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CORNELL LABORATORY FOR ACCELERATOR-BASED SCIENCES AND EDUCATION — CLASSE

REU 2019 Projects

MENTOR STUDENT 2019 PROJECT (click on link to see abstract)
Kevin Nangoi Simon Rothman
Presentation Final Report Mentor Intro
Abstract: Alkali antimonides look promising for next-generation high-brightness sub-picosecond pulsed electron sources (a current subject of active research). These materials have high quantum efficiency (QE, the number of photoelectrons emitted per number of photons incident on the material). Alkali antimonides also show low mean transverse energy (MTE, the average kinetic energy of the photoelectrons parallel to the material surface).

To extract sufficient electrons for high-brightness sub-picosecond electron-source applications, very high laser intensities are required. At these intensities, multi-photon photoemission effects may significantly increase the MTE, thereby reducing the beam brightness significantly. Furthermore, basic optical properties, such as complex index of refraction and absorption spectrum, due to multi-photon absorptions have not been well studied in alkali antimonides, hindering the understanding of the physics underlying multi-photon photoemission in these materials.

In this project the student, working closely with the mentor, will use ab initio (first-principles) computational methods to calculate the complex index of refraction, absorption spectrum, QE, and MTE due to 1- and 2-photon processes for various alkali antimonides (e.g. NaxKyCs3−x−ySb). Calculations will be for ideal single-crystal alkali antimonides, and, time permitting, alkali antimonides with defects to account for imperfections found in actual experimental samples.

Required skills: Some familiarity with (or willingness to learn about) Linux terminal commands for navigation and basic text editing; some experience in data analysis using python or Octave/MATLAB.

[Optional additional skills: Some familiarity with basic concepts in solid state physics (e.g. electronic band structure).]
Jim Crittenden Co-mentors: Adam Bartnik, Colwyn Gulliford, Nilanjan Banerjee Greg Suczewski
Presentation Final Report Mentor Intro
Abstract: The Cornell-Brookhaven Electron-Recovery-Linac Test Accelerator (CBETA) will provide a 150 MeV electron beam using four acceleration and four deceleration passes through the Cornell Main Linac Cryomodule housing six 1.3-GHz superconducting RF cavities. The return path of this 76-m-circumference accelerator is provided by 106 fixed-field alternating-gradient (FFA) cells which guide the four beams of 42, 78, 114 and 150 MeV in a vacuum chamber of 84x24 mm interior dimensions.

This REU project concerns the splitter/combiner lines which serve to match the on-axis linac beam to the off-axis beams in the FFA cells, providing the path-length adjustment necessary to control the acceleration and deceleration phases for each of the beams. In these regions of the accelerator immediately upstream and downstream of the linac, each beam energy has its own 36x24 mm vacuum chamber roughly 10 m long. The splitter/combiner lines are comprised of a total of 44 dipole electromagnets (with trim windings for fine adjustment), 64 quadrupoles, 16 vertical correctors and 4 septa.

The project provides the rare opportunity to learn from the early commissioning phase of a new accelerator, which will begin on April 1 and continue throughout the summer.
Matthew Andorf Catherine Dema
Presentation Final Report Mentor Intro
Abstract: Optical Stochastic Cooling (OSC) is an advanced beam cooling technique that can improve the luminosity in heavy-ion and hadron colliders. Cornell is planning a proof-of-principal demonstration of OSC with electrons in the Cornell Electron Storage Ring (CESR). The OSC works by interfering the radiation between two insertion devices called ‘undulators’ which have been tuned to be resonant at an optical wavelength (in the case of CESR 800 nm). In order to get cooling the path-length between the undulators must be set and stabilized to a fraction of the optical wavelength; this requires an optical system capable of a fast-feedback mechanism that varies the path-length accordingly. Additionally focusing elements must be employed to optimize the interference between the undulators and finally the OSC can be augmented with an optical-laser amplifier further complicating the design.

The student will help with the design of the optical system, feedback system and potentially do a bench mark test using a low-powered laser. This work requires a basic understanding of optics principles. Additional knowledge of ultra-fast lasers is beneficial. Simulations will be done using custom codes written in Python.
Luca Cultrera and Jai Kwan Bae Grace Mattingly
Presentation Final Report Mentor Intro
Abstract: Spin polarized electron source is one of the key components of future nuclear and high energy physics facilities, such as the Electron Ion Collider. GaAs based photocathodes are considered as the optimal choice for spin polarized electron sources due to their capability to produce highly spin polarized electron beam at high current. To achieve such high quantum efficiency and spin polarization, superlattice structure of GaAs has been developed for the past few decades. In a cryogenic temperature, spin related scatterings of photoexcited electrons will be suppressed, and it is suspected to result in higher spin polarization. In this project, the student will experience characterizing photocathode properties of superlattice structured GaAs in cryogenic temperature regime.
Chris Pierce Jamal Khayat
Presentation Final Report Mentor Intro
Abstract: Finding new materials to generate low temperature electron beams is the most promising way to improve our ability to probe matter at atomic length and time scales. [1] In this project, you will help determine if electron beams generated by photoemission from the conduction band of a low effective mass semiconductor are as cold as theory predicts. We will measure beam temperature (usually called mean transverse energy or MTE) using a technique called voltage scan where by recording the size of the beam at a fixed location and for a variety of beam energies we can work back to find the MTE. This measurement will be performed using a newly built detector that is capable of detecting bunches of electrons containing as few as 10-100 particles.

Students who are interested in this project can expect to work with the following:
Electron beam optics
Ultra high vacuum (UHV) techniques
Python based data collection and analysis
Ultrafast and nonlinear optics
Basic programming experience is expected.

[1] https://youtu.be/fCLU2yvD3hU?t=1606
William Li Grant Rutherford
Presentation Final Report Mentor Intro
Abstract: Photoinjectors are the key first part of many modern accelerators, the source of electrons for the rest of the accelerator. Liouville's theorem puts an upper limit on the brightness of the electron beam: the brightness of the beam when it is born in the injector at the photocathode, a material that emits electrons when illuminated by a laser.

Traditionally, the cathodes used have been flat, and much effort has been placed into finding the best materials to fabricate them out of. However, an interesting alternative avenue for improvement is to change the geometry of the cathode, specifically to enhance the electric field at the point that the electrons are emitted. This project will consist of using WARP, a self-consistent field solver and particle tracker, to simulate the dynamics of the electrons immediately at birth and determine optimal cathode geometries.

Proficiency in Python and standard Python libraries (numpy, matplotlib, etc.) is expected. Experience in WARP is not required.
Alice Galdi Noah Hoppis
Presentation Final Report Mentor Intro
Abstract: Innovative photocathode materials need to be characterized to determine the intrinsic emittance of the generated electron beams, in order to find new electron sources to generate high quality electron beams for state-of-art applications (free electron laser, ultrafast electron microscopy…)

A new photocathode characterization systems, allowing high resolution measurements of the momentum spread of photoemitted electrons at cryogenic temperatures, is being set up at Cornell University. This system would allow to characterize materials fabricated with state-of-art techniques, thanks to a universal sample exchange system, with unprecedented resolution.

In particular a beamline where the electron beam is focused by magnetic lenses is used to perform these measurements. The beam size is measured onto two scintillator screens. The project consists in setting up the beamline element with a solenoid lens, corrector coils and two screens. The elements power supplies and the cameras used for the acquisition of the beam images will be interfaced with a computer to automate the measurements using LabView VIs. Test measurements on standard samples will be finally performed.

Required skills:
Basic computer programming (any language), Electric circuits, Basic electromagnetism,
Additional skills: Labview
Ryan Porter Matthew Tao
Presentation Final Report Mentor Intro
Abstract: Superconducting radio-frequency (SRF) cavities are used to accelerate particles in modern particle accelerators. The development of high efficiency, high accelerating gradient SRF cavities requires cryogenic performance testing. During the testing of SRF cavities, temperature mapping is used to determine the distribution of RF loses on the cavity wall, and locate and identify material defects that detriment performance. Historic temperature mapping systems read-out temperature at rate of ~1 s, allowing only the measurement of steady state temperatures. New hardware has been developed to acquire temperature readings at a high rate so that thermal transients can be studied. The high time resolution should provide new information on cavity behavior and provide more on defects the impact performance.

As part of this project, you will work on setting up, testing, and commissioning this new hardware. You will test readout electronics, write software for data acquisition and analysis, and participate in the cryogenic testing of SRF cavities. Strong programming skills is desired.
Thomas Oseroff and Pete Koufalis Rosalyn Koscica
Presentation Final Report Mentor Intro
Abstract: Magnetic fields play a critical role in the behavior of radio frequency superconducting resonators used to accelerate charged particle beams in many modern and future accelerators. The magnetic flux vortices that become trapped within a superconductor can account for a significant fraction of the energy losses of the resonator. Minimizing the resistance due to trapped magnetic vortices is important for optimizing resonator performance and efficiency. Thus, understanding how magnetic vortices are trapped during the normal-to-superconducting transition, their geometry, and effect on different types of superconducting materials or surface treatments is crucial.

The student will be involved in modeling single and multilayer magnetic shielding structures using CST EM Studio, experimentally testing these simulations, using existing theories of trapped magnetic flux losses to model the frequency dependence of the sensitivity to trapped flux, and data analysis to compare these models to experimental data. Basic programming skills are required. Experience in MATLAB is beneficial but not required.
Colwyn Gulliford and Adam Bartnik Brandon Hunt
Presentation Final Report Mentor Intro
Abstract: Development of Advanced Optimization and Online Modeling Tools for CBETA. Finding the optimum settings in order to produce the highest beam quality in the CBETA machine requires state-of-the-art optimization algorithms. One such technique is Multi-objjective Genetic Algorithm, which is particularly useful for tuning the low energy section of CBETA where the beam's self fields contribute to the overall dynamics. In this project, the student will set up and test a new Python based MOGA optimization software currently under development. The student will then apply this to some portion of the CBETA machine, with a reach goal of being able to perform optimization on a start to end simulation of the CBETA machine spanning multiple particle simulation codes. This project will require learning the basics of several particle tracking codes as well as python and Matlab.
Kirsten Deitrick Kara Hokenstad
Presentation Final Report Mentor Intro
Abstract: Compton Light Sources produce x-rays for a variety of applications in research and industry; the best of these produce x-ray beams with extremely high brilliance in a narrow bandwidth. These x-rays are produced by inverse Compton scattering - colliding a high-power laser and a high-quality, high-energy electron beam produced by an accelerator.

Currently, the Cornell-BNL ERL Test Accelerator (CBETA) is being commissioned; in the future, CBETA will be capable of producing a high-quality electron beam necessary to generate these high brilliance x-rays. This project will focus on the design of an extraction line from the existing CBETA layout where Compton scattering can occur. This design work will be done through beam dynamics simulations and optimizations. The student will gain a working knowledge of accelerators, beam dynamics (theory and simulation), and inverse Compton scattering. Previous experience with programming is highly suggested.
Nilanjan Banerjee Malida Hecht
Presentation Final Report Mentor Intro
Abstract: The Cornell-BNL ERL Test Accelerator (CBETA) is a high current electron accelerator currently being commissioned at Wilson Laboratory. CBETA continuously accelerates a beam of electrons and recirculates them along a path shaped like a racetrack to yield a high current beam with an energy of 150 MeV. This will be the world’s first accelerator using superconducting cavities that accelerates electrons in 4 turns (laps) while in the next 4 turns, recovers the particles’ kinetic energy for further use. In another first, this accelerator will use permanent magnets in the majority of the machine to guide electrons of different energies simultaneously through the same beam pipe along their designated paths.

Stray electrons inadvertently hitting the surface of the beam pipe generates a considerable amount of radiation in particle accelerators, and the permanent magnets of CBETA are particularly sensitive to damage from such effects. This project will focus on measuring this unwanted radiation coming from beams of different energies, at different time scales and comparing them with simulations. The data will then be used to configure the Equipment Protection System to turn off CBETA if the radiation exceeds some threshold in an effort to protect the permanent magnets.
Yevgeniy Lushtak Derek Hammar
Presentation Final Report Mentor Intro
Abstract: Non-Evaporable Getter (NEG) pumps are increasingly common in particle accelerator applications because of their small size and their strong performance for hydrogen, the principal UHV gas. However, these pumps present a challenge to vacuum system design because their complicated geometry results in unreasonably complicated vacuum simulations. This project seeks to develop a database of NEG pump performance as a function of installation geometry. The results produced would be used in lieu of full pump geometry in future simulations at Wilson lab.

The participant would build 3D models of NEG pumps and their environments in AutoDesk Inventor and simulate their performance in MolFlow. They would then attempt to simplify the pump geometry without sacrificing simulation accuracy. Key results would be verified experimentally.

A basic understanding of surface chemistry is required for this project. Knowledge of 3D CAD and Monte Carlo simulation principles preferred but not required.
Carl Franck Anna Faretty
Presentation Final Report Mentor Intro
Abstract: In this project, the participant will be engaged in the pursuit of breakthrough weak signal technology at synchrotron radiation sources we have been running and planning that involve the detection of coincident photon pairs in order to suppress extraneous backgrounds. This summer we propose to take this a step further by exploiting precise knowledge of the source's time structure. The participant will have the opportunity to engage in our group’s (https://physics.cornell.edu/carl-franck) ongoing uses of these techniques to test fundamental theory of photon/ bound electron processes in atoms and uncover new correlated electron dynamics in quantum materials.
Jim Shanks Alexandria Udenkwo
Presentation Final Report Mentor Intro
Abstract: The Cornell Electron/positron Storage Ring (CESR) was recently reconfigured to operate as a dedicated x-ray light source, CHESS-U. Beam for CESR is generated by thermionic emission from a cathode, which is then accelerated down a linear accelerator (linac) before entering into a booster ring (synchrotron), ramping to high energy, and transferring into the storage ring. The linac is comprised of a series of accelerating radio-frequency (rf) cavities and focusing elements. The fields in the linac optics must be precisely understood in order to maximize the efficiency of charge transfer into the storage ring.

The student working on this project will help us to model the linac optics, matching measurements from the actual accelerator in their model. A partially-functional simulation suite exists, based on a combination of Java and accelerator-specific codes (GPT and Bmad). The student will bring the simulation suite up-to-date, take measurements on the CESR linac, and generate a model which accurately reflects conditions during CESR injection.
Arthur Woll Emma Huckestein
Presentation Final Report Mentor Intro
Abstract: X-ray fluorescence mapping and spectroscopy provide “ground truth” information about the spatial distribution and chemical state of elements — especially metals — in heterogeneous samples. In combination with powerful x-ray beams produced by synchrotrons, these techniques are becoming increasingly critical to many scientific fields — from biology and environmental science to energy-related research into batteries and fuel cells. This project will focus on implementing existing simulations of x-ray fluorescence intensity from a variety of samples under different assumptions about sources and measurement geometry. The goal will be, first, to validate these simulations against existing data, and second, to evaluate the possible outcomes of experiments with detector technology expected to become available within the coming year, at beamlines currently under construction at CHESS.

Projects are being added; check back periodically for updated project listing. You don't have to wait for all the projects to be posted here to apply - if you get selected for our program, we will contact you further with selection options.