Cadet Development Through Accelerator-Based
Independent Study
A.K. Pallone
Department of Physics, United States Military Academy
West Point, NY 10996
Abstract. The Department of Physics at the United States Military Academy owns and operates an HVEC LC-400 Van
de Graaff accelerator. After a few years of limited use, interest among the faculty in the accelerator as a learning tool
increased. Four cadets responded to an offer for independent study with the accelerator. The cadets were tasked to
measure the diffusion coefficient of boron along tungsten grain boundaries. Two identified objectives were the
preparation of the accelerator for the measurements and the development of a coincidence detector to reduce interference
from Compton scattered and natural background radiations. How the cadets attacked these objectives, their successes
and set backs, and the evolution of their thought process will be presented.
processes is explored within the structure of the Kolb
learning cycle.
INTRODUCTION
The students of today require more than the ability
to digest and regurgitate information. Students must
develop the ability to analyze and respond to new
information in possibly unfamiliar situations.
Accelerator-based, experimental physics provides
undergraduate students opportunities to develop as
critical and creative thinkers. The Department of
Physics at the United States Military Academy
obtained an HVEC LC400 Van de Graaff accelerator
to serve as a learning tool for cadets. After a few years
of limited use, faculty interest in the accelerator
increased. Reintegration of the accelerator into the
curriculum began with a proposal for a cadet
independent research project.
FIGURE 1. Typical depleted uranium sabot round [2]
BRIEF DESCRIPTION OF THE KOLB
LEARNING CYCLE
Four cadets responded to the proposal. The desire
of the United States Army to replace the current
generation of depleted uranium sabot rounds with
more environmentally friendly rounds provided the
framework for the project [1]. The cadets were tasked
with two objectives – to improve accelerator
performance and to develop a coincidence detector
that reduces interference from Compton scattered and
natural background radiations.
How the cadets
attacked these objectives, examples of their successes
and set backs, and the evolution of their thought
Experiential learning theory identifies four learning
modes.
Concrete experience (CE) and abstract
conceptualization (AC) describe how learners perceive
experiences. Reflective observation (RO) and active
experimentation (AE) describe how learners process
information [3]. Representing perception along one
axis and processing along an orthogonal axis, David
Kolb created a quadrant scheme to identify learning
CP680, Application of Accelerators in Research and Industry: 17th Int'l. Conference, edited by J. L. Duggan and I. L. Morgan
© 2003 American Institute of Physics 0-7354-0149-7/03/$20.00
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boron-doped tungsten will lead to the ability to predict
the performance of boron-doped tungsten in sabot
rounds with changes in composition and processing.
Comparison of boron depth profiles of annealed and
untreated samples can be used to determine the
diffusion coefficient of lightly doped boron in
tungsten [1].
styles. The learning styles are characterized by the
types of questions asked by learners [4].
Type 1 learners (divergers) search for meaning.
They want to understand why the material or task is
relevant to their lives or to an overall plan. Kolb
identified the questions asked by type 1 learners as
motivational and grouped these questions into the
subject question of “Why” for quadrant 1 in his
scheme. Type 2 learners (assimilators) apply logic and
deductive problem solving to connect new information
and experiences to existing knowledge. They often
rely on others as expert sources of information. Kolb
grouped the questions asked by type 2 learners into the
subject question “What” for quadrant 2 in his scheme.
Type 3 learners (convergers) combine abstract
knowledge and common sense to solve practical
problems. They tend to focus their efforts to obtain
“the solution.” Kolb grouped the questions asked by
type 3 learners into the subject question “How” for
quadrant 3 in his scheme.
Type 4 learners
(accommodators) operate effectively with little to no
supervision. They tend to learn by trial and error.
Kolb grouped the questions asked by type 4 learners
into the subject question “What if” for quadrant 4 in
his scheme [5].
The Academy accelerator operates in the correct
energy range to apply resonant nuclear reaction
analysis to determine the boron depth profiles.
Improving accelerator performance and developing an
appropriate detection system were the first steps
toward obtaining the boron depth profiles. The cadets
focused on this mid-range goal for their primary
motivation and on detection of a nuclear reaction as an
intermediate goal.
