09-02-2013, 10:39 AM
Absorption of Gamma Radiation by Lead
[attachment=50292]
Aim ●
To determine the relation between thickness of the absorbing material and intensity of the transmitted γ radiation.
● To measure the half-value thickness of lead for the γ radiation emitted by a source of cobalt-60.
Set-up
The set-up consists of a scintillation detector, a pulse counter and a source of cobalt-60 (60 Co). The counter can be set to an automatic measuring time of 10 s or to ‘continuous’. In the latter case, after starting the counter will continue counting until the stop button is pressed. For measuring time, then use a stopwatch.
Sheets of lead of different thickness can be inserted in the equipment set-up between the detector and the source. The thickness of the absorbing lead can be varied further by combining sheets of different thickness.
Instructions
● Plot your measurements in a graph. > From this graph, determine the half-value thickness d1/2 of lead for the γ radiation of 60Co. ● Information about an accurate way of determining the half-value thickness from a graph on single logarithmic graph paper can be found on page 31-32 in the booklet ISP Experiments. > Compare the accuracy of determining the half-value thickness d1/2 of lead from your measurements when using a graph on normal, linear graph paper and on single logarithmic graph paper. ● The half-value thickness of lead as found in this experiment can be used to calculate the half-value thickness of other materials. The half-value thickness d1/2 appears to be inversely proportional to the density ρ of the absorbing material. This means: a material with a twice as large density has a twice as small half-value thickness. > Calculate the half-value thickness of aluminium and of water with the help of the half-value thickness of lead as found in this experiment.
[attachment=50292]
Aim ●
To determine the relation between thickness of the absorbing material and intensity of the transmitted γ radiation.
● To measure the half-value thickness of lead for the γ radiation emitted by a source of cobalt-60.
Set-up
The set-up consists of a scintillation detector, a pulse counter and a source of cobalt-60 (60 Co). The counter can be set to an automatic measuring time of 10 s or to ‘continuous’. In the latter case, after starting the counter will continue counting until the stop button is pressed. For measuring time, then use a stopwatch.
Sheets of lead of different thickness can be inserted in the equipment set-up between the detector and the source. The thickness of the absorbing lead can be varied further by combining sheets of different thickness.
Instructions
● Plot your measurements in a graph. > From this graph, determine the half-value thickness d1/2 of lead for the γ radiation of 60Co. ● Information about an accurate way of determining the half-value thickness from a graph on single logarithmic graph paper can be found on page 31-32 in the booklet ISP Experiments. > Compare the accuracy of determining the half-value thickness d1/2 of lead from your measurements when using a graph on normal, linear graph paper and on single logarithmic graph paper. ● The half-value thickness of lead as found in this experiment can be used to calculate the half-value thickness of other materials. The half-value thickness d1/2 appears to be inversely proportional to the density ρ of the absorbing material. This means: a material with a twice as large density has a twice as small half-value thickness. > Calculate the half-value thickness of aluminium and of water with the help of the half-value thickness of lead as found in this experiment.