POWDERTOY STANDARD MODEL OF PARTICLE PHYSICS
This is intended as a model for the physical interactions and mechanics at the subatomic  level in powdertoy. It is tentative and completely open so please feel free to contribute, edit, copy, completely rewrite or anything else. It's goal is a mathematical model based on experiments. That way, we can figure out how things work precisely and where to suggest thing so we can one day, hopefully, be able to make any (normal, earthly) element by mixing the right building blocks in the right conditions.

FIELDS
There are two fields in PT, temperature (t) and pressure (p). The pressure is the pressure of the 'air' and ever present. It always tends to fall back to zero; wether positive or negative it is impossible to maintain a perfect vacuum. Temperature uses the air as it's carrier, it is not created in it but in particles that then transfer it to the air and vice-versa.

SUBATOMIC PARTICLES
All subatomic particles are subject to decay.
Q: How long is the decay time?
Q: Is the decay time the same for all particles?
Q: Is the decay time affected by something?

Photon ("γ", Boson)
Energy emission quanta
Subject to wavelength and temperature change
Propreties well documented
Travels only in 8 directions
No electric charge

Neutron ("n", Hadron)
Nuclear force emission quanta
Creates pressure
Unidirectional
No electric charge

Electron ("e", Lepton)
Electrical force quanta
Unidirectional
Electrically Charge

ATOMIC PARTICLES
Hydrogen (h)
Gas
Undergoes Step 1 Fusion
Formed from one electron and one neutron
The nuclear fusion of hydrogen is the first event in the nuclear chain. It's fusion is the basic model for the following steps until the singularity.

Combustible

Noble gas
Formed from Step 1 Fusion
Undergoes Step 2 Fusion
Transitions to Plasma on electrical charge, pressure and heat emission

Carbon Dioxide (co2)
Formed from Step 2 Fusion
Undergoes Step 3 Fusion

Oxygen (o2)

Formed from Step 3 Fusion

Undergoes Step 4 Fusion

Combustible

It's fusion is very interesting. It requires a strong gravity field, may create black holes and creates broken metal; the first solid matter to come from fusion. This then explains the provenance of metal in the PT universe, the core of stars.

FUSION MODEL
The Fusion model is written with statistical average experiments. An atomic particle must be subjected to both heat and pressure energy above the thresholds for the fusion to take place; this is a clear barrier. The fusion process is characterized by a production of pressure energy, energy release heated particles and finally the heavier particle. There are 4 steps of fusion; from the three kinds of fuel; hydrogen, noble gas, co2 and oxygen.

Electron-Neutron capture can occur instantaneously after the fusion, giving the impression that the reaction has produced hydrogen. This is a major contributing factor in a self-sustaining reaction, providing the pressure and temperature are maintained and singularities avoided.

FUSION STEPS
(Fuel) -(Fusion)-> (Byproducts)
Step 1: (h -> n + γ + e + Plasma + noble + p)
Step 2: (noble -> n + γ + e + Plasma + co2 + p)
Step 3: (co2 ->  n + γ + e + Plasma + o2 + p)

Step 4: (o2 -> n + γ + e + Plasma + BRMT +? Black Hole)*

ENERGY "THRESHOLDS"
Particle-Temperature-Pressure
h = t(2000), p(50)
noble = t(5000), p(100)
co2 = t(9500), p(200)

o2 = t(9700), p(250)*

*: Step 4/O2 Fusion is a special case and requires a total |x| and |y| gravity field of greater than 20 units.

A WORD ON SINGULARITIES

They have been, thank god, excluded from the fusion process but i will keep the information here because it is extremely interesting as it is in itself a miniature big-bang! This is often forgotten but at very high power they create amazing amounts of energy like a miniature supernova.

Singularity ("ψ" (pronounced "psi"))
Collapsed State of matter. Very little is known about it's creation and itself; but it creates a constant vacuum around it and absorbs everything around it. It will eventually decay by singularity collapse, unable to support itself. Singularity collapse releases a significant amount of energy by the way of a large number of electrons and neutrons; presumably those from the matter it ingested. It has been subject of enough research to warrant itself a chapter.

SINGULARITY COLLAPSE
Here i'll describe in length what goes on when a singularity explodes

Singularity collapses can release a gigantic amount of energy; easily starting new chain reactions. Experiments with exploding lone singularities (at tmp=1024) reveal an incredible amount of energy being released; overflowing the 256p pressure limit to 1024 and producing an average of 2560 particles in a single frame, a massive electron-neutron-photon cloud with an average temperature of 4725 degrees. This is T0; the moment the singularity collapses on itself and releases all the energy it has accumulated.

At the next frame; gas particles created at t0 are ejected at extremely high speeds (they are only visible for one frame) and the core of the particle cloud explodes in a burst of interactions; 78% of the particles are consumed in approximately 1,000 absorbptions. This hydrogen instantly undergoes fusion and begins a chain-reaction of fusion reactions within the center of the high-pressure area. A large proportion of the gas escapes before undergoing fusion, as well as the fusion byproducts. The shockwave expands, cools down, pressure drops.

The core then undergoes a massive production of particles. It shoots off photons in the 8 directions; but in the center a small pack of very slow photons linger on longer than the rest. Spectrometric analysis (ask me for it; one of my saves) of some of them reveal the spectrum of noble gas. Here is the strongest production of gasses, shooting out faster than light.

If the Fusion reaction is contained into an airtight container capable of withstanding the heat and pressure; the fusion reaction becomes self-sustaining. In a non-contained SC; there may be, at most, a handful of co2 particles produced by high pressure and temperature hotspots. In the contained reaction, a significant amount of Co2 will be produced and will form distinctive "clouds" of co2. As the fusion of co2 create singularities; the singularity production and absorbtion process will begin again. The vacuum created by the singularities generally prevents another chain-reaction from taking place. The final number of remaining particles and gasses in equilibrium will be approximately 17% of the particle number at t0.

A much larger explosion, with many, many simutaneously exploding singularities, will excacerbate the power of the reaction to the point of a miniature big-bang. The photonic emission is much more pronounced and after many frustrations, their spectrum was sucessfully analyzed. A large majority of them have a spectrum resembling, but a fraction wider, than that of Uranium, a small portion of them have a spectrum similar to that of Plutonium.

Q: What is the proportion between "stored energy" (tmp) and SC power?

QUESTIONS AND COMMENTS
This is only what i have observed, so everyone is encouraged to make their own experiments and models and to share them.

Thanks! I updated the text with your information; i like the way they are going. I'm thinking up some ideas on what the team could implement. If we implemented the proton we would have to change the model for hydrogen to an electron and a proton; it would be more realistic but "would saves be broken?"

Bumping this to announce i'm porting the guide to wiki while also polishing it
https://powdertoy.co.uk/Wiki/W/Nuclear_Physics.html