2. • Are simple ,easy to use detectors of radiation and
have been sued by the unclear industry for many
years.Introduced in 1928 by Geiger and Mueller but
still find application today .
• It is the sensing element of the Geiger
counter instrument used for the detection
of ionizing radiation.
• It is to measure al types of radiation:
ALPHA
BETA
GAMMA
3.
4.
5. What are the walls usually
made out off?
• A metal or it has it is inside surface coated
with a conducting medium to form the
cathode while a thin anode passes through
the center of the tube.
6. The radiation enters throught a very thin
window at one end of the tube this
window is usually made of micra .
Micra is a mineral that forms in layers
cailed sheets.
7. What is a side
window for?
The detection general radiation
8.
9. PROCEDURE
1. Put a radioactive source in a holder. Fix this in a clamp
on a retort stand.
2. Put the Geiger-Müller tube in a stand. Adjust it so that
it is pointing at the source, and is about 5 cm away
from it.
3. Plug the Geiger-Müller tube into the scaler (counter)
and switch on.
10. 4- Start the voltage at about 200 volts. Make a note of
the number of counts in, say, a 15 second interval.
5- Increase the voltage in steps of 25 volts.
6-You will find that the counts vary with voltage and
then reach a plateau. A graph would look like this (you
do not need to plot the graph):
11. 7- After the threshold voltage, the count will reach
a plateau. It will stay constant over a range of
voltages. Set the voltage at a value of between 50
to 100 V above the threshold.
8- If the clicking increases when you increase the
voltage, then you have moved off the plateau. Turn
the voltage back down.
9- Put the source back in a safe place until you
carry out the demonstration.
12. Carrying out the demonstration?
1. 1- Switch on the Geiger-Müller tube counting system.
2. Highlight the fact that there is a background count.
3. Bring a radioactive source up to the Geiger-Müller tube and draw attention
to the increase in counts.
4. . You could measure the background count and the count with the source
nearby. Do this over a period of 30 seconds. Draw attention to the
difference.
