Jason Sharpe, Master's Student

Supervised by Dr. Adam Sarty - 2009- 2012

Jason completed his master’s of applied science at Saint Mary’s University. Jason’s focus is in nuclear and particle physics, and while with Dr. Sarty he designed a prototype scintillating fiber tracker (SFT) for tracking and detecting subatomic particles.

SFT's are a modern type of detector that will someday replace wire chambers for tracking particles, as they are much faster, allowing them to be put in higher rate environments, and more precise, allowing better measurements of momentum and position. 

The standard use of an SFT is the determination of a particles momentum inside a particle accelerator. Typically, particles are bent through a magnet, and depending on their momentum and charge, they will follow different circular paths. When a particle strikes the SFT, its position is found, giving its circular radii and finally its momentum. 

His major contribution to the development of SFTs is by finding ways to reduce cross talks associated with SFTs and their primary readouts - photomultiplier tubes.  Jason investigated if a light tight coating is needed to reduce scintillating fiber cross talk, and if adjacent channels needed to be separated on the face of multi-channel photomultiplier tubes.

Graduate Thesis Topic:  Designing and Prototyping a Scintillating Fiber Detector for Hall A at Jefferson Laboratory

Abstract (Graduate): In many nuclear and particle physics experiments, it is necessary to ascertain precise information about a particles trajectory, or its position at specific locations (as a means for then determining angle or momentum). A common way to determine this information is by using a scintillating fibre tracker, a device that relies on scintillation light from ionizing charged particles (such as electrons or protons) within scintillating fibres, and guiding the produced scintillation light through standard fibre optics to determine which scintillating fibre detected the particle. This thesis discusses, and presents results for technical issues associated with designing and constructing such a detector: (1) adjacent scintillating fibre-to-fibre cross-talk, and (2) the effect on light transmission of the combination of different fibre-end finishes and clear-to-scintillating fibre optical couplants. These results will be directly incorporated into the construction of a scintillating fibre coordinate detector to be built for future experiments at Jefferson Lab's Hall A in Newport News, VA, USA.


Gail MacInnis, B.Sc. Honours Astrophysics

Supervised by Adam Sarty 2007-2009

Gail graduated from SMU and pursued a Master's degree at Concordia University.

Undergraduate Thesis:  "A Feasibility Study: Using A Rotating Coil Magnetometer as an Improved Compass for the Polarized 3He Target at Jefferson Lab's Hall A"

Abstract:  At the Thomas Jefferson National Accelerator Facility (Jefferson Lab) in Virginia, one category of electron-scattering experiments are those done in order to measure the electric response of the neutron.  These experiments involve the use of a polarized Helium-3 target, wherein large Helmholtz coils provide a constant holding field along which the polarization of the Helium nucleus remains aligned.  In order to achieve the most precise results for electron-scattering from the polarized 3He target, the direction of this magnetic holding-field must be known to a high accuracy.  A feasibility study was done to determine whether a rotating coil magnetometer can be used to improve the currently used compass system, with an ultimate goal of measuring the magnetic field direction to within 0.03°.  The design and testing of three prototype magnetometers will be discussed, along with the accuracy achieved with each of these designs. 


Emily McCullough, B.Sc. Honours Astrophysics

(In photo from left to right: Jackie, Emily, Dr. Sarty)

Supervised by Adam Sarty 2006-2007.

Emily graduated from SMU and is now pursuing a Master's degree at the University of Western Ontario. 

Undergraduate Thesis: "Upgrading the Electron Beam Current Monitor System at Jefferson Lab's Hall A"

 

 


Jackie Glister, Ph.D. Student

Supervised by Dr. Adam Sarty 2004-2009

Undergraduate Thesis: "Novel Light Guide for Scintillation Counters in Hall A of Jefferson Lab"

Graduate Thesis Topic: "Polarization Observables in Low Energy Deuteron Photodisintegration"

