The purpose of this course is to familiarize you with experimental physics by carrying out your own measurements and interpreting the results. The experiments you will perform are based upon phenomena described in theoretical courses, and will utilize modern experimental techniques and computational procedures for analyzing the data. After two terms work in this laboratory you should be well prepared to function independently in a physics research laboratory.
Thirteen experiments are instrumented with instruction sheets available. They are:
# Students not completely familiar with the use of an oscilloscope or with the concepts of counting statistics and detector efficiency are advised to sign up for Experiments 1 and 2 before attempting any of the NUCLEAR AND PARTICLE PHYSICS EXPERIMENTS.
(1) GENERAL INFORMATION:
Experiments must be performed during supervised laboratory sessions, which are provided Tuesday, Wednesday, and Friday from 1 p.m. to 6 p.m., when T.A.'s, the Instructor, and a staff member will be available.
YOU MAY VISIT THE LABORATORY ANY DAY OF THE WEEK, INCLUDING MORNINGS AND DAYS WHEN NO SUPERVISED SESSIONS ARE SCHEDULED to freely utilize the laboratory reference material and the computer facilities. See a T.A., the lab supervisor, or the instructor to have the laboratory opened.
Students are encouraged to work in pairs, with an independent and complete notebook produced by each. Tables of data and plots may be photocopied (available through the T.A.), but all narrative material, calculations, and analysis must be performed independently. Consult freely with your partner (or anyone else) in analyzing your data, but do not simply copy another's results.
Write-ups for each experiment are provided in the lab. Most of these write-ups have been recently revised to reflect the current state of the experiments. While informative, these write-ups do not contain all of the information you will need. It is vital that you study the specified references for each topic. Most of the books listed in the write-ups are available in the Laboratory Library for use ONLY IN THE LABORATORY. Most experiments have a binder of reference material for use at the experiment bench, with additional copies that may be signed out for OVERNIGHT use. Check with the T.A. about the procedure for borrowing these last items.
(2) REQUIREMENTS:
You and your partner should average one session of 4 - 5 hours in the Laboratory each week in order to complete an adequate number of experiments. All experimental work must be performed only during the regularly scheduled supervised hours when teaching staff is available. The number of experiments required in one quarter depends upon their difficulty, with typical times for completion of each of the experiments listed on Page 1. After completion of an experiment at the bench, the next week will be devoted to completion of the NOTEBOOK entries (p. 5), in the laboratory, where you will have easy access to the advice and guidance of a T.A., or the Instructor. It is during this same week that you will prepare for the RECITATION SESSION (see item 4) for the next lab, as shown in the examples under SCHEDULING below. Typically, this schedule calls for you to spend 5 to 6 weeks at the bench. Normal requirement will be 3 - 4 experiments per quarter . Three (3) weeks of bench work should be completed before mid-term (7 November, 1994).
(3) SCHEDULING:
This laboratory requires that you be responsible for organizing your time, i.e., scheduling the preparation (RECITATION SESSION, above), execution (bench time), and completion (see NOTEBOOK, page 4) for each experiment in synchronism with subsequent experiments. A subsequent experiment cannot be started until the notebook entries for the previous experiment are submitted and graded. The time limit for completing notebook entries for each experiment and submitting them for grading is one week after completion of taking data for that experiment. Late submission carries a 2/3 letter grade penalty.
Advanced scheduling is necessary. Prerequisites for some experiments are listed on Page 1. When you choose an experiment, reserve the equipment for the number of sessions listed on Page 1 on the appropriate sheet in the laboratory. If you finish in less time, erase the unneeded reservation as early as possible to allow others to use the equipment. If you need more time, sign up for another session. If you are unable to perform an experiment at the time reserved, cancel your reservation as early as possible. Please be especially careful regarding the Low Temperature liquid helium experiments; liquid helium is expensive and must be ordered only as needed.
