View source for Dense plasma focus

{{Short description|Ionized gas-generating "pinch" machine}}
A '''dense plasma focus''' ('''DPF''') is a type of [[plasma (physics)|plasma]] generating system originally developed as a [[fusion power]] device starting in the early 1960s. The system demonstrated scaling laws that suggested it would not be useful in the commercial power role, and since the 1980s it has been used primarily as a fusion teaching system, and as a source of [[neutron]]s and [[X-ray]]s.

The original concept was developed in 1954 by N.V. Filippov, who noticed the effect while working on early pinch machines in the USSR.<ref>Petrov DP, NV Filippov, TI Filippova, VA Khrabrov "Powerful pulsed gas discharge in the cells with conducting walls." In the Sun. Plasma physics and controlled thermonuclear reactions. Ed. Academy of Sciences of the USSR, 1958, т. 4, с. 170-181.</ref> A major research program on DPF was carried out in the USSR through the late 1950s, and continues to this day. A different version of the same basic concept was independently discovered in the US by J.W. Mather in the early 1960s. This version saw some development in the 1970s, and variations continue to be developed.

The basic design derives from the [[z-pinch]] concept. Both the DPF and pinch use large electrical currents run through a gas to cause it to ionize into a plasma and then ''[[pinch (plasma physics)|pinch]]'' down on itself to increase the density and temperature of the plasma. The DPF differs largely in form; most devices use two concentric cylinders and form the pinch at the end of the central cylinder. In contrast, z-pinch systems generally use a single cylinder, sometimes a torus, and pinch the plasma into the center.

The plasma focus is similar to the ''high-intensity plasma gun device'' (HIPGD) (or just ''plasma gun''), which ejects plasma in the form of a plasmoid, without pinching it. A comprehensive review of the dense plasma focus and its diverse applications has been made by Krishnan in 2012.<ref>{{cite journal | title= The Dense Plasma Focus: A Versatile Dense Pinch for Diverse Applications
 | last= Krishnan | first= Mahadevan 
 | journal= [[IEEE Transactions on Plasma Science]] | volume= 40 | issue= 12 | pages= 3189–3221
 |date=December 2012 | doi= 10.1109/TPS.2012.2222676 | bibcode= 2012ITPS...40.3189K| s2cid= 43566399 }}</ref>

==Pinch concept==
Pinch-based devices are the earliest systems to be seriously developed for fusion research, starting with very small machines built in London in 1948. These normally took one of two forms; ''linear pinch'' machines are straight tubes with electrodes at both ends to apply the current into the plasma, whereas ''toroidal pinch'' machines are donut-shaped machines with large magnets wrapped around them that supply the current via [[Electromagnetic induction|magnetic induction]].

In both types of machines, a large burst of current is applied to a dilute gas inside the tube. This current initially ionizes the gas into a plasma. Once the ionization is complete, which occurs in microseconds, the plasma begins to conduct a current. Due to the [[Lorentz force]], this current creates a magnetic field that causes the plasma to "pinch" itself down into a filament, similar to a lightning bolt. This process increases the density of the plasma very rapidly, causing its temperature to increase.

Early devices quickly demonstrated a problem with the stability of this process. As the current began to flow in the plasma, magnetic effects known as the "sausage" and "kink" appeared that caused the plasma to become unstable and eventually hit the sides of the container. When this occurred, the hot plasma would cause atoms of the metal or glass to spall off and enter the fuel, rapidly cooling the plasma. Unless the plasma could be made stable, this loss process would make fusion impossible.

In the mid-1950s, two possible solutions appeared. In the ''fast-pinch'' concept, a linear device would undergo the pinch so quickly that the plasma as a whole would not move, instead only the outermost layer would begin to pinch, creating a [[shock wave]] that would continue the process after the current was removed. In the ''stabilized pinch'', new magnetic fields would be added that would mix with the current's field and create a more stable configuration. In testing, neither of these systems worked, and the pinch route to fusion was largely abandoned by the early 1960s.{{citation needed|date=April 2020}}

==DPF concept==
During experiments on a linear pinch machine, Filippov noticed that certain arrangements of the electrodes and tube would cause the plasma to form into new shapes. This led to the DPF concept.

In a typical DPF machine, there are two cylindrical electrodes. The inner one, often solid, is physically separated from the outer by an insulating disk at one end of the device. It is left open at the other end. The end result is something like a coffee mug with a half hot dog standing on its end in the middle of the mug.

When current is applied, it begins to arc at the path of least resistance, at the end near the insulator disk. This causes the gas in the area to rapidly ionize, and current begins to flow through it to the outer electrode. The current creates a magnetic field that begins to push the plasma down the tube towards the open end. It reaches the end in microseconds.

