Fusion Definition and 76 Discussions

Nuclear fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between the reactants and products is manifested as either the release or the absorption of energy. This difference in mass arises due to the difference in atomic binding energy between the nuclei before and after the reaction. Fusion is the process that powers active or main sequence stars and other high-magnitude stars, where large amounts of energy are released.
A fusion process that produces nuclei lighter than iron-56 or nickel-62 will generally release energy. These elements have relatively small mass per nucleon and large binding energy per nucleon. Fusion of nuclei lighter than these releases energy (an exothermic process), while fusion of heavier nuclei results in energy retained by the product nucleons, and the resulting reaction is endothermic. The opposite is true for the reverse process, nuclear fission. This means that the lighter elements, such as hydrogen and helium, are in general more fusible; while the heavier elements, such as uranium, thorium and plutonium, are more fissionable. The extreme astrophysical event of a supernova can produce enough energy to fuse nuclei into elements heavier than iron.
In 1920, Arthur Eddington suggested hydrogen-helium fusion could be the primary source of stellar energy. Quantum tunneling was discovered by Friedrich Hund in 1929, and shortly afterwards Robert Atkinson and Fritz Houtermans used the measured masses of light elements to show that large amounts of energy could be released by fusing small nuclei. Building on the early experiments in artificial nuclear transmutation by Patrick Blackett, laboratory fusion of hydrogen isotopes was accomplished by Mark Oliphant in 1932. In the remainder of that decade, the theory of the main cycle of nuclear fusion in stars was worked out by Hans Bethe. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project. Self-sustaining nuclear fusion was first carried out on 1 November 1952, in the Ivy Mike hydrogen (thermonuclear) bomb test.
Research into developing controlled fusion inside fusion reactors has been ongoing since the 1940s, but the technology is still in its development phase.

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  1. Strato Incendus

    Writing: Input Wanted A dangerous space mission that requires a lot of helping hands

    As I've mentioned in a few previous threads, at the midpoint of my sci-fi story on a generation ship, I need a disaster that wipes out about a third of the (male half of) the crew. Several people have suggested things like "a virus that disproportionately affects men", but that didn't quite cut...
  2. D

    Nuclear fusion energy calculations

    Me again! For a sci-fi story I'm working on, I've created a sci-fi technology called an Aneutronic Triple Alpha Fusion Reactor. It works via aneutronic fusion, in this case, fusing Deuterium with Helium 3, but it also mimics the triple alpha process found within stars to maximise fuel use...
  3. A

    Fusion of Western musical instruments

    Western musical instruments Western musical instruments images Trumpet and Saxophone. Is it possible to design and construct western musical instruments as a fusion of two or more functions and features? I mean to say Guitar, Violin, Trumpet, Saxophone, Piano etc integrated into a single...
  4. hyperiontorus

    Levels of Civilization Based on Deuterium

    Summary:: Similar to the Kardashev Scale, create a means for forming a hierarchy of civilization based on deuterium access. I'm interested in the fusion process using deuterium, and I've noted that it remains (to this day) the greatest source of energy of any reactions. Because of this reason...
  5. prodigylock

    A What pressure would be needed to cause fusion of water?

    So in a DnD story, someone made a bomb by putting 3375ft^3 of water into a 0.5ft radius sphere and caused it to make a nuke. I was thinking if this was possible then what would actually happen, so I spent an afternoon looking for the answer and only got the pressure and density...
  6. hagopbul

    I What is hydrogen boron fusion

    Hello All: Read an article about new trend in fusion science about hydrogen-boron 11 fusion Called HB-11 fusion and a start up are doing a research on it using pulsed laser What I don't understand how it is considered a possible new method for energy production when we know hydrogen and...
  7. patrykh18

    Physics Internship possibilities: Plasma physics

    Hi guys. I'm a third year physics student. Next year I'll be in my final year. I'm interested in studying fusion in the future. Unfortunately I have not done plasma physics as part of my degree so I don't know much about it yet. However I'd like to do an internship abroad this summer. Ideally I...
  8. patrykh18

    Plasma physics project ideas

    Summary:: I am looking for topics to give a presentation on. Hi everyone. If this is in the wrong section feel free to move it. Anyway, as part of our lab course, on top of doing experiments we will also have to prepare a 20 minute presentation on a chosen topic on physics. This is not like...
  9. C

    I Can a fusion reaction propagate in a cappilary?

