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Full-Text Articles in Engineering Physics
Detecting Anomalous Srf Cavity Behavior With Unsupervised Learning, Hal Ferguson, Jiang Li, Adam Carpenter, Chris Tennant, Dillon Thomas, Dennis Turner
Detecting Anomalous Srf Cavity Behavior With Unsupervised Learning, Hal Ferguson, Jiang Li, Adam Carpenter, Chris Tennant, Dillon Thomas, Dennis Turner
Electrical & Computer Engineering Faculty Publications
We present an unsupervised learning framework for detecting anomalous superconducting radio-frequency (SRF) cavity behavior at the Continuous Electron Beam Accelerator Facility (CEBAF), emphasizing its initial performance and effectiveness. Key to the system’s success was the development of data acquisition systems (DAQs) that capture fast-sampled, information-rich signals, essential for detecting transient effects. The approach involves creating daily cavity-specific models using principal component analysis to handle variations in rf signal behavior and mitigate performance degradation from data drift. This unsupervised method eliminates the need for expensive labeling by continuously updating models with recent data. Deployed and operational for 3 months before a …
Optimizing Superconducting Nb Film Cavities By Mitigating Medium-Field Q-Slope Through Annealing, B. Abdisatarov, G. Eremeev, H. E. Elsayed-Ali, D. Bafia, A. Murthy, Z. Sung, A. Netepenko, A. Romanenko, C. P.A. Carlos, G. J. Rosaz, S. Calatroni, S. Leith, A. Grassellino
Optimizing Superconducting Nb Film Cavities By Mitigating Medium-Field Q-Slope Through Annealing, B. Abdisatarov, G. Eremeev, H. E. Elsayed-Ali, D. Bafia, A. Murthy, Z. Sung, A. Netepenko, A. Romanenko, C. P.A. Carlos, G. J. Rosaz, S. Calatroni, S. Leith, A. Grassellino
Electrical & Computer Engineering Faculty Publications
Niobium films are of interest in applications in various superconducting devices, such as superconducting radiofrequency cavities for particle accelerators and superconducting qubits for quantum computing. In this study, we address the persistent medium-field Q-slope issue in Nb film cavities, which, despite their high-quality factor at low RF fields, exhibit a significant Q-slope at medium RF fields compared to bulk Nb cavities. Traditional heat treatments, effective in reducing surface resistance and mitigating the Q-slope in bulk Nb cavities, are challenging for Nb-coated copper cavities. To overcome this challenge, we employed DC bias high-power impulse magnetron sputtering to deposit …
Field, Frequency, And Temperature Dependencies Of The Surface Resistance Of Nitrogen Diffused Niobium Superconducting Radio Frequency Cavities, P. Dhakal, B. D. Khanal, A. Gurevich, G. Ciovati
Field, Frequency, And Temperature Dependencies Of The Surface Resistance Of Nitrogen Diffused Niobium Superconducting Radio Frequency Cavities, P. Dhakal, B. D. Khanal, A. Gurevich, G. Ciovati
Physics Faculty Publications
We investigate the rf performance of several single-cell superconducting radio-frequency cavities subjected to low temperature heat treatment in nitrogen environment. The cavities were treated at temperature 120–165 °C for an extended period of time (24–48 h) either in high vacuum or in a low partial pressure of ultrapure nitrogen. The improvement in 𝑄0 with a 𝑄 rise was observed when nitrogen gas was injected at ∼300 °C during the cavity cooldown from 800 °C and held at 165 °C, without any degradation in accelerating gradient over the baseline performance. The treatment was applied to several elliptical cavities with frequency ranging …
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
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 …
Nonlinear Meissner Effect In Nb3Sn Coplanar Resonators, Junki Makita, C. Sundahl, Gianluigi Ciovati, C. B. Eom, Alex Gurevich
Nonlinear Meissner Effect In Nb3Sn Coplanar Resonators, Junki Makita, C. Sundahl, Gianluigi Ciovati, C. B. Eom, Alex Gurevich
Physics Faculty Publications
We investigated the nonlinear Meissner effect (NLME) in Nb3Sn thin-film coplanar resonators by measuring the resonance frequency as a function of a parallel magnetic field at different temperatures. We used low rf power probing in films thinner than the London penetration depth λ(B) to significantly increase the field onset of vortex penetration and measure the NLME under equilibrium conditions. Contrary to the conventional quadratic increase of λ(B) with B expected in s-wave superconductors, we observed a nearly linear increase of the penetration depth with B. We concluded that this behavior of λ(B) is due to weak linked grain …
Evidence Of Increased Radio-Frequency Losses In Cavities From The Fundamental Power Coupler Cold Window, Frank Marhauser, Gianluigi Ciovati
Evidence Of Increased Radio-Frequency Losses In Cavities From The Fundamental Power Coupler Cold Window, Frank Marhauser, Gianluigi Ciovati
Physics Faculty Publications