When it reaches the end, it continues moving for a short time, but the endpoints of the current sheet remain attached to the end of the cylinders. This causes the plasma sheet to bow out into a shape not unlike an umbrella or the cap of a mushroom.

At this point further movement stops, and the continuing current instead begins to pinch the section near the central electrode. Eventually this causes the former ring-shaped area to compress down into a vertical post extending off the end of the inner electrode. In this area the density is greatly increased.

The whole process proceeds at many times the [[speed of sound]] in the ambient gas. As the current sheath continues to move axially, the portion in contact with the anode slides across the face of the anode, axisymmetrically. When the imploding front of the [[shock wave]] coalesces onto the axis, a reflected shock front emanates from the axis until it meets the driving current sheath which then forms the axisymmetric boundary of the pinched, or focused, hot plasma column.

The dense plasma column (akin to the [[Z-pinch]]) rapidly [[pinch (plasma physics)|pinch]]es and undergoes instabilities and breaks up. The intense electromagnetic radiation and particle bursts, collectively referred to as ''multi-radiation'' occur during the dense plasma and breakup phases. These critical phases last typically tens of [[nanoseconds]] for a small (kJ, 100&nbsp;kA) focus machine to around a [[microsecond]] for a large (MJ, several&nbsp;MA) focus machine.

The process, including axial and radial phases, may last, for the Mather DPF machine, a few microseconds (for a small focus) to 10&nbsp;microseconds for a larger focus machine. A Filippov focus machine has a very short axial phase compared to a Mather focus.

==Applications==
When operated using [[deuterium]], intense bursts of [[X-ray]]s and charged particles are emitted, as are [[nuclear fusion]] byproducts including [[neutron]]s.<ref>{{cite journal | title= Correlated deuteron energy spectra and neutron yield for a 3 kJ plasma focus 
 | last= Springham | first= S V |author2=S Lee |author3=M S Rafique
 | journal= [[Plasma Physics and Controlled Fusion]] | volume= 42 | issue= 10 | pages= 1023–1032 
 |date=October 2000 | doi= 10.1088/0741-3335/42/10/302 
 |bibcode = 2000PPCF...42.1023S | s2cid= 250834004 }}</ref> There is ongoing research that demonstrates potential applications as a soft X-ray source<ref>{{cite journal | title= A Powerful Soft X-ray Source for X-ray Lithography Based on Plasma Focusing 
 | last= Bogolyubov | first= E P |display-authors=etal 
 | journal= [[Physica Scripta]] | volume= 57 | issue= 4 | pages= 488–494 
 | year= 1970
| doi= 10.1088/0031-8949/57/4/003 
 |bibcode = 1998PhyS...57..488B | s2cid= 250814654 }}</ref> for next-generation [[microelectronics]] [[lithography]], [[surface micromachining]], pulsed X-ray and [[neutron]] source for medical and security inspection applications and materials modification,<ref>{{cite journal | url= http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JAPIAU000095000012007725000001&idtype=cvips&gifs=yes 
 | title= Effect of energetic ion irradiation on {{chem|CdI|2}} films 
 | last= Rawat | first= R. S. |author2=P. Arun |author3=A. G. Vedeshwar |author4=P. Lee
  | journal= [[Journal of Applied Physics]] | volume= 95 | issue= 12 | pages= 7725–30 
 | date= 15 June 2004 | doi= 10.1063/1.1738538 
 | access-date= 2009-01-08 |arxiv = cond-mat/0408092 |bibcode = 2004JAP....95.7725R | s2cid= 118865852 
 }}</ref> among others.

For [[nuclear weapons]] applications, dense plasma focus devices can be used as an external [[neutron source]].<ref>[[U.S. Department of Defense]], Militarily Critical Technologies List, Part II: Weapons of Mass Destruction Technologies (February 1998) [https://fas.org/irp/threat/mctl98-2/p2sec05.pdf Section&nbsp;5. Nuclear Weapons Technology] ([[PDF]]), Table&nbsp;5.6-2, p.&nbsp;II-5-66. Retrieved on 8&nbsp;January 2009.</ref> Other applications include simulation of nuclear explosions (for testing of the electronic equipment) and a short and intense neutron source useful for non-contact discovery or inspection of nuclear materials (uranium, plutonium).

==Characteristics==
An important characteristic of the dense plasma focus is that the [[energy density]] of the focused plasma is practically a constant over the whole range of machines,<ref name="Dimensions"/> from sub-kilojoule machines to megajoule machines, when these machines are tuned for optimal operation.<ref name="speedbull1"/> This means that a small table-top-sized plasma focus machine produces essentially the same plasma characteristics (temperature and density) as the largest plasma focus. Of course the larger machine will produce the larger volume of focused plasma with a corresponding longer lifetime and more radiation yield.

