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 . . A project of the department of physics, California Institute of Technology, in collaboration with K-12 schools, colleges, and universities throughout the Los Angeles area.






The CHICOS project, based in the Kellogg Laboratory in the department of physics at Caltech, represents a unique blending of cutting-edge scientific research and broad-based educational outreach. CHICOS is an active research array for the detection of ultra-high energy cosmic rays – subatomic particles slamming into the Earth’s atmosphere with the energy of a brick falling from a rooftop. These ultra-high energy cosmic rays, or UHECRs, interact with the atmosphere to produce large showers of secondary particles at the surface of the Earth. Detection of UHECRs therefore depends on an array of particle sensors deployed like a net over many square kilometers to catch the incoming shower. In the CHICOS project, schools across the Los Angeles area provide the “net” of detector sites with ready-made infrastructure and a valuable population of teachers and students who participate in the project.
CHICOS adds an active dimension to the existing K-12 science curriculum by involving teachers and students in science as an ongoing enterprise. In this way, CHICOS provides a uniquely direct, collaborative relationship between K-12 schools and scientific researchers, renewing teachers’ enthusiasm for their field and encouraging student interest in science and higher education. CHICOS classroom activities and research opportunities reach out to a broad cross-section of schools and academic levels, helping to inspire today’s students to become tomorrow’s scientists and scientifically literate citizens.
CHICOS cosmic ray detectors are painted in school colors and surrounded by flower beds at Chaminade Middle School in Chatsworth. The two detectors are connected to a computer in the nearby science classroom for round-the-clock cosmic ray observations.




Scientific Background

The energetic subatomic particles that pervade the universe are known as "cosmic rays." The history of the discovery of these particles is a fascinating story which takes us from the turn of the 20th century to the present. Along the way, cosmic rays are intimately tied to many steps in scientific understanding, not only in physics and astronomy but in fields as far flung as medicine and archaeology. Today the most puzzling of these particles may be telling us something unexpected about the distant reaches of the observable universe.
Cosmic Rays in…
• Nuclear science: cosmic-ray discovery coincided with early studies of nuclear science / radiation
• High-energy particle physics: many exotic particles first seen in cosmic rays
• Biology: cosmic rays and mutation rates on Earth
• Archaeology: Carbon-14 dating and “cosmic ray tomography” of the pyramids
• Earth science: connections to climate change and ice ages
• Astronomy: cosmic rays reveal composition of the stars and other objects that make them
• Space exploration: will manned space exploration be limited by cosmic ray exposure limits?
During the last decade, the community of high-energy cosmic ray physicists has constructed a number of very large (1-100 km2) arrays to study cosmic rays at the very highest energies ever detected (1020 electron Volts, or nearly 10 Joules, in a single particle). These particles are over one hundred million (108) times more energetic than those that can be produced in modern accelerator laboratories. The astrophysical origin of these particles is still unknown, but it has been generally assumed that they are protons (Hydrogen nuclei). These particles produce huge “showers” of many secondary particles when they collide with atomic nuclei in the upper atmosphere; the most energetic of these showers can simultaneously trigger detectors over a several kilometer radius at the earth's surface. The study of these extended air showers affords us an occasional glimpse of the very highest energy particles ever observed, and a unique view of extraordinary astrophysical processes. The rate of incidence for cosmic rays at the highest energies (1020 eV) is quite low: in a 100 square kilometer area only about one event occurs




per year. Therefore, it is essential to sample a large surface area (hundreds of square kilometers) to observe a significant number of these ultra-high energy particles. An observatory for ultra-high energy cosmic rays often looks nothing like a classic astronomical “observatory;” instead it consists of many small particle detector stations arranged in a far-flung network or array. In the last several years, the largest previously built array (in Japan) has produced extremely interesting results (see article Science, vol. 281, August 14, 1998, page 891). It appears that these primary particles may be more energetic than previously thought, and so the assumption that they are protons is being seriously questioned. There is even speculation that one could identify point-like sources of these particles in the sky. These results have energized the field and even larger arrays

A high-school senior displays his CHICOS involvement on the license plates of his first car.
. are being proposed and built. The primary research goal is to collect more events at these ultra-high energies and characterize their energies and apparent direction of origin for these strange visitors from the outer reaches of space.



Present Status and Plans


The Los Angeles basin is ideal for this type of project due to the very large area (> 5000 km2) of dense population with existing school infrastructure. CHICOS is deploying over 180 scintillation detectors at 90 school sites to form an array with area of more than 400 km2 in the San Gabriel and San Fernando Valleys.
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CHICOS installation sites are shown as triangles across the Los Angeles basin. Yellow and orange triangles are operational or planned as of April 2005. Blue triangles indicate the potential for future expansion.




Each site has a detection system with a computer to acquire data, and operates in an autonomous mode using GPS time-stamping of events. The data from each site is transmitted via internet to a central computer at Caltech where the data is logged, analyzed, and accessible to the high schools. The availability of existing infrastructure in the Los Angeles school system with internet connections, power, shelter, and willing collaborators provides an excellent opportunity to develop such a large array. Very capable PC's, GPS receivers, and high-speed computer network connections are all recent technical developments that are crucial to the feasibility of a project like CHICOS.
Deployment of the CHICOS array began in fall 2001, and 67 detector sites are active as of April 2005. The full CHICOS-90 array will be complete by 2006 and will operate as a major research facility. Individual sites in this array are hosted by a unique collaboration of colleges, universities, high schools, middle schools, and elementary schools, crossing both grade-level and public-private boundaries to represent a diverse cross-section of L.A. area educational institutions.


