# Difference between revisions of "Solutions 5"

1:

1. Thermal neutrons have a kinetic energy of about 0.025eV
2. Fast neutrons are “braked” with elastic collisions with particles with the same size as the neutrons. A moderator also needs to have a low cross-section for absorbing neutrons.
3. A moderator is a material that brakes the neutrons, for instance H2O, D2O, C, Be. A neutron absorbent catches the neutrons and reacts with the neutron. Good absorbants are borium and gadolinium.
4. From the nuclide carte we can see that 3He has a high cross-section for the n,p-reaction.
5. The reaction 3He+n arrow 3H++1H(+2e-). The charged particles from the reaction creates more ionisations when they travel towards the anode and the cathode, this gives a electric signal.
6. The Q-value from the reaction is 764 keV, the reaction is exothermic.
7. 3H+ and 1H+ is created.
8. The two products in the reaction recives opposing recoils 180 degrees. Conversion of momentum m1v1=m2v2 gives:

2:

1. Q-Value_ 2.224MeV
2.  And 3. The energy of the deuterium is not calculated relativistic but the γ-ray is completely relativistic, we then get: