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ODU/Jlab REU Program

Research Projects

Accelerator Physics

1. Development of a Compact THz Radiation Source

Mentor: Geoffrey Krafft

Project Description: The Jefferson Laboratory free-electron laser is the world's highest average power source of radiation in the THz (1012 Hz) frequency band of the electromagnetic spectrum. There is great interest in developing THz sources of equivalent average THz beam power, but whose dimensions are smaller and whose total cost is much smaller than the FEL. High average power THz sources based on small linear accelerators seem possible, and might revolutionize scientific studies in the THz band, a band that has not been developed to present from the lack of suitable sources. Schematic designs of such compact THz sources exist and are published, but detailed designs, which could be used as a basis for engineering designs of such a source do not yet exist.

REU Student participation: In this project the student will assist in the theoretical design and optimization of THz sources based on small linear accelerators. He/she will be introduced to accelerator design computer programs and more general ideas in accelerator physics, RF and microwave components and their characteristics, radiation production by relativistic electrons, and coherence phenomena in electromagnetic radiation. Student experience in the areas of numerical calculation and computer graphics is desirable, but not required.

 

2. Resistive Wall Wakefield and Instabilities

Mentor: Jean Delayen, Old Dominion University and Jefferson Lab

Project Description: In Free Electron Lasers (such as the JLab FEL) and other proposed light sources, large electron beam currents are transported through narrow-gap undulators. The resistive wall wakefields generated in that geometry can lead to excessive heating and may pose a fundamental limit to the beam currents that can be transported. Our knowledge of resistive wall wakefields is, at present, incomplete especially for very short bunches where the anomalous skin effect and the frequency dependence of the conductivity can be important. The predictions of our existing models are more than a factor of 2 away from experiments done on the JLab FEL, and improvement is needed if higher-current machines are to be designed and built.

REU Student participation: The student will assist in analytical studies and computer simulation of resistive wall effects. In particular, the anomalous skin effect and the frequency dependence of the conductivity will be incorporated. A solid foundation in applied mathematics and experience with computer modeling are desirable.

 

3. Control of Microphonics in High-Q Superconducting Cavities

Mentor: Jean Delayen, Old Dominion University and Jefferson Lab

Project Description: In all existing cw superconducting linacs using high-Q superconducting cavities, each cavity is controlled and powered by its own low-level and high-level rf system. Such a scheme has been successful in the past but would be cost-prohibitive for larger machines which are being proposed, in particular for energy-recovering linacs. The ability of controlling and powering a large number of cavities from a single rf source is needed to make those machines affordable. However we have at present no analytical model and few simulations of the ponderomotive instabilities that can exist in such multi-cavity systems to guide us, and it is unknown what their limitations would be or even if they are feasible.

REU Student participation: The student will assist in analytical studies and computer simulation of ponderomotive instabilities of multi-high-Q cavities driven by a single rf sources. Good analytical and computer simulation skills, as well as experience with Matlab/Simulink are desirable.

 

4. Polarized Electron Source - Photocathode Development

Mentor: Marcy Stutzman, Old Dominion University and Jefferson Lab

Project Description: The polarized electron guns and gun group test chambers at Jefferson Lab use many extractor gauges to measure pressures down to 1x10-12 Torr. Near this lower pressure limit, understanding individual gauge differences is crucial. Several cross calibration techniques have been used by other groups to quantify the x-ray limits and other characteristics of the gauges at the lowest pressures. As the polarized electrons are emitted, a possibility for polarization enhancement exists when the laser's incident angle is conducive to emitting electrons of one polarization state and prohibiting emission from the other polarization state.

REU Student participation:

 

5. The Beam-Beam Interaction in ELIC

Mentor: Geoffrey Krafft and Yuhong Zhang, Jefferson Lab

Project Description: The Electron-Light-ion collider (ELIC) based on the CEBAF at Jlab is a proposed instrument for probing hadronic structure to answer crucial questions, e.g., the contribution of gluons to the binding and the spin of the nucleon, and the dynamics of quark confinement leading to the formation of hadrons. In the conceptual design of ELIC, spin polarized electron (up to 7 GeV) and light-ion (up to 150 GeV) beams circulate inside a figure-8 shaped rings and continuously collide with each other at four interaction points. The ELIC conceptual design uses several cutting-edge accelerator technologies including high average current polarized electron source and DC injector, energy recovery linac, electron cooling, figure-8 ring and crab-crossing.

The electromagnetic interactions between two colliding beams and perturbations they induce on the colliding beams are called beam-beam effects. These effects are the dominating limitation on ELIC performance. The scheme of electron cooling of the ion beams and frequently replacing stored electron beam with new one is introduced to fight the beam-beam effects and to preserve the collider's luminosity lifetime. Due to the large number of particles involved, computer simulations based on direct calculation of particle interactions play very important role in understanding the beam-beam effects of the ELIC.

REU Student participation:

 

6. Computer Simulation and Optimization of the Polarized Injector for ELIC

Mentor: Geoffrey Krafft and Yuhong Zhang, Jefferson Lab

Project Description: In ELIC, space charge effects (Coulomb interaction between non-relativistic charged particles) in the low energy section of a DC injector are the major cause of beam transverse emittance growth and longer bunch length. Computer simulation is a crucial tool for understanding and suppressing the space charge effect and to improve the design of the DC injector for ELIC project.

REU Student participation:

By participating in these projects, students will gain knowledge of world-class accelerator facilities and future large scale scientific projects; understand real world physics problems and apply basic physics principles to these problems; and use computer simulations and visualizations as tools for solving complex scientific problems.

 

7. Development of RF control algorithms

Mentor: Curt Hovater , Joh Musson, Trent Allison

Project Description: Jefferson Lab provides state-of-the-art cavity RF control for internal projects and the accelerator community. Stable field control is critical for many accelerators utilizing superconducting RF (future light sources. FEL/ERLs, accelerators for nuclear and high-energy research). In addition we are developing RF control algorithms to meet the CEBAF energy upgrade accelerator performance requirements.

REU Student participation:The student will assist in the development and optimization of RF algorithms for cavity field control. She or he will be introduced to accelerator design, superconducting cavities, RF/microwave components, digital signal processing and control theory. Student experience in the areas of digital design and linear systems is desirable, but not required.

 

8. Multipass Orbit Correction in the CEBAF Accelerator

Mentor: Yu-Chiu Chao and Michael Tiefenback

Project Description: The CEBAF accelerator at Jefferson Lab has many novel properties for a large-scale accelerator. Among them is the fact that, because the accelerated beam passes through the accelerator up to five times, the accelerated beam passes through the linear accelerators within CEBAF on a common orbit that is ideally the same straight line for all the different passes. Steering errors, which may be different on the different beam passes, are not easily corrected using standard methods because each of the different beam passes through the accelerator have beams of different energies.

REU Student participation:In this project the student will assist in constructing the working algorithm for CEBAF multipass orbit analysis and correction. This effort will give the student good experience in the analysis of data applicable to accelerator control, and is expected to have substantial impact on CEBAF performance.

The student is expected to be proficient in one standard scientific programming language (FORTRAN, C++); linear algebra concepts such as matrix, determinant, and eigenvalues; and elementary statistical arguments regarding error propagation, error distributions, and least squares analysis. It is desirable that the student has experience in numerical analysis, or have used related software tools such as MATHEMATICA.

 

9. Plasma Treatment of Bulk Niobium Surface for Superconducting RF Cavities Surface Preparation

Mentor: Leposava Vušković and Svetozar Popović, Old Dominion University

Project Description: Preparation of cavity walls has been one of the major problems in superconducting radio-frequency (SRF) accelerator technology. Accelerator performance depends directly on the physical and chemical characteristics at the SRF cavity surface. Plasma based processes provide an excellent opportunity to achieve these goals and, in addition, offer a unique opportunity to provide an immunity to subsequent exposure to atmosphere through plasma passivation processes while the etched surface is still under vacuum and in an oxide free state. Additionally, a plasma etching process may consist of different sequential etches in the same process for the purpose of providing a fast niobium removal of many tens of microns if required, followed by a slower etch tailored to provide a finished surface optimized for the best RF performance. This can be accomplished by exploring the effects of various types of electric discharge plasmas to minimize surface roughness and eliminate or minimize deterioration of cavity properties by oxygen, hydrogen and other chemical contaminants.

In the previous phase of this project, a microwave glow discharge system was used for Cl2/Ar reactive gas mixture interaction with disk shaped bulk Nb samples. An exceptionally high etching rate of up to 100 mm/hour was achieved at certain plasma conditions. In the next phase, one of the SCF test cell will be adapted into a barrel type plasma reactor with the goal to demonstrate favorable RF performance. Besides, a number of in situ optical diagnostic techniques will be developed process monitoring. The results of optical diagnostics will be correlated with surface analysis and RF performance tests, with the objective to optimize plasma treatment of Nb surface and further demonstrate the feasibility of implementing this technology for the SRF cavity development and production.

REU Student participation:

 

Nuclear Physics

10. Longitudinal Stern-Gerlach Experiment

Mentor: Douglas Higinbotham

Project Description: Attempts have been made to conduct the Stern-Gerlach experiment with a beam of free electrons. But, the Lorentz force I along with the uncertainty principle blurs the splitting of the beam. Brillouin suggested that a longitudinal Stern-Gerlach apparatus would minimize the effect of the Lorentz force. Recent papers have supported this idea. Computer simulations are positive and the intention is to build an apparatus.

REU Student participation: Design, construct and operate a longitudinal Stern-Gerlach device in the Jefferson Lab Injector Test Cave.

 

11. Hall C Polarimeters

Mentor: David Gaskell

Project Description: The Hall C Moller Polarimeter will be upgraded to function after the JLab 12 GeV upgrade. This project will entail magnet optics design and systematics (Monte Carlo) studies to ensure that the Moller Polarimeter will achieve the required 1% absolute precision. Hall C is also constructing a Compton Polarimeter that will be used for the QWeak experiment. A key component of this system is a high power laser system that will interact with the high energy electron beam. This project will entail working with the laser in the lab to set up and test the laser transport. This will involve making the alignment remotely adjustable, setting up the proper laser focusing optics, and determining the approriate geometry of the laser electron scattering chamber.

REU Student participation:

 

12. Study of Exotic Hybrid Mesons using Lattice QCD

Mentor: Jozef Dudek, Old Dominion University and Jefferson Lab

Project Description: Our group uses large computer simulations to increase our understanding of QCD, the fundamental theory of strong interactions. This 'Lattice QCD' research is based at ODU and Jefferson Laboratory where it ties in with the hadronic physics experimental program. These calculations seek to understand the nature of exotic hybrid mesons whose detection in the proposed GlueX experiment would help us understand how quarks are confined inside hadrons.

REU Student participation: The student, working in collaboration with the mentor and other scientists, will assist in the development of analysis software used by the lattice group to interpret the data extracted from supercomputer calculations. The student will learn not only the coding aspects of the research, but also the underlying physics. He/she will work primarily at Jefferson Lab where the opportunity to attend regular seminars and colloquia will provide an excellent overview of the state of the art in hadronic physics research. This student must have some prior programming experience, preferably in C++. The theory group at Jefferson Lab is very large and includes graduate students at all levels, postdocs and staff. A student inclined toward theoretical work will find this atmosphere very stimulating.

 

13. Construction and testing of scintillation counters for charged particle detection using silicon photomultipliers

Mentor: Stepan Stepanyan, Mac Mestayer

Project Description: The scintillation counters will consist of extruded scintillators, green wave shifting fibers and Silicon Photomultipliers(SiPMs). The extruded scintillators will have a hole in the middle of the bar. Wave shifting fibers will be glued inside the hole using optical cement. Light readout from the fiber ends will be done using 3x3 mm2 SiPMs attached to the fiber. Light yield and time characteristics of the counters will be measured using fast electronics and a data acquisition system.

REU Student participation:Students involved in this project will help, construct the detectors, Set up the Data Acquisition system, Analyze the data conduct benchmark tests between simulation and SLAC B factory measurement results setup a simulation deck for the ELIC collider and conduct simulations with design parameters.

 

14. Test of a Radial Time Projection Chamber (RTPC)

Mentor: Stepan Stepanyan, Mac Mestayer

Project Description: The RTPC, together with thin target, allows detection of low energy heavy particles. Several improvements will be made on the already existing detector to enhance particle identification capability. After modifications are done, tests of chamber performance using a laser and cosmic particles will be performed. The project will include preparation of the hardware for the test setup.

REU Student participation:Students involved in this project will help, prepare the hardware, evaluate the implemented enhancements.