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I. Title of Experiment:

The Characteristic of Radioactivity

II. Purpose of Experiment:

1. To learn about how to use the radioactivity detector.

2. To determine the characteristic of voltage of Geiger-Muller tube.

3. To learn about the characteristic of radioactivity ray.

III. Basic Theory:

Radioactivity was first discovered in 1896 by French scientist Henri Becquerel

while working with fosforen material. Such material will glow in the dark after

previous exposure to get light, and he thinks landing produced by cathode-ray tube X

may be associated with fosforesensi. Because of he wraps a photo plate with black

paper and put the various materials fosforen above it. All of them do not show results

until when he used uranium salts. Black spots occur on the photo plate when he used

the uranium salt.

Radioactivity or radioactive decay is the event emission energy in the form of

radioactive rays from the nucleus is unstable to form a stable core. Radioactivity by

definition of Herman Chamber in his book titled Health Physics Introduction is

transformations of core (nuclear) happens spontaneously and cause the formation of

the new elements. Radioactivity or radioactive decay events took place

spontaneously and is usually accompanied by emission of alpha particles (), and

betta particle (). For example, it was found that the electric field or magnetic field

1

Trefoil symbol image is used to indicate a radioactive material

Figure 1


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can be split into three beams of radiation emission. For the sake of ease of naming,

these rays are named according to the Greek alphabet alpha, beta and gamma, these

names still survive today. Then from the direction of electromagnetic force, it is

known that alpha rays contain a positive charge, negatively charged beta rays, and

gamma rays are neutral. From the direction of reflection, is also known that alpha

particle much heavier than beta particle. With alpha rays pass through a thin glass

membrane and trap in a fluorescent light tube led researchers to study the emission

spectrum of gas produced, and proved that alpha particles the reality is a helium

nucleus. Other experiments showed the similarity between beta radiation with

cathode ray and gamma radiation similar to X-rays.

Alpha particles cant through a sheet of paper; beta particles cant through

aluminum plate. To stop gamma required metal layers thick, but because of

absorption of the exponential function will have a few sections that may through

sheet metal.

All radioactive radiation such as charged of particles has characteristic can

ionize the air or gas. This property is used as the principle of a device to detectradiation. Because the decay of radioactive radiation cant be detected directly by our

senses, then the detection should be done with the help of some device called a

detector. As a radioactive ray detector can be used Geiger Mullers tube which

detects the intensity of the transmitted beam of radioactive material. Geiger Muller

tube is connected with a tool counter. Each ion is formed due to radiation will be

recorded by the counter as the counting of radiation that is strong or weak the size of

a radioactive radiation.

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Figure 2 shooting of particle in materials

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resulted in the media that have gone through ionization. Finally, alpha

particles will capture two electrons and changed into atoms .4

2H

b. Betta rays()

Beta rays are negatively charged particle radiation. Beta rays is an electron

beam that comes from the nucleus. Beta particles that charged -1e and with

mass 1/836 sma. Because very small of betta particles are considered

massless so are stated by the notation e0

1 Beta ray energy is varied, has a

greater penetrating power than alpha ray, but power is weaker pengionnya.

The most energetic beta rays can travel up to 300 cm in dry air and can

penetrate the skin. All forms of radiation have the nature ionize the air whenpassed and cause flouresensi on a particular substance. Particles betta and

alpha particles are also deflected by magnetic fields and electric field on

ionization events and flouresensi particle or photon radiation likely to change

from its original state asdue to deflection or absorption. Events adsorption of

particles through a material with thickness t can be described as follows.

Suppose there is a radioactive rays has initial intensity I0 through a material

with thickness x. After passing through the material, the intensity of light transmitted

by I. Relations with the initial intensity of the transmitted intensity is

I = I0e-x

Where is absorption coefficient (m-1) whose value depends on the type of

material, while e is the natural numbers or natural numbers the values is 2,71828.

