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2023

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Articles 61 - 86 of 86

Full-Text Articles in Engineering Physics

Tuning Microwave Losses In Superconducting Resonators, Alex Gurevich Jan 2023

Tuning Microwave Losses In Superconducting Resonators, Alex Gurevich

Physics Faculty Publications

Performance of superconducting resonators, particularly cavities for particle accelerators and micro cavities and thin film resonators for quantum computations and photon detectors has been improved substantially by recent materials treatments and technological advances. As a result, the niobium cavities have reached the quality factors Q ~ 1011 at 1-2 GHz and 1.5 K and the breakdown radio-frequency (rf) fields H close to the dc superheating eld of the Meissner state. These advances raise the question whether the state-of-the-art cavities are close to the fundamental limits, what these limits actually are, and to what extent the Q and H limits …

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Development Of A Prototype Superconducting Radio-Frequency Cavity For Conduction Cooled Accelerators, Gianluigi Ciovati, J. Anderson, S. Balachandran, G. Cheng, B. Coritron, E. Daly, P. Dhakal, Alex Gurevich, F. Hannon, K. Harding, L. Holland, F. Marhauser, K. Mclaughlin, D. Packard, T. Powers, U. Pudasaini, J. Rathke, R. Rimmer, T. Schultheiss, H. Vennekate, D. Vollmer Jan 2023

Development Of A Prototype Superconducting Radio-Frequency Cavity For Conduction Cooled Accelerators, Gianluigi Ciovati, J. Anderson, S. Balachandran, G. Cheng, B. Coritron, E. Daly, P. Dhakal, Alex Gurevich, F. Hannon, K. Harding, L. Holland, F. Marhauser, K. Mclaughlin, D. Packard, T. Powers, U. Pudasaini, J. Rathke, R. Rimmer, T. Schultheiss, H. Vennekate, D. Vollmer

Physics Faculty Publications

The higher efficiency of superconducting radio-frequency (SRF) cavities compared to normal -conducting ones enables the development of high-energy continuous-wave linear accelerators (linacs). Recent progress in the development of high-quality Nb3Sn film coatings along with the availability of cryocoolers with high cooling capacity at 4 K makes it feasible to operate SRF cavities cooled by thermal conduction at relevant accelerating gradients for use in accelerators. A possible use of conduction-cooled SRF linacs is for environmental applications, requiring electron beams with energy of 1-10 MeV and 1 MW of power. We have designed a 915 MHz SRF linac for such …

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Development And Performance Of Rfd Crab Cavity Prototypes For Hl-Lhc Aup, L. Listori, P. Berrutti, M. Narduzzi, A. Castilla, S. U. De Silva, J. R. Delayen, N. A. Huque, Z. Li, A. Ratti Jan 2023

Development And Performance Of Rfd Crab Cavity Prototypes For Hl-Lhc Aup, L. Listori, P. Berrutti, M. Narduzzi, A. Castilla, S. U. De Silva, J. R. Delayen, N. A. Huque, Z. Li, A. Ratti

Physics Faculty Publications

The US will be contributing to the HL-LHC upgrade at CERN with the fabrication and qualification of RFD crabbing cavities in the framework of the HL-LHC Accelerator Upgrade Project (AUP) managed by Fermilab. AUP received Critical Decision 3 (CD-3) approval by DOE in December 2020 launching the project into the production phase. The electro-magnetic design of the cavity was inherited from the LHC Accelerator Research Program (LARP) but needed to be revised to meet new project requirements and to prevent issues encountered during beam tests performed at CERN in the R&D phase. Two prototype cavities were manufactured in industry and …

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Investigation Of The Multilayer Shielding Effect Through Nbtin-Ain Coated Bulk Niobium, Iresha Harshani Senevirathne, D. R. Beverstock, A-M Valente-Feliciano, Alex Gurevich, Jean R. Delayen Jan 2023

Investigation Of The Multilayer Shielding Effect Through Nbtin-Ain Coated Bulk Niobium, Iresha Harshani Senevirathne, D. R. Beverstock, A-M Valente-Feliciano, Alex Gurevich, Jean R. Delayen

Physics Faculty Publications

We report measurements of the dc field onset Bp of magnetic flux penetration through NbTiN-AlN coating on bulk niobium using the Hall probe experimental setup. The measurements of Bp reveal the multilayer shielding effect on bulk niobium under high magnetic fields at cryogenic temperatures. We observed a significant enhancement in Bp for the NbTiN-AlN coated Nb samples as compared to bare Nb samples. The observed dependence of Bp on the coating thickness is consistent with theoretical predictions.

