PHYS 433 A: Advanced Laboratory: Nuclear and Particle Experiments

Physics 433 - 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

Alejandro Garcia
Office: Physics/Astronomy Building, Room C509
Phone: 616-3598
Email: agarcia3@uw.edu
Office hours: Usually available for short (5-10 min) meetings 8:30-4:30 daily, by appointment for longer meetings

Class Hours

Required Material

Website https://canvas.uw.edu/courses/1583770 (Standard URL link to Canvas page)

Text

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

References (optional):

• An Introduction To Error Analysis, 3rd ed., John R. Taylor (University Science Books, Sausalito, CA, 2022). Older editions fine to use.
• Radiation Detection and Measurement, 4th ed., Glenn F. Knoll (John Wiley & Sons, New York, 2010). Older editions fine to use.
• 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. 

Measurement techniques, data analysis, and experiment interpretation form the three main emphases of the advanced labs.  The first, measurement techniques, concern the things one usually associates with a lab course: experimental apparatus and its use.  In the nuclear/particle physics lab, you will learn the basic idea of radiation detection and assemble detectors and electronics into functional measurement systems.  You will learn the concepts and practice of measuring particle energies and the timing of events.  These basic methods will then be used to study, for example, the scattering of photons from electrons (Compton scattering), the passage of charged particles through gases (alpha range/energy and drift velocity of electrons) and the physics of cosmic rays (muon decay and cosmic-ray counting). 

The advanced labs focus much more on data analysis and experiment interpretation than introductory labs.  Data analysis include basic tasks often called data reduction, usually done with a variety of computer programs and computer coding, and further analysis of the reduced data to look at it in different ways, i.e., with different types of graphs, with fits to complex curves, and to consider any calibration steps.  Often, the goal of data analysis is to derive final results from the measurements to compare to predictions from theory or to the results of other experiments. 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).  

Learning Goals

"Learning goals" are the most important skills and understanding you should expect to learn by taking this course.  At the end of this Nuclear and Particle Physics Experiments Laboratory course, you should be able to

• Explain the basic concepts and operation of detectors used in radiation measurements, including photomultiplier tubes, scintillators, and possibly gas detectors and solid-state detectors.
• Demonstrate the ability to assemble electronic components, detection equipment and analysis apparatus (e.g, multichannel analyzers, oscilloscopes, counter/timers) into working particle detection systems.
• Describe the effects of cable propagation and cable impedance on signals seen in particle detection systems.
• Explain the distinction between timing measurements and energy measurements and how they are implemented in a measurement system.
• Explain the features in a typical gamma-ray spectrum taken with an energy-sensitive detector (NaI scintillator).
• Carry out complete numerical analysis of experimental data using Python and common computer libraries (numpy, LMFit, matplotlib, etc.)
• Describe the measurement systems used in the advanced experiments: layout of apparatus, measurement concept (how the measurement system leads to the intended measurement, e.g., the Compton scattering prediction of energy loss versus scattering angle, the lifetime of cosmic-ray muons)
• Explain features in experimental data in terms of known physics, and point out features of data that may not be captured by the expected models.

Rules

The following are rules.  The first two may be subject to modification by the instructor, depending on circumstance.  The second two are safety rules which cannot be violated.

• Experimental groups must be no larger than three persons. With four persons or more, there is not enough to do to keep everyone busy.
• Each student must carry out their own data analysis and write their own individual report. Students will work together on experiment operation, data recording, and record keeping, and they are encouraged to discuss their results with each other (and with other students) but each must independently create their own individual analysis computer coding and their own written reports.
• No food or drink may be consumed in the lab. Washington State Law forbids the consumption of food or drink in these labs because they are officially "radiation laboratories:" there are radioactive substances in the lab.
• No students may work in the lab without the presence of lab staff.

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 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 class will be sorted into different experiments for the remainder of the course.  Each group will complete two from among the following experiments: Proportional tube detector, Electron drift in gases, Compton scattering, Muon lifetime measurement, Cosmic-ray counting & statistics, and Alpha particle range & energy loss.

Each experimental cycle will include between 3 and 4 class meetings (i.e., be 2 weeks in length).  All assignments associated with an experiment should be completed before starting a new experiment.  The first meetings of a cycle will mostly involve learning the apparatus and making measurements; later meetings will mostly involve data analysis and interpretation.

