Cosmic Rays Through the Heartland
Daniel R. Claes and Gregory R. Snow
 Introduction
The National Research Council's National Science Education
Standards [1] call for enhanced "science as process" in which
students actively develop an understanding of the scientific
process as combining knowledge with reasoning skills. This "process" should
include opportunities for students to engage in extended investigations.
The cookbook style "experiments" through which high school
students are too often led tend to give the expectation that scientific
results should follow 40-minute exercises, or worse, that such frustrating
efforts are best finished by fudging easily predicted data.
At the University of Nebraska-Lincoln (UNL), an innovative
program is underway to build high school teachers' technical skills
and knowledge base, as well as provide for student participation in
a genuine long-term research experience.
UNL's Cosmic Ray Observatory Project
was launched in earnest in the summer 2000 when 20 participants from
five Lincoln/Omaha area schools attended the first summer research
program. CROP is a statewide outreach experiment whose goal is to involve
Nebraska high school students, teachers, and college undergraduates
in a multi-faceted, hands-on research effort to study extended cosmic
ray air showers. We like to think of CROP as a means of merging the
three primary missions of professors at a land grant institution: research,
teaching, and outreach.
Particles from extended showers will be sampled by
arrays of student-built and maintained scintillation counters placed
on high school rooftops, while a PC-based data acquisition system located
inside the school building records events. A GPS receiver will provide
a time stamp so that time coincidences with other sites, signaling
the presence of extended cosmic ray showers, can be detected. Student
participants will compare data with other sites via the Internet and
share experiences through regional workshops organized around the state's
19 Educational Service Units. A schematic of a typical high school
setup is shown in the figure.
 In 4-week summer research experiences, CROP will provide
intensive teacher/student training in state-of-the-art particle detection
and computer monitoring. This will be followed by year-round, long-term
studies of cosmic rays. The experiments begin right in the classroom,
continue through the school year, and via coordinated Internet sharing
of data, extend beyond the schoolyard's boundaries. Conceived as a
genuine research project, CROP will be developed in stages, and its
success measured incrementally.
The Scientific Potential of CROP
An excellent and accessible review of observations
made to date of ultrahigh-energy cosmic rays can be found in [2]. Although
the main thrust of CROP is to expose its participants to the physics
of cosmic rays, air showers, particle detectors, data acquisition and
analysis, CROP addresses physics topics which will complement major
ground-based arrays (CASA [3], AGASA [4], the Pierre Auger Observatory
[5]) in three areas. Primary cosmic ray energies and direction-of-origin
distributions will be collected for (i) building-sized showers (E > 1015 eV,
plenty of rate) using the detector array at each school and (ii) city-sized
showers (E > 1019 eV, much lower rate) using time-coincidences
among schools in populated areas like Omaha and Lincoln for comparison
with the above experiments. In addition, CROP will make a unique scientific
contribution, since CROP detector sites will eventually cover the 75,000
mi2 area of the state, many times the coverage of the above
arrays. A map of Nebraska with dots showing the locations of the state's
314 high schools is shown below. The sparsely spaced sites in western
Nebraska will allow CROP participants to investigate very long-distance
correlations which would indicate extensive cosmic-ray bursts. In simple
terms, when an Omaha school detects an energetic shower, does the whole
state light up? The scientific impact of CROP will be strengthened
in proportion to the number of sites collecting data simultaneously,
making expansion across the state the primary goal after the pilot
year.
 Recycling Hardware
The main CROP detector components - acrylic scintillator
tiles, photomultiplier tubes (PMTs), and power supplies - are being
recycled from the now-complete Chicago Air Shower Array (CASA) [3].
Operated between 1990-1998 by physicists from the Universities of Chicago,
Utah and Michigan, CASA employed 1089 separate detector stations arranged
in a 0.25-km2 grid within the Dugway Proving Grounds (operated
by the U.S. Army) in western Utah. Each station housed four 61 cm W 61
cm scintillation counters and a low- and high-voltage power supply.
The retired CASA equipment has been donated to CROP. Spare CASA
counters formed the basis for prototype detector development led by
our undergraduate assistants.
In late September 1999, a CROP team traveled to the
CASA site and loaded a rented truck with sufficient hardware to outfit
the first 10 CROP schools. Most of the equipment was found to be in
good working order. We had originally planned to make annual trips
to Dugway to recover additional materials as needed, but the Army base
now insists that the site be cleared promptly. Hence, we are making
plans for a single, large-scale retrieval effort in May 2001.
We are also grateful to Fermilab for the long-term
loan of a large supply of electronic modules previously used in high-energy
physics experimentsNIM crates and modules. These are used for pilot-year
measurements at the schools and for instruction during the CROP research
workshops.
