PHYS 433 A: Modern Physics Laboratory

Physics 433 (Online) - Nuclear and Particle Physics Experiments

Experimental techniques in nuclear and particle physics. Detector design and use, energy and timing measurements, cosmic ray measurements, gamma ray scattering and spectra, passage of radiation through matter.

Instructor

David B. Pengra
Office: Physics/Astronomy Building, Room B256A
Phone: 543-4783
Email: dbpengra@uw.edu

Class Hours (Online)

Section A – Monday & Wednesday, 1:30–4:20
Section B – Tuesday & Thursday, 1:30–4:20

First 30-45 minutes may be used for lecture and general comments.
Each section will be divided into tutorial discussion sections, meeting separately, for about 30 minutes (see below).

Required Reading/Viewing Material

Website

http://courses.washington.edu/phys433 (Standard URL links to Canvas page)

Text

Required: Techniques for Nuclear and Particle Physics Experiments, 2nd ed., W. R. Leo (Springer-Verlag, New York, 1994).

References:

• Radiation Detection and Measurement, 2nd ed., Glenn F. Knoll (John Wiley & Sons, New York, 1989).
• Experiments in Modern Physics, Adrian C. Melissinos (Academic Press, San Diego, CA, 1966).
• The Art of Experimental Physics, Daryl W. Preston and Eric R. Dietz (John Wiley & Sons, New York, 1991).

Overview

The 43x series of advanced laboratories are intended to provide a bridge between introductory labs, which are mostly "canned," in the sense that there is a fixed sequence of activities and a fairly rigid analysis to perform, and the kind of "open-ended" research found in real experiments, where you don't really know what will happen or how you should interpret the results. The physics itself is also more complicated than in the intro labs, both in terms of the underlying phenomena and the operation and interpretation of the experimental apparatus. 

In practice, the advanced labs focus much more on data analysis and interpretation.  Basic data reduction is often done with a computer program.  Data sets may be looked at in different ways, i.e., with different types of graphs, with fits to complex curves, and with extra attention paid to calibration steps. In some cases uncertainty calculations must be carried out to complete one's interpretation of the results.  

Interpretation of experimental results is distinct from data analysis.  To interpret the results means to construct a story to explain them within the framework of physical theory, and to note and describe trends, patterns and anomalies in the data.  Interpretation also combines the physics of the phenomena being measured (e.g., gamma rays) with the physics of the apparatus (e.g., a scintillation detector).  

"Online lab" - what does that even mean?   When you think of a "lab" course, you think of a class in which you gather with your partners around a lab bench to manipulate apparatus.  It is a hands-on activity that gives you the experience of learning to turn knobs, connect wires, and fiddle with oscilloscopes and the like.  This kind of experience is the foundation of all "in-person" lab courses.  Learning of essential skills and a direct encounter with the phenomena are to be found in such courses, and this part of a "lab" course cannot be replaced by purely online tools.

You may wonder, with the loss of such practical hands-on experience, how any online course could call itself a "lab." This loss is real and should not be downplayed.  However, in actual experimental research, hardware manipulation and direct data collection usually forms only a small part of an experimental project.  Indeed, if one conducts experiments at certain large facilities, such as a telescope or particle accelerator, one may never set foot in the lab itself, since the apparatus may be inaccessible (orbiting around the earth or in a desert in Australia), or it may be too specialized and delicate to allow anyone other than trained technicians to operate it.  Even when you have all of the apparatus to yourself in a single room, most of your time and effort will not be on taking data.  Instead, you spend your days (and sometimes nights) staring at your data, writing code, making graphs, deriving formulas, checking units, staring at your data, talking to your colleagues, reading the literature, staring at your data, and finally writing your paper.

Thus, the "online" course will concentrate on these aspects.  The "experiment operation" part will be presented in video form, and the videos will mainly deal with how the apparatus is assembled and used, and what the experiment looks like when it is running properly.  Data sets will be recorded in a form that most closely matches what you would do yourself were you to be in the lab room; these may be handwritten tables and notes, digital files produced by data collection software, or photographs of oscilloscope traces.  After that, you will carry out the rest of the experimental investigation in the same manner that you would in the normal "in-person" version of the class.