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Status And Future Plans For C³ R&D, Emilio A. Nanni, Martin Breidenbach, Zenghai Li, Caterina Vernieri, Faya Wang, Glen White, Mei Bai, Sergey Belomestnykh, Pushpalatha Bhat, Tim Barklow, William J. Berg, Valery Borzenets, John Byrd, Ankur Dhar, Ram C. Dhuley, Chris Doss, Joseph Duris, Auralee Edelen, Claudio Emma, Joseph Frisch, Annika Gabriel, Spenser Gessner, Carsten Hast, Chunguang Jing, Arkadiy Klebaner, Dongsung Kim, Anatoly Krasnykh, John Lewellen, Matthias Liepe, Michael Litos, Xueying Lu, Jared Maxon, David Montanari, Pietro Musumeci, Sergei Nagaitsev, Alireza Nassiri, Cho-Kuen Ng, David A. K. Othman, Marco Oriunno, Dennis Palmer, J. Ritchie Patterson, Michael E. Peskin, Thomas J. Peterson, John Power, Ji Qiang, James Rosenzweig, Vladimir Shiltsev, Muhammad Shumail, Evgenya Simakov, Emma Snively, Bruno Spataro, Sami Tantawi, Harry Van Der Graaf, Brandon Weatherford, Juhao Wu, Kent P. Wootton Jan 2023

Status And Future Plans For C³ R&D, Emilio A. Nanni, Martin Breidenbach, Zenghai Li, Caterina Vernieri, Faya Wang, Glen White, Mei Bai, Sergey Belomestnykh, Pushpalatha Bhat, Tim Barklow, William J. Berg, Valery Borzenets, John Byrd, Ankur Dhar, Ram C. Dhuley, Chris Doss, Joseph Duris, Auralee Edelen, Claudio Emma, Joseph Frisch, Annika Gabriel, Spenser Gessner, Carsten Hast, Chunguang Jing, Arkadiy Klebaner, Dongsung Kim, Anatoly Krasnykh, John Lewellen, Matthias Liepe, Michael Litos, Xueying Lu, Jared Maxon, David Montanari, Pietro Musumeci, Sergei Nagaitsev, Alireza Nassiri, Cho-Kuen Ng, David A. K. Othman, Marco Oriunno, Dennis Palmer, J. Ritchie Patterson, Michael E. Peskin, Thomas J. Peterson, John Power, Ji Qiang, James Rosenzweig, Vladimir Shiltsev, Muhammad Shumail, Evgenya Simakov, Emma Snively, Bruno Spataro, Sami Tantawi, Harry Van Der Graaf, Brandon Weatherford, Juhao Wu, Kent P. Wootton

Physics Faculty Publications

C3 is an opportunity to realize an e+e- collider for the study of the Higgs boson at √s = 250 GeV, with a well defined upgrade path to 550 GeV while staying on the same short facility footprint [2,3]. C3 is based on a fundamentally new approach to normal conducting linear accelerators that achieves both high gradient and high efficiency at relatively low cost. Given the advanced state of linear collider designs, the key system that requires technical maturation for C3 is the main linac. This paper presents the staged approach towards a …

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Eic 197 Mhz Crab Cavity Rf Optimization, Zenghai Li, Subashini U. De Silva, Jean R. Delayen, Robert A. Rimmer, Qiong Wu, Binping Xiao, Wencan Xu Jan 2023

Eic 197 Mhz Crab Cavity Rf Optimization, Zenghai Li, Subashini U. De Silva, Jean R. Delayen, Robert A. Rimmer, Qiong Wu, Binping Xiao, Wencan Xu