Funding History
During the R&D years prior to 2000, CROP caught
the attention of UNL administrators and was awarded seed grants from
various internal sources. Our Vice Chancellor of Academic Affairs sponsored
the 1999 equipment recovery trip to the CASA site in Utah. As collaborators
on CERN's CMS experiment, we also received support from its Education/Outreach
task, since CROP serves as a model for local outreach efforts led by
active high-energy physicists. A major boost came with the award of
a 4-year, $1.34 million grant from the National Science Foundation.
The grant is funded jointly by the Division of Elementary, Secondary,
and Informal Education and the Division of Physics. During its February
2000 Committee of Visitors review, the Division of Physics repeatedly
cited CROP as an exemplary initiative helping to meet its education
and research charge. CROP's unique collaboration between university
researchers and high schools in a long-term, viable experimental program
was recognized as having great potential to increase the impact of
experimental physics research on the nation.
The NSF grant primarily supports the participant workshops
and educational assessment activities described below. We have had
success finding funds for supplementary hardware from individual school
districts and state of Nebraska sources. Identifying funding sources
to ensure our expansion across the state and the continuation of CROP
post-NSF funding is a primary goal of our institutionalization plan.
CROP's Inaugural Year Recruitment
First-year recruitment focussed on the Lincoln and
Omaha metropolitan areas through presentations at regional Nebraska
Association of Teachers of Science and Nebraska-AAPT meetings as well
as a special Lincoln Public School in-service day conducted at UNL.
This local focus has facilitated frequent meetings and maximized the
supervision necessary in the initial effort to get multiple detector
sites up and running.
Through blanket e-mail solicitations to Nebraska high-school
physics teachers and word of mouth we have accumulated a waiting list
of schools across the state which are anxious to become CROP participants.
Almost daily, we also receive inquiries from schools in adjacent states,
across the country, and abroad. In the next few years, teams will be
recruited from each of Nebraska's 19 Educational Service Units, with
ESU Directors providing insight into the unique needs of their region.
We place high priority on the recruitment of teachers and students
from groups underrepresented in science, which in western Nebraska
includes schools in very remote, rural locations.
The Summer Research Experience
The first annual summer session was held in July-August
2000. Six physics teachers with a total of 14 students represented
five participating high schools: Kent Reinhard from Lincoln Northeast
High School,
 De Tonack from the Lincoln Science Focus Program, Father
Michael Liebl from Mount Michael Benedictine High School in Elkhorn,
Bruce Esser and Sharon Genoways from Marian High School in Omaha, and
Dennis Miller from Norfolk High School.
Days typically were divided between morning classroom
sessions and afternoon lab work. Mini-courses explored relevant topics
in high-energy physics, astronomy, charged particle detection, Monte
Carlo applications, triggering, data acquisition, and the Global Positioning
System. Afternoons were devoted to hands-on work with prototype detectors.
Participants polished scintillator and glued PMTs, wrapping and checking
their assemblies for light leaks which required them to learn to use
an oscilloscope. They also measured the detection efficiency of each
counter. Through these exercises, they became familiar with the assembly,
testing, and operation of the detectors they now use at their own high
school. The photograph shows Marian High School student Amanda Carney
preparing to glue a PMT to a scintillator tile. Teacher input has proven
crucial to the evolution of the detector set-up which we feel helps
guarantee its safe, durable, and foolproof operation. The logistics
of, and possible problems with, the installation and operation in a
variety of school settings were discussed in the summer session.
During the summer 2000 session, "All Things Considered",
National Public Radio's afternoon news program, carried a story on
CROP which was produced locally by Nebraska Public Radio and featured
interviews with both students and teachers in the project [7].
First-Year Mini-Experiments
The schools have embarked on two mini-experiments
to be performed during the 2000-01 academic year. The first -- measuring
the (small) variation of cosmic-ray rate vs. barometric pressure with
detectors stacked in a vertical telescope will help us determine
how well the school teams, working independently, can measure the same
effect. The second measuring coincidence rates with detectors spread
horizontally in various configurations will help us optimize the
detector set-up for each school's study of extended air showers.
The school teams have impressed us with their ideas
for supplementary measurements which become independent student projects.
Mount Michael H.S. is busy checking for diurnal variations with 15-minute
runs made six times a day. Norfolk H.S. varies the detector separation
in their vertical telescope, effectively controlling how narrow a window
they view of the sky. Marian H.S. is assembling small trigger counters
to map the light-collection efficiency across the face of their scintillator
tiles (studying signal attenuation).
Academic Year Workshops
Twice each school year, nominally December and April,
one-day workshops will be scheduled as an opportunity for team leaders
to meet, share experiences, critically evaluate the program, and make
plans for both continued data-taking and statewide expansion. On December
2, 2000, our first academic year workshop was held at UNL, attended
by the summer participants, the UNL CROP staff, and the project's Advisory
Panel. Students from each school reported on their progress, and collectively
we discussed how to complete the mini-experiments that were just getting
underway. Some of the teachers whose school teams will join CROP in
the summer 2001 also attended to get oriented.
