|MENTOR||STUDENT||2017 PROJECT (click on link to see abstract)|
|Gennady Shvets||Bassel Saleh Presentation Final Report||
Abstract: Plasma acceleration is the next frontier in accelerator physics. Plasma accelerators do not require any solid structures. Instead, they rely on intense laser pulses to create trailing plasma wakes (also known as "plasma bubbles") that can accelerate electrons to ultra-high energies over short distances. Both laser and particle drivers can be used for creating such plasma bubbles. The project will involve numerical simulations of the electron dynamics in such plasma wakes. Of particular interest is the interaction of electron beams inside the plasma bubble with a co-propagating laser pulse. Such interaction is referred to as the Direct Laser Acceleration. The student should possess strong interest in computational physics and working knowledge of programming (MATLAB, C++, Fortran are preferred).
|Jim Crittenden||Sean Buechele Presentation Final Report||
Abstract: The buildup of low-energy electron densities has been shown to limit the performance of storage rings such as the B-meson factories KEK-B in Japan and PEP-II at the SLAC National Laboratory. In 2008, the Cornell Electron Storage Ring (CESR) was reconfigured as a test accelerator in order to study cloud buildup. In 2013 we obtained the first-ever measurements of electron cloud trapping in a quadrupole magnet in a positron storage ring. It had long been surmised that cloud electrons may become trapped in the quadrupole field, but no measurements of the effect were available to validate modeling codes. Owing to its potential for imposing operational limitations on the SuperKEKB e+e- collider to be commissioned this year in Japan, as well as on the positron damping ring for the proposed International Linear Collider, an additional quadrupole magnet and detector was installed in the CESR ring in 2016, making possible an expanded measurement program. This REU project will concentrate on the analysis of the first data set obtained in December 2017 and on modeling the performance of the new detector design.
|Gennady Shvets||Dalila Robledo Presentation Final Report||
Abstract: The project involves simulating the interaction of charged particles with a photonic topological insulator (PTI)-based accelerating structures. PTIs are special photonic structures that enable reflections-free propagation of electromagnetic waves along sharply bend pathways. Unlike conventional accelerating structures, that require sidewalls to confine the microwaves, as well as three-dimensional disc-loading to provide synchronicity, PTIs use photonic bandgaps to confine radiation and to match its phase velocity to the speed of the accelerated electrons. The actual project will involve numerical simulations of such structures using COMSOL and CST Microwave Studio electromagnetics codes. The students can also participate in the fabrication and testing of the structure if they have experimental skills and interest.
|Luca Cultrera||Philip DiGiacomo Presentation Final Report||
Abstract: Next generation of nuclear physic facilities like the electron-ion collider will require high intensity and high polarization electron beams. As of today the generation of high polarization electron beams using photoinjector is limited to the use of GaAs/GaAsP superlattice structures activated to Negative Electron Affinity by exposure to Cs and O. These photocathodes can provide the required high polarization and relatively high QE but due to their high vacuum sensitivity they suffer of a relatively short operating lifetime if compared with other photocathode materials. The photocathode group has recently initiated an R&D activity aimed at the generation and measure of highly polarized electron beam and the student will be involved in the commissioning of a retarding field Mott polarimeter and on measurements of the electron beam polarization from GaAs activated to NEA using ultra thin layer of CsTe.
|Jim Crittenden||Rachel Bass Presentation Final Report||
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 will be provided by 106 fixed-field alternating-gradient (FFAG) cells which carry the four beams of 42, 78, 114 and 150 MeV in a vacuum chamber of 84x24 mm interior dimensions. This REU project concerns tracking studies the splitter/combiner regions which serve to match the on-axis linac beam to the off-axisbeams in the FFAG cells, providing the path-length adjustment necessary to energy recovery for each of the four beams. The summer of 2017 will see the definitive engineering design and modeling of the magnets required to run the beams: dipole, quadrupole, and vertical corrector magnets. Systematic comparative studies of tracking through idealized models and discrete field maps will provide information on the required tolerances in the magnet fabrication and positioning, and on the numerical approximations inherent in field maps and tracking models.