    Can fusion reaction propagate inside a (very thick walled) cappilary if fusion has been initiated at one end? In this situation it seems like all the energy would have nowhere to go but into heating and pressurizing the fuel, providing conditions for further reaction. I imagine this is a...
  10. N

    China's Experimental Advanced Superconducting Tokamak (EAST)

    A team of scientists from China's Institute of Plasma Physics announced this week that plasma in its Experimental Advanced Superconducting Tokamak (EAST) would be ready to begin attempting to generate more energy than it uses, in a world first. I am dubious about more news that comes out of...
  11. N

    B A New Way to Make Fusion Reactors More Efficient

    I am quite new to this site. I have been following this technology (fusion) for many years now. It never seems to be any closer to actual deployment. Do you think we are getting closer? What do you think are the major stumbling blocks? The article below I read today. My understanding is that...
  12. T

    New approach to stabilize fusion plasmas

    https://phys.org/news/2019-01-scientists-stabilizes-fusion-plasmas.html By applying more RF power to the unstable 'bubbles' that form in the plasmas.
  13. Basil Currie

    B Fusion of Hydrogen Isotopes

    Hi, Does a T-D or a D-D fusion release more energy? Even if D-D needs higher temperatures, would it produce more energy in a fusion reactor?
  14. N

    I Why do stars only produce up to iron and nickel

    I know it's a common question but I've found no answers online so far. My professor has made a point out of saying that fusion reactions after iron and nickel do release energy but just not enough to keep the star from imploding. This didn't make sense to me. How would fission release energy if...
  15. M

    Trying to understand the entropy of different situations....

    I just read a book by nuclear physicist Carlo Rovelli on the subject of "Time" and he says that 'entropy' is the only non-reversible process in the basic equations of physics, and he believes time and entropy are related (if I understand him correctly). So this started me thinking on entropy...
  16. Javier Lopez

    A What is the key parameter in fusion: momentum or energy?

    The released products of a transmutation reaction (I say transmutation when 2 particles reacts to generate more than one) follows the conservation of kinetic energy law. Also particles moving in opposite direction can have equal speed one with respect the other than rather if one of them is...
  17. Javier Lopez

    I Stopping power for a proton ion gun through a Boron-11 sheet 1mm thick

    Hello, I need the stopping power for a proton ion gun through Boron-11 sheet 1mm thick. I have the following table obtained from here: https://www-nds.iaea.org/stopping/stopping_hydr.html Where the unit is in 1-15*eV*cm2/atom: Then I calculated for 600keV protons at table 5.1eV*cm2/atom. I...
  18. O

    A Positron Catalyzed Fusion

    Hi, I recently came across Positron Dynamics, a company working on a fusion propulsion system. You can watch this presentation given at Breakthrough Discuss 2018. They also got a grant from NIAC. Rather than trying to create and store positrons, they use Na-22 as a source. They also patented...
  19. J

    CNO fusion using particle accelerator?

    The CNO cycle (see https://en.wikipedia.org/wiki/CNO_cycle) is a catalytic fusion reaction that produces energy in stars larger than the sun. It converts four protons into a helium-4 nucleus using a cycle of carbon, nitrogen and oxygen isotopes as catalysts and releases 26.7 MeV of energy mostly...
  20. NikolaTesla2

    B Doubts in Calculating Nuclear Reactions

    I am not talking about the reactions of simple atoms in chemistry, I am speaking, for example deuterium, heavy water, isotopes of hydrogen, oxygen, carbon, etc.I would like to know how to calculate when two atoms merge, to know mathematically what atom will form, example deuterium + deuterium =...
  21. T

    B Neutron star collisions

    When neutron stars collide, heavy elements, such as gold, are created. Are these elements ejected from the system to be found, say, here on earth? Or do they fall back into the newly created black hole?
  22. T

    B Why don't high mass stars expand and cool?

    When a high mass star starts to fuse heavier elements, the core heats up the outer layers enough to for them to begin fusion of their own. My question is: because the star hasn't gained any mass, but it has increased in temperature a lot, why doesn't the star expand and cool like a red giant...
  23. Ryan Doucette

    Nuclear Fusion: Electron Thermal Transport Terminology

    I am an undergrad physics major in my final semester currently taking Intro to Thermodynamics. As a final project, each student must choose a topic related to thermodynamics that is more advanced than what is covered in the curriculum and write a paper and present our findings to the class on...
  24. Sebastiaan

    A How to calculate the energy of Gamma rays in fusion

    Lets say you have your basic fusion reaction D + H → He3 + γ + 5.49 MeV Now exactly how much of the energy is carried away by the gamma ray and how much by the Alfa particle ?
  25. L

    Engineering Career advice to become a Fusion Engineer

    Hello, I am posting to get some career advice about pursuing a career in fusion physics/engineering. With the construction of ITER in France and all the worldwide research into fusion as an energy source, I am extremely interested in the field and I want to help develop fusion technology. I am...
  26. V

    B Schrödinger Equation for the fusion of Deuterium(2H) and a Proton(H)

    In fact I am not sure if this is the right place to ask such a question but I'm going to ask anyways, just tell me if I am in the wrong place. So I doing a little experiment with the Schröndinger's equation, but the problem is I can't find a certain function. You all know the Schrödingers...
  27. R

    Is the Hohlraum the Key to Fusion Energy?

    The Threshold to Fusion Energy I'd like to start some conversation on Hohlraum design, particularly on the opportunity to construct a fullerene capsule as the ignition chamber for indirect-drive fusion. Given more than two decades of evolution in hohlraum configuration* there are many...
  28. chandrahas

    Lockheed's compact fusion reactor question

    Magnetic mirrors were thought to be a viable solution for fusion power. But then, we found out that most of the plasma would simply escape. Is this right? So, then we realized that this method might not work. So after many years, Lockheed has come up with a similar model. Lockheeds model is...
  29. chandrahas

    How do tokamaks extract helium from the fusion plasma?

    If tokamaks were to be run continuously, somehow, then fusion would produce a lot of helium. But since the charge to mass ratio of helium is exactly the same as deuterium, both of them behave almost exactly he same in electric or magnetic fields. And tritium on the other hand has a lower charge...
  30. E

    The difference between the first wall and plasma-facing

    I have read an article talking about material research in fusion. One part in the context is divided into three aspects about the material capable of using in a fusion power reactor. Material selection in the first wall and plasma-facing components are two of the aspects. But it does not mention...
  31. rebc

    Tokamaks and plasma confinement

    I have the fundamental understanding of how tokamaks work. Now, why is it not ideal to confine plasmas using a z- or theta- pinch configurations?
  32. chandrahas

    A What is wrong with particle acceleration based fusion?

    Recently, I was thinking about fusion and this thought struck my mind. In tokamaks, the plasma is heated to extremely high temperatures in order to supply enough energy to the ions for them to fuse. But since, the plasma follows a Boltzmann maxwell distribution curve,only a few ions have have...
  33. chandrahas

    I How large is the collision cross section compared to nuclear fusion cross section

    Most Fusion reactors, and the leading ones like JET, use high temp. plasma and confine it. So, the plasma would approximate the Maxwell- Boltzmann distribution. This means that only a small portion of the plasma has enough energy to fuse. But, collisions are much more often, right? Since not all...
  34. Klupa

    Fission/fusion vs radiation

    Why does fission/fusion occur instead of alpha/beta/gamma radiation?
  35. Brunolem33

    B Formation of stars

    Recently watching a documentary about stars (how the universe works), I was wondering about two things. The first one is: how is it possible to have stars with such a wide range of sizes? As far as I understand, stars are created in swirling gas clouds, nebulae. When the accumulation of gas...
  36. dykuma

    Why are stars "hot"?

    Homework Statement Why are stars hot? Homework Equations Non specifically, it's a conceptual question. The Attempt at a Solution I have always heard that stars are hot because (as a quick very basic example) stars are large collections of mass which collapse in on itself. Eventually the...
  37. V

    A Is Positron-Catalyzed Fusion Possible?