Even the smallest plasma focus has essentially the same dynamic characteristics as larger machines, producing the same plasma characteristics and the same radiation products. This is due to the [[Plasma scaling|scalability of plasma]] phenomena.

See also [[plasmoid]], the self-contained magnetic plasma ball that may be produced by a dense plasma focus.

==Design parameters==
The fact that the plasma energy density is constant throughout the range of plasma focus devices, from big to small, is related to the value of a design parameter that needs to be kept at a certain value if the plasma focus is to operate efficiently.

The critical 'speed' design parameter for neutron-producing devices is <math>\frac{I}{a\sqrt{p}}</math><!-- removed the confusing duplication without math markup as (I/a)/p^1/2-->, where <math>I</math> is the current, <math>a</math> is the anode radius, and <math>p</math> is the gas density or pressure.<ref name="Dimensions">{{cite journal | title= Dimensions and lifetime of the plasma focus pinch 
 | last= Lee | first= Sing |author2=Serban, A. 
 | journal= [[IEEE Transactions on Plasma Science]] | volume= 24 | issue= 3 | pages= 1101–1105 
 |date=June 1996 | doi= 10.1109/27.533118 | issn= 0093-3813 
 |bibcode = 1996ITPS...24.1101L }}</ref>

For example, for neutron-optimised operation in deuterium the value of this critical parameter, experimentally observed over a range of machines from kilojoules to hundreds of kilojoules, is:  9&nbsp;kA/(mm·Torr<sup>0.5</sup>), or 780&nbsp;kA/(m·Pa<sup>0.5</sup>), with a remarkably small deviation of 10% over such a large range of sizes of machines.

Thus if we have a peak current of 180&nbsp;kA we require an anode radius of 10&nbsp;mm with a deuterium fill pressure of {{convert|4|Torr|Pa|abbr=on}}. The length of the anode has then to be matched to the risetime of the capacitor current in order to allow an average axial transit speed of the current sheath of just over 50&nbsp;mm/μs. Thus a capacitor risetime of 3&nbsp;μs requires a matched anode length of 160&nbsp;mm.

The above example of peak current of 180&nbsp;kA rising in 3&nbsp;μs, anode radius and length of respectively 10 and 160&nbsp;mm are close to the design parameters of the UNU/ICTP PFF (United Nations University/International Centre for Theoretical Physics Plasma Fusion Facility).<ref>Lee, S and Zakaullah, M et al. and Srivastava, M P and Gholap, A V et al. and Eissa, M A and Moo, S P et al. (1988) [http://eprints.ictp.it/31/ ''Twelve Years of UNU/ICTP PFF- A Review''] {{webarchive|url=https://web.archive.org/web/20080329233338/http://eprints.ictp.it/31/ |date=2008-03-29 }}. IC, 98 (231). Abdus Salam ICTP, Miramare, Trieste. Retrieved on 8&nbsp;January 2009.</ref> This small table-top device was designed as a low-cost integrated experimental system for training and transfer to initiate/strengthen experimental plasma research in developing countries.<ref>{{cite journal | url= http://eprints.ictp.it/273/ | title= Initiating and Strengthening Plasma Research in Developing Countries | last= Lee | first= Sing | author2= Wong, Chiow San | journal= [[Physics Today]] | volume= 59 | issue= 5 | pages= 31–36 | year= 2006 | issn= 0031-9228 | access-date= 2009-01-08 | doi= 10.1063/1.2216959 | bibcode= 2006PhT....59e..31L | url-status= dead | archive-url= https://archive.today/20060509064357/http://eprints.ictp.it/273/ | archive-date= 2006-05-09 }}</ref>

It can be noted that the square of the drive parameter is a measure of the "plasma energy density".

On the other hand, another proposed, so called "energy density parameter" <math>{28E \over a^3}</math>, where E is the energy stored in the capacitor bank and a is the anode radius,  for neutron-optimised operation in deuterium the value of this critical parameter, experimentally observed over a range of machines from tens of joules to hundreds of kilojoules, is in the order of <math>{5 \cdot 10^{10}}</math> J/m<sup>3</sup>.<ref name="speedbull1">{{cite journal|last=Soto|first=Leopoldo |author2=C. Pavez |author3=A. Tarifeño |author4=J. Moreno |author5=F. Veloso|title=Studies on scalability and scaling laws for the plasma focus: similarities and differences in devices from 1MJ to 0.1J|journal=Plasma Sources Science and Technology|date=20 September 2010|volume=19|issue=55001–055017|doi=10.1088/0963-0252/19/5/055017|bibcode = 2010PSST...19e5017S |pages=055017|s2cid=122162772 }}</ref> For example, for a capacitor bank of 3kJ, the anode radius is in the order of 12mm. This parameter has a range of 3.6x10^9 to 7.6x10^11 for the machines surveyed by Soto. The wide range of this parameter is because it is a "storage energy density" which translates into plasma energy density with different efficiency depending on the widely differing performance of different machines. Thus to result in the necessary plasma energy density (which is found to be a near constant for optimized neutron production) requires widely differing initial storage density.

