2013

Welcome to Advanced Physics Lab 2013!

Instructors

Professor: Tobias Marriage (marriage@pha.jhu.edu), Office: Bloomberg 215

TAs: Sean Cantrell (seancan@pha.jhu.edu), Ian Anderson (ianderso@pha.jhu.edu)

Lab Guru: Steve Wonnell (wonnell@pha.jhu.edu)

Wiki

Source of much course-related knowledge: https://wiki.pha.jhu.edu/advlab_wiki/index.php/2013

General Description

In this class, you will carry out six experiments, some of which helped form the basis for modern physics. More importantly, you'll learn

• how to conduct an experiment with special attention to estimating systematic and statistical measurement errors,
• how to model the data/understand the goodness of fit (<math>\chi^2 </math>) and errors on model parameters,
• and how to present your work through scientific writing.

These three aspects essentially define the course. Each lab will be evaluated based on how well the three aspects are realized.

Groups

Labs are done in groups. In the first week students divide into 10 groups of 3-4 students each. Email the professor your group membership and he'll enter it on the groups list.

Schedule

Lab times: Mondays 10:00-12:50, 13:30-16:20. You may come at any time to either class period. This is essentially when the professor and TAs will be available. Each lab is associated with either the professor or a TA. Schedule meetings in advance with TAs as they may not be around for the full 6 hours. The professor will be around for both sessions. Each lab takes two weeks and therefore has two associated lab periods.

First Lab Period. Before the first lab period you should write an overview of the experiment and the procedure (essentially a draft of the introduction and the experiment sections of your report). To get credit for the draft, you should submit this before class starts (10am) on Monday. You will discuss the experiment with the professor and/or the TAs. The instructors will give high level comments and a grade on the draft. In the first lab period you also take a first pass at conducting the experiment and data taking. For many labs you will continue taking data throughout the week, and you will save time by having the instructors there to clarify any issues that arise during the initial data taking.

Second Lab Period. The next week you should have an initial analysis done of your data. You should submit a draft of your report with an initial data analysis section and any preliminary discussion before 10am on this day to receive credit. You should come to the lab in order to discuss your results with the professor and/or TAs.

The semester goes as follows. Unless noted otherwise below, final drafts of lab reports are due at midnight the day before the next lab begins.

Jan 28: Welcome Lecture

Feb 04: First Lab Begins

Feb 11: LaTeX Tutorial

Feb 18: Second Lab Begins

Mar 04: Third Lab Begins (Mar 18-24 is Spring Break; Lab 3 due before Mar 25)

Mar 25: Fourth Lab Begins

Apr 08: Fifth Lab Begins

Apr 22: Sixth Lab Begins (Due the day after reading period)

Labs 2013

Responsibility for assistance and grading of labs will be split between the professor and TAs. Here is the Lab-Instructor association. You should get in touch with your instructor to set up a time to meet on Monday with your group regarding the lab.

Tobias Marriage: PE/SL, MOD, ZE, NMR

Ian Anderson: FH, NS, RS

Sean Cantrell: ML, BM, HE

The labs are done in groups according to the following schedule: Schedule 2013. In the first week, lab groups send a wish list of six labs to the professor. The labs will be assigned on a first-come-first-serve basis.

The labs are all located in the PUC lab either in the main room or in small side rooms. Here are the current locations.

The labs are rather open ended, and it is left to you to decide exactly what procedure you will follow to make your measurement. These decisions can of course be made in conjunction with advice from your instructors (or peers), but it should come primarily from you. A couple of the labs are very open ended and you could spend forever on them if you did not get some limit. For this reason, we include the following restrictions this year:

• PNMR: You only need to measure <math>T_1</math> and <math>T_2</math> for a single substance, such as mineral oil.
• Nuclear Spectroscopy: You only need do the labs through to the Experiment 4 (Compton Scattering).

Safety

Use your common sense in all situations. In these labs you'll encounter high magnetic fields (don't handle ferrous metals near them), weak radioactive materials (respect them), lasers (don't stare into the beam), high temperatures (don't touch them) and other manageable hazards. When in doubt: ask the professor, Steve Wonnell or a TA.

Grading

Grades breakdown as

• 80% Labs
• 20% Preparation (submission of drafts as described in Schedule)

Each lab grade will be divided into three equal sections: experiment execution (20 pts), data analysis (20 pts), and presentation (20 pts).