Abstract (Undergraduate): Two scintillating panels (S1 and S2) are used as triggers in the high resolutions spectrometers located in Hall A of the Thomas Jefferson National Accelerator Facility (Jefferson Lab).  Ninety-degree twisted acrylic light guides transport light from the scintillator to the photomultiplier tube by means of total internal reflection.  The S1 andS2 layers are to be replaced by upgraded panels labeled S1m and S2m, and it is proposed that the light guides in the S1 layer be replaced by a new adiabatic S-shape pattern inward, toward the PMT.  The 3-strip design contains a rectangular piece lying in between two of the S-shape strips.  Using CERN’s Guide7 computer code, Monte Carlo simulations were performed on four different light guide geometries: rectangular, standard fishtail, 2-strip S-shape, and 3-strip S-shape – using high collection efficiency and time resolution as criteria for an optimal design.  A 1.8 – 2.1 x increase in collection efficiency (C.E) and an 1.2 – 1.4 x improvement in time resolution were found for S-shape guides over simple light guides (i.e., rectangular and standard fishtail).  Both S-shape guides are recommended for the S1m triggering layer, although the 3-strip option performs better than the 2-strip one at the dimensions tested: initial thickness and width of 1cm and 10cm, respectively, and total length of 28.5cm.  Averaging of all points of emission gives 2-strip C.E of 30.0% and time resolution of 0.10ns, while 3-strip has 31.2% C.E and 0.09ns time resolution.  Experimental comparison of twisted and S-shape guides is recommended since the twisted strip cannot be accurately modeled in Guide7. 


Ashley Campbell, B.Sc. Honours Mathematics/Honours Physics 

Supervised by Adam Sarty 2009-2011

Ashley completed her BSc (Combined honors) in Mathematics and Physics at Saint Mary's University.  She is currently working towards her BSc in Electrical Engineering at Dalhousie University.  

This past summer Ashley worked towards writing her undergraduate thesis topic into an article for publishing.  In addition, she also spent time designing and producing simulation results for a scintillating fiber detector system for the BigCal at JLab's Hall C. This system will be implemented and used to detect and track high-energy particles.

Undergraduate Thesis:  "Tracking Performance of a Scintillating Fiber Detector System"

Abstract: A unique particle detector design using scintillating fibers was being considered as Saint Mary’s contribution towards the Super-Bigbite Spectrometer (SBS) Third Tracker (TT) 12 GeV upgrade for the Thomas Jefferson National Accelerator Facility (JLab), in Virginia, USA.  In support of this effort, a simulation for this unique detection and tracking system was developed taking care to ensure that the physical characteristics of the scintillating fibers were modeled sufficiently to generate realistic firing behavior in the presence of high-energy collision particles. 

Particle trajectories and their corresponding detections across a number of fiber planes was simulated in order to estimate the particle’s path through the detector.  Furthermore, the “angular and spatial resolution” performance of the detector’s reconstructed tracks were examined using a tracking algorithm based upon a simple geometric approach to track reconstruction.  The tracking method used and the spatial and angular resolution performances are also presented.  A spatial resolution of 0.2662 mm with resolutions of 1.75 x 10-3° for θ and 61.6 x 10-3° for Φ were attained, which meets or exceeds the performance requirements for the SBS TT upgrade.  Moreover, this requirement was met or exceeded in all cases provided five or more fibers were used in track reconstruction with an overall efficiency approaching 96%. 


Rikki Roche, Ph.D. Student (Florida State University) 

Supervised by Dr. Adam Sarty 1997 - 2003

Graduate Thesis: "Measurement of Polarization Observables in the Electro-excitation of the Proton to its First Excited State"


Adam Dooley, Ph.D. Student (Florida State University)

Supervised by Dr. Adam Sarty 1997 - 2001

Graduate Thesis: "High-Resolution Study of the 3He(e,ep) Reaction in the Quasielastic Region"


Mehran Saadat, B.Sc. Honours Physics and Mathematics (Dalhousie University)

Co-supervised by Dr. Adam Sarty (with Dr. Kevin Hewitt) 2006 - 2007

Undergraduate Thesis: "Deposition and Characterization of a Superconductor Composition Spread Library: La2-xSrxCuO4  (0 < x < 0.16) with ∆x=0.0033"

