Z machine

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This article is about the X-ray generator. For the Infocom virtual machine, see Z-machine.
The Z machine at Sandia National Laboratory. Due to the extremely high voltage, the power feeding equipment is submerged in concentric chambers of 2 megalitres (2,000 m³) of transformer oil and 2.3 megalitres (2,300 m³) of deionized water, which act as insulators. Nevertheless, the electromagnetic pulse when the machine is discharged causes impressive lightning, referred to as "arcs and sparks" or "flashover", which can be seen around many of the metallic objects in the room. Courtesy, Sandia National Laboratories
The Z machine at Sandia National Laboratory. Due to the extremely high voltage, the power feeding equipment is submerged in concentric chambers of 2 megalitres (2,000 m³) of transformer oil and 2.3 megalitres (2,300 m³) of deionized water, which act as insulators. Nevertheless, the electromagnetic pulse when the machine is discharged causes impressive lightning, referred to as "arcs and sparks" or "flashover", which can be seen around many of the metallic objects in the room. Courtesy, Sandia National Laboratories

The Z machine is the largest X-ray generator in the world and is designed to test materials in conditions of extreme temperature and pressure. It is operated by Sandia National Laboratories to gather data to aid in computer modeling of nuclear weapons. The Z machine is located at Sandia's main site in Albuquerque, New Mexico.

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[edit] Operation overview

When the Z machine fires, the energy from a 20-million-ampere electrical discharge vaporizes an array of thin, parallel tungsten wires, creating plasma. Simultaneously, the electrical current creates a powerful magnetic field that compresses and implodes the plasma by means of a z-pinch process. The imploding cylindrical plasma produces an X-ray pulse which can create a shock wave in a target structure. The powerful fluctuation in the magnetic field (an "electromagnetic pulse") also generates electric current in all of the metallic objects in the room (see picture at right). The cylinder's axis is conventionally termed the z-axis.

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. Z releases 80 times the world's electrical power output for a few billionths of a second; however, only a moderate amount of energy is consumed in each test (roughly equal to the electrical energy consumed by 100 U.S households in two minutes). Marx generators are slowly charged with energy prior to firing.

Sandia announced the fusing of deuterium in the Z machine on April 7, 2003. A 60 million dollar refurbishment program was announced in 2004 that will raise the power output to 350 terawatts. The refurbishment, which started in July of 2006, includes the installation of newly designed hardware and components and more powerful marx generators. The de-ionized water section of the machine has been reduced to about half its old size while the oil section has been expanded signifigantly in order to house larger intermediate storage lines (i-stores) and brand new laser towers, which used to sit in the water section. The refurbishment is estimated to be finished in May of 2007. The X-ray output will be 2.7 megajoules.

The Z machine is now able to propel small plates at 34 kilometers a second, faster than the 30 kilometers per second that Earth travels in its orbit around the Sun, and three times Earth's escape velocity.

In 2006, Z produced plasmas with temperatures in excess of 2 billion kelvins (GK, 109 K) or 3.6 billion °F. It was achieved in part by replacing the tungsten wires by 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. Thus far, it is currently the highest man-made temperature ever achieved. It is theorized that small-scale turbulence and viscous damping are converting magnetic energy into thermal energy of the ions, which then transfer their energy to the electrons through collisions.

[edit] The Sandia Z-IFE project

Further information: Inertial fusion power plant

The Sandia Laboratories Z-IFE project[1] is based upon a repetitive process ensuring the implosion of a fuel capsule every 10 seconds, planned to produce around 3 GJ (3×109 joules) of fusion energy; the technique used is a z-pinch inertial confinement.

Cutaway of a planned Z-IFE reactor, with a human being (on the left) for scale.
Cutaway of a planned Z-IFE reactor, with a human being (on the left) for scale.

The figure represents a cutaway of a reactor as proposed by Sandia; a production plant would be made up of several such reactors (12 in the ZP-3 demonstration plant, of which 10 would operate simultaneously). Using the analogy previously introduced, such a design is equivalent to the multiple cylinders of a gasoline engine.

Without going into technical details (further information is available in the links at the bottom of the article), it is possible to distinguish the following elements:

  • The red triangular device ("cartridge") corresponds to a cartridge formed by the fuel microcapsule, the "wires array" and the power transmission device; cartridges are transported to the top of the reactor chamber by an automatic loading mechanism, the rail which can be seen in the upper part of the image being a part of it.
  • The thick horizontal blue line, tangent to the reaction chamber, is the power transmission line which carries an extremely short and powerful electrical pulse to the "wires array" device[2] necessary to the z-pinch process;
  • The reactor chamber is filled by an inert gas under low pressure (20 Torr or 2.6 kPa), the normal atmospheric pressure being 760 Torr or 101 kPa).
  • The internal blanket of the reactor chamber is a thick-liquid wall of flibe (liquid mixture of lithium fluoride and beryllium difluoride) intended to protect the external wall, to absorb the fusion neutron energy, and to produce tritium[3].
  • Finally, the system is intended to recycle the cartridges' debris, collected by the flibe "pool", after their destruction at the time of the fusion.

[edit] Notes and references

  1. ^ An introduction to the Z-IFE project may be found here.
  2. ^ For further details, see Pulsed power article.
  3. ^ tritium is produced when neutrons created during the fusion irradiates flibe lithium.

[edit] See also

[edit] External links


Fusion power
v  d  e
Atomic nucleus | Nuclear fusion | Nuclear power | Nuclear reactor | Timeline of nuclear fusion
Plasma physics | Magnetohydrodynamics | Neutron flux | Fusion energy gain factor | Lawson criterion
Methods of fusing nuclei

Magnetic confinement: - Tokamak - Spheromak - Stellarator - Reversed field pinch - Field-Reversed Configuration - Levitated Dipole
Inertial confinement: - Laser driven - Z-pinch - Bubble fusion (acoustic confinement) - Fusor (electrostatic confinement)
Other forms of fusion: - Muon-catalyzed fusion - Pyroelectric fusion - Migma

List of fusion experiments

Magnetic confinement devices
ITER (International) | JET (European) | JT-60 (Japan) | Large Helical Device (Japan) | KSTAR (Korea) | EAST (China) | T-15 (Russia) | DIII-D (USA) | Tore Supra (France) | ASDEX Upgrade (Germany) | TFTR (USA) | NSTX (USA) | NCSX (USA) | UCLA ET (USA) | Alcator C-Mod (USA) | LDX (USA) | H-1NF (Australia) | MAST (UK) | START (UK) | Wendelstein 7-X (Germany) | TCV (Switzerland) | DEMO (Commercial)


Inertial confinement devices
Laser driven: - NIF (USA) | OMEGA laser (USA) | Nova laser (USA) | Novette laser (USA) | Nike laser (USA) | Shiva laser (USA) | Argus laser (USA) | Cyclops laser (USA) | Janus laser (USA) | Long path laser (USA) | 4 pi laser (USA) | LMJ (France) | Luli2000 (France) | GEKKO XII (Japan) | ISKRA lasers (Russia) | Vulcan laser (UK) | Asterix IV laser (Czech Republic) | HiPER laser (European)
Non-laser driven: - Z machine (USA) | PACER (USA)


See also: International Fusion Materials Irradiation Facility