5

Figure 4. Events absorption of particles

I0

I

x


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c. Gamma Ray

Gamma radioactivity is composed ofelectromagnetic rays. It is distinguished

from x-rays only by the fact that it comes from the nucleus. Most gamma rays

are somewhat higher in energy than x-rays and therefore are verypenetrating.

It is the most useful type of radiation for medical purposes, but at the same

time it is the most dangerous because of its ability to penetrate large

thicknesses of material.

IV. Apparatus of Experiment

There are also tools and materials used in the experiment this time is as

follows.

1. Geiger-Muller tube (GM tube)

2. Counter and Timer

3. Radioactive source alpha, betha and gamma.

4. Some absorber

a. Aluminum 0.125

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http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html#c4http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html#c6http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/ems1.html#c1http://hyperphysics.phy-astr.gsu.edu/hbase/ems3.html#c4http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html#c6


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8. Determine the radiation background several times with a record count per

minute and find the average.

10.Put alpha source on holders sample and put it in holes buffers 5th fromabove.

11. Note the activity of radiation sample without absorber.

12. Put the aluminum absorber 0.125 and record back the radiation activity.

13. Repeating step of 9-11for beta and record the activity of radioactive

radiation.

14. Search for data activity radiation radioactive sources alpha to girth different

absorber.

15. Record the data of that activity

VI. Technique of Data Analysis

Analysis of data used in the experiment was the technique in a qualitative

analysis and quantitative analysis. In a qualitative is to analyze the graph of the

relationship between besar voltage and many a permenit to determine the voltage

theoperation suitable for use . In a quantitative analysis is find the relationship

between the input and output in the equation 0112 I2

1IdanI

2

1I ==

VII. DATA OF EXPERIMENT

Table 1.

NoVoltage

(Volt)Calculation

Time

(minute)

Calculation/

minute

1 300 1 1 1

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2 320 3 1 3

3 340 4 1 4

4 360 5 1 5

5 380 5 1 56 400 20 1 20

7 420 21 1 21

8 440 22 1 22

9 460 21 1 21

10 480 23 1 23

11 500 24 1 24

12 520 25 1 25

Table 2.(Beta)

NoVoltage

(Volt)Calculation

Time

(minute)

Calculation/

minute

1 400 336 1 336

2 400 319 1 319

3 400 316 1 316

4 400 288 1 288

5 400 303 1 303

Table 3. (Gamma)

NoVoltage

(Volt)Calculation

Time

(minute)

Calculation/

minute

1 400 98 1 98

2 400 97 1 973 400 99 1 99

4 400 101 1 101

5 400 102 1 102

Table 4. (Background)

NoVoltage

(Volt)Calculation

Time

(minute)

Calculation/

minute

1 400 19 1 19

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2 400 20 1 20

3 400 24 1 24

4 400 15 1 15

5 400 20 1 20

Table 5. (Same absorber with different thickness)

Source Absorber Thickness1c 2c 3c averagec

Beta Aluminum 849(p)/0.125 24 26 33 29.30

Aluminum 645(o)/0.100 34 26 28 29.30

Aluminum 590(n)/0.090 26 26 22 24.67

Gamma Aluminum 849(p)/0.125 77 79 70 75.30

Aluminum 645(o)/0.100 68 69 68 68.30

Aluminum 590(n)/0.090 87 79 81 82.30

Table 6. Different Absorber with same thickness

Source Absorber Thickness1c 2c 3c averagec

Beta Aluminum 849(p)/0.125 28 33 34 31.6

Lead 3632(s)/0.12

5

18 29 22 23.0

Aluminum 258(j)/0.040 63 48 48 53.0

Plastic 102(f)/0.040 170 166 146 160.6

Gamma Aluminum 849(p)/0.125 71 58 78 69.0

Lead 3632(s)/0.12

3

62 63 48 57.6

Aluminum 258(j)/0.040 66 66 70 67.3

Plastic 102(f)0.040 83 73 96 84

VIII. Data Analysis

a. Operation Voltage

To find the operation voltage we can draw the graph from the data in

table below:

NoVoltage

(Volt)Calculation

Time

(minute)

Calculation/

minute

1 300 1 1 1

2 320 3 1 3

3 340 4 1 4

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4 360 5 1 5

5 380 5 1 5

6 400 20 1 20

7 420 21 1 218 440 22 1 22

9 460 21 1 21

10 480 23 1 23

11 500 24 1 24

12 520 25 1 25

The Graph

From the graph above we can get the value of operation voltage from the

plateau area. So the best value of operational voltage is defined from the average

value from 400-480 volt:

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Operational Voltage =( )

voltVolt

3702

380360=

+

b. Background Radiation

NoVoltage

(Volt)Calculation

Time

(minute)

Calculation/

minute

1 370 4 1 4

2 370 6 1 6

3 370 5 1 5

4 370 5 1 5

5 370 6 1 6

No. ic c cci 2)( cci

1 4 -1.2 1.44

2 6 0.8 0.64

3 5 -0.2 0.04

4 5 -0.2 0.04

5 6 0.8 0.64

26 5.2 2.8

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For Calculate c

2.5

526

=

=

=

c

c

n

xc

i

For Calculate the uncertainty c

( )

)1(

2

=

nn

xxc

i

)15(58.2

=c

37.0

14.0

=

=

c

c

So the value of c

( )

( )Cpmc

ccc

37.02.5 =

=

Relative error

%100

=c

cRE

%2.7

%1002.5

37.0

=

=

RE

RE

c. Same Absorber (Aluminum) with different thickness

Source Beta

Source Absorber Thickness 1c 2c 3c averagec

Beta

Aluminum 0,025 32 34 37 34,33

Aluminum 0,020 38 36 37 37

Aluminum 0,032 24 27 25 25,33

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The Graph

Source Gamma

Source Absorber Thickness 1c

2c

3

caverage

c

Gamma

Aluminum 0,025 37 38 37 37,33

Aluminum 0,020 30 31 33 31,33

Aluminum 0,032 27 29 27 27,67

The Graph

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d. Different absorber

Between Aluminum and Lead (thickness 0.125)

1. Source Beta

Gamma Aluminum 0,125 25 27 24 25,33

Lead 0,125 25 24 24 24,33

Aluminum 0,040 24 21 23 22,67

Plastic 0,040 30 32 33 31,67

Absor

ber

Calculation/

minute n

cc

i= cci

2)( cci ( )

)1(

2

=

nn

ccc

i

Alumi

num

10

9.33

0.67 0.450.18

9 -0.33 0.11

9 -0.33 0.11

Lead

18

4,33

0.67 0.450.1829

-0.33 0.11

22-0.33 0.11

2. Source Gamma

Absor

ber

Calculation/

minute n

cc

i= cci

2)( cci ( )

)1(

2

=

nn

ccc

i

Alumi

num

25

25.33

0.33 0.110.48

27 1.67 2.78

24 -1.33 1.78

Lead 25 24.33 0.67 0.44

0.1824 -0.33 0.11

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24-0.33 0.11

Between Aluminum and Plastic (thickness 0.040)

3. Source Beta

Absor

ber

Calculation/

minute n

cc

i= cci

2)( cci ( )

)1(

2

=

nn

ccc

i

Alumi

num

21

19.33

1.67 2.77 0.48

19 -0.33 0.1118 -1.33 1.78

Plasti

c

170

160.6

9.4 88.3655.11166 5.4 29.16

146-14.6 213.16

4. Source Gamma

Absor

ber

Calculation/

minute n

cc

i= cci

2)( cci ( )

)1(

2

=

nn

ccc

i

Alumi

num

24

22.67

1.33 1.77 0.48

21 -1.67 2.77

23 0.33 0.11

Plasti

c

30 31.67-1.67 2.78

0.4832 0.33 0.11

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331.33 1.78

IX. Result and Discussion

Results

Based on the chart above shows that the plateau region located between the

voltage of 400 V and 480 V. So that the best operating voltage can be obtained by

finding the average value of voltage between 400 V-480V, which amounted to 190

Volt.