Physics Faculty Publications

Crab cavities, operating at 197 MHz and 394 MHz respectively, will be used to compensate the loss of luminosity due to a 25 mrad crossing angle at the interaction point in the Electron Ion Collider (EIC). Both crab cavities are of the RF Dipole (RFD) shape. To meet the machine design requirements, there are a few important cavity design considerations that need to be addressed. First, to achieve stable cavity operation at the design voltages, cavity geometry details must be optimized to suppress potential multipacting. Incorporating strong HOM damping in the cavity design is required for the beam stability and …

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Crab Cavities For Ilc, P. A. Mcintosh, S. A. Belomestnykh, G. Burt, R. Calaga, S. U. De Silva, J. R. Delayen, I. V. Gonin, T. N. Khabiboulline, A. Lunin, T. Okugi, Y. M. Orlov, S. Verdú-Andrés, B. P. Xiao, V. P. Yakovlev, A. Yamamoto Jan 2023

Crab Cavities For Ilc, P. A. Mcintosh, S. A. Belomestnykh, G. Burt, R. Calaga, S. U. De Silva, J. R. Delayen, I. V. Gonin, T. N. Khabiboulline, A. Lunin, T. Okugi, Y. M. Orlov, S. Verdú-Andrés, B. P. Xiao, V. P. Yakovlev, A. Yamamoto

Physics Faculty Publications

For the 14 mrad crossing angle proposed, crab cavity systems are fundamentally anticipated for the viable operation of the International Linear Collider (ILC), in order to maximise its luminosity performance. Since 2021, a specialist development team have been defining optimum crab cavity technologies which can fulfil the operational requirements for ILC, both for its baseline centre-of-mass energy of 250 GeV, but also extending those requirements out to higher beam collision intensities. Five design teams have established crab cavity technology solutions, which have the capability to also operate up to 1 TeV centre-of-mass. This presentation showcases the key performance capabilities of …

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Superconducting Non-Elliptical Cavities (Tem Cavity Designs), Subashini De Silva Jan 2023

Superconducting Non-Elliptical Cavities (Tem Cavity Designs), Subashini De Silva

Physics Faculty Publications

This lecture will present fundamental of RF to accelerate or reflect beams. The lecture will cover the electrical design method of the SRF high/medium/low beta cavities. The difference in the cavity design between TM mode and TE will be emphasized.

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Numerical Calculations Of Superheating Field In Superconductors With Nanostructured Surfaces, M.R.P. Walive Pathiranage, A. Gurevich Jan 2023

Numerical Calculations Of Superheating Field In Superconductors With Nanostructured Surfaces, M.R.P. Walive Pathiranage, A. Gurevich

Physics Faculty Publications

We re­port cal­cu­la­tions of a dc su­per­heat­ing field Hs in su­per­con­duc­tors with nanos­truc­tured sur­faces. Par­tic­u­larly, we per­formed nu­mer­i­cal sim­u­la­tions of the Ginzburg-Lan­dau (GL) equa­tions for a su­per­con­duc­tor with an in­ho­mo­ge­neous pro­file of im­pu­rity con­cen­tra­tion, a thin su­per­con­duct­ing layer on top of an­other su­per­con­duc­tor, and S-I-S mul­ti­lay­ers. The su­per­heat­ing field was cal­cu­lated tak­ing into ac­count the in­sta­bil­ity of the Meiss­ner state at a fi­nite wave­length along the sur­face de­pend­ing on the value of the GL pa­ra­me­ter. Sim­u­la­tions were done for the ma­te­ri­als pa­ra­me­ters of Nb and Nb₃Sn at dif­fer­ent val­ues of the GL pa­ra­me­ter and the mean free paths. We show …

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Quantum Computations Of The O(3) Model Using Qumodes, R. Jha, Felix Ringer, G. Siopsis, Shane Thompson Jan 2023

Quantum Computations Of The O(3) Model Using Qumodes, R. Jha, Felix Ringer, G. Siopsis, Shane Thompson

Physics Faculty Publications

We express the discrete 1+1-dimensional O(3) non-linear sigma model (NLσM) in a form well-suited for the continuous variable approach to quantum computing. Within the Schwinger boson formulation, we need two qumodes (quantum-mechanical oscillators) at each lattice site. We envision that it might be possible to reach the scaling regime of this model and observe asymptotic freedom on near-term photonic quantum devices in the coming decade.

