TY - CONF AU - Khanal, B.D. AU - Balachandran, S. AU - Chetri, S. AU - Dhakal, P. AU - Lee, P.J. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Magnetic Flux Expulsion in Superconducting Radio-Frequency Niobium Cavities Made from Cold Worked Niobium J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Trapped residual magnetic field during the cool down of superconducting radio frequency (SRF) cavities is one of the primary sources of RF residual losses leading to lower quality factor. Historically, SRF cavities have been fabricated from high purity fine grain niobium with grain size ~50 to 100 µm as well as large grain with grain size of the order of few centimeters. Non-uniform recrystallization of fine-grain Nb cavities after the post fabrication heat treatment leads to higher flux trapping during the cool down, and hence the lower quality factor. We fabricated two 1.3 GHz single cell cavities from cold-worked niobium from different vendors and processed along with cavities made from SRF grade Nb. The flux expulsion and flux trapping sensitivity were measured after successive heat treatments in the range 800 to 1000°C. The flux expulsion from cold-worked fine-grain Nb cavities improves after 800°C/3h heat treatments and it becomes similar to that of standard fine-grain Nb cavities when the heat treatment temperature is higher than 900°C. PB - JACoW Publishing CP - Geneva, Switzerland SP - 611 EP - 614 KW - cavity KW - SRF KW - niobium KW - radio-frequency KW - ECR DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEZE5 UR - https://jacow.org/napac2022/papers/weze5.pdf ER - TY - CONF AU - Bruker, M.W. AU - Grames, J.M. AU - Hernandez-Garcia, C. AU - Lizárraga-Rubio, V.M. AU - Poelker, M. AU - Valerio-Lizárraga, C.A. AU - Yoskowitz, J.T. AU - Zhang, S. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - New Results at JLab Describing Operating Lifetime of GaAs Photo-guns J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Polarized electrons from GaAs photocathodes have been key to some of the highest-impact results of the Jefferson Lab science program over the past 30 years. During this time, various studies have given insight into improving the operational lifetime of these photocathodes in DC high-voltage photo-guns while using lasers with spatial Gaussian profiles of typically 0.5 mm to 1 mm FWHM, cathode voltages of 100 kV to 130 kV, and a wide range of beam currents up to multiple mA. In this contribution, we show recent experimental data from a 100 kV to 180 kV setup and describe our progress at predicting the lifetime based on the calculable dynamics of ionized gas molecules inside the gun. These new experimental studies at Jefferson Lab are specifically aimed at exploring the ion damage of higher-voltage guns being built for injectors. PB - JACoW Publishing CP - Geneva, Switzerland SP - 644 EP - 647 KW - gun KW - cathode KW - electron KW - laser KW - experiment DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA13 UR - https://jacow.org/napac2022/papers/wepa13.pdf ER - TY - CONF AU - Mamun, M.A. AU - Bullard, D.B. AU - Delayen, J.R. AU - Grames, J.M. AU - Hernandez-Garcia, C. AU - Krafft, G.A. AU - Palacios Serrano, G.G. AU - Poelker, M. AU - Suleiman, R. AU - Wijethunga, S.A.K. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Improved Electrostatic Design of the Jefferson Lab 300 kV DC Photogun and the Minimization of Beam Deflection J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - An electron beam with high bunch charge and high repetition rate is required for electron cooling of the ion beam to achieve the high luminosity required for the proposed electron-ion colliders. An improved design of the 300 kV DC high voltage photogun at Jefferson Lab was incorporated toward overcoming the beam loss and space charge current limitation experienced in the original design. To reach the bunch charge goal of ~ few nC within 75 ps bunches, the existing DC high voltage photogun electrodes and anode-cathode gap were modified to increase the longitudinal electric field (Ez) at the photocathode. The anode-cathode gap was reduced to increase the Ez at the photocathode, and the anode aperture was spatially shifted with respect to the beamline longitudinal axis to minimize the beam deflection introduced by the geometric asymmetry of the inverted insulator photogun. The electrostatic design and beam dynamics simulations were performed to determine the required modification. Beam-based measurement from the modified gun confirmed the reduction of the beam deflection, which is presented in this contribution. PB - JACoW Publishing CP - Geneva, Switzerland SP - 655 EP - 658 KW - gun KW - cathode KW - electron KW - high-voltage KW - laser DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA17 UR - https://jacow.org/napac2022/papers/wepa17.pdf ER - TY - CONF AU - Ahammed, K. AU - Carpenter, A. AU - Li, J. AU - Suleiman, R. AU - Tennant, C. AU - Vidyaratne, L.S. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Field Emission Mitigation in CEBAF SRF Cavities Using Deep Learning J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - The Continuous Electron Beam Accelerator Facility (CEBAF) operates hundreds of superconducting radio frequency (SRF) cavities in its two main linear accelerators. Field emission can occur when the cavities are set to high operating RF gradients and is an ongoing operational challenge. This is especially true in newer, higher gradient SRF cavities. Field emission results in damage to accelerator hardware, generates high levels of neutron and gamma radiation, and has deleterious effects on CEBAF operations. So, field emission reduction is imperative for the reliable, high gradient operation of CEBAF that is required by experimenters. Here we explore the use of deep learning architectures via multilayer perceptron to simultaneously model radiation measurements at multiple detectors in response to arbitrary gradient distributions. These models are trained on collected data and could be used to minimize the radiation production through gradient redistribution. This work builds on previous efforts in developing machine learning (ML) models, and is able to produce similar model performance as our previous ML model without requiring knowledge of the field emission onset for each cavity. PB - JACoW Publishing CP - Geneva, Switzerland SP - 676 EP - 678 KW - cavity KW - radiation KW - detector KW - neutron KW - linac DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA25 UR - https://jacow.org/napac2022/papers/wepa25.pdf ER - TY - CONF AU - De Silva, S.U. AU - Delayen, J.R. AU - Guo, J. AU - Li, Z. AU - Rimmer, R.A. AU - Xiao, B.P. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - 197 MHz Waveguide Loaded Crabbing Cavity Design for the Electron-Ion Collider J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - The Electron-Ion Collider will require crabbing systems at both hadron and electron storage rings in order to reach the desired luminosity goal. The 197 MHz crab cavity system is one of the critical rf systems of the col-lider. The crab cavity, based on the rf-dipole design, ex-plores the option of waveguide load damping to suppress the higher order modes and meet the tight impedance specifications. The cavity is designed with compact dog-bone waveguides with transitions to rectangular wave-guides and waveguide loads. This paper presents the compact 197 MHz crab cavity design with waveguide damping and other ancillaries. PB - JACoW Publishing CP - Geneva, Switzerland SP - 679 EP - 682 KW - cavity KW - HOM KW - GUI KW - impedance KW - electron DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA26 UR - https://jacow.org/napac2022/papers/wepa26.pdf ER - TY - CONF AU - Khanal, B.D. AU - Dhakal, P. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Effect of Duration of 120 °C Baking on the Performance of Superconducting Radio Frequency Niobium Cavities J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Over the last decade much attention was given in increasing the quality factor of superconducting radio frequency (SRF) cavities by impurity doping. Prior to the era of doping, the final cavity processing technique to achieve the high accelerating gradient includes the "in situ" low temperature baking of SRF cavities at temperature ~ 120°C for several hours. Here, we present the results of a series of measurements on 1.3 GHz TESLA shape single-cell cavities with successive low temperature baking at 120°C up to 96 hours. The experimental data were analyzed with available theory of superconductivity to elucidate the effect of the duration of low temperature baking on the superconducting properties of cavity materials as well as the RF performance. In addition, the RF loss related to the trapping of residual magnetic field refereed as flux trapping sensitivity was measured with respect to the duration of 120°C bake. PB - JACoW Publishing CP - Geneva, Switzerland SP - 683 EP - 686 KW - cavity KW - niobium KW - SRF KW - radio-frequency KW - accelerating-gradient DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA27 UR - https://jacow.org/napac2022/papers/wepa27.pdf ER - TY - CONF AU - Rahman, M. AU - Carpenter, A. AU - Iftekharuddin, K.M. AU - McGuckin, T.S. AU - Tennant, C. AU - Vidyaratne, L.S. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Real-Time Cavity Fault Prediction in CEBAF Using Deep Learning J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Data-driven prediction of future faults is a major research area for many industrial applications. In this work, we present a new procedure of real-time fault prediction for superconducting radio-frequency (SRF) cavities at the Continuous Electron Beam Accelerator Facility (CEBAF) using deep learning. CEBAF has been afflicted by frequent downtime caused by SRF cavity faults. We perform fault prediction using pre-fault RF signals from C100-type cryomodules. Using the pre-fault signal information, the new algorithm predicts the type of cavity fault before the actual onset. The early prediction may enable potential mitigation strategies to prevent the fault. In our work, we apply a two-stage fault prediction pipeline. In the first stage, a model distinguishes between faulty and normal signals using a U-Net deep learning architecture. In the second stage of the network, signals flagged as faulty by the first model are classified into one of seven fault types based on learned signatures in the data. Initial results show that our model can successfully predict most fault types 200 ms before onset. We will discuss reasons for poor model performance on specific fault types. PB - JACoW Publishing CP - Geneva, Switzerland SP - 687 EP - 690 KW - cavity KW - network KW - cryomodule KW - SRF KW - experiment DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA29 UR - https://jacow.org/napac2022/papers/wepa29.pdf ER - TY - CONF AU - Shakel, M.S. AU - Cao, W. AU - Elsayed-Ali, H. AU - Eremeev, G.V. AU - Pudasaini, U. AU - Sayeed, Md.N. AU - Valente-Feliciano, A-M. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Nb₃Sn Coating of a 2.6 GHz SRF Cavity by Sputter Deposition Technique J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Nb₃Sn is of interest as a coating for SRF cavities due to its higher transition temperature Tc ~18.3 K and superheating field Hsh ~400 mT, both are twice that of Nb. Nb₃Sn coated cavities can achieve high-quality factors at 4 K and can replace the bulk Nb cavities operated at 2 K. A cylindrical magnetron sputtering system was built, commissioned, and used to deposit Nb₃Sn on the inner surface of a 2.6 GHz single-cell Nb cavity. With two identical cylindrical magnetrons, this system can coat a cavity with high symmetry and uniform thickness. Using Nb-Sn multilayer sequential sputtering followed by annealing at 950°C for 3 hours, polycrystalline Nb₃Sn films were first deposited at the equivalent positions of the cavity’s beam tubes and equator. The film’s composition, crystal structure, and morphology were characterized by energy dispersive spectroscopy, X-ray diffraction, and atomic force microscopy. The Tc of the films was measured by the four-point probe method and was 17.61 to 17.76 K. Based on these studies, ~1.2 micron thick Nb₃Sn was deposited inside a 2.6 GHz Nb cavity. We will discuss first results from samples and cavity coatings, and the status of the coating system. PB - JACoW Publishing CP - Geneva, Switzerland SP - 691 EP - 694 KW - cavity KW - SRF KW - site KW - target KW - plasma DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA30 UR - https://jacow.org/napac2022/papers/wepa30.pdf ER - TY - CONF AU - Tiskumara, J.K. AU - Delayen, J.R. AU - Eremeev, G.V. AU - Pudasaini, U. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Lower Temperature Annealing of Vapor Diffused Nb₃Sn for Accelerator Cavities J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - Nb₃Sn is a next-generation superconducting material for the accelerator cavities with higher critical temperature and superheating field, both twice compared to Nb. It promises superior performance and higher operating temperature than Nb, resulting in significant cost reduction. So far, the Sn vapor diffusion method is the most preferred and successful technique to coat niobium cavities with Nb₃Sn. Although several post-coating techniques (chemical, electrochemical, mechanical) have been explored to improve the surface quality of the coated surface, an effective process has yet to be found. Since there are only a few studies on the post-coating heat treatment at lower temperatures, we annealed Nb₃Sn-coated samples at 800 C - 1000 C to study the effect of heat treatments on surface properties, primarily aimed at removing surface Sn residues. This paper discusses the systematic surface analysis of coated samples after annealing at temperatures between 850 C and 950 C. PB - JACoW Publishing CP - Geneva, Switzerland SP - 695 EP - 698 KW - cavity KW - SRF KW - superconductivity KW - experiment KW - electron DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA31 UR - https://jacow.org/napac2022/papers/wepa31.pdf ER - TY - CONF AU - Huang, H. AU - Lin, F. AU - Luo, Y. AU - Morozov, V.S. AU - Satogata, T. AU - Xiao, B.P. AU - Xu, D. AU - Zhang, Y. AU - Zhao, S. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Emittance Growth Due to RF Phase Noise in Crab Cavities J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - The Electron-Ion Collider (EIC) incorporates beam crabbing to recover geometric luminosity loss from the nonzero crossing angle at the interaction point (IP). It is well-known that crab cavity imperfections can cause growth of colliding beam emittances, thus degrading collider performance. Here we report a particle tracking study to quantify these effects. Presently the study is focused on crab cavity RF phase noise. Simulations were carried out using Bmad. Dependence of emittance growth on phase noise level was obtained which could be used for developing crab cavity phase control specifications. We also benchmarked these simulations with theory. PB - JACoW Publishing CP - Geneva, Switzerland SP - 708 EP - 710 KW - cavity KW - emittance KW - simulation KW - collider KW - betatron DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA36 UR - https://jacow.org/napac2022/papers/wepa36.pdf ER - TY - CONF AU - Luo, Y. AU - Berg, J.S. AU - Blaskiewicz, M. AU - Hao, Y. AU - Huang, H. AU - Montag, C. AU - Morozov, V.S. AU - Ptitsyn, V. AU - Qiang, J. AU - Satogata, T. AU - Willeke, F.J. AU - Xu, D. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - {6-D} Element-by-Element Particle Tracking with Crab Cavity Phase Noise and Weak-Strong Beam-Beam Interaction for the Hadron Storage Ring of the Electron-Ion Collider J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - The Electron Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with luminosity up to 10³⁴ cm⁻² s⁻¹ in the center mass energy range of 20 to 140 GeV. Crab cavities are used to compensate the geometric luminosity due to a large crossing angle in the EIC. However, it was found that the phase noise in crab cavities will generate a significant emittance growth for hadron beams and its tolerance from analytical calculation is very small for the Hadron Storage Ring (HSR) of the EIC. In this paper, we report on 6-D symplectic particle tracking to estimate the proton emittance growth rate, especially in the vertical plane, for the HSR with weak-strong beam-beam and other machine or lattice errors. PB - JACoW Publishing CP - Geneva, Switzerland SP - 809 EP - 812 KW - emittance KW - cavity KW - simulation KW - proton KW - electron DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-WEPA75 UR - https://jacow.org/napac2022/papers/wepa75.pdf ER - TY - CONF AU - Pokharel, S. AU - Bruker, M.W. AU - Grames, J.M. AU - Hofler, A.S. AU - Kazimi, R. AU - Krafft, G.A. AU - Zhang, S. ED - Biedron, Sandra ED - Simakov, Evgenya ED - Milton, Stephen ED - Anisimov, Petr M. ED - Schaa, Volker R.W. TI - Bunch Length Measurements at the CEBAF Injector at 130 kV J2 - Proc. of NAPAC2022, Albuquerque, NM, USA, 07-12 August 2022 CY - Albuquerque, NM, USA T2 - International Particle Accelerator Conference T3 - 5 LA - english AB - In this work, we investigated the evolution in bunch length of beams through the CEBAF injector for low to high charge per bunch. Using the General Particle Tracer (GPT), we have simulated the beams through the beamline of the CEBAF injector and analyzed the beam to get the bunch lengths at the location of chopper. We performed these simulations with the existing injector using a 130 kV gun voltage. Finally, we describe measurements to validate these simulations. The measurements have been done using chopper scanning technique for two injector laser drive frequency modes: one with 500 MHz, and another with 250 MHz. PB - JACoW Publishing CP - Geneva, Switzerland SP - 917 EP - 920 KW - laser KW - electron KW - simulation KW - cavity KW - gun DA - 2022/10 PY - 2022 SN - 2673-7000 SN - 978-3-95450-232-5 DO - doi:10.18429/JACoW-NAPAC2022-FRXD6 UR - https://jacow.org/napac2022/papers/frxd6.pdf ER -