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Full-Text Articles in Physics
Bunch Length Measurements At The Cebaf Injector At 130 Kv, Sunil Pokharel, M. W. Bruker, J. M. Grames, A. S. Hofler, R. Kazimi, Geoffrey A. Krafft, S. Zhang
Bunch Length Measurements At The Cebaf Injector At 130 Kv, Sunil Pokharel, M. W. Bruker, J. M. Grames, A. S. Hofler, R. Kazimi, Geoffrey A. Krafft, S. Zhang
Physics Faculty Publications
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 …
New Results At Jlab Describing Operating Lifetime Of Gaas Photo-Guns, M. Bruker, J. Grames, C. Hernández-García, M. Poelker, S. Zhang, V. Lizárraga-Rubio, C. Valerio-Lizárraga, Joshua T. Yoskowitz
New Results At Jlab Describing Operating Lifetime Of Gaas Photo-Guns, M. Bruker, J. Grames, C. Hernández-García, M. Poelker, S. Zhang, V. Lizárraga-Rubio, C. Valerio-Lizárraga, Joshua T. Yoskowitz
Physics Faculty Publications
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 …
Cebaf Injector Model For KL Beam Conditions, Sunil Pokharel, Geoffrey A. Krafft, A. S. Hofler, R. Kazimi, M. Bruker, J. Grames, S. Zhang
Cebaf Injector Model For KL Beam Conditions, Sunil Pokharel, Geoffrey A. Krafft, A. S. Hofler, R. Kazimi, M. Bruker, J. Grames, S. Zhang
Physics Faculty Publications
The Jefferson Lab KL experiment will run at the Continuous Electron Beam Accelerator Facility with a much lower bunch repetition rate (7.80 or 15.59 MHz) than nominally used (249.5 or 499 MHz). While the proposed average current of 2.5 - 5.0 µA is relatively low compared to the maximum CEBAF current of approximately 180 µA, the corresponding bunch charge is atypically high for CEBAF injector operation. In this work, we investigated the evolution and transmission of low-rep-rate, high-bunch-charge (0.32 to 0.64 pC) beams through the CEBAF injector. Using the commercial software General Particle Tracer, we have simulated and analyzed the …
Modeling A Nb3Sn Cryounit In Gpt In Uitf, Sunil Pokharel, Geoffey A. Krafft, A. S. Hofler
Modeling A Nb3Sn Cryounit In Gpt In Uitf, Sunil Pokharel, Geoffey A. Krafft, A. S. Hofler
Physics Faculty Publications
Nb₃Sn is a prospective material for future superconducting RF (SRF) accelerator cavities. The material can achieve higher quality factors, higher temperature operation and potentially higher accelerating gradients (E_{acc} 96 MV/m) compared to conventional niobium. 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 voltages 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 framework of General Particle Tracer (GPT). Our calculations show …
Improved Electrostatic Design Of The Jefferson Lab 300 Kv Dc Photogun And The Minimization Of Beam Deflection, M. A. Mamun, D. B. Bullard, J. R. Delayen, J. M. Grames, C. Hernandez-Garcia, Geoffrey A. Krafft, M. Poelker, R. Suleiman, S.A.K. Wijethunga
Improved Electrostatic Design Of The Jefferson Lab 300 Kv Dc Photogun And The Minimization Of Beam Deflection, M. A. Mamun, D. B. Bullard, J. R. Delayen, J. M. Grames, C. Hernandez-Garcia, Geoffrey A. Krafft, M. Poelker, R. Suleiman, S.A.K. Wijethunga
Physics Faculty Publications
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 …
Redesign Of The Jefferson Lab -300 Kv Dc Photo-Gun For High Bunch Charge Operations, S.A.K. Wijethunga, J. Benesch, Jean R. Delayen, C. Hernandez-Garcia, Geoffrey A. Krafft, Gabriel Palacios-Serrano, M.A. Mamun, M. Poelker, R. Suleiman
Redesign Of The Jefferson Lab -300 Kv Dc Photo-Gun For High Bunch Charge Operations, S.A.K. Wijethunga, J. Benesch, Jean R. Delayen, C. Hernandez-Garcia, Geoffrey A. Krafft, Gabriel Palacios-Serrano, M.A. Mamun, M. Poelker, R. Suleiman
Physics Faculty Publications
Production of high bunch charge beams for the ElectronIon Collider (EIC) is a challenging task. High bunch charge (a few nC) electron beam studies at Jefferson Lab using an inverted insulator DC high voltage photo-gun showed evidence of space charge limitations starting at 0.3 nC, limiting the maximum delivered bunch charge to 0.7 nC for beam at -225 kV, 75 ps (FWHM) pulse width, and 1.64 mm (rms) laser spot size. The low extracted charge is due to the modest longitudinal electric field (Ez) at the photocathode leading to beam loss at the anode and downstream beam pipe. To reach …
Compact Srf Linac For High Brilliance Inverse Compton Scattering Light Source, Kirsten E. Deitrick, Jean R. Delayen, Geoffrey A. Krafft, Balša Terzić
Compact Srf Linac For High Brilliance Inverse Compton Scattering Light Source, Kirsten E. Deitrick, Jean R. Delayen, Geoffrey A. Krafft, Balša Terzić
Physics Faculty Publications
New designs for compact SRF linacs can produce micron-size electron beams. These can can be used for inverse Compton scattering light sources of exceptional flux and brilliance.