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Understanding The Field And Frequency Dependence Of Rf Loss In Srf Cavities, Pashupati Dhakal, G. Ciovati, Alex V. Gurevich, Bashu D. Khanal Jan 2023

Understanding The Field And Frequency Dependence Of Rf Loss In Srf Cavities, Pashupati Dhakal, G. Ciovati, Alex V. Gurevich, Bashu D. Khanal

Physics Faculty Publications

SRF cavities subjected to heat treatment below 200 °C in the presence of nitrogen showed an improvement in quality factor while maintaining an accelerating gradient above 25 MV/m. Here, we report the rf performance of several single-cell superconducting radio frequency cavities with frequency ranging from 0.75 - 3.0 GHz subjected to low temperature heat treatment in nitrogen environment. The cavities were treated at temperature 120 - 175 oC for 24 - 48 hours in low partial pressure of ultra-pure nitrogen gas. The improvement in Q₀ with Q-rise was observed when nitrogen gas was injected ~300 °C during the furnace treatment. …

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Simulations Of Radiations Reaction In Inverse Compton Scattering, E. Breen, E. Rogers, E. Johnson, B. Terzić, G. Krafft, G. Wilson Jan 2023

Simulations Of Radiations Reaction In Inverse Compton Scattering, E. Breen, E. Rogers, E. Johnson, B. Terzić, G. Krafft, G. Wilson

Physics Faculty Publications

The effect of radiation reaction is often negligible in inverse Compton scattering. However, in the nonlinear Compton regime, at high laser fields and high electron beam energies where electron recoil must be properly accounted for, there is experimental data which demonstrates the onset of radiation reaction * . We model the radiation reaction as a series of emissions from individual electrons with decreasing energy. This allows us to use the code we previously developed for simulating single-emission inverse Compton scattering events ** . We use the new code to simulate the experiment reported in Cole et al. 2018, and to …

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Numerical Simulations Of Radiation Reaction Using Lorentz-Abraham-Dirac Formalism, E. Rogers, B. Terzic, E. Breen, E. Johnson, G. Krafft Jan 2023

Numerical Simulations Of Radiation Reaction Using Lorentz-Abraham-Dirac Formalism, E. Rogers, B. Terzic, E. Breen, E. Johnson, G. Krafft

Physics Faculty Publications

An accelerating charged particle emits electromagnetic radiation. The motion of the particle is further damped via self-interaction with its own radiation. For relativistic particles, the subsequent motion is described via a correction to the Lorentz force, known as the Lorentz-Abraham-Dirac force. The aim of this research is to use the Lorentz-Abraham-Dirac force to computationally simulate the radiation damping that occurs during nonlinear inverse Compton scattering. We build on our previous work and the code which simulates single-emission inverse Compton scattering to incorporate the effect of multiple emissions, thereby modeling the radiation reaction.

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Analytic And Numerical Calculation Of Collider Luminosity With Crab Dynamics, H. Huang, T. Satogata, Y. Zhang, Y. Roblin, F. Lin, S. Zhao Jan 2023

Analytic And Numerical Calculation Of Collider Luminosity With Crab Dynamics, H. Huang, T. Satogata, Y. Zhang, Y. Roblin, F. Lin, S. Zhao

Physics Faculty Publications

For an integral part of electron-ion collider (EIC) design, the crab crossing scheme provides a head-on collision for beams with a nonzero crossing angle. Recently we provided a framework for accurate numerical simulations of beam-beam effects with crabbing crossing dynamics. The framework was implemented in a simulation code package named “CASA BeamBeam”. We offer com-prehensive formulas for calculation of collider luminosity for various cases in the code package. The luminosity calculation module of CASA Beam-Beam now includes the hourglass effect, the beam-tilt effects and the beam offset effect. The benchmarking results show good agreement between the numerical calculation and analytic …

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Modeling A Nb3Sn Cryounit In Gpt At Uitf, Sunil Pokharel, A. S. Hofler, Geoffrey A. Krafft Jan 2023

