"Image correction algorithms for high-speed x-ray radiography"

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The Forming and Shaping Technology (FAST) beamline at CHESS focuses on in-situ high-energy diffraction and imaging measurements of structural materials under various thermomechanical loading and processing conditions. High-speed (e.g. kHz - MHz) radiography is one of several capabilities currently under development to enable studies of high-rate dynamic processes at FAST. Preliminary experiments in this mode have revealed significant beam intensity and profile fluctuations on these timescales. These fluctuations must be corrected for in order to extract meaningful information about specimen dynamics from the raw detector images. In this project, the student will perform measurements at FAST to characterize the intensity and beam profile fluctuations at various x-ray energies, perform a literature review to identify existing image correction techniques and determine their applicability to this use-case, and develop image correction codes to efficiently remove these effects from high-speed radiography data collected at FAST.

"Upgrading Nb3Sn Vapor Diffusion Furnace Control"

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Nb3Sn emerges as a promising alternative material for superconducting radiofrequency (SRF) cavities, nearing practical application. Currently, the state-of-the-art growth method for producing high-quality Nb3Sn cavities is thermal vapor diffusion. This process entails subjecting a niobium cavity to vaporized tin within a high-temperature vacuum furnace. This project aims to upgrade the control interface (GUI) for the Nb3Sn vapor diffusion furnace at Cornell University. The task involves the integration of software and hardware to operate the high vacuum furnace during coating runs. The student will gain familiarity with the vacuum systems and its controls, including the safety interlock. The student will gain hands-on cleanroom experience through participation in furnace runs. 

"Designing a High-Pressure Rinse Mount for Superconducting Material Samples"

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Superconducting radio frequency (SRF) cavities are one of the vital organs of an accelerator -- improving their performance allows for higher beam energies, which opens new frontiers for high energy physics. The material properties of the superconductors used to make these SRF cavities are one of the major factors in determining how well they will perform in an actual accelerating structure. The Cornell High Pulsed Power Sample Host Cavity (CHPPSHC, or CHIP for short) is a system recently commissioned by our research group. Its purpose is to test the material limits of candidate SRF materials with samples. These samples must be extremely clean before they can be assembled into the sample host cavity. Typically, we use a high pressure rinser with high purity de-ionized water for our accelerating cavities, however the sample geometry currently cannot be accommodated by our system. The student will assist in the design, fabrication, and testing of a sample mounting structure. This project will involve learning to use 3D design software, cleanroom practices, as well as observing high pulsed power testing of the CHIP cavity.

"Improving Control GUI and Plasma System for Chemical Vapor Deposition"

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Nb3Sn is the most promising alternative material for achieving superior performance in Superconducting Radio-Frequency (SRF) cavities, outstripping the conventional Nb cavities now used in accelerators. Chemical vapor deposition (CVD) is an alternative to the predominantly used vapor-diffusion-based Nb3Sn growth technique and it might allow reaching superior RF performance. Cornell University developed a remote plasma-enhanced chemical vapor deposition (CVD) system to complement the currently operating vapor diffusion furnace used for Nb3Sn deposition. This project aims to make the plasma section of this system operational and the student will be involved in setting up the plasma system and ensuring it’s safe operation. We will also upgrade the control interface (GUI) for the Chemical Vapor Deposition system for SRF cavities at Cornell University. The task involves the integration of software and hardware and improving the current control software.

"Temperature Mapping System Design for 2.6 GHz Superconducting Radio-Frequency Cavities"

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Superconducting Radio-Frequency (SRF) cavities are a key component of particle accelerators. Currently, bulk niobium is the standard material of choice for construction of these cavities. However, at high operating energies, cavities can suffer from impurities and defects that cause localized heating of the niobium. This localized heating causes the SRF cavity to heat up and lose its superconducting properties in a process known as a quench, which limits the performance of the cavity. One way of studying such quenches is to surround the cavity with temperature sensors, allowing for mapping of the localized heating to better understand the quench process. In this project, the REU student will work to create and test a Temperature Mapping (T-Map) system for 2.6 GHz SRF cavities. This will involve designing and 3D printing components to hold temperature sensors to the cavities, as well as assembling circuit boards to read out the data from the sensors. The student will learn about topics including RF dissipation and quench, RF testing, 3D printing, PCB fabrication, T-Map software, heat flow, and thermal conductivity.

"Consideration of microwave cavity ports in electromagnetic FEM solvers"

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Electromagnetic resonators require some form of connection to external circuitry to be useful. For three-dimensional resonators, where the electromagnetic fields are confined within a structure, this connection is done by adding a small opening (port). The design of these structures often requires the use of finite element method (FEM) solvers to obtain relevant metrics. A variety of these solvers are commercially available, but they handle these open ports differently. For applications where the electromagnetic fields in the vicinity of the open port are relevant, this can lead to discrepancies between the simulation and reality. The purpose of this project is to systematically explore these effects focusing on the electromagnetic FEM solver Ansys HFSS. In addition to improving our understanding of simulation results and identifying when care must be observed in their interpretation, it is hoped that this project will help implement an algorithm to be used with Ansys HFSS results that can reliably produce realistic simulations of microwave cavities with open ports.