On the Path To A Pair Spectrometer
Example of the Type 1 Learning Style
The cadets divided themselves into two teams. The
first team attacked the task of modifying the
accelerator. The second team attacked the task of
developing a pair spectrometer. The cadets had
limited exposure to γ-photon detection in previous
courses. Based on that experience, they questioned the
need for a pair spectrometer. To answer that question,
the cadets were tasked to collect γ-photon spectra with
a single, thallium-activated, sodium iodide [NaI(Tl)]
detector. They were then asked to determine the true
counts in their spectra due to γ-photons from specific
isotopes. The cadets had difficulty determining the
true counts for weaker sources.
In this miniexperiment, a weaker source corresponded to a lower
concentration of boron in the tungsten. The outcome of
this mini-experiment convinced the cadets that a real
need to increase the signal to noise ratio (SNR) by
decreasing the natural background and Compton
scattered radiations existed. That need motivated their
work for the remainder of the course.
Traditional learning environments focus on
techniques, such as the classic lecture format, that suit
type 2 learners. This focus is no longer adequate to
prepare people to function in a world where
information overload is the norm. Successful persons
learn how to learn and to move among the learning
types as appropriate for the situation. One goal of any
learning experience should be to help persons develop
these abilities [3].
EXAMPLES OF CADET LEARNING
THROUGH THE KOLB CYCLE
Focusing The Big Picture – Project
Motivation
Examples of the Type 2 and Type 3 Learning Styles
The cadets arrived the first day of class with lots of
enthusiasm, few preconceived notions, and many
questions. Most of those questions probed the reasons
for the project. The framework on which the project
was justified is the United States Army’s ongoing
search for the replacement material for depleted
uranium (DU) in sabot rounds. Boron-doped tungsten
has been offered as one alternative to the DU. A
systematic determination of the properties of the
A detector system on loan from the Colorado
School of Mines (CSM) to the Academy consisted of a
cylindrical NaI(Tl) detector surrounded by an annular
NaI(Tl) crystal separated into two equal halves capable
of operating as independent detectors. Each halfannular crystal was mated to three photomultipliers.
The cadets had only worked with a single-crystal,
862
Beginning with a pulse generator, a dual-trace
oscilloscope, and some references that explain the
functions of the modules and expected output signals
for given input signals, the cadets tested various
modules [6,7]. Most modules performed as expected;
however, when a Linear Gate and Delay module did
not, the cadets chose to believe that the module was
broken rather than accept that it operated slightly
different from their expectations. This behavior is
typical of type 2 learners. The cadets chose not
include that module in their final design.
single-phototube detector before beginning this
project. They had never had to balance the responses
of a multi-crystal, multiple-tube system.
The cadets were given standard γ-sources and were
reminded one final time of the safety procedures for
handling radioactive sources.
After receiving
instruction on the effects that the gain and the focus
controls have on a photomultiplier tube, the cadets
tested the response of each photomultiplier tube with a
common γ-source. Their first data set indicated that
the photomultiplier tubes responded differently to the
same stimulus (irradiation parameters). The cadets
proceeded to adjust the values of the gain and focus on
each photomultiplier tube until all the photomultiplier
tubes responded the same to the same stimulus.
Once the cadets learned to operate the individual
NIM modules, they were shown a system consisting of
two cylindrical NaI(Tl) detectors placed exactly
opposite each other around a 60Co button source and a
combination of NIM modules. The system selected
the 1.17 MeV γ-photons from a 60Co source that
deposited their energy in one detector source and
rejected the extensive Compton continuum generated
by the scatter of 1.33 MeV γ-photons from that same
60
Co source. The cadets examined the system,
changed settings on the modules, and made predictions
about and observed the resulting changes in the
spectra. They determined how the NIM modules
worked together in coincidence mode to achieve the
selective separation of the 1.17 MeV γ-photons. These
actions are typical of type 3 learners. To check their
understanding, the cadets were then tasked to
reproduce the 60Co results; however, they were free to
try other combinations of NIM modules to accomplish
that task.
The electronics for this project consisted of
standard Nuclear Instruments and Methods (NIM)
modules. Cadets had no previous experience with
these modules and were given minimal initial
instruction concerning their operation; yet, by the end
of the course, they had successfully assembled the
modules into the electronics required to form a pair
spectrometer when used with the CSM detector as
shown in FIGURE 2.