|Carl Franck||Tiago Schaeffer Presentation Final Report||
Abstract: We know a lot about how purposefully accelerated electrons can radiate in engineered systems, e.g. going around in orbits in accelerators. However, electrons accelerated out of atoms present fundamental photon science challenges. Specifically, it was predicted decades ago that a continuous spectrum of photons, diverging in intensity with diminishing energy would occur if a deep level atomic electrons were ejected. While theory for this phenomenon, an example of an infrared divergence" (IRD are now in place (1), experimental evidence is weak (2). The REU participant will be fully engaged in our attempt to exploit the 3E3 higher photon flux now available at CHESS compared to an earlier effort (3) applying techniques developed at CHESS (4) to provide a serious test of our understanding of this effect. Depending on our progress in this adventure at the start of the REU program the candidate can expect to participate in two or more of the following aspects of the project: design of new experimental configurations for sample excitation and scattering measurement, operation of the experiment at our synchrotron radiation source, preparation of specimens of varying depth of atomic binding and comparison between our observations and theoretical predictions. Therefore: the day-to-day hands-on activities might include: operation of our inelastic X-ray scattering with X-ray fluorescence system at the CHESS high energy radiation facility, sample fabrication by operation of a thin film evaporation station, computer programing and resultant computation to model the predicted signal and assess background effects, modelling of the anticipated results arising from new configurations of the specimens and detectors and most importantly brainstorming over large amounts of coffee (an option) over what the correct theory might be if we show the current predictions to be wrong! (1) R.H. Pratt, et. al., Radiation Physics and Chemistry 79, 124 (2010); (2) P.M. Bergstrom and R.H. Pratt, Radiat. Phys. Chem. 50, 3 (1997); (3) V. Marchetti and C. Franck, Phys. Rev. A 39, 647 (1989); (4) V. Marchetti and C. Franck, Rev. Sci. Instrum. 59, 407 (1988)
|Adam Bartnik||Arman Guerra Presentation Final Report||
Abstract: Over the next three years the CBETA accelerator is planned to be built and commissioned at Cornell. Before the accelerator is finished, there is a desire to have a "virtual accelerator", which uses an identical user interface and produces identical diagnostic outputs as the actual accelerator. With this tool, strategies for commissioning can be tested, beam physics can be studied, and operators can practice using this novel type of accelerator before it is completed. This summer, the REU student will take the first steps towards creating this, by creating a virtual accelerator for a simpler test case. This simpler case will allow us to fully construct the computational framework for the virtual accelerator, while avoiding unnecessary complications inherent in modeling the full CBETA machine.
|Mike Billing, Jim Shanks||Laura Salo Presentation Final Report||
Abstract: When an electron or positron bunch circulates around the Cornell electron-positron storage ring (CESR), its accompanying electromagnetic (EM) fields will interact with any discontinuities in the vacuum chamber's walls. In a smooth vacuum chamber pipe the EM fields travelling with the beam have a static distribution. However when there are discontinuities of the vacuum chamber cross section, the bunch's EM fields scatter off of these discontinuities and thus become "disconnected" from the moving bunch, being reffered to as wakefields. The wakefields represent an energy loss mechanism for the bunch. As such they can modify the longitudinal dynamics of the bunch, changing the beam's stability and modifying the shape of the longitudinal distribution as a function of the charge in the bunch. Likewise in the transverse directions the strength of the wakefields depend on the displacement of the beam with respect to the "electrical axis" of the vacuum chamber. In this case the bunch-current-dependent wakefields can shift the natural transverse oscillation frequencies (tunes of the beam) and can change the transverse stability of the bunch. This effect could be a limitation for the maximum charge that can be placed in a single bunch in CESR, which in turn could affect the performance of CESR for future operations in a "timing mode" for x-ray users for Cornell High Energy synchrotron Source (CHESS.) This project will create a program to read the storage ring's design optical functions and the pre-calculated wakefield functions for different vacuum chamber discontinuities around CESR and compute the change in tunes as a function of beam current. Using this program, the present CESR operating configuration will be evaluated and compared with existing measurements. The program will also be used to predict the behavior for future CHESS operations. If time permits, an expansion of the program would compute the change in transverse damping of the beam.