Because of the loss of the experiential part of the lab, more emphasis will be placed on other aspects of experimental work than in the in-person course: you will be asked to read more deeply into how apparatus works, to learn to apply modern computational methods to data analysis, to work with your partners to complete group work, and to write about your experiment - interpret it, critique it, explain it.

Rules

The following are rules which you can't violate unless there are special reasons to do so, such as family emergencies, illness, equipment failure, and such.

• Experimental groups must be no larger than three persons. With four persons or more, there is not enough to do to keep everyone busy.  Tutorial discussion sections will consist of 2-3 experimental groups.
• Each student must write an individual report. Students will work together on experiment observation, data reduction and analysis, and they are encouraged to discuss their results with each other (and with other students) but each must independently create their own individual written reports.
• Only if and when University restrictions on in-person instruction are lifted may a student or group of students enter the physical lab space in the Physics/Astronomy Building.

Every person is welcome in this course.  Instances of discrimination (e.g., shunning, belittling, bullying, harassment) for any reason (e.g., ethnicity, religion, sexual orientation, gender identity, different-ability, or political beliefs) will incur thorough investigation and possible sanction through University approved processes.  If you believe you have been subject to such discrimination, please contact the instructor directly, or see University Policies for information on how to contact University officials.

Course Structure

The lab will consist of five to six experiment "cycles".  The first three will cover the basic operation and use of particle detectors and associated equipment.  These are Nuclear Electronics, Timing and Counting, and Energy Measurements.  Then the techniques learned in these experiments will be put to work to measure the Muon Lifetime and to study Compton Scattering.  Finally, we will branch into either gas detectors with Proportional Tubes or solid-state detectors with Alpha Particle Range and Energy Loss. The later experiments are subject to change, depending on the overall progress of the course.

Experiment cycles will be either 1 or 2 weeks in length.  Nuclear Electronics, Timing and Counting and Muon Lifetime are scheduled to last 1 week; the others 2 weeks.  The assignments associated with 1-week experiments will be shorter, for example, the written report will be limited to 1 page in length, as compared to 3 pages for 2-week experiments.

Basic requirements

There is no final exam (or any exam).  Your grade is based on the work submitted and your active participation in the online meetings.

Graded work:

1. Participation (30%)
   • Meeting attendance
   • Discussion board postings
2. Experimental work (40%)
   • Individual analysis tasks
   • Group document contribution
3. Individual reports (30%)

Each of these items is discussed below, along with how they will be graded.

Weekly Tasks

Over each experimental cycle, students should plan to accomplish the following tasks (expected to take 7-9 hours/week), more-or-less in this order:

1. Watch the lecture video(s) concerning basic theory.  Watch the experimental videos that walk through the experiment structure, operation and data collection. (1-1.5 hrs)
   
   • Post a question or item on the discussion board for your tutorial discussion.
2. Attend the live Zoom sessions: (1) the overview/general comments at beginning of class period and (2) the tutorial discussion as scheduled for your group. (0.5 hrs first meeting, 1 hrs second meeting)
   
   • Meet with group members to determine who will do what for the group document.
3. Carry out assigned tasks for experiment: typically this involves your individual data analysis plus agreed-upon contribution for group document. (3-5 hours, including additional group meetings)
4. Write individual report, based on assigned prompt(s). (1 hr)
5. Before due date: review and sign-off on group document. Upload group document, individual data analysis task and written report.

Videos

The core content of this course will be delivered via Panopto videos.  There are two basic types: Theory Lectures and Experiment Operation and Data Collection.

Theory Lectures will be about 15-20 minutes in length, one per class meeting (i.e., 2 videos per week).  These are voice-over-slide videos that discuss the important theoretical ideas behind the week's experiments.  The focus of the "theory" is to help you make sense of the experiments themselves: how the apparatus works, how/where the high-energy particles come from, and how to understand the ways that the experiment illustrates the underlying physics.

Experiment Operation and Data Collection videos show an experiment in detail: what the apparatus is, how it is assembled, how the electronics are configured and connected together, and any other important physical detail you would need to know in order to operate it. The videos will also show how data are collected, plus other measurements needed for calibration or analysis.  Experiment videos will be broken up into sections of variable length, typically between 5 and 25 minutes each.  For example, one video may give an overview of the apparatus, another may delve into its setup and calibration, and a third may show how data are collected.