==Current research==
A network of ten identical DPF machines operates in eight countries around the world. This network produces  research papers on topics including machine optimization & diagnostics (soft X-rays, neutrons, electron and ion beams), applications (microlithography, micromachining, materials modification and fabrication, imaging & medical, astrophysical simulation) as well as modeling & computation. The network was organized by Sing Lee in 1986 and is coordinated by the Asian African Association for Plasma Training, [[AAAPT]]. A simulation package, the Lee Model,<ref name="review">{{cite journal | title= Plasma Focus Radiative Model: Review of the Lee Model Code 
 | last= Lee | first= Sing | journal= [[Journal of Fusion Energy]] | volume= 33 | issue= 4 | pages= 319–335 
 |date=August 2014 | doi= 10.1007/s10894-014-9683-8 | s2cid= 123087082 | issn= 0164-0313
 }}</ref> has been developed for this network but is applicable to all plasma focus devices. The code typically produces excellent agreement between computed and measured results,<ref>{{cite web
 |url         = http://www.intimal.edu.my/school/fas/UFLF/
 |title       = Universal Plasma Focus Laboratory Facility at INTI-UC
 |date        = 24 November 2008
 |publisher   = [[INTI University College]] (INTI-UC) [[Malaysia]].
 |access-date  = 2009-01-08
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20081028222802/http://www.intimal.edu.my/school/fas/UFLF/
 |archive-date = 28 October 2008
}}</ref> and is available for downloading as a Universal Plasma Focus Laboratory Facility. The Institute for Plasma Focus Studies IPFS<ref>{{cite web | url= http://www.plasmafocus.net 
 | title= Institute for Plasma Focus Studies 
 |date= 19 November 2008 | access-date= 2009-01-08 }}</ref>  was founded on 25&nbsp;February 2008 to promote correct and innovative use of the Lee Model code and to encourage the application of plasma focus numerical experiments. IPFS research has already extended numerically-derived neutron scaling laws to multi-megajoule experiments.<ref>[http://www.intimal.edu.my/school/fas/UFLF/Papers/PP5PublishedPPCF%2050%282008%29%20105005.pdf] (PDF)  {{webarchive|url=https://web.archive.org/web/20120325033941/http://www.intimal.edu.my/school/fas/UFLF/Papers/PP5PublishedPPCF%2050%282008%29%20105005.pdf|date=March 25, 2012}}</ref>  These await verification. Numerical experiments with the code have also resulted in the compilation of a global scaling law indicating that the well-known neutron saturation effect is better correlated to a scaling deterioration mechanism. This is due to the increasing dominance of the axial phase dynamic resistance as capacitor bank impedance decreases with increasing bank energy (capacitance).  In principle, the resistive saturation could be overcome by operating the pulse power system at a higher voltage.

The International Centre for Dense Magnetised Plasmas (ICDMP) in Warsaw Poland, operates several plasma focus machines for an international research and training programme. Among these machines is one with energy capacity of 1&nbsp;MJ making it one of the largest plasma focus devices in the world.

In Argentina there is an Inter-institutional Program for Plasma Focus Research since 1996, coordinated by a National Laboratory of Dense Magnetized Plasmas ([http://www.pladema.net www.pladema.net]) in Tandil, Buenos Aires. The Program also cooperates with the Chilean Nuclear Energy Commission, and networks the Argentine National Energy Commission, the Scientific Council of Buenos Aires, the University of Center, the University of Mar del Plata, The University of Rosario, and the Institute of Plasma Physics of the University of Buenos Aires. The program operates six Plasma Focus Devices, developing applications, in particular ultra-short tomography and substance detection by neutron pulsed interrogation. PLADEMA also contributed during the last decade with several mathematical models of Plasma Focus. The thermodynamic model was able to develop for the first time design maps combining geometrical and operational parameters, showing that there is always an optimum gun length and charging pressure which maximize the neutron emission. Currently there is a complete finite-elements code validated against numerous experiments, which can be used confidently as a design tool for Plasma Focus.

