INTRODUCTION
Nuclear radiation techniques have become powerful testing tools in many disciplines
including Science, engineering and medicine. Nuclear physics lab is an essential
part of the education experience. Therefore, it is very important that students,
trainees and specialists are properly educated in this field. The associated
expense, time, space and maintenance are major difficulties to make the teaching
of this course very effective. Such labs also require highly skilled technicians
to run and maintain its equipment. Although many universities have well-organized
laboratories in nuclear physics but experiments installed in these laboratories
are not commonly accessible (Tiftikci and Kocar, 2010).
Because of some misuse of radioactive sources and the fear of losing radioactive
sources, the nuclear national regulatory in some countries have imposed restrictions
in importing certain radioactive sources. This has created additional difficulties
for institutions to have the radioactive sources they require.
Nuclear and radiation physics courses are compulsory courses in all physics
departments. In Saudi Arabia, some new universities and colleges have lack in
the facilities and licensure needed to offer a nuclear lab. Ideally, students
are required to perform about eight to ten experiments in the nuclear and radiation
lab. Many diverse concepts are covered in these experiments. It is always a
challenge for instructors to cover these concepts in one semester and at the
same time, it is always very difficult for students to grasp the concept to
the required level of understanding. The amount of work required and limited
time available to perform a full experiment is always problematic. In addition,
many female students are afraid of performing nuclear experiments because of
the misconception of the radiation hazards that they may be exposed to. Expanding
the nuclear and radiation laboratory to cover advanced experiments and projects
would therefore be impractical.
The available advanced educational technologies, powered by the recent advances
in the Internet, provide an opportunity to present the material of nuclear and
radiation laboratory in a new way where many difficult concepts can be made
more tangible and easy to understand. This should have a huge impact on students’
level of comprehension whether the virtual lab is used as a standalone course
or as a supportive material for the traditional lab.
After learning most of the concepts in nuclear and radiation courses, usually,
students have to practice a great deal on different problems to master these
concepts and their applications in new different settings. This is an essential
part of the learning process, not only for passing the examinations but also
for applying these concepts in innovative ways in the students’ future
fields. Usually the lectures or recitations do not offer enough of this kind
of practice. A virtual lab, on the other hand, can be designed to provide enough
practice and conduct the experiment and facilitate the process of supervising
many students who do their share on their own paces (Crosier
et al., 2000).
A virtual lab (sometimes is labeled as simulation-based lab) can be designed
to provide ample opportunities for students to learn from their mistakes without
the embarrassment of doing it in the traditional lab. Good communications and
feedback with instructors and among students themselves also can be available.
This should encourage more students to have an active role in the learning process
(Kopp, 2011; Pechousek, 2011).
Another important aspect of the virtual nuclear lab, if designed carefully,
is that it does not allow students to jump to a new material before mastering
the old material. This is especially important in nuclear science in which many
concepts are built on each other. Making sure that the knowledge base for students
is solid before introducing new material because this is usually very difficult
to accomplish in a traditional class setting. Also, if it is used effectively,
the online technologies should reduce the burden of managing the affairs of
a large number of students (Tlaczala et al., 2005).
Tiftikci and Kocar (2010) developed a software with
a capability of creating experimental setup that is suitable for a specific
virtual radiation lab with minimum cost and to accelerate the training in radiation
physics for students. The results obtained can be analyzed by Multichannel Analyzer
(MCA). Several academic institutions have successfully implemented interactive
computerized laboratories with software such as LabVIEW and MATLAB (Crosier
et al., 2000; Tlaczala et al., 2006).
In Clemson University, remote radiation detection and measurements lab was developed
in LabVIEW environment. Distance students are allowed to control physical instruments
and acquire and analyze actual data in real-time (Kopp, 2011).
Park et al. (2005) proposed web-based nuclear
physics laboratory and used HTTP, HTML and CGI program to construct the remote
control lab.