High Current High Charge Magnetized And Bunched Electron Beam From A Dc Photogun For Jleic Cooler, S. Zhang, P. A. Adderley, J. F. Benesch, D. B. Bullard, Jean R. Delayen, J. M. Grames, J. Guo, F. E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey A. Krafft, M. A. Mamun, M. Poelker, R. Suleiman, M.G. Tiefenback, Y.W. Wang, S.A.K. Wijethunga
High Current High Charge Magnetized And Bunched Electron Beam From A Dc Photogun For Jleic Cooler, S. Zhang, P. A. Adderley, J. F. Benesch, D. B. Bullard, Jean R. Delayen, J. M. Grames, J. Guo, F. E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey A. Krafft, M. A. Mamun, M. Poelker, R. Suleiman, M.G. Tiefenback, Y.W. Wang, S.A.K. Wijethunga
Physics Faculty Publications
A high current, high charge magnetized electron beamline that has been under development for fast and efficient cooling of ion beams for the proposed Jefferson Lab Electron Ion Collider (JLEIC). In this paper, we present the latest progress over the past year that include the generation of picosecond magnetized beam bunches at average currents up to 28 mA with exceptionally long photocathode lifetime, and the demonstrations of magnetized beam with high bunch charge up to 700 pC at 10s of kHz repetition rates. Detailed studies on a stable drive laser system, long lifetime photocathode, beam magnetization effect, beam diagnostics, and …
Simulation Study Of The Emittance Measurements In Magnetized Electron Beam, S.A.K. Wijethunga, J. Benesch, Jean R. Delayen, F. E. Hannon, Geoffrey A. Krafft, M. A. Mamun, G. Palacios-Serrano, M. Poelker, R. Suleiman, S. Zhang
Simulation Study Of The Emittance Measurements In Magnetized Electron Beam, S.A.K. Wijethunga, J. Benesch, Jean R. Delayen, F. E. Hannon, Geoffrey A. Krafft, M. A. Mamun, G. Palacios-Serrano, M. Poelker, R. Suleiman, S. Zhang
Physics Faculty Publications
Electron cooling of the ion beam is key to obtaining the required high luminosity of proposed electron-ion colliders. For the Jefferson Lab Electron Ion Collider, the expected luminosity of 10³⁴ 〖 cm〗⁻² s⁻¹ will be achieved through so-called ’magnetized electron cooling’, where the cooling process occurs inside a solenoid field, which will be part of the collider ring and facilitated using a circulator ring and Energy Recovery Linac (ERL). As an initial step, we generated magnetized electron beam using a new compact DC high voltage photogun biased at -300 kV employing an alkali-antimonide photocathode. This contribution presents the characterization of …
Magnetized Electron Source For Jleic Cooler, R. Suleiman, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.R. Delayen, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M.A. Mamun, M. Poelker, M.G. Tiefenback, Y.W. Wang, S.A.K. Wijethunga, J. T. Yoskowitz, S. Zhang
Magnetized Electron Source For Jleic Cooler, R. Suleiman, P.A. Adderley, J.F. Benesch, D.B. Bullard, J.R. Delayen, J.M. Grames, J. Guo, F.E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, G.A. Krafft, M.A. Mamun, M. Poelker, M.G. Tiefenback, Y.W. Wang, S.A.K. Wijethunga, J. T. Yoskowitz, S. Zhang
Physics Faculty Publications
Magnetized bunched-beam electron cooling is a critical part of the Jefferson Lab Electron Ion Collider (JLEIC). Strong cooling of ion beams will be accomplished inside a cooling solenoid where the ions co-propagate with an electron beam generated from a source immersed in magnetic field. This contribution describes the production and characterization of magnetized electron beam using a compact 300 kV DC high voltage photogun and bialkali-antimonide photocathodes. Beam magnetization was studied using a diagnostic beamline that includes viewer screens for measuring the shearing angle of the electron beamlet passing through a narrow upstream slit. Correlated beam emittance with magnetic field …
Space Charge Study Of The Jefferson Lab Magnetized Electron Beam, Sajini A.K. Wijethunga, J. F. Benesch, Jean R. Delayen, F. E. Hannon, C. Hernandez-Garcia, Geoffrey A. Krafft, M. A. Mamun, M. Poelker, R. Suleiman, S. Zhang
Space Charge Study Of The Jefferson Lab Magnetized Electron Beam, Sajini A.K. Wijethunga, J. F. Benesch, Jean R. Delayen, F. E. Hannon, C. Hernandez-Garcia, Geoffrey A. Krafft, M. A. Mamun, M. Poelker, R. Suleiman, S. Zhang
Physics Faculty Publications
Magnetized electron cooling could result in high luminosity at the proposed Jefferson Lab Electron-Ion Collider (JLEIC). In order to increase the cooling efficiency, a bunched electron beam with high bunch charge and high repetition rate is required. We generated magnetized electron beams with high bunch charge using a new compact DC high voltage photo-gun biased at -300 kV with alkali-antimonide photocathode and a commercial ultrafast laser. This contribution explores how magnetization affects space charge dominated beams as a function of magnetic field strength, gun high voltage, laser pulse width, and laser spot size.
