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Graduate Physics Laboratory Handbook: Introduction |
| Guide · Table of Contents · Experiment List · Calendar · Student Roster |
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Graduate Physics Laboratory Handbook: Introduction |
| Guide · Table of Contents · Experiment List · Calendar · Student Roster |
The object of this course is to give you an in-depth experience in experimental physics as a means to understanding how laboratory measurements test concepts in physics. To this end we have assembled a number of experiments of varying difficulty and theoretical sophistication, together with support facilities that often make it possible to extend an experiment or even to build a new one. What will be new to many of you is the lack of detailed instructions. From little more than a few literature citations you will be expected to design an experiment, assemble and perhaps partially construct the apparatus, and report on the results in the form of a scientific paper.
We hope that this experience will give you some insight into what it is that an experimental physicist does. We also hope that from it you will begin to develop a proper respect for measurements, seeing them as neither sacrosanct nor ignorable at will. Fi nally, we expect that you will improve your record-keeping skills andyour ability to give a coherent, readable account of the work you have done according to a previously arranged and fixed schedule.
Were one to ask a number of experimental physicists what techniques they considered to be most useful in their research, almost all would mention machine shop practice, electronics techniques, and digital computer programming. Some would list, in addition , high voltage techniques, microwave techniques, cryogenics, high vacuum technology, and optics.
Time permitting, all of these techniques could be studied, but clearly this is not possible in the Graduate Laboratory. In the limited time available you will learn some of these techniques while performing experiments which you have chosen. It is assumed that you will acquire some degree of skill as you attempt to perform a good physics experiment using and understanding the concomitant techniques.
The future theorist has here a unique opportunity to get first-hand insight into the world of your future experimental colleague and to explore the experimental aspects and techniques of the field into which he intends to go. If you are going to be an exp erimentalist, it is our belief that in this lab you will learn both some physics and some techniques that you otherwise would not and that will be useful to you.
For the purposes of the course it will be assumed that you are experimentalist. Emphasis is on independent work. This implies that you should be able to demonstrate to the instructor's satisfaction the actual set-up and operation of the experimental appar atus.
As you proceed in your chosen experiments, the following should receive your careful consideration:
The number of experiments you will perform during this semester is not rigidly fixed. Nominally, the number of experiments you are required to do is two in both PHYS 621 and PHYS 429. (Students in the latter course should read the specia l note on PHYS 429; students enrolled in the Special Projects course should see the note peculiar to the PHYS 798 course.) However, one of these experiments can consist of the extension of a previous experiment. Such an extension should be discussed with the instructor a nd should also be covered by a proposal and paper which could be an addendum to the earlier paper.
The number of experiments you perform is not directly related to the grade you will receive. The progress you make in understanding experimental physics will, in part, determine your grade in the course. Each experiment should be selected in consultation with your instructor. The student is encouraged to select experiments in fields as diverse as possible, in the hope that one (or all!) may be found to be of sufficient interesting to require further study at some later time. Your activities as you perform your experiment should be discussed with the instructor frequently (a progress report at the midpoint of the experiment will be required). Attendance for the first scheduled hour of class, and for at least three hours of the scheduled laboratory session is mandatory. It is important to note, however, that in addition to the time spent in the lab, an almost equal amount should be spent in study and planning. Attendance is required in order to provide regular contact between you and the staff, so that the staff can be available to give you any help you might need. For almost all experiments additional time in the lab beyond the prescribed hours will be necessary. This can be arranged with the approval of the teaching assistant or the instructor and through the Laboratory Coordinator.
The specific requirements of the course are:
PHYS 429 meets concurrently with PHYS 621 for a scheduled 5 hours per week instead of the 6 hours for PHYS-621.
Although the courses meet concurrently, the standards for grading are different in the two courses. In particular, an undergraduate student is not expected to have the theoretical sophistication of the graduate student. Finally, the sections in both cours es are very small, leading to a tutorial situation and extensive free-discussion. In such an atmosphere the undergraduate should expect, and ask for, more help in the solution of problems and/or difficulties than the graduate student.
