| Paper | Title | Page |
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| MOPOPT066 | Gas Sheet Diagnostics Using Particle in Cell Code | 410 |
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Funding: This work was supported by the STFC Liverpool Centre for Doctoral Training on Data Intensive Science (LIV. DAT) under grant agreement ST/P006752/1 and DE-SC0019717. When intense particle beam propagates in dense plasma or gas, ionization can yield valuable information on the drive beam properties. Impact ionization and tunnel ionization are the two ionization regimes that must be accounted for varying beam properties. Due to these ionization mechanisms, new plasma electrons are generated causing different instabilities, dependent on the dominant ionization process considered. In order to accomplish the ambitious experimental goals of sophisticated beam diagnostics using ionization imaging, careful studies on the different ionization regimes, and the cross-over periods, required. Here we will discuss the impact ionization using fully parallel PIC code OSIRIS. We focus on understanding the gas sheet ionization diagnostics for characterizing high intensity charged particle beams. We study the interaction of neutral gas with an electron beam and varying density. We will also investigate the principle of detecting photon emission, rather than direct primary ion imaging, from the ionization induced in the interaction between the gas jet and charged particle beams. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT066 | |
| About • | Received ※ 07 June 2022 — Revised ※ 19 June 2022 — Accepted ※ 21 June 2022 — Issue date ※ 26 June 2022 | |
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| MOPOPT067 | Electron Beam Phase Space Reconstruction From a Gas Sheet Diagnostic | 414 |
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Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of High Energy Physics under Award Number DE-SC0019717. Next generation particle accelerators craft increasingly high brightness beams to achieve physics goals for applications ranging from colliders to free electron lasers to studies of nonperturbative QED. Such rigorous requirements on total charge and shape introduce diagnostic challenges for effectively measuring bunch parameters prior to or at interaction points. We report on the simulation and training of a non-destructive beam diagnostic capable of characterizing high intensity charged particle beams. The diagnostic consists of a tailored neutral gas curtain, electrostatic microscope, and high sensitivity camera. An incident electron beam ionizes the gas curtain, while the electrostatic microscope transports generated ions to an imaging screen. Simulations of the ionization and transport process are performed using the Warp code. Then, a neural network is trained to provide accurate estimates of the initial electron beam parameters. We present initial results for a range of beam and gas curtain parameters and comment on extensibility to other beam intensity regimes. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT067 | |
| About • | Received ※ 08 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 10 July 2022 | |
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| WEPOST046 | Beam Matching in an Elliptical Plasma Blowout Driven by Highly Asymmetric Flat Beams | 1802 |
| SUSPMF037 | use link to see paper's listing under its alternate paper code | |
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Funding: This work was performed with the support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914. Particle beams with highly asymmetric emittance ratios, or flat beams, are employed at accelerator facilities such as the AWA and foreseen at FACET-II. Flat beams have been used to drive wakefields in dielectric structures and are an ideal candidate for high-gradient wakefields in plasmas. The high aspect ratio produces a blowout region that is elliptical in cross section and this asymmetry in the ion column structure creates asymmetric focusing in the two transverse planes. The ellipticity of the plasma blowout decreases as the normalized peak current increases, and gradually approaches an axisymmetric column. An appropriate matching condition for the beam envelope inside the elliptical blowout is introduced. Simulations are performed to investigate the ellipticity of the resultant wakefield based on the initial drive beam parameters, and are compared to analytical calculations. The parameter space for two cases at the AWA and FACET facilities, with requirements for plasma profile and achievable fields, is presented. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST046 | |
| About • | Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 29 June 2022 | |
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| WEPOST048 | Excitation of Very High Gradient Plasma Wakefields From Nanometer Scale Beams | 1806 |