This project is a compromise between two conflicting demands; reducing the
cost of establishing and running nuclear and radiation lab and making such lab
available to all physics students and instructors wherever they are and whenever
they need. The number of physics departments in Saudi Arabia that may benefit
from such project exceeds 100 departments. This would include both boys and
girls sections. Teachers and students in the General Education sector would
also benefit from such a project.
The Virtual Labs Project has been initiated at the physics department at Taif
University. A major goal of this project is to increase scientific literacy
by using interactive multimedia to educate the fundamental concepts of physics
and to contribute those resources through the Internet. The Virtual Labs objects
are presently hosted on a password-protected site and are generously accessible
to concerned parties for educational exercise. Students will be able to think
about and interact with dynamic methods in the body. The learning modules have
been urbanized. The ideas in these modules place the groundwork for different
experiment of physics.
The aim of this project is to create a number of online and interactive virtual
nuclear experiments for physics students. It is specifically focused on the
lab and associated experiments conducted in the course titled Nuclear Physics
(203460-4) offered at Taif University. The project is designed to help students
to learn about radiation concepts and the basic of gas-filled detectors without
the need to experience a physical laboratory environment. The Virtual Nuclear
Laboratory (VNL) is based on results that have been achieved earlier in real-life
experiments.
MATERIALS AND METHODS
The physics department at most Saudi universities offer 3-credit nuclear physics
course with 1 credit (3 h) undergraduate level lab on the fundamentals of radiation
detection and measurements. This lab features 10 laboratory experiments centered
gas-filled and scintillation detectors. In this project, three basic experiments
were chosen for simulation:
| • |
Plotting a geiger plateau |
| • |
Inverse square law |
| • |
Absorption of gamma particles |
Each simulated experiment is equipped with controls that represent real instrument
controls. Student can change parameters, such as counting time and voltage which,
would enable the user to interact with the experiment in varying degrees, depending
on the type of lab. The results obtained from the physical lab are mathematically
modeled to represent the expected results. The simulation-based lab can be used
in class education and distance education. The equipment, tools and 3 radioactive
sources used in the nuclear lab are provided by Spectrum
Techniques (2002).
|
| Fig. 1: |
General structure of the virtual nuclear lab |
Each physical experiment was conducted according to the lab’s manual
(Spectrum Techniques, 2002). All experimental data, variables
and results are fed to the simulation-based lab to perform the exact function
as the actual experiment.
The structure of the virtual nuclear laboratory: Figure
1 shows the structure of each experiment.
Student information: This section includes student’s
profile (name, university, lab section, date, contact..., etc).
Introduction: This section is intended to be a descriptive of the theory
underlying the laboratory to be performed, particularly describing the equations,
the variables to be measured and the quantities to be determined from the measurements.
In addition to the text and pictures, there will be some video (animation with
voice) explaining these information so that the student can fully understand
this subject.
Objectives: This section explains briefly the purpose and the learning
outcomes of the experiment.
Equipment: A list of the equipment needed to perform the laboratory
and a picture of each equipment/tool with some explanation of what it is for,
its functions, precautions... etc.
Experimental procedure: The procedure is written details. It attempts
to give very explicit instructions on how to perform the measurements. The data
tables provided include the units in which the measurements are to be recorded.
Measurements can be repeated again and again. This is the simulation section
of the experiment through which the student will conduct virtually the assigned
experiment and be able to change values and record results.
Analysis: Student would be able to see/view the recorded data taken
from the virtual equipment and perform calculations such as calculate the unknown
quantity, determine the mean and the standard error. A graph is required in
most of the experiments. The student would first plot the obtained data in a
spread sheet, determine the slope and calculate the unknown quantity.
Laboratory assignment: Each laboratory (experiment) would include an
assignment based upon the laboratory description and results. The student should
answer a series of questions about the theory and working numerical problems
related to the calculations in the laboratory. The purpose of this section is
to evaluate the student’s understanding.
Laboratory report: The student should be able to print a summary report
of the experiment including the data, graphs and calculation data, answers.
This report can be sent electronically to the lab’s
instructor.
