Physics project labs for advanced undergraduates at Caltech · Thin-Film Deposition Quantized...
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Physics project labs for advanced undergraduates at Caltech Thin-Film Deposition Quantized Conductance Ion Trapping Magnetic Levitation “Simple demonstration of storing macroscopic particles in a Paul trap,” H. Winter and H. W. Ortjohann, Am. J. Phys. 59, 807 (1991). “An undergraduate laboratory experiment on quantized conductance in nanocontacts,” E. L. Foley et al., Am. J. Phys. 67, 389 (1999). “A magnetic suspension system for atoms and bar magnets,” C. Sackett, E. Cornell, C. Monroe, and C. Wieman, Am. J. Phys. 61, 304 (1993). NSF Grant #0940681 “Developing a low-cost, design-driven course in experimental physics” Eric D. Black and Kenneth G. Libbrecht Norman Bridge Laboratory of Physics California Institute of Technology MC 264-33, Pasadena CA 91125 [email protected] Conference on Laboratory Instruction: Beyond the First Year of College University of Pennsylvania and Drexel University 25-27 July, 2012 Thin-film deposition is of- fered as a traditional experi- ment in our Senior Physics lab (ph77). Students grow a sample that they will later use to measure weak local- ization, sometimes referred to as Anderson localization, learning a variety of low-noise measurement techniques in the process. In the fall of 2011, we sought to upgrade the deposition system and its associated vacuum hardware, and we decided to in- volve students in the process. Two under- graduates volunteered for the project, and they set about, with some guidance, learn- ing vacuum engineering and the physics behind thin-film deposition. Starting with a pump and a bell jar, they designed a system that would improve the performance of the existing apparatus by at least a factor of ten in pumping speed and a factor of two in de- position efficiency. Given a budget, they purchased the necessary parts, assembled the new system, and achieved successful pumpdown by the end of the first quarter, 2010-11 academic year. They achieved successful deposi- tion at the end of the second quarter, and they installed the rate monitor and successfully monitored deposition by the end of third quarter. The objective of this grant is to develop a new type of undergraduate laboratory course at Caltech that we call the Physics Design Lab, in which stu- dents design, build, and debug their own physics experiments in a profes- sional laboratory setting. A primary goal for this course is to teach techniques in experimental physics through hands-on experience, and to give students a better understanding of how to create and fabricate real hardware on their own. Beyond teaching essential laboratory skills, however, a broader goal for the Physics Design Lab is to create a different kind of laboratory experience that better fosters an imaginative and inventive spirit in our students. Our wildest ambitions are that this new course goes viral and eventually becomes the norm in physics teaching labs across the country. For the present, how- ever, we just want to see if we can make it work at Caltech. When the physical dimensions of a conductor become small enough, electron transfer begins to show quantum effects. The conduc- tance comes in integer muliples of e^2/h, approximately 1/26 kΩ. Nor- mally, this effect is studied in mesoscopic structures at low tempera- tures, but Foley, et al. showed that it could be demonstrated in air and at room temperatures, using nanocontacts formed between fine gold wires. Our students have reproduced those results and have further demonstrated the effect with simpler, cheaper materials and in an opti- cal analog. Publication of these results is in preparation. Atoms do not have to be charged to be trapped. A neutral atom with a non-zero magnetic dipole moment can be trapped dynamically. The same process can be used to levitate a permanent magnet, which is, after all, just a collection of neutral atoms with permanent dipole mo- ments. Rare-earth magnets made from materials such as Samarium Cobalt or Neodymium Iron Boride have magnetic-moment-to-mass ratios approaching those of single atoms and make excellent samples for students to practice on. Magnetic levitation of perma- nent magnets must be done dy- namically (Earnshaw’s theorem). In this experiment, two large static coils counter the gravita- tional force, while smaller coils carrying an AC current confine the particle horizontally. Students analyze the region of stability in paremeter space and try to adjust Ion trapping is a cornerstone of modern experimental Atomic Phys- ics, and one of the most basic designs for implementing it, the Paul trap, is quite accessible to junior- and senior-level undergraduates. Students can, with some work, understand the basic principles of the design and then use it to trap macroscopic, charged particles in air. The trap can be constructed from very simple materials, up to and including an ordinary paper clip, as shown in the photograph below. Making an approximate, “back-of-the-envelope” design and demon- strating a working trap is relatively straightforward, but a full, quantita- tive understanding of the fields and dynamics of the trap can challenge even the best students.
Transcript of Physics project labs for advanced undergraduates at Caltech · Thin-Film Deposition Quantized...
