the heck are recoil fragments

RADboy

i know the key word is "recoil" but, I'm reading a nuclear fission book and it keeps bringing up "fission recoil fragments" "recoil particles" what exactly are these particls? how are they formed? are they different from other ionizing particles other than the fact that they recoil?

A scientist was using thin sheets of aluminum (.57mg/cm thcik) to reflect the particles of neutron bombarded uranium. by measuring the radioactivity in each sheet he obtained a rough absorption curve 2.2+/- .2

Astronuc

Well alpha particles are reflected by foils, so I suspect fission fragments are recoiling from the Al plate. Some will travel into the plate.

Look at Ernest Rutherford's experiments on the scattering of alpha particles at high angles.

RADboy

what's absorption curve? depending on the radioactive element can the particles ionize masses differently? does U-235 ionize mass differently than plutonium?

Astronuc

They could be looking for Linear Energy Transfer rate or distance that a fission product travels in a medium.

The fission fragments of U-236* and Pu-240* (* = composite nucleus after neutron absorption) are about the same. The lower mass population shift upward by Z=1, A=2 somewhat. The complementary pairs are different.

In UO2 or MOX, the fission tracks are about 3-6 microns, while in Al, they should be greater because the Al atom is lighter.

Drakkith

I think the recoil fragments are the pieces of the nucleus left over that recoil away from the emitted neutrons and alpha particles?

RADboy

"The fission fragments of U-236* and Pu-240* (* = composite nucleus after neutron absorption) are about the same. The lower mass population shift upward by Z=1, A=2 somewhat. The complementary pairs are different."


what exactly do you mean by the lower mass populatin shift upward by Z=1, A=2?

Astronuc

When plotting yield vs atomic mass, one see a two hump/peak (bimodal) distribution, because the fissile nucleus splits into two nuclei.

http://hyperphysics.phy-astr.gsu.edu...u235cs.html#c1

http://hyperphysics.phy-astr.gsu.edu...e/u235chn.html

http://hyperphysics.phy-astr.gsu.edu...e/fisfrag.html