PHYS 2126 Alpha Spectroscopy 5

ASSIGNMENT

1 Plot channel no. vs distance, x, (i.e. micrometer reading). Taking d0 into consideration, what is the range in air of alpha particles emitted by 241Am?

Figure 1. Plot of distance vs. channel no. the do which is 9mm+/-1mm had been taken into account. And from the graph it was identified that the range in the air of the alpha particle is approximately 41.61 which is the y-intercept of the general equation.

2 Plot channel no. vs corrected distance, d (taking into account your d0 estimate)

By curve fitting, (A polynomial fit may be required choose the polynomial degree

sensibly!) determine an energy calibration for your system. (i.e. convert channel no. to Energy) using the known energy of the alphas at d=0, and E=0 when d=range. Plot E vs d.

Figure 2: the distance had been corrected with do of 9.75mm+/-1mm , as the trenline was deployed and extrapolated to the y-intercept, we could predict that the the channel number at where the distace (x) is equal to zero is 2197.8kev

3. Plot resolutions versus distance for air. Note that the peak resolution gets worse as the distance travelled through air, and the E values increase. Why does the peak resolution change?

Figure 2. The peak resolution is changing since Alpha particles are monoergic that is they have only one certain amount of energy when they leave the nucleus. However, they interact with anything they come in contact with and thus their energy is always spread out slightly over a small range that is less than the maximum value that the alpha particle energy is emitted. From the graph, it was observed that the resolution increase parabolaly with the increase of the distance. And the energy spread out slightly as it travelled, so the shape of the peak will be flatter, and the resolution is given by the difference between the two extreme values of the independent variable at which the dependent variable is equal to half of its maximum value. So the resolution increased respectively. However as it kept on travelling, the resolution decreases due to the loss of energy.4 Plot intensity (total number of counts under peak) versus distance for air. Comment on the relationship between Intensity and distance.

Figure 3.

From the figure above, the detected intensity which is the number of counts of the alpha particles remain at a certain amount in the travelled distance of 0mm up to 42 mm, however as it exceed 42 mm which has been identified as the range of the alpha particle, the intensity decrease dramatically. Unlike the energy of the alpha particle, the loss of intensity is tiny during the travelling. Since every single alpha particle have the equal amount of energy to travel in certain distance. So the range of the alpha particle is actually the distance where the energy of the alpha particle depletes. 6.Stopping power: the average energy loss of the particle per unit path length, the stopping power depends on the type and energy of the particle and on the properties of the material it passes. Since the production of an ion pair requires a fixed amount of energy.CSDA range : an approximation to the average path length travelled by a charged particle as it slows down to rest, it is calculated in the continuous-slowing-down approximation. In this approximation, the rate of energy loss at every point along the track is assumed to be the same as the total stopping power.

Figure 4 : This is the CSDA range graph of the alpha particle.

Figure 5 : The projected range of alphas is clos to the what I expected. Since the energy of the the alphas particle is actually the kinetic energy. The alpha particle will slow down gradually due to the loss of energy and eventually come to the stop.