Voltage is what we will use to determine the count per minute background

radiation, radiation and radiation using different absorber and absorber using the

same but with different thicknesses.

Because the best operating voltage is 440 volt, the background radiation is the

average value calculation / min is shown in the voltage between 400-480 volts,

which is 19 cpm.

Graph showing the relationship between the number of count or count per

minute with a good absorber thickness for the radioactive sources of beta () and

gamma () is inversely proportional. Where, the thicker the absorber the count value

of count per minute which can be observed on the counter will be less. This means,

the thicker the absorber, the less the radiation beams beta () and gamma () that can

penetrate the absorber so that the count per minute count will be smaller.

Radioactive properties of beta and gamma particles are also influenced by the

type of absorber used. Can be seen from the above experimental results which count

values generated using the absorber aluminum, lead and plastic have different values.

This is because each absorber has the ability to absorb the beta and gamma particles

different.

Discussion

Threshold voltage is the voltage at the Geiger Muller tube starts particles

which strike a note of the electrodes on the Geiger Muller. From the observations we

obtained in the tube using a Geiger Muller Counter and Timer, a large threshold

voltage is equal to 440 Volt. This figure can be seen in the table of observations.

Observation area in the tube R is the region where the voltage changes in the tube

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causes the counter did not perform a meaningful calculation. From the observations

we obtained(400-480) Volt. Best use of the operating voltage of the Geiger Muller

tube is 520 Volt. We get that number by averaging the voltage on the Plateau area so

we get the average value is:

Operation Voltage: Volt4405

480460440420400=

++++

Observations on the radioactive properties of beta and gamma particles can be

observed with respect to fractional count Geiger Muller. To find out the penetrating

power of beta particles and gamma can search through the experiments using

different absorber thickness equal and using the same absorber, but with different

thicknesses.

X. Answer The Question

1. When high voltage is turned on first time has appointed 500 V, the

calculation is not observed although there is a radioactive source close to GM

tube. That's because the Geiger Muller tube is not given barrier material so

that the breakdown of radioactive beams is large enough to get away with it.

At the time of the radioactive source is near the GM tube these particles will

penetrate the thin window at one end and go into it. These radioactiveparticles then mashing the gas atoms so that the gas atoms will emit electrons

and generate secondary ions. Secondary ions as primary ions will also

produce other ions and so on until the last ions reach the electrodes. This

cascade effect is called "avalanche" of the ion. Arrival of the avalanche of

charged ions on the electrode potential difference causing the sudden between

the two electrodes so that the resulting current pulses are passed to the R

series and eventually arise when a voltage pulse is amplified loud speaker

could sound or recorded with a counter. However, at a voltage of 500 V

radiation radioactive sources are not detected by the tube is not the case

records or calculations. It is not independent of the random nature of

collisions so that the radiation does not enter the Geiger Muller tube. Because

the collisions of atoms so that the electron gas occurs despite the very short

time. Tube can not capture radioactive radiation sources. So in the absence of

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a radioactive beam barrier will be difficult to detect due to the penetrating

power and random particle collisions.

2. The addition of a smaller voltage is required for a small portion of the first set

of data. This is because the rate of ions in a tube connected to the potential

difference between electrodes, so the calculation will depend on the potential

difference. Therefore, the addition of a small voltage would cause the rate of

ion that is more detailed.

3. Steps to get the data to be more subtle plateau curve at the point of operation

is to perform repeated experiments by adding the voltage slowly and observe

the calculations that are detected by the counter. Then look for the calculation

of the value or the count per minute relatively the same. Further define the

best operating voltage. The best operating voltage obtained from the average

looking from the top and the bottom end of the plateau. In the plateau region

are small voltage fluctuations are very small effect on the calculation.