Modeling A Nb3Sn Cryounit In Gpt At Uitf, Sunil Pokharel, A. S. Hofler, Geoffrey A. Krafft

Physics Faculty Publications

Nb3Sn is a prospective material for future superconducting radio frequency (SRF) accelerator cavities. Compared to conventional niobium, the material can achieve higher quality factors, higher temperature operation, and potentially higher accelerating gradients (Eacc ≈ 96 MV/m). In this work, we performed modeling of the Upgraded Injector Test Facility (UITF) at Jefferson Lab utilizing newly constructed Nb3Sn cavities. We studied the effects of the buncher cavity and varied the gun voltage from 200-500 keV. We have calibrated and optimized the SRF cavity gradients and phases for the Nb3Sn five-cell cavities' energy gains with the …

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Characterization Of Dissipative Regions Of A N-Doped Superconducting Radio-Frequency Cavity, Eric M. Lechner, Basu Dev Oli, Junki Makita, Gianluigi Ciovati, Alex Gurevich, Maria Lavarone Jan 2023

Characterization Of Dissipative Regions Of A N-Doped Superconducting Radio-Frequency Cavity, Eric M. Lechner, Basu Dev Oli, Junki Makita, Gianluigi Ciovati, Alex Gurevich, Maria Lavarone

Physics Faculty Publications

We report radio-frequency measurements of quality factors and temperature mapping of a nitrogen doped Nb superconducting RF cavity. Cavity cutouts of hot and cold spots were studied with low temperature scanning tunneling microscopy and spectroscopy, X-ray photoelectron spectroscopy and secondary electron microscopy. Temperature mapping revealed a substantial reduction of the residual resistance upon cooling the cavity with a greater temperature gradient and hysteretic losses at the quench location, pointing to trapped vortices as the dominant source of residual surface resistance.Analysis of the tunneling spectra in the framework of a proximity effect theory shows that hot spots have a reduced pair …

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Surface Properties And Rf Performance Of Vapor Diffused Nb₃Sn On Nb After Sequential Anneals Below 1000 °C, Jayendrika K. Tiskumara, Jean R. Delayen, U. Pudasaini, G. Eremeev Jan 2023

Surface Properties And Rf Performance Of Vapor Diffused Nb₃Sn On Nb After Sequential Anneals Below 1000 °C, Jayendrika K. Tiskumara, Jean R. Delayen, U. Pudasaini, G. Eremeev

Physics Faculty Publications

Nb₃Sn is a next-generation superconducting material that can be used for future superconducting radiofrequency (SRF) accelerator cavities, promising better performance, cost reduction, and higher operating temperature than Nb. The Sn vapor diffusion method is currently the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Among post-coating treatments to optimize the coating quality, higher temperature annealing without Sn is known to degrade Nb₃Sn because of Sn loss. We have investigated Nb₃Sn/Nb samples briefly annealed at 800-1000 °C, for 10 and 20 minutes to potentially improve the surface to enhance the performance of Nb₃Sn-coated cavities. Following the sample studies, …

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Superheating Field In Superconductors With Nanostructured Surfaces, W. P. M. R. Pathirana, A. Gurevich Jan 2023

Superheating Field In Superconductors With Nanostructured Surfaces, W. P. M. R. Pathirana, A. Gurevich

Physics Faculty Publications

We report calculations of a dc superheating field Hsh in superconductors with nanostructured surfaces. Numerical simulations of the Ginzburg-Landau (GL) equations were performed for a superconductor with an inhomogeneous impurity concentration, a thin superconducting layer on top of another superconductor, and superconductor-insulator-superconductor (S-I-S) multilayers.The superheating field was calculated taking into account the instability of the Meissner state with a nonzero wavelength along the surface, which is essential for realistic values of the GL parameter κ. Simulations were done for the materials parameters of Nb and Nb3Sn at different values of κ and the mean free paths. We …

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Magnetic Field Mapping Of A Large-Grain 1.3 Ghz Single-Cell Cavity, Ishwari Prasad Parajuli, Jean R. Delayen, Alex V. Gurevich, Gianluigi Ciovati Jan 2023