Plan to spend some time with these videos.  They are not meant as entertainment but as vehicles for presenting crucial information that would be difficult to transmit in purely written form.  You will often need to extract numerical data from them, as well as construct a detailed diagram of the apparatus.  You are recommended to use the tools under Panopto to set bookmarks, take notes, and generally keep track of the most important sections.

Writing prompts for the individual reports may also refer to topics discussed in these videos, so it is a good idea to have a look at the prompts before watching them.

Zoom Meetings

Each scheduled class period will contain two different Zoom meetings. 

The first meeting will start promptly at 1:30 pm, Pacific Time, and may last from 10 minutes to about 30 minutes.  All students in the section are expected to attend because this will be the meeting where information concerning the course as a whole will be discussed, for example, class management and due dates, general questions about the week's activities, or additional lecture material not included in the videos.  The first meeting will be automatically recorded and saved in the Zoom folder.

The second meeting will start at a later time (e.g., 2:30 or 3:00) and consist of approximately half the students in the section (5-9 persons), comprising 2 to 3 experiment groups.  It will last about 30 minutes.  The second meeting will provide participation credit.   The purpose of the second meeting is for you and your partners to discuss with the instructor, TAs, and other students topics related to the experiment.  These topics may come from prompts provided by the instructors (a question like. "why does the pulse size depend on the PMT voltage?") or from your own contributions to the discussion board for the experiment.  The second meeting will not be recorded.

To earn the participation credit for the second meeting, you must be present and you must join the conversation.  To be "present" means you appear on the list of attendees for the Zoom meeting.  To "join the conversation" means you must either speak up with a comment or question, or submit something similar through the "chat" feature.  If you choose the latter mode of communication, chat communication that is "private" to the host or instructor will remain anonymous.

SPECIAL NOTE:   If you are unable to join the second meeting at the scheduled time, you may satisfy the participation credit by an alternate mode.  This could be a Zoom meeting with the instructor at a different time, a phone call, or an email conversation.  You should contact the instructor directly to set this up.

The Prime Directive: Communicate with the instructor no less than two times per week concerning the content of the course.

Success in this course requires communication.  I need to hear from you each individually and often.  Only when I know what you are thinking and what you need can I help you to understand the material and meet the requirements.

Office hours. In addition to the scheduled meetings above, the instructor and TAs will be available on Zoom for "office hours" at other times during the week.  The schedule for these office hours will be worked out as the course progresses.  You may also request specific times to meet via email (use the Canvas email feature).

Discussion Boards

Posting on the weekly discussion board for your tutorial group is the second component to the participation grade. You should plan to post at least 2 questions or comments on the board per week, or one per class meeting.  The questions or comments will motivate the discussion in the tutorial meetings.  The discussion board due dates will be approximately one hour before the start of class (12:30 pm).

Working Groups

Research is a collaborative process.  Most scientific work is done in teams, some quite large.  Even if you are a solo theorist, you need to talk to others to refine your ideas, brainstorm and challenge assumptions.  Thus, learning how to work in a group is essential.  In experimental research, projects are broken down into specific tasks to be accomplished by subject experts (e.g., coding, hardware, sample preparation) and those who may be learning the field (e.g., grad students).

You will be expected to form a group of 2-3 persons in your section.  Group membership will be assigned by the instructor, and initially it will be based on your answers to a short survey that will also ask about your personal preferences.  For example, are you a strong computer coder or are you just beginning to learn?  Do you like to plan your tasks in detail or just start fiddling with the data?  Which would you rather do: experiments or theory?  Also, do you know someone in the class that you have worked well with in the past (or conversely, someone you may have had a bad experience with)?  The goal of the survey is to get information to form groups whose members can complement each other, but who also have a good chance of forming productive working relationships.

After the first two experiments, you will be asked to assess your group's performance.  Group members are not  bound to the same group for the duration of the course, but if possible, those groups working well together will be preserved.

What Your Group Should Do

At minimum, your group has two main tasks:

1. Decide which members are primarily responsible for which tasks to complete the group document.
2. Decide when and how to meet/communicate, outside of the scheduled class meetings, to accomplish and assess your group's progress.