4. From the graph of radioactive beta source () and gamma () obtained a

difference. Graph beta () looks steeper when compared with the graph

gamma (), where gamma graph tends to look flat. This means, the thickness

of the absorber provides a huge influence on the results of a radioactive

source count per minute for beta (). As for the radioactive sources of gamma

(), the thickness of the absorber does not significantly affect the results of a

legible tattoo count per minute on a counter.

5. Benefits of the reaction gamma rays () of the material is to study the

characteristics of a metal.

6. Protective gamma rays () is good to protect the protective effect of gamma

rays which have a thickness that is high enough. This is because gamma rayshave a very high penetrating power. If the thickness of the protective small,

then the gamma rays would be translucent, so it will not be able to protect

from the effects of gamma rays ().

7. Proof:

teII = 12

)log(log 12teII =

teII += logloglog 12

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etII logloglog 12 =

718,2logloglog 12 tII =

434,0loglog 12 tII =

1000

434loglog 12 tII =

4341000

1loglog 12 tII =

3,2

1loglog 12 tII =

3,2loglog12

t

II

=

8. According to the equation in problem 7:

3,2loglog 12

tII

=

3,2loglog 21

tII

= ; We have known that 12

2

1II =

3,22loglog 11

tII

=

3,2)2log(loglog 11

tII

=

3,22logloglog 11

tII

=+

3,22log

t=

3,2301,0

t=

6923,0=t

XI.Conclusion

1. From the experiments we do can be summarized as follows.

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a. Geiger Muller tube is a useful tool for detecting radiation. GM tube

connected with a counter. Each ion is formed due to radiation will be

recorded by the counter as a chopped radiation is strong or weak a

measure of radioactive radiation. Radioactive detector operated in the

following way.

b. Coarse and fine is a button to adjust the voltage. Voltage regulation is

intended to determine the size of the calculations can be calculated by the

counter.

c. Counter used to count the number of counts each time. Counter will

work if the voltage is selected to be in the threshold.

d. Reset is used to repeat the calculation.

e. Stop is used to stop the calculation. Stop button will turn on

automatically if the count calculation is complete.

2. Voltage characteristics of the Geiger Muller tube is the best operating voltage

on the results of the experiment is 440 volts. This figure is obtained from

finding the average of the upper end and lower end of the plateau region.

3. Radioactive properties.

a. Can ionize the air or gas.

b. At the same operating voltage and the same absorber thickness, the

penetrating power of beta particles and gamma is different.

c. At the same operating voltage and by using different absorber

penetrating power of beta particles and gamma is different.

4. From the analysis of data on the experiments there is deviation from the

standard value. This is because at the time of experiment occur several errors,

as follow:a. Parallax error

Error occur because human error. The parallax error occurs during the

practicum.

Lack of skilled us in regulating both the coarse and fine

control. Such as difficulty in the round accuracy on fine control for

precise pointing the desired scale.

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Lack of our patience in doing lab work while awaiting the

results of the calculation.

b. Systematic ErrorsErrors caused by measuring devices at the time of the experiment, can be

caused by conditions which are quite old equipment (hardware

limitation), so that means of diminishing sensitivity.

c. Random error

Errors occur without the knowledge of the observer. For example, the

presence of radiation, random radiation which we know nothing about its

existence (sun radiation, radiation electronic items brought us and so

forth).

In this experiment we were having some problems such as.

Prior knowledge we have about the experiment and operating

equipment is less so this resulted in the time required to conduct lab

work long enough.

Obstacles place is also much influenced. Where is the place to

conduct lab work less so comfortable, visible in the presence of noises

that occurs in the room due from other groups held practicum

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REFERENCES

Anonim. GeigerMller tube.2008 acessed from Wikipedia.com ( April 10th 2012).

Anonim. Radiaoctivy. 2010 Accessed from hyperphysics.phy-

astr.gsu.edu/hbase/nuclear/radact.html (April 10th 2012).

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