"Density-Functional Theory Investigation of Impurity Interactions Near Niobium Surfaces"

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Niobium superconducting Radio-Frequency (SRF) cavities are a key component of particle accelerators. Recent work alloys the niobium surface with other metallic elements, specifically gold or zirconium, in order to improve superconducting properties of the cavity. However, the effect of metallic impurities like gold and zirconium on “interstitial” gaseous impurities such as oxygen and hydrogen, which sit between niobium atoms in the crystal lattice, is unknown. The REU student will learn to use the computational physics method of density-functional theory (DFT) to calculate energies for interstitial impurities in Nb. Based on these calculated energies, the student will calculate occupancy probabilities of interstitial impurity sites in the presence of metallic impurities. In addition to learning the popular computational method of DFT, the student will learn statistical mechanics relevant to the solvation of impurities in a solid, and the student will learn the basics of how different impurities can affect SRF cavity performance.

"Impurity Diffusion Modeling of Niobium Surfaces for Superconducting Radio-Frequency"

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Superconducting Radio-Frequency (SRF) cavities are a key component of particle accelerators. The performance of SRF cavities is closely linked to the concentrations of different impurities near the niobium surface. Exposing cavities to high temperatures, either under vacuum or in the presence of impurity elements, is known to affect the concentration-vs-depth profile of impurities near the surface. However, our understanding of this effect is still somewhat qualitative. In this project, the REU student will use the finite-element method to solve the diffusion equation for impurities in one dimension, allowing for fully quantitative predictions for the effect of an arbitrary high-temperature cavity treatment. The student will learn the basics of how different impurities affect SRF cavity performance, statistical mechanics relevant to the solvation and diffusion of impurities in a solid, and the finite element method of simulation.

"Theoretical study of the effects of capping layers on photocathodes using ab initio molecular dynamics "

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Alkali antimonide based photocathodes, such as Cs3Sb, are notorious for reacting strongly with natural atmospheric molecules in normal working conditions and high energy ions when used as a source for electrons. To prolong the lifetime for this class of photocathodes, we are embarking on a theoretical study of the effects of the application of graphene monolayers on the material surface. The student working on this project will use density-functional theory to calculate, directly from first principles and the laws of quantum mechanics, the results of various collisions with ionized molecules after the application of graphene monolayers to the surface of Cs3Sb. These studies will provide insights that cannot be obtained in any other way into fundamental physical processes that are not currently understood and, ultimately, will enable the development of better electron beams for particle accelerators and next-generation electron microscopes.

"Studying Time Dependent Ion-back Bombardment Effects in HERACLES"

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During the operation of a photoinjector at high average current, residual gas in the accelerator is ionized. Consequently, the positive ions are accelerated backwards toward the photocathode electron source causing damage and limiting the operational lifetime of the photocathode. Although a variety of techniques have demonstrated mitigation of ion-back bombardment, ions generated inside the cathode anode gap near the photocathode active material still contribute significant damage. In this project, we will study the effect that a time-dependent electron beam structure has on the generation and possible mitigation of bombardment rates via electron ion repulsion. Both analytic and computer simulation methods will be used.

"Synthesis and characterization of alkali antimonide films"

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Some electron sources use photoemissive materials to generate the desired electron beam. Ideally, researchers look for bright electron beams, which can be understood as well-collimated electron beams. Some figures of merit that can help to define the brightness of the electron beam are related to the efficiency of the material in producing electrons when radiation of suitable frequency is incident on it, these are called Quantum Efficiency (QE) and Spectral Response. Therefore, materials with high-quality beams and high QEs are desired. In this direction, materials such as alkali antimonide are promising candidates for many high-brightness electron sources because they produce very well-collimated beams with high QEs. However, these materials require ultra-high vacuum (UHV) storage to avoid oxidation, which affects their performance. In this project, a REU student will participate in synthesizing and characterizing the alkali antimonide films grown in the PHOEBE lab. This project aims to characterize materials in terms of QE, spectral response, and oxidation response.

"Modeling Ultrafast Electron Diffraction Data"

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Electron diffraction is a method used to directly observe physical phenomena on the atomic scale. Experimental diffraction data can be difficult to interpret due to several factors including thermal effects, unintentional scattering from residue material, and detector noise. To help in interpreting experimental results, simulation codes are often used to predict the expected diffraction pattern. While several diffraction codes exist, it can be difficult or in some cases impossible to add features to these codes to study less common phenomena such as spin-charge interaction in antiferromagnetic samples. In this project, a student will develop a diffraction simulation framework upon which we will be able to predict experimental results for our ultrafast electron diffraction beamline.