For each experiment there will be a set of tasks assigned to the group.  For example, to create a diagram of the apparatus, to perform basic data reduction, to carry out a particular calculation, or to do outside reading on a topic and write up a few paragraphs on it.  Your group should decide who is most responsible for a particular task, and also decide on how the other members will monitor progress, offer advice, ask questions, etc.  Some of these decisions and communication can happen within the tutorial "second meetings,"  but you should set up a separate scheme for communication among the group outside of normal class times.

Members should also plan to rotate tasks from experiment to experiment.  In other words, do not always have the same person draw the apparatus diagram, or carry out basic data reduction coding.

The other main purpose of the group is to work together to accomplish the data analysis tasks that should be completed by every member.  Such tasks are important enough that these will be assigned to all students.  However, it is expected that your group may work together and help each other solve these problems.

Group Documents

The "group document" is the primary product of the working group.  It should be created with a collaboration platform such as Google Docs.  The group document should be made accessible to the TAs and instructor so that they can view and comment on it during the course of the experiment.  To create such a document automatically, use the Collaborations feature on Canvas.  This will create a link for the instructor and TAs as well as a link to each member's UW Google account.

What Goes in the Group Document?

To complete the group document, use the template for the particular lab (posted on the experiment page).  The template lists the tasks to be completed and some information on how to accomplish them.  The template also indicates spaces for other information, such as the group members and contact info, who is assigned primary responsibility for which part, and reminders for the other members to review and sign-off on each section.

The templates are designed to guide you to good documentation practices.  As the quarter progresses, the templates will become less schematic; you should carry on with the same record-keeping practices you used earlier.

More information on how to set up the group documents and criteria for them are in Getting Started with Group Documents.

Individual Data Analysis Assignments

Some data analysis assignment will be broken out of the group document and assigned separately to all students. You may think of these like "homework" for a lecture class, but distinct from the writing focus of the Individual Reports.

There are two reasons for making such assignments not part of the group. 

First, such assignments usually concern core concepts, such as creating a calibration, or comparing the Compton scattering angle vs. energy relationship to the data.  Everyone in the class should know how to do these things, not just the one person who might be assigned to that task in the group.

Second, among the learning goals of this course involve building skills with computation as applied to experimental physics.  Data analysis tasks will be carried out with Python on Jupyter Notebooks.  This is part of an overall department effort to teach computation within the physics major.  The use of Python is based upon current trends in physics research, data science generally, and the growth and maturation of collaborative tools associated with Python.  See Python and Jupyter Notebooks for more information.

Individual Reports

Each student must also write and submit their own individual report, as a PDF uploaded to a Canvas assignment.  The structure and content of the report will be described in the assignment, and will vary as the course proceeds, but there are a few common aspects:

• It must conform to strict formatting rules and length limits.  Typically,  a report must be between 1 and 4 pages, be typed, use 11 or 12 point font and 1 inch margins. (Shorter reports are expected for shorter experiments.)
• It must be written well, with complete, grammatically correct sentences and structured paragraphs.
• It must address certain questions or topics in a certain order.  For example, the first paragraph should state the experimental measurement done, the method of the measurement or experimental technique, and the main quantitative result.  Later paragraphs should answer specific questions requested in assignment.

More information is given in the page About Individual Reports.

Experiments

As noted above, the experiments are

Nuclear Electronics (1  wk)
Timing and Counting (1 wk)
Energy Measurements (2 wks)
Muon Lifetime (1 wk)
Compton Scattering (2 wks)
Proportional Tubes or Alpha Range & Energy Loss (2 wks)

The later experiments are subject to change depending on how the course goes. 

Grading

Overall grade portions are 30% participation, 40% experiment, 30% individual report.  These are further broken down as described below.

Participation

Zoom meetings

Credit for participation in the tutorial "second meeting" will be assessed on each scheduled day. The participation credit will also follow a trinary scheme: A = Present and contributed to the conversation;  C = Present but did not contribute; F = Absent.  To "contribute" you must speak or write (chat) in at least one fully formed sentence or thought.  Minimal comments like "Yes," "no questions," or "I'm fine, thanks" do not qualify as a contribution.   