Collaboration Policy

Execution of the experiment is a group effort, so is necessarily collaborative. Furthermore, students are encouraged to discuss experiments, analysis, and other course related issues with their peers (and, of course, with the instructors). However, each person should carry out their own data analysis (e.g., no code sharing), produce their own plots, and write their own report. Violations of academic ethics (e.g., plagiarism) will be handled according to JHU Policy.

Work Submission and Late Reports

Work should be submitted by email in PDF format to the instructor at marriage@pha.jhu.edu -- you may also want to send them to the TA grading the lab (it will get to the TA in any case). To help us organize, the subject of the email should be "Advanced Lab: [last name]" where [last name] is your last name. Also the PDF should be titled [lab number]_[lab initials]_[last name].pdf. For instance if it's your first lab and you are doing Franck Hertz, and your last name is Smith, then you would title your report "01_FH_Smith.pdf".

The reports are due by midnight on the day before the next lab begins. Sometimes, circumstances are such that one cannot get a report in on time (illness, grad school visits, etc). For this reason, each student is allowed one late report, which may be up to one week late. Use this wisely! After the first instance, a late report will result in having the awarded point total multiplied by 0.5. For example, an 88% score would become a 44% score.

All reports will be returned as soon as possible and no later than 2 weeks from the submission due date. If you are missing a report evaluation, then notify the professor immediately.

Anatomy of an Experiment

This is an overview -- more detailed discussion will take place in tutorials.

Experiment Execution. The first step in executing an experiment is to have a good idea of the phenomenon being measured -- the reason why you're doing the experiment. Then you need to have a thorough knowledge of the experimental apparatus. With this preparation you will be able to take data. But obtaining measured values is not enough. You need both values and errors. You need to conduct the experiment in a way that estimates systematic errors and statistical errors. Systematic errors can be checked for by conducting the experiment in more than one way that should, e.g., give the same result and checking for discrepancies. Statistical errors may be obtained by repeating the experiment and evaluating the sample variance of the data or there might be an analytic expectation for the statistical error, as in the case of counting experiments.

Data Analysis and Interpretation. The input to data analysis consists of measured values and their errors. You then fit this data with some physical model. If the fit is "good", then you can believe the best-fit model parameters and associated model parameter errors. These model parameters tell you something about the physical world. One big thing: No spread sheets.

Presentation Lab reports constitute the language of the course. The sections of a report are

• Abstract -- Summarily say the aim of the experiment and what you used to measure the phenomenon. Then quote your result which is usually some physical parameter with errors.
• Introduction -- Describe the phenomenon being measured and any historical info. This should not contain much information about what you did in the experiment-- just roundly what you aim to do. The intro is mainly useful background.
• Experiment Description -- Describe the experiment setup and procedure, including apparatus etc.
• Data Analysis -- Describe the model that you used to fit the data. Discuss the goodness of the fit and, if the fit was good, the derived model parameters and errors.
• Discussion -- Interpret your results and discuss what may have gone wrong if, e.g., the fit in the Data Analysis section was not good.
• Conclusion -- A short section where you summarize the paper.

Lab Report Specifications

The reports are to be created on a computer with computer generated graphics, plots, etc. The document preparation system for the reports is LaTeX. The computers in the PUC lab have various installations of LaTeX editors/compilers. You can also download freeware for your personal computers.

The lab reports should have an abstract, an introduction, description of the experiment (apparatus and procedure), description of the analysis, discussion of results, a conclusion (including future directions), and a bibliography.

The format should have 1" margins with no smaller than 11 point font. The maximum number of pages is 6, including figures. Be concise.

A standard strategy is to create your figures first in order to guide the body of the text.

Useful Texts

Data Analysis

• Bevington & Robinson, Data Reduction and Error Analysis for the Physical Sciences
• Press, Teukolsky, Vetterling, Flannery, Numerical Recipes in C (Available online)
• Lupton, "Statistics in Theory and Practice"

LaTeX

• Lamport, LaTeX: A Document Preparation System
• A Not Too Short Introduction to LaTeX: media:not_too_short.pdf

You might also find useful websites from previous years.

Tutorials

You have lots to learn to put into practice during the labs. Try to get through these in the first week.

• Basic LaTeX
• Analysis 1: Mean, Variance, and Error Propagation
• Analysis 2: Goodness of Fit
• Analysis 3: Linear Model Fitting and Error Propagation
• Analysis 4: Linear Fit Example
• Analysis 5: Nonlinear Fit Example

• Media:WarmUp.pdf