Students in PHYS 798 are expected to follow the schedule set for PHYS 621 students. If one experiment is required, it will be performed during the time allocated for the PHYS 621 first experiment; if two, during the time allocated for the two PHYS 621 exp eriments. The time allocated for any one of these experiments will not be permitted to extend through the course of the semester. These experiments should be somewhat more advanced than the typical first experiment.
All of the facilities of the laboratory are available for student use.
Copies of some books and most journal articles referenced in this handbook are available in room PHY-3333. The remaining reference material may be found in the Engineering and Physical Sciences Library. The "Operation" portions of equipment manu als are also available. This material is for use in the laboratory only and must not be removed from the laboratory area. Please return all reference materials to their respective files. These reference materials are part of the Graduate Laboratory's i nventory. They are not to become part of the student's reference library.
A drill press and soldering irons as well as a selection of small hand tools are available for use in the laboratory. For more involved work the department has a student machine shop in Room PHY-0125. Mr. Mark Giddings, a skilled and patient teacher, is t he supervisor and will be pleased to answer questions and give advice. It is necessary to see him before initiating any project in the student shop. For reasons of safety unsupervised work in the shop is not permitted. Plastic and metal supplies ar e available in the student shop and in the main shop stockroom.
Modular nuclear instrumentation is stored in Room PHY-3323, as are all radioactive materials. Radiation monitoring film badges are stored in the gray wall cabinet in Room PHY-3333 and must be returned there when not in use. These personal radiation monito rs must be worn at all times when in Room PHY-3323 or when using any radioactive materials. Radiation badge reports will be sent directly to the badge-holders.
Most of the instruments are stored in Room PHY-3307 and expendable supplies stocked by the laboratory are stored in Room PHY-3313. Unlike most teaching laboratories, we grant students self-service privileges in our stockrooms. It is assumed that you will return all equipment or supplies to their proper places of storage when finished with them. The purpose of returning equipment is to save the time and energy spent searching for needed equipment or supplies. Students are the chief beneficiaries of this po licy. Those who do not abide by it will be blacklisted and will lose the self-service privilege.
Expendables and other small items not available in the laboratory may be obtained at the physics store (PHY-0104) and chemistry store (CHM-0202) with a pick-up authorization available from the Laboratory Coordinator.
Out-of-hours work is permitted subject to safety restrictions. You may sign out a card-key to the room you must use beyond the end of the working day. Keys must be returned at the end of the semester. In any case they will be disabled at semester's end. A fter-hours work with power tools byunsupervised students is strictly forbidden. Permission is never given for unsupervised work in the radiation areas (PHY-3323 or the Solid State X-Ray Room, PHY-2315).
The purpose of these notes is to make students aware of the damage they may do to some items of equipment if they do not take appropriate precautions. Read the manual before using any instrument for the first time. These manuals are found in the Gr aduate Laboratory Library, Room PHY-3333, in the files labeled "Manuals".
Most electronic instruments can be easily damaged by excessive voltage or current. Excessive voltage can be as low as 7 volts for some instruments.
There are numerous mechanical vacuum pumps in the laboratory. They should never be turned off and left with a vacuum at the pump intake port because oil may be drawn into the system. They may be left on overnight, but not pumping at atmospheric pressure.
Oil diffusion pumps are easily damaged and very tedious to clean. Exposure to air results in either cracked or oxidized pump oil, which can be a tarry mess. Read the manual for the system very carefully.
Photomultiplier tubes exposed to light become noisy and remain so for an extended period. Photomultiplier tubes exposed to light with accelerating voltage applied make expensive junk suddenly.
The heat of vaporization of helium is a minuscule 6 cal/gm; by comparison, that of water is 596 cal/gm and that of nitrogen is 93 cal/gm. It is for this reason that helium transfers will only be done by the staff.
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