In Chile, at the Chilean Nuclear Energy Commission the plasma focus experiments have been extended to sub-kilojoules devices and the scales rules have been stretched up to region less than one joule.<ref>{{cite journal|last=Soto|first=Leopoldo|title=New Trends and Future Perspectives on Plasma Focus Research|journal=Plasma Physics and Controlled Fusion|date=20 April 2005|volume=47|issue=5A|doi=10.1088/0741-3335/47/5A/027|bibcode = 2005PPCF...47A.361S|pages=A361–A381|hdl=10533/176861|s2cid=123567010 |hdl-access=free}}</ref><ref name="speedbull2">{{cite journal|last=Soto|first=Leopoldo|author2=P. Silva |author3=J. Moreno |author4=M. Zambra |author5=W. Kies |author6=R. E. Mayer| author7=L. Altamirano| author8=C. Pavez| author9=L. Huerta|title=Demonstration of neutron production in a table top pinch plasma focus device operated at only tens of joules|journal=Journal of Physics D: Applied Physics| date=1 October 2008|volume=41|issue=202001–205503|doi=10.1088/0022-3727/41/20/205215|bibcode = 2008JPhD...41t5215S | pages=205215|hdl=10533/141980|s2cid=120743451 |hdl-access=free}}</ref>
<ref name="speedbull3">{{cite journal|last=Pavez|first=Cristian|author2=Leopoldo Soto|title=Demonstration of x-ray Emission from an ultraminiature pinch plasma focus discharge operating at 0.1 J. Nanofocus|journal=IEEE Transactions on Plasma Science|date=6 May 2010|volume=38|issue=5|doi=10.1109/TPS.2010.2045110|bibcode = 2010ITPS...38.1132P|pages=1132–1135|s2cid=30726899 }}</ref><ref>{{cite journal|last=Silva|first=Patricio.|author2=José Moreno |author3=Leopoldo Soto |author4=Lipo Birstein |author5=Roberto E. Mayer|author6=Walter Kies| author7=L. Altamirano|s2cid=122201072|title=Neutron Emission from a Fast Plasma Focus of 400 Joules|journal= Applied Physics Letters|date=15 October 2003|volume=83|issue=16|doi=10.1063/1.1621460|bibcode = 2003ApPhL..83.3269S |pages=3269|hdl=10533/174369|hdl-access=free}}</ref> Their studies have contributes to know that is possible to scale the plasma focus in a wide range of energies and sizes keeping the same value of ion density, magnetic field, plasma sheath velocity, Alfvén speed and the quantity of energy per particle. Therefore, fusion reactions are even possible to be obtained in ultraminiature devices (driven by generators of 0.1J for example), as they are in the bigger devices (driven by generators of 1MJ). However, the stability of the plasma pinch highly depends on the size and energy of the device.<ref name="speedbull1"/> A rich plasma phenomenology it has been observed in the table-top plasma focus devices developed at the Chilean Nuclear Energy Commission: filamentary structures,<ref>{{cite journal|last=Soto|first=Leopoldo|author2=C. Pavez |author3=F. Castillo |author4=F. Veloso |author5=J. Moreno|author6=S. K. H. Auluck|title=Filamentary structures in dense plasma focus: current filaments or vortex filaments|journal=Physics of Plasmas|date=1 July 2014|volume=21|issue=7|doi=10.1063/1.4886135|bibcode = 2014PhPl...21g2702S |pages=072702|s2cid=122169647 }}</ref> toroidal singularities,<ref>{{cite journal|last=Casanova|first=Federico|author2=Ariel Tarifeño-Saldivia |author3=Felipe Veloso |author4=Cristian Pavez |author5=Alejandro Clausse|author6=Leopoldo Soto|title=Toroidal high-density singularities in a small Plasma Focus|journal=Journal of Fusion Energy|date= 6 September 2011|volume=31|issue=3|doi=10.1007/s10894-011-9469-1|bibcode = 2012JFuE...31..279C |pages=279–283|s2cid=121105885 }}</ref> plasma bursts <ref>{{cite journal|last=Soto|first=Leopoldo|author2=C. Pavez |author3=J. Moreno |author4=M. J. Inestrosa-Izurieta |author5=F. Veloso|author6=G. Gutiérrez |author7=J. Vergara |author8=A. Clausse |author9=H. Bruzzone |author10=F. Castillo |author11=L. F. Delgado-Aparicio |title=Characterization of the axial plasma shock in a table top plasma focus after the pinch and its possible application to testing materials for fusion reactors|journal=Physics of Plasmas|date=5 December 2014|volume=21|issue=12|doi=10.1063/1.4903471|bibcode = 2014PhPl...21l2703S |pages=122703|hdl=11336/180619|hdl-access=free}}</ref>
and plasma jets generations.<ref>{{cite journal|last=Paves|first=Cristian|author2=J. Pedreros |author3=A. Tarifeño Saldivia |author4=L. Soto |title=Observations of plasma jets in a table top plasma focus discharge|journal=Physics of Plasmas|date=24 April 2015|volume=22|issue=4|doi=10.1063/1.4919260|bibcode = 2015PhPl...22d0705P |pages=040705}}</ref> In addition, possible applications are explored using these kind of small plasma devices: development of portable generator as non-radioactive sources of neutrons and X-rays for field applications,<ref name="speedbull2"/><ref name="speedbull3"/> pulsed radiation applied to biological studies, plasma focus as neutron source for nuclear fusion-fission hybrid reactors,<ref>{{cite journal|last=Clausse|first=Alejandro|author2=Leopoldo Soto |author3=Carlos Friedli |author4=Luis Altamirano |title=Feasibility study of a hybrid subcritical fission system driven by Plasma-Focus fusion neutrons|journal=Annals of Nuclear Energy|date= 26 December 2014|volume=22 |doi=10.1016/j.anucene.2014.12.028 |pages=10–14|hdl=11336/33206 |hdl-access=free}}</ref> and the use of plasma focus devices as plasma accelerators for studies of materials under intense fusion-relevant pulses.<ref>{{cite journal|last=Inestrosa-Izurieta|first=Maria José|author2=E. Ramos-Moore |author3=L. Soto |title=Morphological and structural effects on tungsten targets produced by fusion plasma pulses from a table top plasma focus|journal=Nuclear Fusion |date=5 August 2015 |volume=55|issue=93011|pages=093011|doi=10.1088/0029-5515/55/9/093011|bibcode = 2015NucFu..55i3011I |s2cid=123295304 }}</ref> In addition, Chilean Nuclear Energy Commission currently operates the facility SPEED-2, the largest Plasma Focus facility of the southern hemisphere.