Grades will be derived from three distinct "deliverables": the Group Notebook (GN), the Individual Analysis (IA), and the Individual Report (IR).  The Group Notebook is the group's data collection and analysis record.  It includes information about the apparatus, links to data sets, and copies of hand-written notes or calculations, and may pull items from members' Individual Analysis.  The Group Notebook will consist of discussion threads/chats via Google docs.  The Individual Analysis is a Jupyter Notebook written in Python, and submitted as a PDF for grading.  The Individual Report may include a written summary of the experiment and/or answers to specific questions concerning the interpretation of the experiment, also submitted as a PDF to Canvas.

There is no final exam (or any exam).  Your grade is based on the work submitted.

Weekly Tasks

Attend class every scheduled session.  Lectures on related theory will be given at the beginning of most sessions.  You also need to meet with your group to carry out the measurements as well as work on data analysis and discuss your interpretations. It is expected that students will work approximately 9 hours/week on this course, 6 hours/week in the lab and 3 hours/week at home. A full experimental cycle should take about 18 hours to complete, sometimes less, other times more. Over each experimental cycle, students should plan to accomplish the following tasks during the course sessions and at home.  

1. Watch the videos associated with the current experiment.  These give overview of the experiment and how the apparatus is to be used. (1 hour)
2. Do the experiment: assemble apparatus, take data, document the experiment in your Group Notebook. (4-6 hours)
3. Carry out data reduction and analysis in your Jupyter notebook for the Individual Analysis. (5 hours)
4. Annotate, discuss, and check each other's contributions to the Group Notebook (4-5 hours)
5. Write your Individual Report, based on assigned prompt(s). (2 hours)

Videos

Course materials include two different types of videos.

Theory Lectures are about 15-20 minutes in length.  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. Not all experiments have the same number and/or duration of videos.  

Class Meetings

Most class meetings will start with a lecture or whole-class discussion about what the day's tasks will be.  Toward the end of the term, when every group is working on a different experiment, the whole class discussion will be brief.  In these cases, you may be expected to review the theory & experiment videos, or there may be a focused meeting on the experiment between your group and a TA or instructor.

During most of the meeting time students will work with their group on the experiment and data analysis.  See Working Groups below for details. You are expected to attend the full scheduled period.

Remote Participation

In the event that you are unable to attend in person, you may coordinate with the instructor to attend remotely and work with your group via a Zoom session.  This would happen, for example, if you contracted a mild or asymptomatic case of COVID-19 or needed to quarantine but could otherwise attend to your courses. 

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 determined during the first class meeting.  You may already know people in the class you would like to work with.  We will have a class discussion on working styles and your own and others' experience: 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?

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 must decide which members are primarily responsible for which tasks to complete the Group Notebook.  Other members will be expected to review the work entered into the Group Notebook, comment on it and correct it, if necessary.

For each experiment there will be a set of tasks assigned to the group.  For example, to create a diagram of the apparatus, to record and plot a data set, 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 primarily responsible for a particular task. 

The person primarily responsible for a task will complete that task by including comments and work via the google doc.  The other members are expected to comment on, annotate, or sign-off on the task by Responding to the post.  The collection of Posts and Responses will constitute the Group Notebook for the experiment.

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 Notebooks

The Group Notebook is the primary product of the working group.  In modern research, collaborative notebooks are usually created and stored online using a variety of platforms.  In this course we will use Google docs. 

What Goes in the Group Notebook?

For each experiment there will be a start-up Google doc.  It will include information in outline form about specific tasks, as well as links to relevant other materials. The outline can serve as a template for the main information you should build your own posts around.  The outline will also provide information on how to accomplish the tasks.

The outlines are designed to guide you to good documentation practices, however they are only outlines.  As the quarter progresses, the outlines will become less detailed; you are expected to internalize and continue to practice complete, coherent  documentation even though the outlines become less specific.

More information on what should go into Group Notebooks, such as expectations for graphs, apparatus diagrams and annotations, discussion of data and results, inclusion of calculations and computer code, etc., are in Getting Started with Group Notebooks.

Individual Analysis

Some data analysis assignments 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 is building skills with computation as applied to experimental physics.  Data analysis tasks will be carried out with Python on Jupyter Notebooks.  This is also 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, single-spaced, and use 11 or 12 point font and 1 inch margins.
• 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 might require you to state the experimental measurement done, explain the method of the measurement or experimental technique used, and describe the main quantitative result.  Later paragraphs might be in the form of self-contained answers to specific questions requested in the writing prompt.

More information is given in the page About Individual Reports.