Magnetic Field Mapping Of A Large-Grain 1.3 Ghz Single-Cell Cavity, Ishwari Prasad Parajuli, Jean R. Delayen, Alex V. Gurevich, Gianluigi Ciovati

Physics Faculty Publications

A new magnetic field mapping system for 1.3 GHz single-cell cavities was developed in order to reveal the impact of ambient magnetic field and temperature gradients during cool-down on the flux trapping phenomenon. Measurements were done at 2 K for different cool-down conditions of a large-grain cavity before and after 120 °C bake. The fraction of applied magnetic field trapped in the cavity walls was ~ 50% after slow cool-down and ~ 20% after fast cool-down. The results showed a weak correlation between between trapped flux locations and hot-spots causing the high-field Q-slope. The results also showed an increase of …

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Fabrication And Testing Of A Prototype Rf-Dipole Crabbing Cavity, S. U. De Silva, J. R. Delayen, H. Park Jan 2023

Fabrication And Testing Of A Prototype Rf-Dipole Crabbing Cavity, S. U. De Silva, J. R. Delayen, H. Park

Physics Faculty Publications

Crabbing cavities are essential in particle colliders to compensate the luminosity degradation due to beam collision at a crossing angle. The 952.6 MHz 2-cell rf-dipole crabbing cavity system was proposed for the Jefferson Lab Electron-Ion Collider to restore the head-on collisions of electron and proton bunches at the interaction point. A prototype cavity was designed and developed to demonstrate the performance of multi-cell rf-dipole structures. This paper presents the fabrication process and cold test results of the first 2-cell rf-dipole prototype cavity.

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Temperature, Rf Field, And Frequency Dependence Performance Evaluation Of Superconducting Niobium Half-Wave Coaxial Cavity, N. K. Raut, G. Ciovati, S. U. De Silva, J. R. Delayen, P. Dhakal, B. D. Khanal, J. K. Tiskumara Jan 2023

Temperature, Rf Field, And Frequency Dependence Performance Evaluation Of Superconducting Niobium Half-Wave Coaxial Cavity, N. K. Raut, G. Ciovati, S. U. De Silva, J. R. Delayen, P. Dhakal, B. D. Khanal, J. K. Tiskumara

Physics Faculty Publications

Recent advancement in superconducting radio frequency cavity processing techniques, with diffusion of impurities within the RF penetration depth, resulted in high quality factor with increase in quality factor with increasing accelerating gradient. The increase in quality factor is the result of a decrease in the surface resistance as a result of nonmagnetic impurities doping and change in electronic density of states. The fundamental understanding of the dependence of surface resistance on frequency and surface preparation is still an active area of research. Here, we present the result of RF measurements of the TEM modes in a coaxial half-wave niobium cavity …

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First Use Of A Longitudinally Polarized Target With Clas12, C. D. Keith, J. Brock, C. Carlin, T. Kageya, V. Lagerquist, J. Maxwell, P. Pandey Jan 2023

First Use Of A Longitudinally Polarized Target With Clas12, C. D. Keith, J. Brock, C. Carlin, T. Kageya, V. Lagerquist, J. Maxwell, P. Pandey

Physics Faculty Publications

Run Group C comprises eight experiments utilizing the CLAS12 detector system in Hall B at Jefferson Lab to study the multidimensional partonic structure of nucleons. The experiments scatter electrons from polarized protons and neutrons in samples of solid NH3 and ND3, dynamically polarized at a temperature of 1 K in a 5 T magnetic field. After a brief description of the target system, the current status of the target and preliminary results of its performance in the experiment are presented.