High school physics teachers participate in the installation of CHICOS equipment at their schools.



Education

CHICOS promotes K-12 science and math education with an emphasis on subject matter related to physical sciences and mathematics. The program aims to spark student interest in science via direct involvement in a cutting-edge research project such as our cosmic ray detector network. CHICOS ties particularly into curricular content in the areas of physics, chemistry, and astronomy by adding an active dimension to existing science classroom experiences. Instead of selecting only for the




brightest students or the best-performing schools, we offer students of many education levels and diverse experience the opportunity to be involved in research at the forefront of particle astrophysics. Teachers and students are exposed to experimental design, uncertainties and error analysis, exploration of the unknown, and collaboration with other researchers locally as well as nationally and beyond. It is our goal to foster student interest in learning science, pursuing higher education, and hopefully, choosing a scientific or technical career. Due to the ethnic and racial diversity of the Los Angeles high schools this program also provides a novel mechanism for broadening the participation of underrepresented groups in society in scientific research. Teachers and students work with Caltech scientists to experience the scientific process first-hand and to apply concepts and skills that may otherwise seem to exist only in textbooks. CHICOS participation includes classroom presentations from research personnel, Caltech-campus workshops on cosmic rays and related science, CHICOS-related teaching modules on topics within the existing science/math curriculum, and informal interaction with scientific researchers.
Teachers and students participate directly in scientific research via independent projects, as well as a summer research program on the Caltech
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campus. Because CHICOS serves a broad range of schools and grade levels, we offer these opportunities as a set of options rather than a fixed program; schools and teachers tailor their participation to the needs of their own students and curricular goals.




Some CHICOS education offerings…
• Classroom materials: worksheets and activities developed by teachers and researchers
• Web-based reference materials: interactive tutorials and reference links on related topics
• Teacher workshops: quarterly Saturday workshops at Caltech
• Class visits and presentations: on-request presentations for a variety of grade levels
• Summer program: students work at the Caltech lab building equipment for the research array
• Independent research opportunities: CHICOS data and guidance for science fair and other independent projects
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CHICOS affords teachers a unique opportunity for professional development and participation in forefront research. A group of CHICOS teachers, collaborating with Professor R. Seki of CSUN and the CHICOS Project Coordinator, has developed high school level curriculum materials relevant to cosmic ray research that are closely coupled to the California state science education standards. Working relationships between teachers and university personnel
also provide crucial opportunities to renew teachers' involvement in the enterprise of science, expand their understanding of recent developments in the field, and even uncover important flaws in textbook science content.


Plans for Expansion

A major future goal is to expand the scope of CHICOS to cover a larger fraction of the Los Angeles area and include a much larger percentage of junior and senior high schools. Increasing the area to over 1000 km2 would establish a major world-class facility in ultra-high energy cosmic ray physics. Such an expansion would clearly increase the importance of CHICOS as a facility for ultra-high energy cosmic ray research in the Northern Hemisphere. Furthermore, the
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Monroe HS student studies the proposed locations of new CHICOS stations in schools across the entire LA basin.




educational program would then reach more than 10,000 high school students and 300 high school teachers. This proposed expansion would have a major impact on both cosmic ray research and high school science education in the Los Angeles area.
There is huge potential for growth in the CHICOS program's impact nationwide as a model for other educational partnerships, and as a resource center for teaching tools in high energy physics and astronomy. Existing national connections include the CHICOS project’s interaction with the NSF-funded, national QuarkNet program and the North American NALTA consortium of cosmic-ray-based education efforts. Formalizing our materials to make them useful in a broader setting will require further development of web-based teaching materials and self-contained classroom kits.


Collaborators and Donors

CHICOS is a collaborative project involving Caltech, Cal State Northridge, UC Irvine, community colleges, and local schools. Participation from Los Angeles area teachers and schools extends to public and private, and elementary through high school.
The project is coordinated through the Kellogg Radiation Laboratory at Caltech under the direction of Professor of Physics Robert McKeown. Cal State Northridge provides coordinated continuing education courses for high school teachers to help deepen their participation in the research project and its incorporation in the high school curriculum. Initial funding for the

Crew of students, high school teachers, and research personnel retrieving detectors in the mountains of New Mexico in summer 2000.
. project was provided by the Weingart Foundation, the National Science Foundation and Caltech. The Los Alamos National Laboratory donated over 180 surplus detectors from the decommissioned CYGNUS array (another cosmic ray project), and photomultiplier tubes were obtained from the Palo Verde experiment; these form the core of the hardware system used in the CHICOS 90-site array.




IBM donated a significant fraction of the computers used in data collection at each site. Ongoing operational expenses of the project are provided by the National Science Foundation.
CHICOS actively seeks additional grants, both public and private, to enable expansion and better educational support as described above.


Further Information

For more information contact Dr. Theresa Lynn, CHICOS project coordinator, at chicos@caltech.edu.



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