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Funding: This work was performed with the support of the US Department of Energy under Contract No. DESC0009914. The plasma based terawatt attosecond project at SLAC, termed PAX, offers near mega-Ampere beams that could be used to demonstrate plasma wakefield acceleration at very high gradients (TV/m). The beam has a large aspect ratio which allows it to be used at high densities since the longitudinal beam size is lower than the plasma skin depth. This beam can be focused using a permanent magnitude quadrupole (PMQ) triplet to further reduce its transverse size. Since the beam is extremely short compared to the plasma skin depth, it behaves like a delta-function perturbation to the plasma. This reduces the expected focusing effect of the ion column and simulations show that only the tail of the beam is notably focused and decelerated. This scenario is investigated with attendant experimental considerations discussed. The creation of the witness beam by the deceleration of the tail of the beam is also discussed. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST048 | |
| About • | Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 29 June 2022 | |
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| MOPOPT063 | Reconstruction of Beam Parameters from Betatron Radiation Using Maximum Likelihood Estimation and Machine Learning | 407 |
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Funding: US Department of Energy, Division of High Energy Physics, Contract No. DE-SC0009914 STFC Liver-pool Centre for Doctoral Training on Data Intensive Science, grant agreement ST/P006752/1 Betatron radiation that arises during plasma wakefield acceleration can be measured by a UCLA-built Compton spectrometer, which records the energy and angular position of incoming photons. Because information about the properties of the beam is encoded in the betatron radiation, measurements of the radiation can be used to reconstruct beam parameters. One method of extracting information about beam parameters from measurements of radiation is maximum likelihood estimation (MLE), a statistical technique which is used to determine unknown parameters from a distribution of observed data. In addition, machine learning methods, which are increasingly being implemented for different fields of beam diagnostics, can also be applied. We assess the ability of both MLE and other machine learning methods to accurately extract beam parameters from measurements. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOPT063 | |
| About • | Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 26 June 2022 | |
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| TUPOPT035 | Introduction of Westwood Linear Accelerator Test Facility in University of California Los Angeles | 1085 |
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Funding: U.S. DOE: DE-SC0009914 U.S. DOD: DARPA GRIT Contract 20204571 U.S. DOE: DE-SC0020409 - Cryo RF An electron linear accelerator test facility located on UCLA’s southwest campus in Westwood, SAMURAI, is presently being constructed. A RF-based accelerator consists of a compact, 3 MeV S-band hybrid gun capable of velocity bunching to bunch lengths in the 100s fs range with 100s pC of charge. This beam is accelerated by an 1.5 m S-band linac with a peak output energy of 30 MeV which can be directed to either a secondary beamline or remain on the main beamline for final acceleration by a SLAC 3 m S-band linac to an energy of 80 MeV. Further acceleration by advanced boosters such as a cryo-cooled C-band structure or numerous optical or wakefield methods is under active investigation. In combination with a 3 TW Ti:Sapphire laser, initial proof of principle experiments will be conducted on topics including the ultra-compact x-ray free-electron laser, advanced dielectric wakefield acceleration, bi-harmonic nonlinear inverse Compton scattering, and various radiation detectors. Furthermore, development of a tertiary beamline based on an ultra low emittance, cryo-cooled gun will eventually enable two-beam experiments, expanding the facility’s unique experimental capabilities. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT035 | |
| About • | Received ※ 08 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 24 June 2022 | |
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| WEPOST042 | Radiation Diagnostics for AWA and FACET-II Flat Beams in Plasma | 1791 |
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Funding: This work was performed with support of the US Department of Energy, Division of High Energy Physics, under Contract No. DE-SC0009914, DE-SC0017648 - AWA and STFC grant ST/P006752/1 , In energy beam facilities like FACET and AWA, beams with highly asymmetric emittance are of interest because they are the preferred type of beam for linear colliders. That is ultimately the motivation: building a plasma based LC. In this case, the blowout region is no longer symmetric around an axis is not equal in the two transverse planes. Focusing is required to keep the particles within the tight apertures and characterizing these accelerators shows the benefits of employing ultra low beam emittances. Beams with high charge and high emittance ratios in excess of 100:1 are available at AWA. If the focusing will not be equal, then we will have different radiation signatures for the flat and symmetric beams in plasma. We use OSIRIS particle-in-cell codes to compare various scenarios including a weak blowout and a strong blowout. Further, we determine the radiation generated in the system by importing particle trajectories into a Liénard Weichert code. We discuss future steps towards full diagnostics of flat beams using radiation. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOST042 | |
| About • | Received ※ 07 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 20 June 2022 — Issue date ※ 05 July 2022 | |
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