The CROP Advisory Panel
CROP is guided by an 8-member Advisory Panel with
varied expertise in high-energy and cosmic-ray physics, secondary science
education, hands-on science museums, other science outreach programs,
and high school science teaching. One full Panel meeting per year overlaps
with the autumn participant workshop, and selected Panel representatives
observe the summer and spring workshops. At its meeting in December
2000, the Panel heard progress reports from the first-year school teams,
witnessed their enthusiasm, and joined a business meeting with the
CROP staff. The Panel's report provided a valuable critique of the
pilot year and suggestions for the future. The report included ideas
for ensuring effective communication with the schools during the academic
year, technical development hints, and a program of supplementary experiments
the teams can perform with their cosmic-ray detectors.
Educational Evaluation
Significant energy is devoted to formative and summative
assessment. CROP has enlisted an external evaluator whose activities
are supported by NSF funds. The Advisory Panel and UNL's Center for
Instructional Innovation also contribute to project assessment. While
critiquing CROP's success at establishing a statewide network of detector
sites, the evaluation's primary focus is the educational value that
CROP experiences provide participating teachers and students, using
established assessment tools. Among other topics, the evaluation team
will study teachers' self-efficacy for conducting CROP research and
classroom activities and changes in students' interest and attitudes
about science.
Preliminary assessment results from the pilot year
are encouraging. Pre- and post-testing at the 2000 summer workshop
revealed that the participants improved their knowledge of cosmic-ray
physics and particle detection techniques and gained sufficient expertise
in operating their detectors to perform the assigned mini-experiments
during the upcoming academic year. Participant exit interviews identified
which content presentations were deemed most useful and a number of
ways to enhance the laboratory activities of the workshop. There is
also evidence that participating in CROP leads some students to look
more favorably on majoring in physics or another science in college.
Technical Developments in Progress
The ability to link GPS time-stamped data collected
by participating schools depends on developing an inexpensive electronics
card designed to handle the triggering, signal processing, GPS timing,
and data acquisition. The card will interface directly to the data-taking
PC. The GPS-timing part of this card has been developed by our CROP
affiliates at Iowa State University. Its performance was presented
by ISU undergraduate student Nick Mohr at the workshop "Cosmic
Ray Physics with School-Based Detector Networks" held in Seattle
in September 2000 [6].
Statewide Expansion
During each of the remaining years covered by our
NSF grant, we will add 5-6 schools, drawing participants from each
of the state's ESUs. A wide geographical distribution of strategically
placed sites will facilitate our expansion across the state. By identifying
and training local leaders to serve as regional experts, we will form
the centers around which CROP will grow post-NSF funding.
As installation and training become streamlined, more
will be handled through long-distance learning: web-based help pages,
videotaped installation and testing instructions, hot-line response
phone numbers. By the conclusion of this project's NSF funding, we
hope to be able to reduce the duration of the summer workshops and
gradually replace them by small regional workshops operated in part
by experienced teachers in the area.
Conclusion
CROP started as a dream by two high-energy physicists
(the authors) use existing high-school sites as the grid for a ground-based
cosmic-ray experiment, and train teams of remote teacher and student
investigators. Now that the project has begun, the reality is more
exciting than the dream. High school physics teachers represent an
untapped source of enthusiasm and resourcefulness for frontier physics
research. CROP is participant-driven, and the teachers and students
guide the project step-by-step in both its technical and educational
aspects. We are forming a true collaboration, not unlike a large high-energy
physics experiment with collaborating institutions spread all over
the country and the world. We look forward to our first Physical Review
publication, some few years from now, authored by the CROP staff and
our large team of high-school colleagues.
More information about CROP, including milestones
passed to date, can be found on the CROP
web site.
References
1. National
Academy Science Standards are available in html form, as well
as information on purchasing the publication in hardcopy.
2. "Observations and implications of the ultrahigh-energy cosmic
rays", M. Nagano and A. A. Watson, Rev. Mod. Phys. 72,
689 (2000).
3. Chicago
Air Shower Array (CASA) web site
4. Akeno
Giant Air Shower Array (AGASA) web site.
5. Pierre Auger Observatory
web site
6. Workshop
on Cosmic Ray Physics with School-based Networks, held at the
University of Washington Dept. of
Physics in September, 2000.
7. National Public Radio's feature on CROP can be heard
by visiting www.npr.org, selecting "All Things
Considered", and finding Cosmic Rays in the Archives under August
3, 2000.
Daniel R. Claes and Gregory
R. Snow are faculty members in the Department of Physics and
Astronomy, University of Nebraska, Lincoln and co-Principal Investigators
on the NSF funded CROP project.
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