Feedback: The student may send a question/comment/ feedback to the lab’s
instructor.
Appendices: Physical constants, radiation terms, conversion factors,
abbreviations.
In the VNL, three labs were developed: (1) Plotting a geiger plateau, (2) Inverse
square law and (3) Absorption of gamma radiation. Each lab contains theory,
objectives, equipment, procedures, data analysis, lab assignment and lab report.
Details of these sections are explained above. All four labs are using almost
the same equipment and tools. This includes: GM counter, GM tube, power supply,
shelf stand, source holder, aluminum and lead absorbers and radioactive sources
(Cs-137 and Co-60).
Virtual lab research data are automatically inserted into database, a simple
data analysis tool built into provided Graphical User Interface (GUI). On the
basis of their information of the research design they formed, students must
select the suitable data analysis. A virtual private server is used to host
the program. This project has been developed in php programming language, flash
and MySQL database.
RESULTS AND DISCUSSION
Figure 2 shows the VNL user interface (homepage) where the
admin can view student’s activities.
The VNL have been designed to give the student a control to the simulated functions
of the experiment (Fig. 3).
Before conducting any lab, description and explanation of how gamma radiation
interacts with GM tube, what kinds of interactions occur and how signal is collected
(Fig. 4). These are essential for students to understand the
experiments and correctly analyze the results.
|
| Fig. 2: |
Homepage of the Virtual Nuclear Laboratory (VNL) which contains
student’s login and Admin login |
|
| Fig. 3: |
A snapshot of the plotting a Geiger Plateau screen, the user
will follow a detailed description to run the experiment |
|
| Fig. 4: |
Animation of how radiation interacts with GM counter |
For demonstration, two labs are presented below:
Plotting a geiger plateau experiment: The purpose of this lab is to
determine the plateau and optimal operating voltage of a Geiger-Muller counter.
It is a straightforward experiment, no mathematical model was used. A radioactive
source was placed at a depth in the source holder. The actual count was set
to 30 sec. Actual counts versus voltage were collected. This step can be repeated
three times, average count is calculated and saved in a file. This data was
used by the VNL. If the user selects counting time other than 30 sec, the new
calculated count is calculated from the following Eq. 1:
where, C1 is the actual total count. C2 is the new total
count obtained when the counting time is T2 (sec).
Absorption of gamma rays: The purpose of this lab is to investigate
the attenuation of radiation via absorption of gamma rays. The user will find
the attenuation coefficients for aluminum and lead and the half thickness (X1/2)
at which the gamma radiation is cut in half. The data were modeled to conduct
the experiment based on the following Eq. 2:
where, I is the intensity of the beam after passing through x amount of absorbing
material, Io is the original intensity, μ (cm2 g-1)
is the mass attenuation coefficient and X (g cm-2) is the mass thickness.
Aluminum and lead were used as absorbers. The X1/2 is calculated
from the following Eq. 3:
In this lab the user first measures the Io. Then selects the absorber
(Al or Pb) of a known thickness and run the experiment and records I (this is
done by pressing record data). The experiment is repeated to a certain number
of absorbers (thickness). Details of the experimental procedures and data analyses
are written in details. The student can browse between different sections of
the experiment whenever he likes. The VNL produce the similar results as the
actual real-time data. The student would also be able to see the effect of changing
other parameters on the measured count such as no radioactive source, changing
the radioactive source, changing the position of the radioactive source, changing
the activity of the source, changing the operating voltage.
The Virtual Nuclear Lab helps students to get engaged in scientific innovation
processes by giving them the condensed experience of building efficient experimental
strategy decisions with the goal of determining the principles of a difficult
virtual reality.
CONCLUSION
In this study, the importance and benefits of virtual nuclear lab have been
highlighted and three experiments have been simulated. While conducting the
lab, students can change parameters and observe the effect of changing variables
or to the mathematical model. The designed VNL provides students with a firm
grasp of reality concerning the experiments. Student comprehension on using
VNL how this differs from the real life experiments is outside the scope of
this project.
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