Experiments

As noted above, the experiments are

Nuclear Electronics (Oct. 4-15, 4 meetings)
Timing and Counting (Oct. 18-29, 4 meetings)
Energy Measurements (Nov. 1-12, 3 meetings)
Expt 4 (Nov. 15-24, 3 meetings)
Expt 5 (Nov. 29 - Dec. 10, 4 meetings)

Experiments 4 and 5 will vary according to groups, following the scheme below.

Other experiment sequencing may be possible via negotiation with the instructor and affected groups.

Grading

Overall grade portions are 45% Group Notebook, 25% Individual Analysis, 30% Individual Report.  These are further broken down as described below.

Group Notebook

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, (or 100%, 75%, 50%, 25%, 0%) and are based on the typical workplace assessments outstanding, exceeds expectations, meets expectations, does not meet expectations, nothing to assess.  These may also have +/- refinements ("+" adds 0.3 to the numerical grade, "–" subtracts 0.3, i.e., +/- 7.5%).

Although the group document is nominally the product of the group, students will be graded according to their own contributions.  Everyone in the group must be primarily responsible for a task: they denote this primary responsibility through a Google doc entry and everyone must Comment/Reply to the Posts of the others, either to improve, add-to, correct, or sign-off on the Posts given.

Grades will depend on the quality and completeness of the Posts and Comments.  For example, if a Post is essentially complete and correct, the poster will receive an A for the post.  But if the Post is incomplete or incorrect, and the Comment(s) correct the post or cause the poster to improve the post, then the grade for the poster may be lower but the grade for the commenter(s) will be higher.  But if a Post is incomplete/incorrect and the Comments merely sign-off, then all persons would receive a lower grade for that part of the notebook.

All members of the group share responsibility for the whole notebook.

Individual Data Analysis

Individual data analysis assignments will be done in Jupyter notebooks on the JupyterHub for the course, 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 25% of the total Experiment score

Individual Report

The Individual Report will count for 30% of the total.  It will be subject to grading as follows:

If it is turned in by the due date 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. Exceptions to the submission process may occur if there is not enough time to grade, return, and resubmit, such as at the end of the term. A report that falls below a grade of AwR on its final submission will be graded B-, ..., R.  Reports that are originally graded R (0) but not resubmitted will retain the grade of 0.

If it is turned in past the due date, even if submitted within the grace period (see below), it will be graded once on an A, AwR, B-, ..., R scale.  (Note there will be no A-, B+ grades, to make the scale consistent with the preferred submission-cycle scale)

To summarize:

Due dates & Extensions

1. There is one due date for the final version of the Group Notebook and Individual Analysis: midnight (i.e., 11:59 pm) on the last class day of the experiment cycle (typically Thursday or Friday night, depending of section).  But I expect you to be making Posts and Comments on the Group Notebook corresponding to each class day.
2. The due date for the Individual Report is at midnight (11:59 pm) on the first class day of the following experiment cycle, e.g., Tuesday or Wednesday night, depending on section.
3. There is an automatic grace period of 48 hours following the due dates.  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.
4. Extensions beyond the grace period will be granted, but they must be requested before the end of the grace period.  A new date will be assigned to work granted an extension.  New dates will be decided by the TA or instructor.  These will typically be set to 2-3 days following the request.  There is no grace period attached to an extension; the only thing that will change is the availability date.
5. Each student must individually request an extension.  
6. Without an extension granted and set in Canvas, the assignment will become unavailable following the grace period.

For example, if you are in section B (T, Th), you will have lab sessions on Experiment 1 on Oct. 4, 6, 11, 13. The final form of the Group Notebook and the submission of your PDF of the Individual Analysis will be due by the end of Thursday October 13.  You may delay without penalty or special request submitting the final forms of either until the end of Saturday, October 15, at which point the assignment submission will become unavailable. Your score will depend on what has been submitted at that point. But if you need an extension on either assignment it will be granted (without penalty) as long as that request is made before the end of Saturday, October 15.  The canvas assignment due date will be reset.  Any further extensions must be agreed upon by the instructor or TA.  There is no grace period for an extension.

The same rule apples to the submission of the Individual Report: in this example it would be due by the end of Tuesday, October 18, with a grace period set to the end of Thursday October 20.  If it comes in before the due date, it will be subject to the revise/resubmit grading protocol described above.  If it comes in during the grace period, it will be graded once.  If you need an extension on the Individual Report and you want to have it subject to revise/resubmit grading, you must ask for the extension before the due date.  Extensions requested after the due date will make the paper be graded once.

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.