverting asteroids found to be on a collision course with Earth.
See also
*
Stockpile stewardship
Stockpile stewardship refers to the United States program of reliability testing, viability, and the maintenance of its nuclear weapons without the use of nuclear testing.
Because no new nuclear weapons have been developed by the United States si ...
*
Pulsed power Pulsed power is the science and technology of accumulating energy over a relatively long period of time and releasing it instantly, thus increasing the instantaneous power. They can be used in some applications such as food processing, water treatme ...
*
Inertial fusion power plant
References
External links
Home Page Z Pulsed Power Facility an article from ''The Observer''
February 28, 2006
{{authority control
Inertial confinement fusion
Nuclear research institutes
Nuclear stockpile stewardship
Military research of the United States
Plasma physics facilities
Sandia National Laboratories