Al (p,n) Si

Background

The shorthand for this experiment indicates the basics of the process that will take place:

²⁷Al (p,n) ²⁷Si

In other words, protons(p) of sufficient energy incident on an ²⁷Al target will be absorbed by the atom and knock off a neutron(n) to generate ²⁷Si, where in both cases 27 indicates the atomic mass. However, this will only happen if the protons have sufficient energy. In this experiment, you will measure the neutron threshold, or the energy incident protons must be accelerated to in order achieve nuclear fusion.

Accelerator Operation

In order to acquire sufficiently energetic protons for this experiment, you will have to learn to create and direct a proton ion beam in the tandem accelerator. There are a number of components to the accelerator, which you will need to know the function of and how they will affect the nature of the proton beam.

Components

• The Ion Source: Negative H^- are created here and accelerated at relatively low energies.
• The Tandem Accelerator: Negative H^- ions are accelerated to the center of the tandem, stripped of the electrons to create protons, and then accelerated through the rest of the tandem to a high energy.
• The Target Room: The high energy proton beam is directed onto an aluminum foil target, hopefully creating a nuclear fusion reaction.

In addition to these main sections of the accelerator, you will need to be able to use the ion optics in the accelerator effectively to steer and focus the beam.

Technique

To find the neutron threshold, you will have to do the experiment with protons of various different energies, both below and above the threshold.