"Next Generation Barrel Detector Mechanics"

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The current pixel detectors used at CERN in the CMS and Atlas detectors are based on silicon pixel sensors cooled via two phase (boiling liquid) carbon dioxide. The coolant both removes the power dissipated in the device, and also keeps the sensor at -25C where the impact of radiation damage to the sensor can be reduced. With this current solution, there is already a great challenge to remove the large amount of power dissipated and we move to ever more active silicon area in these detectors. This project, a thought experiment, will investigate the possibility of cooling sensors with cryogenic nitrogen, either gas or two phase, at a significantly lower temperature. How will this lower temperature impact the radiation damage aspect? Can we model the thermal performance via finite element analysis? Will the properties of silicon which are highly non-linear in the cryogenic regime help with the heat transfer, perhaps allowing for new geometries that could reduce the mass and complexity of current designs. Hopefully this project will balance paper studies, computation, and even a quick hands on experiment if possible.

"TFPX Module Testing"

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The CMS detector at CERN, one of two detectors used to discover the Higgs boson, is currently being upgraded to handle more events with higher resolution than ever before. This project will center on setting up a test set up for the new pixel sensor modules that populate the innermost part of the detector. This set up will be used to inspect each module when it arrives from our production facilities before they are installed into the detector. This project will give the student experience with semiconductor characterization, Arduinos, data acquisition, benchtop electronics tools, etc.

"Higgs reconstruction at FCC-ee"

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Studying the Higgs boson is essential for understanding the electroweak interactions and the origin of mass. Currently, studies of the Higgs boson are being carried out at the Large Hadron Collider (LHC). However, plans are being developed for next generation colliders that could further our understanding of this particle. One possible future electron-positron collider is the Future Circular Collider (FCC-ee). This project focuses on using simulation to carry out early sensitivity studies for Higgs measurements at an FCC-ee detector. Using programming and data analysis techniques, simulated data of different physics processes and different possible detector designs will be analyzed to better understand the potential of such future experiments.

"Designing, building, and testing instrumentation for novel astronomical cameras"

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The summer research project will involve designing, building, and testing instrumentation for novel astronomical cameras that will be deployed as part of the CCAT Observatory (http://www.ccatobservatory.org) with Michael Niemack’s research group (https://www.classe.cornell.edu/~mdn49/).

"Nonlinear Particle Tracking using GPUs"

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One of the most important steps in designing a particle accelerator, or analyzing an existing one, is performing Monte Carlo simulations of the particles traversing the accelerator. This allows accelerator physicists to observe properties of the particle beam when all nonlinearities of the motion are included. In this REU project, the student will implement GPU-parallelized Monte Carlo particle tracking software in the Julia programming language. The student's software will be used in the next generation of Cornell's own accelerator physics code Bmad, which has been widely adopted in national laboratories and the accelerator industry around the world, including for designing the Electron-Ion Collider at Brookhaven National Laboratory and polarization studies for the Future Circular Collider to be built at CERN.

"Integration of Machine-learning algorithms to MLHub@CHEXS"

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The past decade has witnessed an extraordinary effort of Artificial Intelligence – the field of machine learning dedicated to guiding material discovery [1], comprehensive data analysis searching for unknown order parameters through multidimensional 'big data'[2], and many more [3]. Recently, a collaboration between the research groups of Cornell Physics Prof. Eun-Ah Kim, QM2, and researchers in the Materials Science Division at Argonne National Lab demonstrated and deployed an unsupervised machine learning approach (XTEC) that extracts order parameters, detects subtle intra-unit-cell order, and maps the temperature and doping dependent phase diagrams of quantum materials [2]. In this project, the student will work to integrate this pre-existing community-driven ML algorithm into the “Machine learning as a Service [4]” framework which is a cloud-based system offering machine learning tools, algorithms, and models, with fast access to large QM2 user datasets. The X-ray community needs to create label data – MLHub@CHEXS infrastructure will provide different reference datasets and pre-built ML algorithms. In addition, it will allow the developers, data scientists, and domain scientists to use API- driven common workflows to access a uniform interface, protocol, and data format to analyze QM2 ‘Big data’. 

In this project, the student will learn about the basics of ScikitLearn, matplotlib, seaborn, and Flask framework. In the first phase, the student will convert existing Jupyter notebooks into stand-alone Python programs (separation of ML parts into training and inference parts). Then, write an inference server and provide scripts to work with it. The second part of the project will be focused on the integration of newly created inference servers into the CHESS MLHub infrastructure.

"High Q normal conducting cavites"

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Normal conducting cavities operated at cryogenic temperatures are a promising option for very high field, pulsed particle accelerators. However, RF dissipation at these low temperatures is a concern as it requires large cooling systems with high power consumption. Within this project we will be investigating the best material options for this application.

TBD

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TBD