- #1
Tian En
Homework Statement
The decay path of Na 22 and Strontium 90
Experimental Setup
The beta particle electron from strontium 90 and positron from sodium 22 physical measurement is as shown.
Experimental Result (verified)
Strontium beta particle(electron) Count Rate vs Energy(rest energy inclusive)
Theoretical Plot for beta particle with Maximum Energy 3m_ec^2 and 10m_ec^2 (rest Energy Inclusive with no fermi function) $$\Gamma \propto \sqrt{E_e^2 - m_ec^2} (Q-E_e)^2 E_e$$
From the theoretical plot, we can see that the decay rate goes to 0 upon reaching maximum energy.
However, experimentally, result speaks something different from theory. The maximum energy for Strontium 90 and daughter particle Y extends from 2.274MeV to $$188m_ec^2 => 366.6MeV$$ but decay rate still tends towards 0. The decay rate for Sodium 22 never seems to tend towards 0. Any idea to reconcile the theory and the verified experimental result?
Homework Equations
The Attempt at a Solution
I check at the manufacturer's website about the non zeroing phenomenon for sodium. It is about the annihilation occurring between the electron and positron. How does this electron positron annihilation thing contribute to count rate at higher energy (not a direct measurement of energy but by varying the magnetic field strength to select the beta particle with desired total energy)? Also, how is the annihilation is just 0.511MeV (there are 2 beam of gamma ray of 0.511MeV) which is the rest energy of an electron when the electron and positron are accelerated towards each other during and pick up extra kinetic energy and also partly due to the initial kinetic energy that it possesses from the decay? http://repository.phywe.de/files/versuchsanleitungen/p2523200/e/p2523200.pdf
Also, I know that the GM counter cannot differentiate the types of radioactive particle. I also know that the result is continuous due to the presence of neutrino and the decay energy that it share with the beta particle.