    I was wondering if fusion based on positron-electron annihilation would be possible; my intuition tells me it is, but I'm not completely sure and wanted to consult this community. Essentially, I was wondering if a stream of positrons (ignoring the source and difficulty of production for a...
  38. J

    A Role for Fusion? (to eliminate nuclear waste)

    I know fusion power is not economical but can a fusion reactor be used to eliminate nuclear waste (from old fission reactors)? Regards, JDM
  39. M

    Magnetic Mirror

    Hello! I hope that i am doing this right. This is my first post of a question. So, I've been reading about a design for a fusion reactor called a "Polywell". The Polywell, as I understand it, works by sending electron beams to the device's center which suck in protons/deuterium/tritium/etc. so...
  40. Tiny Rick

    I Nuclear Laser?

    I've been thinking... Is there any way that there could be sort of a one-time use pulse laser that uses something like a mini atomic bomb to create a super high energy laser? I found stuff about a Nuclear pumped laser and "Project Excalibur", but I wanted to ask actual people who know a lot...
  41. G

    I Pressures required for nuclear fusion

    I know that to achieve fusion one has to satisfy the Lawson criterion. My question is: can fusion be achieved only by generating very high pressures but keeping the system at room temperature, or does it necessarily require a combination of both high pressures and high temperatures? If by some...
  42. L

    Binding energy and favorable reactions

    [Moderator note: Thread moved from technical section, thus no template is shown] Hi everyone! I'm currently learning nuclear physics and I have a question: Watching the binding energy per nucleon curve, is the following reaction energetically favorable? 2H + 4He -> 6Li And why? Thanks!
  43. Z

    What is the forefront of research in energy?

    Essentially, I'm wondering (knowing virtually nothing at present), what is at the front of modern research in the realm of energy. Whether this be renewable energy, or simply more efficient ways of using energy (e.g. fuel cells?). I assume nuclear fusion will be mentioned too, so what obstacles...
  44. Toreno

    I Is nuclear fusion induced by gamma photons possible?

    Hi folks, IMO, it should be possible to initiate a nuclear fusion of H1-H2 and H2-H2 in crystals of Lithium Hydride induced by gamma photons emitted form decay of Na24. Could anyone please verify if the following is correct? By using nuclear photodisintegration effect, we need a gamma photon...
  45. Theoden

    What are we striving towards with fusion reactors?

    Hi, I have heard that fusion can generate power and potentially make breeder reactors obsolete; but to even bring atoms close enough to fuse, wouldn't take a significant amount of energy in the first place? I feel like we are allotting high voltage toward fusion and getting a lesser...
  46. N

    I Determining Ion Speed in a Farnsworth Fusion Ion Collider

    I'm looking to figure out how fast ions are traveling in the fusor I have access to. The chamber is roughly 12-14" long, with a central electrode charged to 75 kV and 5 mA. Is the type of ion relevant? What would I have to do to figure out how fast the ions are moving?
  47. N

    I Methods to Prove Existence of Tritium in Fusor Exhaust

    I'm looking into a science fair project involving proving the existence of tritium in the exhaust of a Farnsworth fusor, and was wondering what the ideal method to prove it is. I've thought of three so far. The first is ionizing the gas and analyzing the spectra. The second is placing an alpha...
  48. T

    Should I choose Network Science or Plasma Physics?

    Thank you for opening my first thread. I have just began studying Physics at a university in Hungary and would like to get some information about Network Science and Plasma Phyics/Nuclear Fusion. I am looking for a branche in Physics in which I can do research in the coming years and get a job...
  49. Plok

    Is the sun positively charged?

    Hydrogen fusion as described by proton-proton chain reaction that dominates in the sun produces two positrons for each helium nucleus produced. These annihilate with free electrons while the number of protons remain the same. Over time the sun is supposed to become positively charged, yet the...
  50. A

    Is it possible to fuse more than two atoms at once?

    I'm writing a paper for my teacher, not an assignment, just because I was interested in the topic. I've searched a lot of websites, but most only talk about fusing two atoms, and not saying if it is possible to fuse more than two at the same time.