Since the beginning of 2009, a number of new plasma focus machines have been/are being commissioned including the INTI Plasma Focus in Malaysia, the NX3 in Singapore, the first plasma focus to be commissioned in a US university in recent times, the KSU Plasma Focus at Kansas State University which recorded its first fusion neutron emitting pinch on New Year's Eve 2009 and the IR-MPF-100 plasma focus (115kJ) in Iran.

===Fusion power===
Several groups proposed that [[fusion power]] based on the DPF could be economically viable, possibly even with [[Aneutronic fusion|low-neutron fuel cycles]] like p-B11. The feasibility of net power from p-B11 in the DPF requires that the [[bremsstrahlung]] losses be reduced by quantum mechanical effects induced by an extremely strong magnetic field "[[Alfvén's theorem|frozen into the plasma"]]. The high magnetic field also results in a high rate of emission of [[cyclotron radiation]], but at the densities envisioned, where the [[plasma frequency]] is larger than the [[cyclotron frequency]], most of this power will be reabsorbed before being lost from the plasma. Another advantage claimed is the capability of [[Fusion power#Subsystems|direct conversion]]{{Broken anchor|date=2024-07-25|bot=User:Cewbot/log/20201008/configuration|target_link=Fusion power#Subsystems|reason= The anchor (Subsystems) [[Special:Diff/608749252|has been deleted]].}} of the energy of the fusion products into electricity, with an efficiency potentially above 70%.

==== Lawrenceville Plasma Physics ====
Experiments and computer simulations to investigate the capability of DPF for fusion power are underway at Lawrenceville Plasma Physics (LPP) under the direction of [[Eric Lerner]], who explained his "Focus Fusion" approach in a 2007 Google Tech Talk.<ref>{{cite web | url= http://video.google.com/videoplay?docid=-1518007279479871760
 | title= Focus Fusion: The Fastest Route to Cheap, Clean Energy 
 | last= Lerner | first= Eric | author-link= Eric Lerner 
 |date= 3 October 2007 | format= video  |website= Google TechTalks | access-date= 2009-01-08 }}</ref>  On November&nbsp;14, 2008, Lerner received funding for continued research, to test the scientific feasibility of Focus Fusion.<ref>{{cite web | url= http://www.lawrencevilleplasmaphysics.com/index.php?pr=News 
 | title= LPP Receives Major Investments, Initiates Experimental Project 
 | date= November 22, 2008 | publisher= [[Lawrenceville Plasma Physics]], Inc. 
 | access-date= 2009-01-08 }}</ref>