|Pete Koufalis||Paul Andreini Presentation Final Report||
Abstract: During the cryogenic performance test of superconducting radio-frequency (SRF) cavities, large scale, high sensitivity temperature mapping is used to determine the distribution of the RF losses along the wall of the cavity. This requires operating hundreds of temperature sensors at cryogenic temperatures of a few Kelvin. As part of this project, you will work on commissioning a new temperature mapping system with much increased data sample rates and resolution. You will test readout electronics and write software for data acquisition and data analysis, and participate in the cryogenic testing of SRF cavities.
|Ryan Porter and James Maniscalco||Ruth Strauss Presentation Final Report||
Abstract: As part of this project, you will participate in the RF design of novel microwave host cavities for high-field testing of superconductors. These systems will allow to measure the non-linear surface resistance of superconductors and limits to the maximum field that can be applied. You will use 2D and 3D electromagnetic eigenmodes solvers to optimize the host cavities, and help to develop new methods for testing of small novel superconductor samples.
|Colwyn Gulliford||Nathaniel MacFadden Presentation Final Report||
Abstract: The Cornell Brookhaven ERL Test Accelerator (CBETA) will produce significant beam power which could potentially produce large amounts of radiation. Thus sufficient radiation shielding must be included in the design of the machine to ensure the stringent lab safety requirements are satisfied. To do so requires detailed modeling of the radiation patterns produced in the even of a beam loss in the machine. Several Monte Carlo radiation simulation codes now exist capable of simulated the radiation generated in such events. The goal for the summer will be to learn and set-up one of these codes (likely GEANT4) and model the radiation patterns in different loss situations and work towards developing an understanding the required shielding for the machine. If required and time permits, simulation of the beam dynamics in the machine may also be learned."
|Jacob Ruff||Victoria Kovalchuk Presentation Final Report||
Abstract: Over the past few years, advances in high energy x-ray sources, detectors, and computational power have enabled qualitatively new kinds of measurements of materials. One such area, which has been identified as a thrust for research at the Cornell High Energy Synchrotron Source (CHESS), is the atomic-scale visualization of short-range-ordered local structures in crystalline materials. Enabled by the world-class high energy x-ray beams and high dynamic range detectors at CHESS, we are now able to collect datasets that resolve details well beyond the average crystalline structure probed by traditional crystallography. This may unlock new details critical to understanding complex correlated states, including unconventional superconductivity. Recently, a new analysis technique for reconstructing local structures from high energy single crystal x-ray data, called the 3D Delta-PDF method, has been proposed and developed by researchers at ETH Zurich. The effectiveness of this analysis method when applied to CHESS datasets has also been demonstrated by a user group from Argonne National Lab. CHESS now seeks to develop an in-house capability to perform 3D Delta-PDF analysis for users. The REU candidate who chooses to join this project will collaborate with Staff Scientist Jacob Ruff and Postdoctoral researcher Jooseop Lee to develop a set of python tools to perform 3D Delta-PDF analysis, and apply this to real CHESS datasets collected over the past year. The deliverables of this project are: to determine whether this new method offers insights into ongoing user projects at CHESS-A2, to build software required to perform it, and to help the global community of CHESS users apply it to further their science. The ideal candidate will be interested in scientific computing and condensed matter physics, with some experience programming in python and/or c, and willing to engage in discussion with user groups with varying backgrounds (chemistry, physics, engineering). Success in this project could have a high impact on CHESS science and generate several publications.  "The three-dimensional pair distribution function analysis of disordered single crystals: basic concepts." T. Weber & A. Simonov. Z. Kristallogr. 227, 238-b