High radio-frequency (rf) losses measured for cavities in original Continuous Electron Beam Accelerator Facility (CEBAF) cryomodules, compared to the losses measured in single-cavity tests, have been a long-standing issue related to their performance. We summarize experimental evidence of increased rf losses in CEBAF cavities arising from the fundamental power coupler cold window and waveguide, respectively. Cryogenic rf tests were done on cavities tested in vertical cryostats as well as inside cryomodules in the accelerator tunnel. The cold window metallization losses were assessed by combining numerical results with measured data obtained with an existing cryogenic waveguide resonator setup. The results showed …
Flux Expulsion In Niobium Superconducting Radio-Frequency Cavities Of Different Purity And Essential Contributions To The Flux Sensitivity, P. Dhakal, Gianluigi Ciovati, Alex Gurevich
Flux Expulsion In Niobium Superconducting Radio-Frequency Cavities Of Different Purity And Essential Contributions To The Flux Sensitivity, P. Dhakal, Gianluigi Ciovati, Alex Gurevich
Physics Faculty Publications
Magnetic flux trapped during the cooldown of superconducting radio-frequency cavities through the transition temperature due to incomplete Meissner state is known to be a significant source of radio-frequency losses. The sensitivity of flux trapping depends on the distribution and the type of defects and impurities which pin vortices, as well as the cooldown dynamics when the cavity transitions from a normal to superconducting state. Here we present the results of measurements of the flux trapping sensitivity on 1.3 GHz elliptical cavities made from large-grain niobium with different purity for different cooldown dynamics and surface treatments. The results show that lower …
Temperature Mapping Of Nitrogen-Doped Niobium Superconducting Radiofrequency Cavities, Junki Makita, Gianluigi Ciovati, Pashupati Dhakal
Temperature Mapping Of Nitrogen-Doped Niobium Superconducting Radiofrequency Cavities, Junki Makita, Gianluigi Ciovati, Pashupati Dhakal
Physics Faculty Publications
It was recently shown that diffusing nitrogen on the inner surface of superconducting radiofrequency (SRF) cavities at high temperature can improve the quality factor of the niobium cavity. However, a reduction of the quench field is also typically found. To better understand the location of rf losses and quench, we used a thermometry system to map the temperature of the outer surface of ingot Nb cavities after nitrogen doping and electropolishing. Surface temperature of the cavities was recorded while increasing the rf power and also during the quenching. The results of thermal mapping showed no precursor heating on the cavities …
Nitrogen Doping Study In Ingot Niobium Cavities, Pashupati Dhakal, Gianluigi Ciovati, Peter Kneisel, Ganapati Rao Myneni, Junki Makita
Nitrogen Doping Study In Ingot Niobium Cavities, Pashupati Dhakal, Gianluigi Ciovati, Peter Kneisel, Ganapati Rao Myneni, Junki Makita
Physics Faculty Publications
Thermal diffusion of nitrogen in superconducting radio frequency cavities at temperatures around 800C has resulted in the increase in quality factor with a low-field Q-rise. However, the maximum accelerating gradients of these doped cavities often reduces below the values achieved by standard treatments. In this contribution, we present the results of the nitrogen diffusion into ingot niobium cavities subjected to successive material removal from the inner cavity surface by electropolishing in an effort to explore the underlying cause for the gradient degradation.
Design Of Electron And Ion Crabbing Cavities For An Electron-Ion Collider, A. Castilla, Jean R. Delayen, Geoffrey A. Krafft
Design Of Electron And Ion Crabbing Cavities For An Electron-Ion Collider, A. Castilla, Jean R. Delayen, Geoffrey A. Krafft
Physics Faculty Publications
Beyond the 12 GeV upgrade at the Jefferson Lab a Medium Energy Electron-Ion Collider (MEIC) is being considered. In order to achieve the desired high luminosities at the Interaction Points (IP), the use of crabbing cavities is under study. In this work, we will present up to date designs of superconducting cavities, considered for crabbing both ion and electron bunches. A discussion of properties such as peak surface fields and Higher Order Modes (HOMs) separation will be presented.
A New Tem-Type Deflecting And Crabbing Rf Structure, Jean R. Delayen, H. Wang
A New Tem-Type Deflecting And Crabbing Rf Structure, Jean R. Delayen, H. Wang
Physics Faculty Publications
A new type of rf structure for the deflection and crabbing of particle bunches is introduced. It is comprised of a number of parallel TEM-resonant lines operating in opposite phase from each other. One of its main advantages is its compactness compared to conventional crabbing cavities operating in the TM110 mode, thus allowing low frequency designs. The properties and characteristics of this type of structure are presented.