Two examples of the many possible scheduling sequences are shown below:
Before starting an experiment, an informal (and individual) recitation session (30 minutes) with a T.A., or Instructor, is required. An appointment sheet is posted in the laboratory. Please come to this recitation prepared to discuss the physics of the experiment and the experimental methods to be used. This oral presentation will be graded. You should first visit the laboratory to examine the apparatus and study the equipment manuals and reference material.
Whether you plan to enter graduate school or take up employment in industry it is essential that you be able to communicate orally, be it "reading" a paper to a learned-society meeting, a department seminar, or the defense of a thesis. To this end, you must study the subject in detail and prepare a concise outline that allows a logical and orderly description of the material. Clear schematic figures and diagrams on the blackboard are vital. An important function of this laboratory is to prepare you to meet these responsibilities. For this reason, we have instituted recitation sessions.
(5) NOTEBOOKS:
A laboratory notebook is a record (a journal) of your activities in the laboratory. The entries should contain enough information and narrative to allow anyone with a background in either theoretical or experimental physics to understand the goal of the experiment, the experimental methods used, and the results obtained. This means logging and acknowledging errors as well as correct procedures. It should be possible for the reader to successfully reproduce the experiment from only the material that has been entered in the notebook. All entries must be dated and permanent (WRITTEN IN INK).
If you work with a partner, each will keep an independent notebook. Photocopies of figures, graphs, etc. are acceptable. Consult with a T.A. about copying facilities available through the laboratory. Notebooks must be left in the laboratory regularly, i.e., each week, so that the T.A.'s and Instructor may examine them and comment on the entries, even though your experiment is not yet complete. The T.A.'s examine the validity of the data, the scope of the analysis, and the reasonableness of conclusions. Grades are not assigned. The comments supplied by the T.A.'s should be considered before continuing. Feel free to discuss these with the T.A. at any time.
1. The first entry MUST be a detailed TABLE OF CONTENTS containing the experiment title, dates of activity and completion, partner's name, page numbers, and any other entries that you feel will be useful to the reader (and yourself at a later date).
2. The initial entry for each experiment should be a brief description of the physical concepts of the experiment and the theory behind it, as well as the physical parameters relevant to it. ( i.e., an "Abstract")
3. A description of the experimental setup, complete enough so that the experiment can be reproduced by someone else. Attachment of the diagrams from the experimental write-ups may save you valuable time. Note any revisions you make in the suggested setup.
4. Complete descriptions of the actual procedures followed in the laboratory, including vital parameters such as instrument settings, distances, times, temperatures, etc. THIS INFORMATION SHOULD BE WRITTEN INTO THE NOTEBOOK WHILE THE EXPERIMENT IS BEING PERFORMED, NOT AT SOME LATER TIME.
5. All raw data should be entered in clearly labeled tables, with realistic estimates of all of the uncertainties from all sources of random and systematic errors. An estimate of uncertainties is an integral part of all data. Show the "ball park" calculations used to immediately test the validity of data. Always perform these before altering a setup, or leaving the lab. Describe all of these preliminary calculations clearly.
6. Tables of results should be clearly labeled and set off for the convenience of the reader, supplemented by graphs of data where appropriate. Graphs should have titles and captions, labels on the axes, with all interesting features identified. Provide detailed descriptions of all calculations performed.
7. A discussion of your results, with a comparison with theory and previously published experimental values is essential, i.e., a "Conclusion". If you find inadequacies, or errors, in the experiment, or write-ups, discuss them constructively. Suggestions for improving existing experiments, or proposals for new ones are eagerly solicited. (Experiments 10 and 15 were developed from student proposals and efforts.)
An experiment is successfully completed if you can demonstrate a thorough understanding of the physics and have familiarity with the apparatus. Grades are recorded based on the pre-experiment RECITATION SESSION and the NOTEBOOK, with 1/3 : 2/3 weighting, respectively.
1. RECITATION SESSION: The RECITATION SESSION (30 minutes) with a T.A. or the Instructor, before the start of an experiment, will be graded. Feel free to discuss with your T.A., or the Instructor, any matters raised during the oral session, as well as your grade. Grades will be available to you by at least the next day, probably sooner.
