Quarknet in the Classroom
1) Brenda Pless staged a brief introduction to particle physics and cosmic rays for each of the Introductory Science Classes at Blackman High School, a total of about 400 students. Brenda gave the students in her class hands-on insight into the development of cosmic ray showers. She found a template with lines which represent the particle tracks in a shower. By bisecting the angle between pairs of lines, then the angles between those bisectors, etc., the shower development is traced back to the single originating particle. Excellent illustration of exponential growth, and, in this case, an important lesson in linking angle bisection (geometry class) to physics. That is a lesson in using tools from one course to understand another topic, a lesson which it is important to start early!
2) Nick Horton has completed his first year developing the physics curriculum at the new magnet school in Murfreesboro.
3) Meaghan Berry has just been given responsibility to develop a new course at McGavock High School with the generic title "Scientific Research". She is considering the use our muon counters in one of the modules for her new course.
4) Dianne Gigante includes a discussion of the uncertainty of measurements in her physics classes and she and Med Webster have been exploring the feasibility of using the mean absolute deviation instead of the RMS deviation as a measure of the uncertainty in the average of a set of measurements.
Use of the e-lab to analyze data from our counters
Standard procedure for e-lab workshops requires that the host mentor give a brief discussion of cosmic rays and Med reviewed the topic. Our muon counter control electronics is modeled after that used by the Pierre Auger project to detect the highest energy cosmic ray showers and one of the advanced applications in the e-lab enables us to treat two or more of our units like the modules of the Pierre Auger project and identify showers large enough to hit several schools separated by a few kilometers. In preparation for the e-lab session, Webster had accumulated data over several weeks with two shower arrays side by side and only two meters (instead of a few kilometers) apart so that we could make a high statistics exploration of simultaneous hits recorded by different counters. As a warm-up for this more advanced work we learned about plateauing the counters and how to identify "noise" pulses. Brenda displays the pulse size (width) plot as Bob explains the difference between the big signal bump and that tiny noise bump just before it. We broke into groups of two to study different aspects of uploading and analysis of data. Kevin and Meaghan are hard at work on the analysis under Bob's and Aimee's watchful eyes. Scott and Aimee discuss a fine point of the analysis. Uploads of data and geometry were accomplished, a very small noise signal was identified in the pulse height spectrum, and finally coincidences were found between the two detector systems. But the coincidence gate had to be increased to about a second to find these coincidences. With Bob's help, the problem was identified as a hardware difference between our two control cards. The problem is known and compensation in the e-lab software is under consideration, but the use of such a long coincidence time raises the question of random coincidences, and James and Collin ponder the estimation of the false coincidence rate. Does that 2 belong in the denominator? We thank Bob for coming and helping us learn to use the e-lab data processing system.
WWII, Nuclear fission, and the contribution of Oak Ridge
Oak Ridge is our nearest neighbor among the major research laboratories and several teachers had expressed interest in learning more about the origin of the laboratory and about its role in the development of nuclear fusion applications. Brenda borrowed a DVD which emphasized the local history from the Blackman High School library. Our group, joined by two of Paul Sheldon REU students, enjoyed lunch as we watched the DVD. To broaden the perspective and to emphasize the physics behind the events, Webster gave two talks. The first focused on how the mass defects of atoms and the Einstein mass-energy relation lead empirically to the binding energy curve. This curve is practically important because of its implications for fission and fusion processes and conceptually important because the shape of the curve tells us about the range of the nuclear force. A second lecture emphasized the political significance of the work and the roles of the scientists on both sides of WWII in the development of the atomic bomb.
Oak Ridge, both city and laboratory, were created to solve the problem of separating the isotopes of Uranium. We spent Thursday traveling to Oak Ridge and visiting the museum in town and Friday at the laboratory. The massive Calutrons (souped up mass spectrometers) and the gaseous diffusion plant which did the isotope separation for the first atomic bomb are no longer available for tours, but the graphite reactor has been preserved. The white coated (dummy) figures on the elevator platform represent the workers who inserted uranium rods to activate the reactor. Fred Stohl, our tour guide, recounts the history to our group and a few other visitors. When the reactor was first brought into operation, the operators watched for the signal from the neutron counters which would indicate the onset of the chain reaction. Most of our group visited the control room where the neutron counters were monitored while James explored the model of the reactor on the floor below the control room. The massive Calutrons (souped up mass spectrometers) and the gaseous diffusion plant which did the isotope separation for the first atomic bomb are no longer available for tours, so we turned our attention from history to current research work at Oak Ridge Lab. Nanoparticles (size a few nanometers) play an increasingly important role in exploring the properties of matter and in new technologies. Most of the work must be done in clean rooms and our tour of the nonofabrication let us peer through the windows of several labs. The scientist working in this clean room first needs a long reach to adjust something and then observes the result. Photo etching is often an important part of preparing nanodevices and the etch processing is sensitive to blue light but nor to red light. Thus a room illuminated with red light allows workers to see what they are doing without interfering with the etch process. Oak Ridge Lab has world leading massive computing power and our final stop was the computing center where many racks of modest computers are connected to make one of the most powerful supercomputers in the world.
One of the guides had an interesting message for the teachers: The age distribution of the Oak Ridge work force indicates many retirements at about the time current high school students will be completing college and advanced degrees. Tell your students that there are very likely to be great job opportunities for them at Oak Ridge.
That is pleasant recognition of the importance of the work our teachers are doing, and on that happy note our group is ready to head home.