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| AySz88 2002-08-19 13:44:58 | I suggest having: A maximum [EDIT] and minimum [/EDIT] X-. Y-, and Z-axis bound for particles, to get rid of those particles that fly off into space at the chicane. Something to get rid of the low-energy particles rotating around in the first solinoids of the acclerator; maybe stopping particles having a negative Z velocity when the particle is less than a certain Z coordinate (so as to not confuse it with the bending chicane), or a less than a certain Z coordinate after a certain time in the simulation (a bit more dangerous; could stop "good" particles). BTW, do we need to count the higher- and lower-energy particles in the percentage if all we want is the ones between 120 and 270 MeV? Now that I think of it, do we need to simulate them at all? They bring down the percentages a lot and makes it seem that the percentage of the muons that we're looking for getting through is lower than it is. ----------------- [This message was edited by AySz88 on 2002-Aug-19 at 23:05.] [This message was edited by AySz88 on 2002-Aug-19 at 23:08.] |
| David Bass 2002-08-19 17:31:38 | From the technical report Stephen produced in June: "The decay of the pions into muons adds another unusual element to the system, as the other decay products are emitted at high speed and make significant changes to the original particle's mass and velocity. The pion half-life corresponds to 7.8 light-metres, so the decays happen on the same timescale as it takes the particles to travel through the first few magnets. This is another effect that would make simulation with a traditional tracking code potentially inaccurate." If I understand correctly, this means that all pions must be simulated throughout the entire simulation, because the resulting muon might move into the energy band required. I can't imagine what could affect the muons with energies outside the correct range, so perhaps it would be appropriate to cull those. Generally speaking, whilst looking at the graphical client I have noticed that a few (occasionally 10-20) particles escape the existing traps - lowish energy muons appear to be able to "wrap round" near the chicane entry, for example. Note that 10-20 particles is minuscule compared to the 1000+ for a high percentage run, and additional culling code to eliminate them may make the simulation even slower. It might be appropriate to increase the size of one or more of the existing walls - that shouldn't affect the calculation time too much. Another effect I see is a rough sorting of muons and pions - pions will, by virtue of their higher rest mass, be travelling more slowly than equal energy muons. This can be seen as two bunches of particles passing through the chicane (can be easier to see if you use the function keys to switch each type off in turn). By the time the first muons reach the chicane, about one eigth of the particles remaining should still be pions. As they continue to decay, they will create a spread-out "tail" to the pulse. Of course, I could be talking complete rubbish, I am not a physicist. |
| AySz88 2002-08-20 14:54:52 | The background version might not need the bounds, but for the graphics one with autoview on it's very annoying when I'm showing the power of distributed computing to family and stuff   .I don't think the energy reported in the program decreases when a pion decays into a muon. I would think it would increase, if anything, because it's decaying and putting out energy. Stephan would need to tell us that. Still, for the particles that would have to way of falling into the range, via decaying, etc., Stephan might be able to take them out of the program. (BTW, as I had mentioned to Stephan a long time ago, we could also remove the ones that re-impact. We MIGHT be able to remove the ones that go the wrong way consistantly, but I don't know if the path of any or all of those particles would change if some parameters of the simulation changed.) |
| Stephen Brooks 2002-08-21 01:43:20 | quote: It does. The pion emits a muon and several other things. Since energy is conserved, the muon must have less energy than the pion. quote: The simulation does remove particles that re-impact. quote: It also does that - the particles are removed when they either hit the rod again, or hit a plane "behind" the rod from where they are considered to be going backwards and uncapturable. "As every 11-year-old kid knows, if you concentrate enough Van-der-Graff generators and expensive special effects in one place, you create a spiral space-time whirly thing, AND an interesting plotline" |
| AySz88 2002-08-21 09:34:20 | I meant from the simulation completely, to reduce download size, etc. |