Physics project labs for advanced undergraduates at Caltech
Thin-Film Deposition
Quantized Conductance
Ion Trapping
Magnetic Levitation
“Simple demonstration of storing macroscopic particles in a Paul trap,”H. Winter and H. W. Ortjohann, Am. J. Phys. 59, 807 (1991).
“An undergraduate laboratory experiment on quantized conductance in nanocontacts,” E. L. Foley et al., Am. J. Phys. 67, 389 (1999). “A magnetic suspension system for atoms and bar magnets,”
C. Sackett, E. Cornell, C. Monroe, and C. Wieman, Am. J. Phys. 61, 304 (1993).
NSF Grant #0940681“Developing a low-cost, design-driven course in experimental physics”
Eric D. Black and Kenneth G. Libbrecht Norman Bridge Laboratory of Physics California Institute of Technology MC 264-33, Pasadena CA 91125 [email protected]
Conference on Laboratory Instruction: Beyond the First Year of CollegeUniversity of Pennsylvania and Drexel University 25-27 July, 2012
Thin-�lm deposition is of-fered as a traditional experi-ment in our Senior Physics lab (ph77). Students grow a sample that they will later use to measure weak local-
ization, sometimes referred to as Anderson localization, learning a variety of low-noise measurement techniques in the process. In the fall of 2011, we sought to upgrade the deposition system and its associated vacuum hardware, and we decided to in-volve students in the process. Two under-graduates volunteered for the project, and they set about, with some guidance, learn-ing vacuum engineering and the physics behind thin-�lm deposition. Starting with a pump and a bell jar, they designed a system that would improve the performance of the existing apparatus by at least a factor of ten in pumping speed and a factor of two in de-position e�ciency. Given a budget, they purchased the necessary parts, assembled
the new system, and achieved successful pumpdown by the end of the �rst quarter, 2010-11 academic year. They achieved successful deposi-tion at the end of the second quarter, and they installed the rate monitor and successfully monitored deposition by the end of third quarter.
The objective of this grant is to develop a new type of undergraduate laboratory course at Caltech that we call the Physics Design Lab, in which stu-dents design, build, and debug their own physics experiments in a profes-sional laboratory setting. A primary goal for this course is to teach techniques in experimental physics through hands-on experience, and to give students a better understanding of how to create and fabricate real hardware on their own. Beyond teaching essential laboratory skills, however, a broader goal for the Physics Design Lab is to create a di�erent kind of laboratory experience that better fosters an imaginative and inventive spirit in our students. Our wildest ambitions are that this new course goes viral and eventually becomes the norm in physics teaching labs across the country. For the present, how-ever, we just want to see if we can make it work at Caltech.
When the physical dimensions of a conductor become small enough, electron transfer begins to show quantum e�ects. The conduc-tance comes in integer muliples of e^2/h, approximately 1/26 kΩ. Nor-mally, this e�ect is studied in mesoscopic structures at low tempera-tures, but Foley, et al. showed that it could be demonstrated in air and at room temperatures, using nanocontacts formed between �ne gold wires. Our students have reproduced those results and have further demonstrated the e�ect with simpler, cheaper materials and in an opti-cal analog. Publication of these results is in preparation.
Atoms do not have to be charged to be trapped. A neutral atom with a non-zero magnetic dipole moment can be trapped dynamically. The same process can be used to levitate a permanent magnet, which is, after all, just a collection of neutral atoms with permanent dipole mo-ments. Rare-earth magnets made from materials such as Samarium Cobalt or Neodymium Iron Boride have magnetic-moment-to-mass ratios approaching those of single atoms and make excellent samples
for students to practice on. Magnetic levitation of perma-nent magnets must be done dy-namically (Earnshaw’s theorem). In this experiment, two large static coils counter the gravita-tional force, while smaller coils carrying an AC current con�ne the particle horizontally. Students analyze the region of stability in paremeter space and try to adjust
Ion trapping is a cornerstone of modern experimental Atomic Phys-ics, and one of the most basic designs for implementing it, the Paul trap, is quite accessible to junior- and senior-level undergraduates. Students can, with some work, understand the basic principles of the design and then use it to trap macroscopic, charged particles in air. The trap can be constructed from very simple materials, up to and including an ordinary paper clip, as shown in the photograph below. Making an approximate, “back-of-the-envelope” design and demon-strating a working trap is relatively straightforward, but a full, quantita-tive understanding of the �elds and dynamics of the trap can challenge even the best students.
