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| MOPOMS023 | Start-to-End Beam-Dynamics Simulations of a Compact C-Band Electron Beam Source for High Spectral Brilliance Applications | 687 |
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Funding: This work is partially supported by DARPA under the Contract No. HR001120C0072, by DOE Contract DE-SC0009914, DOE Contract DE-SC0020409, and by the National Science Foundation Grant No. PHY-1549132. Proposals for new linear accelerator-based facilities are flourishing world-wide with the aim of high spectral brilliance radiation sources. Most of these accelerators are based on electron beams, with a variety of applications in industry, research and medicine such as colliders, free-electron lasers, wake-field accelerators, coherent THz and inverse Compton scattering X/’ sources as well as high-resolution diagnostics tools in biomedical science. In order to obtain high-quality electron beams in a small footprint, we present the optimization design of a C-band linear accelerator machine. Driven by a novel compact C-band hybrid photoinjector, it will yield ultra-short electron bunches of few 100’s pC directly from injection with ultra-low emittance, fraction of mm-mrad, and a few hundred fs length simultaneously, therefore satisfying full 6D emittance compensation. The normal-conducting linacs are based on a novel high-efficiency design with gradients up to 50 MV/m. The beam maximum energy can be easily adjusted in the mid-GeV’s range. In this paper, we discuss the start-to-end beam-dynamics simulations in details. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS023 | |
| About • | Received ※ 07 June 2022 — Revised ※ 09 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 03 July 2022 | |
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| MOPOMS052 | 6 MeV Novel Hybrid (Standing Wave - Traveling Wave) Photo-Cathode Electron Gun for a THz Superradiant FEL | 760 |
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| A novel 6 MeV hybrid photo injector was designed and commissioned at Ariel University in Israel as an on-going collaboration with UCLA. This unique, new generation design provides a radically simpler approach to RF feeding of a gun/buncher system, leading to a much shorter beam via velocity bunching owed to an attached traveling wave section of the photo-injector. This design results in better performance in beam parameters, providing a high quality electron beam, with energy of 6 MeV, emittance of less than 3 ’m, and a 150 fs pulse duration at up to 1 nC per pulse. The Hybrid gun is driven by a SLAC XK5 Klystron as the high power RF source, and third harmonic of a fs level IR Laser amplifier (266 nm) to extract electrons from the Cathode. The unique e-gun will produce a bunched electron pulse to drive a THz FEL, which will operate at the super-radiance regime, and therefore requires extraordinary beam properties. It will also be used for MeV UED experiments in a separate line using a dogleg section. Here we describe the gun and presents experimental results from the gun and its sub-systems, including energy and charge measurements, compared with the design simulations. | ||
| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-MOPOMS052 | |
| About • | Received ※ 11 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 18 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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| WEPOMS017 | Space Charge Analysis for Low Energy Photoinjector | 2272 |
| SUSPMF075 | use link to see paper's listing under its alternate paper code | |
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Funding: This work is supported by DARPA under Contract HR001120C0072, by DOE Contract DE-SC0009914 & DE-SC0020409, by the National Science Foundation Grant N.PHY-1549132 and by INFN through the project ARYA. Beam dynamics studies are performed in the context of a C-Band hybrid photo-injector project developed by a collab- oration between UCLA/Sapienza/INFN-LNF/RadiaBeam. These studies aim to explain beam behaviour through the beam-slice evolution, using analytical and numerical approaches. An understanding of the emittance oscillations is obtained starting from the slice analysis, which allows correlation of the position of the emittance minima with the slope of the slices in the transverse phase space (TPS). At the end, a significant reduction in the normalized emittance is obtained by varying the transverse shape of the beam while assuming a longitudinal Gaussian distribution. Indeed, the emittance growth due to nonlinear space-charge fields has been found to occur immediately after moment of the beam emission from the cathode, giving insight into the optimum laser profile needed for minimizing the emittance. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS017 | |
| About • | Received ※ 16 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 01 July 2022 | |
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| WEPOMS045 | Modeling and Mitigation of Long-Range Wakefields for Advanced Linear Colliders | 2350 |
| SUSPMF071 | use link to see paper's listing under its alternate paper code | |