On October 15, 2009, the DPF device "Focus Fusion-1" achieved its first pinch.<ref>{{cite web | url= http://www.lawrencevilleplasmaphysics.com/index.php?option=com_lyftenbloggie&view=entry&category=news&id=8%3Afocus-fusion-1-works&Itemid=90 | title= Focus-Fusion-1 Works! First shots and first pinch achieved October 15, 2009  
 | date= October 15, 2009 | publisher= [[Lawrenceville Plasma Physics]], Inc.
 | access-date= 2009-10-18 }}</ref>  On January 28, 2011, LPP published initial results including experimental shots with considerably higher fusion yields than the historical DPF trend.<ref>{{cite journal | title= Theory and Experimental Program for p-B11 Fusion with the Dense Plasma Focus  
 | date= January 28, 2011 | journal= [[Journal of Fusion Energy]]
 | doi= 10.1007/s10894-011-9385-4 
 | bibcode= 2011JFuE...30..367L 
 | last1= Lerner 
 | first1= Eric J. 
 | last2= Krupakar Murali 
 | first2= S. 
 | last3= Haboub 
 | first3= A. 
 | volume= 30 
 | issue= 5 
 | pages= 367–376 
 | s2cid= 122230379 }}</ref> In March, 2012, the company announced that it had achieved temperatures of 1.8 billion degrees, beating the old record of 1.1 billion that had survived since 1978.<ref>{{cite journal|last=Lerner|first=Eric J. |author2=S. Krupakar Murali |author3=Derek Shannon |author4=Aaron M. Blake |author5=Fred Van Roessel|s2cid=120207711 |title=Fusion reactions from >150 keV ions in a dense plasma focus plasmoid|journal=Physics of Plasmas|date=23 March 2012|volume=19|issue=3|doi=10.1063/1.3694746|bibcode = 2012PhPl...19c2704L |pages=032704}}</ref><ref>{{cite news|last=Halper|first=Mark|title=Fusion breakthrough|url=http://www.smartplanet.com/blog/intelligent-energy/fusion-breakthrough/14516|access-date=1 April 2012|newspaper=Smart PLanet|date=March 28, 2012}}</ref> In 2016 the company announced that it had achieved a fusion yield of 0.25 joules.<ref>{{Cite web|url=http://nextbigfuture.com/2016/06/despite-rocky-start-and-funding-for.html|title=Next Big Future: Despite rocky start and funding for only about 25 shots - LPP Fusion yield is up 50% to a record for any dense plasma focus device|website=[[Next Big Future]]|access-date=2016-06-05|archive-url=https://web.archive.org/web/20160606121041/http://nextbigfuture.com/2016/06/despite-rocky-start-and-funding-for.html|archive-date=2016-06-06|url-status=dead}}</ref> In 2017 the company reduced impurities by mass by 3x and ion numbers by 10x. Fusion yield increased by 50%. Fusion yield doubled compared to other plasma focus devices with the same 60 kJ energy input. In addition, mean ion energy increased to a record of 240 ± 20 keV for any confined fusion plasma. A deuterium-nitrogen mix and corona-discharge pre-ionization reduced the fusion yield standard deviation by 4x to about 15%.<ref>{{cite journal|last=Lerner|first=Eric J.|author2=Syed M. Hassan|author3=Ivana Karamitsos|author4=Fred Von Roessel|title=Confined ion energy >200 keV and increased fusion yield in a DPF with monolithic tungsten electrodes and pre-ionization|journal=Physics of Plasmas|date=2017|volume=24|issue=10|doi=10.1063/1.4989859 |pages=102708|bibcode=2017PhPl...24j2708L}}</ref> 

In 2019, the team conducted a series of experiments replacing tungsten electrodes with [[beryllium]] electrodes (termed Focus Fusion 2B). After 44 shots, the electrode formed a much thinner 10&nbsp;nm oxide layer with correspondingly fewer impurities and less electrode erosion than with tungsten electrodes. Fusion yield reached 0.1 joule. Yield generally increased and impurities decreased with an increasing number of shots.<ref>{{Cite web|url=https://lppfusion.com/wp-content/uploads/2019/07/LPPFFusion-Report-July-3-2019.pdf|title=Beryllium Experiments Begin with FF-2B: Impurities Low, Yield Rising|last=LPPFusion|date=July 1, 2019|website=lppfusion.com|access-date=July 26, 2019}}</ref>