Simulation Study Of The Magnetized Electron Beam, S.A.K. Wijethunga, J.F. Benesch, Jean R. Delayen, F. E. Hannon, Geoffrey A. Krafft, M. A. Poelker, R. Suleiman
Simulation Study Of The Magnetized Electron Beam, S.A.K. Wijethunga, J.F. Benesch, Jean R. Delayen, F. E. Hannon, Geoffrey A. Krafft, M. A. Poelker, R. Suleiman
Physics Faculty Publications
Electron cooling of the ion beam plays an important role in electron ion colliders to obtain the required high luminosity. This cooling efficiency can be enhanced by using a magnetized electron beam, where the cooling process occurs inside a solenoid field. This paper compares the predictions of ASTRA and GPT simulations to measurements made using a DC high voltage photogun producing magnetized electron beam, related to beam size and rotation angles as a function of the photogun magnetizing solenoid and other parameters.
Production Of Magnetized Electron Beam From A Dc High Voltage Photogun, M.A. Mamun, P.A. Adderly, J. Benesch, B. Bullard, J. Delayen, J. Grames, J. Guo, F. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey Krafft, M. Poelker, R. Suleiman, M. Tiefenback, Y. Wang, Sajini Wijethunga, S. Zhang
Production Of Magnetized Electron Beam From A Dc High Voltage Photogun, M.A. Mamun, P.A. Adderly, J. Benesch, B. Bullard, J. Delayen, J. Grames, J. Guo, F. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey Krafft, M. Poelker, R. Suleiman, M. Tiefenback, Y. Wang, Sajini Wijethunga, S. Zhang
Physics Faculty Publications
Bunched-beam electron cooling is a key feature of all proposed designs of the future electron-ion collider, and a requirement for achieving the highest promised collision luminosity. At the Jefferson Lab Electron Ion Collider (JLEIC), fast cooling of ion beams will be accomplished via so-called 'magnetized cooling' implemented using a recirculator ring that employs an energy recovery linac. In this contribution, we describe the production of magnetized electron beam using a compact 300 kV DC high voltage photogun with an inverted insulator geometry, and using alkali-antimonide photocathodes. Beam magnetization was assessed using a modest diagnostic beamline that includes YAG view screens …
300 Kv Dc High Voltage Photogun With Inverted Insulator Geometry And Csk₂Sb Photocathode, Y.W. Wang, P.A. Adderley, J. F. Benesch, D.B. Bullard, J.M. Grames, F. E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey A. Krafft, M. A. Mamun, G. G. Palacios Serrano, M. Poelker, R. Suleiman, M. G. Tiefenback, S.A.K. Wijethunga
300 Kv Dc High Voltage Photogun With Inverted Insulator Geometry And Csk₂Sb Photocathode, Y.W. Wang, P.A. Adderley, J. F. Benesch, D.B. Bullard, J.M. Grames, F. E. Hannon, J. Hansknecht, C. Hernandez-Garcia, R. Kazimi, Geoffrey A. Krafft, M. A. Mamun, G. G. Palacios Serrano, M. Poelker, R. Suleiman, M. G. Tiefenback, S.A.K. Wijethunga
Physics Faculty Publications
A compact DC high voltage photogun with inverted-insulator geometry was designed, built and operated reliably at 300 kV bias voltage using alkali-antimonide photocathodes. This presentation describes key electrostatic design features of the photogun with accompanying emittance measurements obtained across the entire photocathode surface that speak to field non-uniformity within the cathode/anode gap. A summary of initial photocathode lifetime measurements at beam currents up to 4.5 mA is also presented.
Effects Of Plasma Processing On Secondary Electron Yield Of Niobium Samples, M. Basovic, S. Popovic, M. Tomovic, L. Vuskovic, A. Samolov, F. Cuckov
Effects Of Plasma Processing On Secondary Electron Yield Of Niobium Samples, M. Basovic, S. Popovic, M. Tomovic, L. Vuskovic, A. Samolov, F. Cuckov
Physics Faculty Publications
Impurities deposited on the surface of Nb during both the forming and welding of accelerator cavities add to the imperfections of the sheet metal, which then affects the overall performance of the cavities. This leads to a drop in the Q factor and limits the maximum acceleration gradient achievable per unit length of the cavities. The performance can be improved either by adjusting the fabrication and preparation parameters, or by mitigating the effects of fabrication and preparation techniques used. We have developed the experimental setup to determine Secondary Electron Yield (SEY) from the surface of Nb samples. Our aim is …