Engineering Design and Fiber Arrays

About Me

I am soon to be a 7th semester Physics major, and I have been working with Dr. Jones and his lab group since more-or-less the beginning of summer 2008. My current work on the GlueX project relates to the mechanical engineering design and testing of the photon-tagging detector (microscope) which will be used in the Hall D experiment at the Jefferson National Accelerator Facility (J-Lab). I am also extremely involved in USA Cycling, where I work as a neutral support race mechanic at professional cycling races across the country (but mostly in the northeast).

The project that I am working on with Dr. Jones and his UConn lab group is the mechanical design of the tagger microscope enclosure, and the assembly of fiber optic arrays that it will contain. The tagger microscope is a critical part of the GlueX particle accelerator experiment being constructed and run at Thomas Jefferson National Accelerator Facility in Virginia. The GlueX project is overseen (and largely-funded) by the United States Department of Energy, but is executed by an international collaboration of physicists which includes students and faculty members from universities worldwide.

Project Abstract

The GlueX experiment is designed to probe the mechanisms of confinement of quarks and gluons inside hadrons. Quantum chromodynamics (QCD) is the accepted theory of the nuclear strong force, which explains the interactions of the quarks and gluons that compose hadrons. Quarks and gluons are subatomic particles which never live in isolation, but are always bound inside composite objects called hadrons. Gluons create the force that holds quarks together inside hadrons. Hadrons come in two types: mesons existing in their simple state of bound quark/antiquark pairs and baryons in their simplest form of three quarks. Mesons consist of only two fermions, and provide a unique opportunity for studying strong-interacting physics. Such an opportunity is analogous to the hydrogen atom in classical physics.

One fundamental hypothesis in the field of strong-interaction nuclear physics is confinement, which explains how quarks and gluons are the elementary particles of which the nucleus is made, even though isolated quarks and gluons have never been observed in an experiment. Confinement implies that an infinite amount of energy is required to isolate a quark outside of a hadron. One of the predictions of QCD is that the gluonic field inside hadrons has an independent degree of freedom from the quarks, and is capable of being independently excited. The energy and mode structure of the excitations give important information regarding the configuration of the gluonic fields, which ultimately lead to confinement.

The GlueX experiment searches for mesons with internal gluon excitations, called “exotic mesons.” The experiment will map these mesons by producing them with photon-proton collisions and subsequently measuring their quantum numbers by studying the angular distribution of their decay particles. The GlueX experiment will generate a photon beam beginning with a high-energy electron beam from the US Department of Energy’s Thomas Jefferson National Accelerator Facility, using the process of coherent bremsstrahlung. Coherent bremsstrahlung refers to electromagnetic radiation produced by the deceleration of electrons inside a diamond crystal. After the electrons emerge from the diamond, their energies are measured in a magnetic spectrometer called the “tagger”, which “tags” the energy of the photons produced in the diamond as the difference between the pre- and post-bremsstrahlung electron energies.

The tagger is a major component in the engineering design of GlueX. Members of the nuclear physics group at UConn have received funding from the US Department of Energy for the design and prototyping of electron detectors for the tagger. The design goals of this project include selection of optical fibers and waveguides for the electron detectors, the mechanical design and machining of a light-sealed case to contain the detectors, and the development of techniques for gluing them and mounting them on a precise remote-controlled alignment rail system. A prototype of the tagging fiber detector is currently being constructed, and will be tested at the Thomas Jefferson National Accelerator Facility in January 2010.

Summary of Fall 2008 Work

This semester, my work focused on the physics-engineering design of the tagger microscope box to be used for the GlueX particle accelerator project in Hall D at Jefferson National Lab in Virginia. The volume of work that I ultimately produced was not as much as I had hoped for, because I spent the first months of the semester learning the computer programs needed to facilitate my design work. Based on my current knowledge of these programs plus the final data and design files I was able to create, I would consider this semester a definite success.

The main computer program used for my project is TurboCad. TurboCad is a drafting program similar to both AutoCAD and Solid Works, but is better suited to my project because it allows more 2D and isometric views, as well as a full repertoire of snaps and rendering settings. The currently-marketed edition of TurboCad is Version 15.0, but for the GlueX design project I was working primarily with Version 12.0. It took some time into the semester until I could properly install it on my personal laptop, but after that time my work became infinitely more efficient. The TurboCad program was somewhat complicated to learn, but I did so successfully by using the help menus and tutorials, as well as by asking questions at lab meetings and experimenting on my own. The first challenge I gave myself was drafting a bicycle frame, and once I succeeded at this near the end of October, I began working exclusively on the Tagger design. The files I created for the Tagger design still need a lot of revision, which I hope to complete over the winter break and into next semester. Ideally, I would like to have the prototype Tagger box machined and assembled by sometime in February of 2009.

This semester, I learned that the process of designing the Tagger box is entirely experimental. Overall as a lab group, we have a general idea of how the box should be constructed, although this is subject to slight revisions on a weekly basis. Some of the main revisions integrated into the design this semester include the “skeleton” support structure versus a solid box to reduce weight, and the idea of using foil to form the sides of the box to access the fibers and motors inside. As each of these revisions was discussed and sketched out, it was my job to draft the new design in TurboCad – a process that became a great learning experience for me on many levels. In this same vein, I would characterize the entire Fall 2008 semester as a “great learning experience” for my design project. The presentable TurboCad files that I have created are indexed below. While they are not many in number, I believe that they accurately represent my growing confidence and comfort level with using the program. The majority of the Tagger’s skeleton is rendered, and I hope to work with our lab group and the Physics machine shop to expand on all of these designs in the coming weeks and months. For this semester, however, I feel that my greatest victory was learning the TurboCad program, which will be an invaluable tool for me to use in the future.

Summary of Spring 2009 Work

My work over the Spring 2009 semester can be categorized into four main topics:

1. Final CAD Renderings of the Microscope Enclosure

2. Training for the Operation and Safety of CNC Machines

3. Training for and Investigation into Fiber Gluing Techniques

4. "Frontiers of Undergraduate Research" Poster Presentation