==History==
*1958: Петров Д.П., Филиппов Н.В., Филиппова Т.И., Храбров В.А. "Мощный импульсный газовый разряд в камерах с проводящими стенками". В сб. Физика плазмы и проблемы управляемых термоядерных реакций. Изд. АН СССР, 1958, т. 4, с. 170–181.
*1958: [[Hannes Alfvén]]: Proceedings of the Second International Conference on Peaceful Uses of Atomic Energy (United Nations), 31, 3
*1960: H Alfven, L Lindberg and P Mitlid, "[http://www.iop.org/EJ/abstract/0368-3281/1/3/302/ Experiments with plasma rings]" (1961) ''Journal of Nuclear Energy''. Part&nbsp;C, Plasma Physics, Accelerators, Thermonuclear Research, Volume&nbsp;1, Issue&nbsp;3, pp.&nbsp;116–120
*1960: Lindberg, L., E. Witalis and C. T. Jacobsen, "Experiments with plasma rings" (1960) ''Nature'' 185:452.
*1961: Hannes Alfvén: Plasma Ring Experiment in "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...133.1049A On the Origin of Cosmic Magnetic Fields]" (1961) ''Astrophysical Journal'', vol.&nbsp;133, p.&nbsp;1049
*1961: Lindberg, L. & Jacobsen, C., "[http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1961ApJ...133.1043L&amp;db_key=AST&amp;data_type=HTML&amp;format=&amp;high=42ca922c9c03926 On the Amplification of the Poloidal Magnetic Flux in a Plasma]" (1961) ''Astrophysical Journal'', vol.&nbsp;133, p.&nbsp;1043
*1962: Filippov. N.V., et al., "Dense, High-Temperature Plasma in a Noncylindrical 2-pinch Compression" (1962) 'Nuclear Fusion Supplement'. Pt.&nbsp;2, 577
*1969: Buckwald, Robert Allen, "Dense Plasma Focus Formation by Disk Symmetry" (1969) [[Thesis]], [[Ohio State University]].

==Notes==
{{reflist|30em}}

==External links==
* [http://www.plasmafocus.net Institute for Plasma Focus Studies (IPFS)]. 
* Research papers published in 2011 by IPFS staff. [https://web.archive.org/web/20120302171238/http://www.plasmafocus.net/IPFS/2011papers/0%202011%20Papers.htm]
*The Plasma Focus-Trending into the Future([https://web.archive.org/web/20160113012445/http://www.plasmafocus.net/IPFS/2011papers/PFtrendingintotheFuture%20.DOC])
*Dimensions and Lifetime of the Plasma Focus ([http://www.plasmafocus.net/IPFS/otherpapers/DimLifePF96.pdf])
* [https://web.archive.org/web/20071022152326/http://ckplee.myplace.nie.edu.sg/plasmaphysics/ Plasma Radiation Source Lab at the  National Institute of Education in Singapore]
* [https://web.archive.org/web/20060528063104/http://www.icdmp.pl/pf1000.html Plasma Focus Laboratory, International Centre for Dense Magnetised Plasmas, Warsaw, Poland]
* [http://www.fis.puc.cl/~plasma/  Optics and Plasma Physics Group, Pontificia Universidad Católica de Chile]
* Paper by [[Leopoldo Soto Norambuena|Leopoldo Soto]] ([https://web.archive.org/web/20070606214431/http://www.cchen.cl/index.php?option=com_content&task=category&sectionid=11&id=111&Itemid=71 Chilean Nuclear Energy Commission, Thermonucluar Plasma Department]): [http://stacks.iop.org/PPCF/47/A361 New trends and future perspectives on plasma focus research]
* [http://www.focusfusion.org/ Focus Fusion Society]
* Abdus Salam ICTP Plasma Focus Laboratory. [https://web.archive.org/web/20080602140429/http://mlab.ictp.it/plasma/pfd.html]
* Numerical Simulation Package: Universal Plasma Focus Laboratory Facility at INTI-UC. [https://web.archive.org/web/20081028222802/http://www.intimal.edu.my/school/fas/UFLF/]
* [http://www.pladema.net Dense Plasma Focus Network in Argentina]. 
* Research papers published in 2011 by IPFS staff. [https://web.archive.org/web/20120302171238/http://www.plasmafocus.net/IPFS/2011papers/0%202011%20Papers.htm]
* [http://www.fusionenergy.net.au  Fusion Energy Site with links] {{Webarchive|url=https://web.archive.org/web/20210518050514/http://fusionenergy.net.au/ |date=2021-05-18 }}. 
* [http://video.google.com/videoplay?docid=-1518007279479871760&emb=1&hl=en Google talk by Eric J. Lerner, President of Lawrenceville Plasma Physics and Executive Director of the Focus Fusion Society]

{{Fusion power}}
{{Nuclear fusion reactors}}

[[Category:Magnetic confinement fusion]]
[[Category:Neutron sources]]
[[Category:Plasma technology and applications]]
[[Category:Soviet inventions]]