Radioactivity experiment

Characteristic of α and β particles

Objective :

Observe some of the nature of radiation α and β radioactive disintegration.

Review of theory :

Alpha(α) particles.
Alpha particles (α) is the helium particles that have a positive load is the same as the charge two-electron. Particles is radiated from the radioactive nucleus has one or more of the specific energy.
β particles.
Beta(β) is the electron. Unlike α particles, β particles emanated continuously from zero to reach the maximum energy depends on the nature of the core shed.
Absorption of α and β radiation

When the α and β particles through a material, they will lose their energy mainly through the ionization process with the materials. Energy β particles can be lost in the form of a beam wave in electromagnetic that generate the events in "Bremstrahlung" and the production of x-rays, when the electrons in the skin of the subject absorption material. While α particles have a particularity that has a short distance. For example, α particles in the air is able to spread only a few centimeters are absorbed and discharged by a material (such as cigarette paper). β particles (0.6 MeV) is able to penetrate thin aluminum plate which has thickness 0.5 mm.
Equipment is required

Geiger tube counter.
Pulse count and the power balance (with timer).
Buffer and clamp.
Aluminiums plate (some with a different thickness) and a few pieces of cigarette paper.
Radioactive source: α and beta.
Short-term or sliding micrometer.
Permanent magnet "horseshoe beam" (strong power)

Procedure

Absorption of beta radiation.
Place Geiger tube vertically with the head down.
Putting radioactive source material is far enough from the Geiger tube and Count for some time in the interval of 100 seconds, this is done to see the background radiation. When the count is made of 10 seconds, then cut count of background radiation must be repeated again
Measure the thickness of several different aluminum plates.
Place the appropriate source of β radiation in the Geiger tube down on the distance of a few millimeter (Arrange with the appropriate position)
Arrange for the count over time at 100 seconds (such as count background radiation) and also set the voltage at the maximum value. If the count is too high(goes off scale), the time interval Arrange in 10 seconds. (if this is the case, then step 2 should be repeated at 10 seconds in the count)
Take the counting data for 10 times or more.
Specify the average and uncertainty of count for the each count data is ±√n
Place the thinnest aluminum plates just above on the radiation source and take the count data for the interval of 100 seconds.
Do the same as step 8, for plates of different thickness.
Graphs plot the relationship between the number of count material thickness vs absorber material (use semi-log paper if available). (note: you complete the chart with "the uncertainty")
Absorption of β particles to follow a function exponentially.
I=I_0∙e^(-μx)
Use the chart on step10, to determine the absorption coefficient µ, for beta particles in aluminum.

Absorption of Alpha (α )radiation.
Repeat the entire (full) step experiment on the absorption of radiation, such as Beta.
NOTES :
Alpha(α ) particles is very easy to be merged.
Place the sheet of paper cigarettes, and 2 sheets, 3 sheets ,...... and so on.
Plot a graph of the relationship between digital vs. the number of cigarette paper that you use as material α absorber .
Counting results may be smaller than for the absorption of beta particles.
Plot must be accompanied by "the uncertainty line"
Absorption of radiation is not exponentially.

Magnetic Diversion beta particles.
Place the source of beta radiation in the magnets (horseshoe beam).
Seize Geiger tube with a horizontal brace.

Put digital data over time to 10 seconds.
repeat for the interval of 100 seconds when the interval of 10 seconds to give the number 400
Rotate the bar magnet, is such that their magnetic field opposite direction in the previous experiment (1until3 above).
position of radiation source and Geiger tube should be fixed.
To take the digital data of 10 seconds (see step 3).
Specify (from differences in amount) to the direction which the deflection of the particles trajectory and direction of magnetic fields.
NOTE : Direction of magnetic fields shown in the bar magnet.
With the help of the relationship between the style of movement that resulted in beta and capacious, check that the marks on the charge negative β particles is negative.

Reference :
Beiser, A : 12.1- 12.4- 12.6 - 12.8 , 13.4