Example of the Type 4 Learning Style
The cadets were ready to construct a pair
spectrometer. They possessed previous knowledge of
the interactions of photons with matter. They had
balanced the responses of the photomultiplier tubes on
a physical detector system capable of providing the
signals required to perform pair spectrometry. They
had learned how to combine NIM modules to extract
information from signals originating in detectors. The
cadets applied their experiences and knowledge to
develop a successful pair spectrometer. This synthesis
is an example of the type 4 learning style. The cadets
took inventory of the available equipment and
explored different combinations of NIM modules that
would produce a pair spectrometer when used with the
CSM detector system. After some trials, the cadets
settled on the final design for the pair spectrometer.
FIGURE 2. Schematic of cadet pair spectrometer[8].
863
9th Annual Army Research Laboratory - United States
Military Academy Technical Symposium, edited by M.
Johnson, The Mathematical Sciences Center of
Excellence, West Point, New York 2001, online http://www.dean.usma.edu/math/research/msce/9th_AU
TS/default.htm .
SUMMARY AND CONCLUSIONS
Today’s students must have excellent critical and
creative thinking skills to succeed. Accelerator-based
independent study projects provide opportunities for
students to develop those skills. Recently, four cadets
at the United States Military Academy participated in
an independent study project with the short-term
objectives of improving the performance of the
Academy accelerator and developing a pair
spectrometer to improve the signal to noise ratio in
data. Over the course of the project, the cadets moved
between the quadrants as described in the Kolb
learning theory. As they did, they honed their critical
and creative thinking skills.
2. Figure E-1 in Enviromental Exposure Report : Depleted
Uranium in the Gulf (II), report number 20001790000002 version 2.0, Deployment Health Support
Directorate, Falls Church, VA, 2000, online http://deploymentlink.osd.mil/du_library/du_ii/du_ii_tab
e.htm .
3. Kuri, N.P., “Kolb’s Learning Cycle: An Alternative
Strategy for Engineering Education,” in Progress
Through Partnership: Strengthening Alliances –
Proceedings of the International Conference on
Engineering Education –1998, editor unknown,
EPInnovations, Lafayette, IN, 1998 online http://www.ctc.puc-rio.br/icee-98/Icee/papers/225.pdf .
ACKNOWLEDGMENTS
4. Harb. J.N. and Terry, R.E., “A look at Performance
Evaluation Tools Through The Use Of The Kolb
Learning Cycle,” in 1992 ASEE Annual Conference
Proceedings, American Society for Engineering
Education, Washington, DC, 1992, pp.1124-1127.
Genrich L. Krasko, formerly of WMRD-ARL,
inspired the current research that served as motivation
for the cadet project.
Lee Harrell served as one of the faculty advisors to
the cadets.
5. Harb. J.N., Terry, R.E., Hurt, P.K., and Williamson, K.J.,
Teaching Through The Cycle – Application of Learning
Style Theory to Engineering Education at Brigham
Young University, BYU Press, Provo, UT, USA, 1991.
F. Edward Cecil of the Colorado School of Mines
provided the detector system around which the pair
spectrometer was built.
6. Leo, W.R, Techniques for Nuclear and Particle Physics
Experiments – A How-to Approach, 2nd ed., SpringerVerlag, New York, 1994.
Jim Hirvonen and J. Derek Demaree of WMRDARL provided target samples for the project.
7. Bygrave, W., Treado, P., And Lambert, J., Accelerator
Nuclear Physics- Fundamental Experiments with a Van
De Graaff Accelerator, High Voltage Engineering
Corporation, Burlington, MA, USA, 1970, pp. 29-54.
REFERENCES
8. Clark, A.W., Greene, M.D., Sacks, P.D., Scribner, T.D.,
“Kinetic Energy Penetrators”, internal report,
Department of Physics, United States Military Academy,
West Point, NY, USA, 2001.
1. Pallone, A.K., Lamaze, G.P., Chen-Mayer, H.H., and
Hirvonen, J.K., “Preliminary Findings on the Thermal
Diffusion of Boron in Tungsten,” in Proceedings of the
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