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Development Of A Novel Readout Concept For An Eic Dirc, K. Dehmelt, A. Deshpande, R. Dzhygadlo, T. K. Hemmick, Md. I. Hossain, C. E. Hyde, Y. Ilieva, G. Kalicy, P. Nadel-Turonski, C. Schwarz, J. Schwiening, N. Shankman, J. Stevens, N. Wickramaarachchi, C. Woody Jan 2023

Development Of A Novel Readout Concept For An Eic Dirc, K. Dehmelt, A. Deshpande, R. Dzhygadlo, T. K. Hemmick, Md. I. Hossain, C. E. Hyde, Y. Ilieva, G. Kalicy, P. Nadel-Turonski, C. Schwarz, J. Schwiening, N. Shankman, J. Stevens, N. Wickramaarachchi, C. Woody

Physics Faculty Publications

The objective of this program is to pursue opportunities to reduce the material budget and the cost of the DIRC counter for the EIC, without loss of performance, by investigating fundamental DIRC performance limits and new optical configurations. The barrel high-performance DIRC (hpDIRC) has been adopted for the ePIC detector and is an attractive solution for Detector-2. In this program, we study the DIRC performance with an innovative optical configuration consisting of narrow, thin radiator bars coupled to wide plates, focusing lenses, and small expansion volume prisms. The outcomes of these studies would be applicable to both ePIC and, in …

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Quantum Efficiency And Lifetime Study For Negative Electron Affinity Gaas Nanopillar Array Photocathode, Md Aziz Ar Rahman, Md Abdullah Mamun, Shukui Zhang, Hani E. Elsayed-Ali Jan 2023

Quantum Efficiency And Lifetime Study For Negative Electron Affinity Gaas Nanopillar Array Photocathode, Md Aziz Ar Rahman, Md Abdullah Mamun, Shukui Zhang, Hani E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Recent studies showed significant improvement in quantum efficiency (QE) by negative electron affinity (NEA) GaAs nanopillar array (NPA) photocathodes over their flat surface peers, particularly at 500 ─ 800 nm waveband. However, the underlying physics is yet to be well understood for further improvement in its performance. In this report, NEA GaAs NPA photocathodes with different dimensions were studied. The diameter of the nanopillars varied from 200 ─ 360 nm, the height varied from 230 ─ 1000 nm and the periodicity varied from 470 ─ 630 nm. The QE and photocathode lifetime were measured. Mie-resonance enhancement was observed at tunable …

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High Figure Of Merit Spin Polarized Electron Sources Grown Via Mocvd, Benjamin Belfore, Adam Masters, Deewakar Poudel, Greg Blume, Stephen Polly, Erdong Wang, Seth M. Hubbard, Marcy Stutzman, Joseph M. Grames, Matt Poelker, Matt Grau, Sylvain Marsillac Jan 2023

High Figure Of Merit Spin Polarized Electron Sources Grown Via Mocvd, Benjamin Belfore, Adam Masters, Deewakar Poudel, Greg Blume, Stephen Polly, Erdong Wang, Seth M. Hubbard, Marcy Stutzman, Joseph M. Grames, Matt Poelker, Matt Grau, Sylvain Marsillac

Electrical & Computer Engineering Faculty Publications

Spin polarized photocathodes are key to the future operation of electron accelerators such as the ones at Thomas Jefferson National Accelerator Facility and Brookhaven National Laboratory. Currently, these photocathodes come in short supply due to limited production by molecular beam epitaxy. By developing a process to implement similar structures using metal organic chemical vapor deposition, the availability of these devices can be increased. In this paper, we detail the implementation of recent photocathode advancements via metal organic chemical vapor deposition process and show an improvement in both polarization and quantum efficiency of our devices compared to those fabricated via molecular …

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Mechanisms Of Emulsion Destabilization: An Investigation Of Surfactant, Stabilizer, And Detergent Based Formulations Using Diffusing Wave Spectroscopy, Jordan N. Nowaczyk Jan 2023

Mechanisms Of Emulsion Destabilization: An Investigation Of Surfactant, Stabilizer, And Detergent Based Formulations Using Diffusing Wave Spectroscopy, Jordan N. Nowaczyk

Theses and Dissertations

Conventional approaches for studying emulsions, such as microscopy and macroscopic phase tracking, present challenges when it comes to establishing detailed mechanistic descriptions of the impact of emulsifier and stabilizer additives. Additionally, while a combination of sizing methods and macroscopic phase tracking can provide insights into droplet size changes and concentration, the use of multiple measurements can be cumbersome and error-prone. It is the focus of this work, to present a new method for studying water in oil (W/O) emulsions that involves using diffusing wave spectroscopy (DWS) to examine the impact of three different surface stabilizing additives at varying concentrations. By …

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