An improvement to the global software standard for analyzing fusion plasmas

The gold standard for analyzing the behavior of fusion plasmas may have just gotten better. Mario Podestà, a staff physicist at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL), has updated the worldwide computer program known as TRANSP to better simulate the interaction between energetic particles and instabilities - disturbances in plasma that can halt fusion reactions. The program's updates, reported this week in the journal Nuclear Fusion, could lead to improved capability for predicting the effects of some types of instabilities in future facilities such as ITER, the international experiment under construction in France to demonstrate the feasibility of fusion power.

Podestà and co-authors saw a need for better modeling techniques when they noticed that while TRANSP could accurately simulate an entire plasma discharge, the code wasn't able to represent properly the interaction between and instabilities. The reason was that TRANSP, which PPPL developed and has regularly updated, treated all fast-moving particles within the plasma the same way. Those instabilities, however, can affect different parts of the plasma in different ways through so-called "resonant processes."

The authors first figured out how to condense information from other codes that do model the interaction accurately - albeit over short time periods - so that TRANSP could incorporate that information into its simulations. Podestà then teamed up with TRANSP developer Marina Gorelenkova at PPPL to update a TRANSP module called NUBEAM to enable it to make sense of this condensed data. "Once validated, the updated module will provide a better and more accurate way to compute the transport of energetic particles," said Podestà. "Having a more accurate description of the particle interactions with instabilities can improve the fidelity of the program's simulations."

Fast-moving particles, which result from neutral beam injection into tokamak plasmas, cause the instabilities that the updated code models. These particles begin their lives with a neutral charge but turn into negatively charged electrons and positively charged ions - or atomic nuclei - inside the plasma. This scheme is used to heat the plasma and to drive part of the electric current that completes the magnetic field confining the plasma.

The improved simulation tool may have applications for ITER, which will use fusion end-products called alpha particles to sustain high temperatures. But just like the neutral beam particles in current-day-tokamaks, alpha could cause instabilities that degrade the yield of fusion reactions. "In present research devices, only very few, if any, are generated," said Podestà. "So we have to study and understand the effects of energetic ions from neutral beam injectors as a proxy for what will happen in future reactors."

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Citation: An improvement to the global software standard for analyzing fusion plasmas (2015, April 24) retrieved 22 September 2019 from
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Apr 24, 2015
Nice piece of software engineering.

Apr 26, 2015
Finally, the energy of a confined proton-electron, i.e. neutron, and the field, with density of (mp+me)/vol ant time and possible reactions for modal states within the plasma not using GR?

Apr 26, 2015
confined proton-electron, i.e. neutron
Wrong. The fact that a down can decay into an up by releasing a W-, which then decays into an electron and an electron anti-neutrino, or other paths with muons and tauons and their associated anti-neutrinos, does not show that there is an electron "in" a neutron; in fact, the fact that the muon and tauon decay paths for the W- exist shows there cannot be.

not using GR
Wrong. It has nothing to do with GRT. This is a purely quantum interaction, and GRT is specifically excluded from the SM because there is no quantum gravity theory.

Apr 26, 2015
For those not familiar with these interactions, a couple points:

"Down" and "up" are quarks; a neutron is comprised of two downs and an up, a proton of two ups and a down. The down is heavier than the up, so there is a decay path for the down, but not the up; and the half-life of a free neutron is on the order of 16 seconds, due to the existence of this decay path.

The decay of a neutron into a proton producing a muon and a muon anti-neutrino has been observed, though it is very, very rare; AFAIK the tauon/tauon antineutrino decay has not been observed, but this could have happened in the last few years and I might have missed it.

Finally, the SM is the Standard Model of Particle Physics; it is explicitly SRT compliant, and explicitly excludes GRT due to the lack of a quantum gravity theory. Because gravity is so weak, it is very difficult (in fact, so far impossible) to observe its effects in high energy particle physics.

Apr 27, 2015
16 seconds? neutron decay?

No wonder nuclear bombs are so expensive......

Apr 27, 2015
The instability of neutrons is moderated when they are included in a nucleus. In many nuclei they are totally stabilized because by gluon exchange they flash back and forth between neutron and proton so quickly the neutrons have no chance to decay. In large nuclei, and nuclei that are heavily imbalanced between protons and neutrons, however, there is a greater chance of decay, and these are radioactive nuclei, and form radioactive isotopes.

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