It is important that the group participants communicate with each other.  You are encouraged to do more than talk with the instructor during the meeting.  The TAs and the instructor will assess the communication among the members of the meeting.  An ideal case would be when the conversation has minimal to no input from the instructor.  Strive to learn from each other!

If a group, or a member of a group, is unable to join the live Zoom meeting, they should arrange an alternate mode of communication with the instructor and other group members. 

Zoom meeting participation will account for 5/6 of the participation grade (i.e., 25% of total).

Discussion Boards

You should post at least two comments or questions to the discussion board associated with each experiment.  These comments will help motivate the Zoom discussions, and at least one comment is due before the first meeting of the week.  Credit is assigned as follows: 2 relevant comments = A, 1 relevant comment = C, no relevant comments = F.  A "relevant comment" is a fully formed question or remark that may be used in the discussion.  "I have no questions, thanks" is not a relevant comment.  

Discussion board comments/questions will account for 1/6 of the participation grade (i.e., 5% of total).

Experiment

Group Document

Group document grading will reflect "real-world" assessments: the kinds of assessments that are typical in work environments and active research.  Notebook assessments will be listed as letter grades A, B, C, D, F which correspond to numerical grades 4, 3, 2, 1, 0, and are based on the typical workplace assessments outstanding, exceeds expectations, satisfactory, below satisfactory, nothing to assess. 

The Group Document grade will be broken into an overall scoring and an individual scoring.  Because different parts of the group document will be the primary responsibility of different members, the grade for a particular portion will be awarded to the group member with responsibility for it.  Because all members should work together to produce the final document, review, and sign-off on the other parts, the document as a whole will be assigned an overall grade, approximately equal to a weighted average of the individual parts.  (The weighting will depend on the relative importance of different sections, and vary from experiment to experiment).

The group document will account for 5/8 of the experiment grade (i.e., 25% of total).  Within a group document, the individual portion will be worth 3/8 (15% total) and the overall portion will be worth 2/8 (10% total).

Individual Data Analysis

Individual data analysis assignments will be done in Jupyter notebooks, converted to html, and uploaded to canvas for grading.  They will be graded according to the letter scale used for the Group document (A-F) and account for 3/8 of the total experiment grade (15% total).

Individual Report

The Individual Report will count for 30% of the total, and it will be graded on a 3 level scale, corresponding to typical decisions made by scientific journals: accepted (A), accepted with revisions (AwR), and rejected (R).  These will correspond to letter/numeric grades of A/4.0, B/3.0, and F/0.0.  Reports that earn AwR or R may be resubmitted once.  Once a personal report may no longer be resubmitted, the final grade for it will be on the above A-F scale.

To summarize:

Due dates & Extensions

In order to keep things simple but also reduce stress, due dates are stuctured in the following way:

1. There is a single due date for all documents (Group Document, Data Analysis task, Individual Reoprt) for an experiment cycle: midnight (strictly 11:59pm) of the day a new cycle starts.
2. There is an automatic grace period of 48 hours following the due date.  Think of this as an automatic extension, should you need to talk to the TA or instructor.  You do not need to ask for this extension.
3. Extensions beyond the grace period will be granted, but they must be requested before the end of the grace period.  A new due date will be assigned to work granted an extension.
4. Late work that has not been granted an extension according to the above will not be graded, except by appeal to the instructor.

For example, if you are in section B (T, Th), your first set of assignments (Experiment 1) will be due Tuesday, 13 October, at midnight.  You may delay without penalty or special request submitting one or more parts until Thursday, 15 October.  If you need an extension on any part, it will be granted (without penalty) as long as that request is made before the end of Thursday, 15 October.  But, if you do not turn anything in by the end of Thursday, 15 October, your grade will be assigned a zero (F) for the missing work, unless you appeal to the instructor.

Grade Calculation

The final grade will be calculated according to the formula

Thus, to earn a 4.0, you need about 95%.

Writing ("W") Option

A writing "W" credit will be awarded to any student who earns at least 4 "Accept" grades on their Individual Reports.

University Policies

A number of University of Washington policies pertain to this course.  See University Policies.