Talk:Fusion energy gain factor

message: An anonymous editor has slapped three templates on this article, Expert, expansion, and confusing. It would help to have a little more detail on the problems perceived. I already am an expert on the subject, and I find the presentation clear albeit succinct. I'm not sure where expanding it would make it much clearer. Please help me here. --Art Carlson 10:05, 30 April 2006 (UTC)
thread_title: untitled

message: I don't quite understand the high Q value necessary. Wouldn't a fusion reactor be successful if it could deliver more electricity to the net than what it is consuming?
Let's assume that most of the energy that the reactor needs is used for the heating of the plasma. Let's call the required power Pheat. If this power is taken as electricity from the grid, the amount of electricity needed for heating is Pel_heat = Pheat / ɳheat.
The electricity output would be, according to the article, Pelec = ηelec(1-fch)Pfus.
Now, what is wanted is that the output electricity is larger than the input electricity:
Pelec > Pel_heat
insert the definitions of Pelec and Pel_heat:
ηelec(1-fch)Pfus > Pheat / ɳheat
or
(Q = ) Pfus /  Pheat > 1 / ( ɳheatηelec(1-fch) )  
which is the same expression used in the article save for the recirculation of electricity.
Put in the numbers in the article, and the result is Q > 1 / (0.7*0.4*(1-0.2)) = 4.46 ≈ 5. Won't this mean that a fusion reactor with Q > 5 will deliver more power than it uses? Of course you need to deliver more than that to have some energy to sell, but wouldn't, say, Q=10 be enough? --Maccer83 12:07, 14 May 2006 (UTC)
replies: text: A fusion reactor will be successful if it produces electricity at a cost that is competitive with the alternatives. The Q needed to be successful in this sense will depend on the cost of the fusion plant and the cost of the alternatives. With the assumptions of the article and Q=22, f_recirc is 0.20 and you need to produce 25% more electricity than you plan to sell. With Q=10, f_recirc is 0.44 and you need to produce 78% more electricity than you sell. You're right that this could, in priciple, be OK. If a source of energy is cheap enough, it could tolerate a recirculating power fraction of even, say, 99%. The 20% figure is a soft limit that gives you an idea of when it starts to hurt. It is commonly used in studies, but other assumptions can be made. --Art Carlson 19:24, 14 May 2006 (UTC)
thread_title:  Why isn't Q > 5 enough? 

message: Intro says "...the power required to maintain the plasma in steady state." - Does this include any of the power used in toroidal or poloidal magnets ? I guess it only includes the magnet drive power used to induce ohmic heating ? - Rod57 (talk) 10:27, 9 December 2015 (UTC)
replies: text: It depends on the definition, but generally no, only heating sources are considered. However, it should be noted that on modern designs using superconducting magnets, the confinement system uses little energy anyway (after startup) and even the cooling load on the magnets would be low in relative terms. Maury Markowitz (talk) 11:11, 27 July 2017 (UTC)
thread_title:  Whats included in input power 

message: \eta_heat is used in the article but never defined.
::Fixed. Maury Markowitz (talk) 13:47, 4 October 2018 (UTC)
thread_title:  \eta_heat 

message: The description for the image for this page reads.
"The explosion of the Ivy Mike hydrogen bomb. The hydrogen bomb is the only device currently able to achieve fusion energy gain factor significantly larger than 1."
This is not explained at all in the page and none of the references cover it as far as I can see. Should the caption or the image be changed? Xzpx (talk) 08:28, 3 July 2023 (UTC)
thread_title:  Ivy Mike reference has no source 

message: This article says that the NIF claims to have achieve "scientific breakeven" in 2013 but the sources don't provide any mention that they claimed "scientific breakeven." The NIF's publish research shows a breakeven of the "total fuel energy gain" (the ratio of fusion energy to energy absorbed into D-T fuel) but no mention of "scientific breakeven."  Guthrette (talk) 20:59, 24 July 2023 (UTC)
thread_title:  Did the NIF actually claim "scientific breakeven" in 2013? 

message: Even though the units given for the NIF's experiments are given in joules, the article still states that the Q is based of P instead of E. The article is even titled "Fusion Energy Gain Factor." I feel like we need to rewrite parts of this article to note the difference between Q in MCF(given in power) and ICF(given in energy). 
Guthrette (talk) 18:39, 25 July 2023 (UTC)
thread_title:  Q for ICF is based on energy not power