2. NOTEBOOK: Entries for the experiment, organized to present a brief introduction, experimental procedures and data produced, analysis of the data, and conclusions (as outlined in the previous section on NOTEBOOKS) should be completed for presentation to the T.A., or Instructor. These notebook entries will be graded [the grade is weighted by the number of weeks at the bench (see Page 1) for a given experiment]. These notebook entries must be submitted within one (1) week from the conclusion of the experiment. [At the end of the term, notebooks must be in by 9 am Wednesday of finals week (i.e., 3 working days before grades are due at the Registrar's office).] Failure to meet this schedule will result in a reduction of the notebook grade for that experiment of two-thirds (2/3) of a letter grade. The notebook grade reflects the pre-lab preparation and performance in the laboratory, the validity of experimental procedures, and the quality and completeness of notebook entries. Grades will be available from your T.A. expeditiously after the End-Of-Experiment notebook grading.
You may revise, or supplement, any (or all) notebook entries (and are encouraged to do so) before submitting the notebook for its final grading at the end of the experiment. Be sure that all revisions are dated and clearly labeled as such.
LATE WORK: If sufficient work is not completed by the end of the term, and the grade of E is required, the final grade assigned upon removal of this deficiency entails a reduction of grades for the LATE WORK by ONE FULL LETTER GRADE. This is necessary for fairness to people who have completed all required work in the allotted time.
[DROPPING COURSE: If you complete some, but not all, of the experiments required for a quarter, and then drop the course, it may be possible to carry that completed work over to another term - but only with partial credit. The exact nature of this carry-over, and the amount of that partial credit, will be negotiated on an individual basis.]
Seven PC's running MS-DOS are installed. Four units are IBM Model 8580-A16 PS/2's (386/25 MHz with 160 MB hard disks) while the fifth unit is a Gateway table top unit (386/33 MHz with an 80 MB disk) primarily servicing a PC based high-resolution Multichannel Analyzer system, but available for general data analysis. The two newest machines are Intel 80486DX2-66 based PC clones with 420 MB disks running DOS 6.20 and Windows for Workgroups 3.11. All PC's run MS-DOS V 5.0 or higher with Windows 3.0 or 3.1, and are loaded with MathCad, Maple, Microsoft Quick Basic and FFIT. In addition, the IBM units have the following items installed:
System 1 - MathCad for Windows (Ver. 3.1), Word for Windows (Word Processor), and MathType (Mathematical Equation Editor linked to Word for Windows).
System 2 - Windows Version 3.1, Microsoft C/C++ with the Windows SDK, Microsoft Visual Basic, Windows Drafix (Drafting program).
System 3 - PAW Data Analysis-Plotting Program, Borland Turbo C++ for DOS, Borland Turbo C++ for Windows.
System 4 - PAW Data Analysis Plotting Program.
All the above units are connected to a shared Hewlett-Packard LaserJet III printer that will produce output for both text and graphics. Kermit is available on each for transferring data to/from the Tracor-Northern TN-7200 Multichannel Analyzers (MCA).
A PDP-11/73 Time share system (RT-11/TSX-Plus operating system) provides an easy to use Interactive Plotting Program (IPP) for processing data from 6 MCAs. Two video terminals contain graphics processors to permit plotting data on the screen and then "dumping" the display to a shared dot-matrix printer. A group of interactive data analysis programs, integrated with IPP are available. These will allow listing and plotting of data, smoothing, linear transformations, linear regression analysis, quadratic and Gaussian fits, "background" subtraction, etc. Several experiment-specific plotting and analysis programs are also available. The high-level languages available are BASIC-PLUS and FORTRAN-77.
The standard data analysis reference for the laboratory is Data Reduction And Error Analysis For The Physical Sciences by Philip R. Bevington (several copies are in the laboratory Library). The FORTRAN routines listed in the book are available on the PDP-11 computer as both source code and as a compiled link library file. Source code (FORTRAN-77) for the interactive IPP data analysis programs, and the experiment-specific analysis programs, are also available in disk files. Contributions of any useful analysis programs for either type of computer are eagerly solicited.