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Funding: This work is supported by DARPA under Contract N.HR001120C0072, by DOE Contract DE-SC0009914 and DE-SC0020409, by the National Science Foundation Grant N.PHY-1549132 and by INFN. The luminosity requirements of TeV-class linear colliders demand use of intense charged beams at high repetition rates. Such features imply multi-bunch operation with long current trains accelerated over the km length scale. Consequently, particle beams are exposed to the mutual parasitic interaction due to the long-range wakefields excited by the leading bunches in the accelerating structures. Such perturbations to the motion induce transverse oscillations of the bunches, potentially leading to instabilities such as transverse beam break-up. Here we present a dedicated tracking code that studies the effects of long-range transverse wakefield interaction among different bunches in linear accelerators. Being described by means of an efficient matrix formalism, such effects can be included while preserving short computational times. As a reference case, we use our code to investigate the performance of a state-of-the-art linear collider currently under design and, in addition, we discuss possible mitigation techniques based on frequency detuning and damping. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-WEPOMS045 | |
| About • | Received ※ 20 May 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 10 July 2022 | |
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| THPOST045 | Temperature Dependent Effects on RF Surface Resistivity | 2540 |
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Funding: This work was supported by DOE Contract DE-SC0020409 A promising future for linear accelerators such as compact free electron lasers and electron positron colliders is higher gradient RF cavities enabled by cryogenic temperature operation. Breakdown rates have been shown empirically to be significantly reduced at low temperatures allowing for higher gradient. The surface physics associated with this observation is complicated and there many remain questions as to the exact phenomena responsible. One major figure of merit that can better inform the theory of breakdown is the RF surface resistivity which can be used to compute for example the RF pulse heating during operation. We then use techniques developed for previous Xband and Sband low power surface resistivity measurement by way of temperature dependent quality factor measurements to study Cband cavities. We first present a review of low temperature effects that may be responsible for the change in surface resistivity at low temperature. We then explain some of the initial measurements of these low power RF quality factor tests and compare them to a review some of the physical phenomena that could determine the low temperature surface effects. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST045 | |
| About • | Received ※ 08 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 20 June 2022 | |
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| THPOST046 | CrYogenic Brightness-Optimized Radiofrequency Gun (CYBORG) | 2544 |
| SUSPMF021 | use link to see paper's listing under its alternate paper code | |
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Funding: This work was supported by the Center for Bright Beams, National Science Foundation Grant No. PHY-1549132 and DOE Contract DE-SC0020409 Producing higher brightness beams at the cathode is one of the main focuses for future electron beam applications. For photocathodes operating close to their emission threshold, the cathode lattice temperature begins to dominate the minimum achievable intrinsic emittance. At UCLA, we are designing a radiofrequency (RF) test bed for measuring the temperature dependence of the mean transverse energy (MTE) and quantum efficiency for a number of candidate cathode materials. We intend to quantify the attainable brightness improvements at the cathode from cryogenic operation and establish a proof-of-principle cryogenic RF gun for future studies of a 1.6-cell cryogenic photoinjector for the UCLA ultra compact XFEL concept (UC-XFEL). The test bed will use a C-band 0.5-cell RF gun designed to operate down to 45 K, producing an on-axis accelerating field of 120 MV/m. The cryogenic system uses conduction cooling and a load-lock system is being designed for transport and storage of air-sensitive high brightness cathodes. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOST046 | |
| About • | Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 01 July 2022 | |
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| THPOTK027 | Temperature Dependent Effects on Quality Factor in C-band RF Cavities | 2826 |
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Funding: This work was supported by DOE Contract DE-SC0020409 Cryogenic operation and associated skin effects are encouraging fields of study for increasing RF gradients of beams within cavities and decreasing the required size for linear accelerators such as free electron lasers. Notably, a cavity’s RF quality factor Q, the ratio of the outgoing RF signal power to the input power, is theoretically multiplied by over 4 when subjected to cryogenic temperatures. Precise measurements of this Q factor require defining a cryostat unit, which consists of a high vacuum chamber, a coldhead, and MLI shielding. We optimized the cryostat by running several cool down tests at high vacuum, incorporating different geometries of MLI shielding to achieve the lowest possible temperatures. We then performed a low power C-band test after installing a cylindrical copper RF cavity to measure the Q factor. Finally, we improved stability and amplification within the chamber by installing edge welded bellows to the coldhead to reduce vibrations. These measurements provide a basis for the development of cryogenic infrastructure to sustain a cryogenic temperature environment for future RF applications. |
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| DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOTK027 | |
| About • | Received ※ 08 June 2022 — Revised ※ 13 June 2022 — Accepted ※ 14 June 2022 — Issue date ※ 27 June 2022 | |
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