Abstract: A 49-member composition spread library of La2-xSrxCuO4 (0 < x < 0.16) in steps of ∆x=0.0033 was obtained using magnetron sputtering. Two home made targets of La2Cuo4 and La1.84Sr0.16CuO4 were sputtered using 60 W RF and 45 W DC bias respectively at process gass(Ar : O2 = 4 : 1) pressure of 2 mTorr. A linear composition variation is produced using a linear in mask in front of the La2Cuo4 target and a linear out mask in front of the La1.84Sr0.16CuO4 target. The libraries were sputtered onto SrTiO3 through a 49 slot shadow mask. Then films were post annealed at 800ºC for 200 seconds and at 1000ºC for 360 seconds through a shoulder reaction. X-ray diffraction revealed the right phase. EDS analysis showed the Sr composition varies from 0 to 0.17, as expected. This represents the first successful superconductor composition spread library ever deposited. Resistivity measurements were carried out using a specially designed cryostat. The resistivity measurements reveal that a thin impurity layer of the film dominates the temperature dependence of resistivity. Future work will seek to remove this layer in order to determine the intrinsic resistivity trends.


Brynle Barrett, B.Sc. Honours Physics

Supervised by Dr. Adam Sarty 2004 - 2005

Undergraduate Thesis: "Analysis of Space Charge and Dead Zone Effects in the TWIST Spectrometer"

Abstract: Multi-wire chamber ionization detectors experience effects from space charges due to high energy loss of the radiative particles that penetrate them. One of these effects is that due to the dead zone--the region near a primary ionization path that becomes non-responsive to a subsequent particle traversal. This thesis reports a thorough study of the dead zone produce by µ+ in the proportional counters closest to the target stop in the TWIST spectrometer (PC5 and PC6), with emphasis placed on the method of analysis and the use of raw data to measure dead zone effects.

Two parameters that describe the properties of a dead zone are the dead length, Ldead, which is the average length along a wire in the proportional counter that becomes unresponsive, and the healing time, τh , which is the average time it takes for a dead zone to become responsive again. The dead lengths and healing times for the dead zones in PC5 and PC6 were computed from raw data and are listed in Table 1. Brief descriptions are also given of the TWIST experiment and the physics of dead zones. 


Frank Berghaus, B.Sc. Honours Physics and Mathematics

Supervised by Dr. Adam Sarty 2002 - 2003

Undergraduate Thesis: "Efficiency Analysis of the High Resolution Spectrometers at Hall A of the Jefferson Lab"

Abstract:  In order to measure the cross sections for nuclear reactions observed in an experiment, a good knowledge of the acceptance for the spectrometers used to investigate the reaction is essential. Since reaction cross sections depend on both the scattering angle and momentum of the detected particles, both must be examined to get a picture of the acceptance and detection efficiency of the detectors. Efficiency profiles were determined for the HRS detectors in Hall A at the Jefferson Lab by scattering a 4.0 GeV electron beam off a 15 cm liquid hydrogen (LH2) target. The p(e,e')p reaction was observed in the deep inelastic region. The detector central momentum was moved from 1.065 GeV/c to 0.9823GeV/c in 2.0% steps. These measurements were taken for the two HRS spectrometers at a total of five angles, from 43.6 degrees to 46.4 degrees in 0.7 degree steps. Runs using a target of 12C were used to calibrate the position of the detectors for each setting in angle and momentum. 

The normalized counts observed for the same detected particle angle or momentum, but measured at different settings for the central angle and momentum of the spectrometer, were compared to generate profiles for the spectrometers' relative efficiency over it's angular and momentum acceptance. The efficiency profile for the momentum measurements matches previous studies done by Paul Ulmer [4], but this was the first attempt to extract the angular efficiency profiles. 


Joshua Bray, B.Sc. Honours 

Supervised by Dr. Adam Sarty 2002 - 2003

Undergraduate Thesis: "Interactive-Engagement Physics Teaching Methods: An Evaluation and Inventory"

Abstract: It is well documented that traditional methods of teaching physics aren't generally imparting the understanding of fundamental concepts to students. Many new approaches to teaching physics have arisen that attempt to overcome this problem. They are often labelled "interactive engagement" methods, because they promote active student participation in classes and labs. An attempt was made to implement one such method in an introductory physics course at Saint Mary's University. It involved a series of special quizzes at the beginning and end of each lecture. By correlating performance on the quizzes with performance on the final exam (at various levels), it was found that the special quizzes neither cause conceptual change in the students, nor do they indicate whether conceptual change takes place. While the method use at Saint Mary's doesn't show it has improved lecture effectiveness, other methods have been shown in the literature to cause strong improvements. Three of these methods are described, in particular one the closely resembles the method used at Saint Mary's, but that is implemented differently.  

 

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