NAPAC2022 - Classification: 03: Advanced Acceleration

Paper	Title	Page
MOZE1	Demonstration of High-Gradient in a Cryo-Cooled X-Band Structure
	M.H. Nasr SLAC, Menlo Park, California, USA
	We present an experimental demonstration of the high-gradient operation of an X-band, 11.424 GHz, 20-cells linear accelerator (linac) operating at a liquid nitrogen temperature of 77 K. The tested linac was previously processed and tested at room temperature. Low-temperature operation increases the yield strength of the accelerator material and reduces surface resistance, hence a great reduction in cyclic fatigue could be achieved resulting in a large reduction in breakdown rates compared to room- temperature operation. Furthermore, temperature reduction increases the intrinsic quality factor of the accelerating cavities, and consequently, the shunt impedance leading to increased RF-to-beam efficiency and beam loading capabilities. We verified the enhanced accelerating parameters of the tested accelerator at cryogenic temperature using different measurements including electron beam acceleration up to a gradient of 150 MV/m, corresponding to a peak surface electric field of 375 MV/m. We also measured the breakdown rates in the tested structure showing a reduction of 2 orders of magnitude compared to their values at room temperature for the same accelerating gradient.
	Slides MOZE1 [6.217 MB]
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MOZE2	Results of Awake Run 1 and Plans for Run 2 Towards HEP Applications
	M. Bergamaschi CERN, Meyrin, Switzerland
	The high accelerating gradient that plasma wakefield can produce make it a an interesting technology for next generation of particle accelerators. The AWAKE experi-ment at CERN demonstrated during Run1 that thanks to the process of self-modulation an high energy (400 GeV) long (10 cm) proton bunch drive intense wakefield in plasma. Externally injected electrons were successfully accelerated to 2 GeV in a 10m plasma. The main aims of the AWAKE Run 2 phase are to demonstrate that a con-trolled self-modulation process can lead to stable acceler-ating gradient up to 1 GV/m preserving the emittance of injected electron bunches and to be scalable to plasma sources of 100s of meters and beyond for high energy. The AWAKE scheme aim to provide electron beams for particle physics experiments by the end of the Run2 phase. This contribution reports the main achievement of Run1 and summarises the programme of AWAKE Run 2 including possible applications of the AWAKE scheme to novel particle physics experiments.
	Slides MOZE2 [7.505 MB]
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MOZE3	Emittance Measurements and Simulations from an X-Band Short-Pulse Ultra-High Gradient Photoinjector	45
	G. Chen, D.S. Doran, C.-J. Jing, S.Y. Kim, W. Liu, W. Liu, P. Piot, J.G. Power, C. Whiteford, E.E. Wisniewski ANL, Lemont, Illinois, USA C.-J. Jing, E.W. Knight, S.V. Kuzikov Euclid TechLabs, Solon, Ohio, USA C.-J. Jing Euclid Beamlabs, Bolingbrook, USA X. Lu, P. Piot, W.H. Tan Northern Illinois University, DeKalb, Illinois, USA
	Funding: This work is supported by the U.S. DOE, under award No. DE-SC0018656 to NIU, DOE SBIR grant No. DE-SC0018709 to Euclid Techlabs LLC, and contract No. DE-AC02-06CH11357 with ANL. A program is under way at the Argonne Wakefield Accelerator facility, in collaboration with the Euclid Techlabs and Northern Illinois University (NIU), to develop a GeV/m scale photocathode gun, with the ultimate goal of demonstrating a high-brightness photoinjector beamline. The novel X-band photoemission gun (Xgun) is powered by high-power, short RF pulses, 9-ns (FWHM), which, in turn, are generated by the AWA drive beam. In a previous proof-of-principle experiment, an unprecedented 400~MV/m gradient on the photocathode surface* was demonstrated. In the current version of the experiment, we added a linac to the beamline to increase the total energy and gain experience tuning the beamline. In this paper, we report on the very first result of emittance measurement as well as several other beam parameters. This preliminary investigation has identified several factors to be improved on in order to achieve one of the ultimate goals; low emittance. * W. H. Tan et al., "Demonstration of sub-GV/m Accelerating Field in a Photoemission Electron Gun Powered by Nanosecond X-Band Radiofrequency Pulses", 2022. arXiv:2203.11598v1
	Slides MOZE3 [5.565 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE3
About •	Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 14 August 2022
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MOZE4	Ceramic Enhanced Accelerator Structure Low Power Test and Designs of High Power and Beam Tests	49
	H. Xu, M.R. Bradley, L.D. Duffy, M.A. Holloway, J. Upadhyay LANL, Los Alamos, New Mexico, USA
	Funding: Research was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory, under project number 20210083ER. A ceramic enhanced accelerator structure (CEAS) uses a concentric ceramic ring placed inside a metallic pillbox cavity to significantly increase the shunt impedance of the cavity. Single cell standing wave CEAS cavities are designed, built, and tested at low power at 5.1 GHz. The results indicate 40% increase in shunt impedance compared to that of a purely metallic pillbox cavity. A beam test setup has been designed to use a single cell CEAS cavity to modulate a 30-keV direct-current (DC) electron beam at an accelerating gradient of 1 to 2 MV/m to verify the beam acceleration capability of the CEAS concept and to study the potential charging effect on the ceramic component during the operation. Another single cell standing wave CEAS cavity has been designed for high power test at 5.7 GHz for the high accelerating gradient capability.
	Slides MOZE4 [1.652 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE4
About •	Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 07 October 2022
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MOZE5	Simulation and Experimental Results of Dielectric Disk Accelerating Structures	52
	S. Weatherly, E.E. Wisniewski Illinois Institute of Technology, Chicago, Illinois, USA D.S. Doran, C.-J. Jing, J.F. Power, E.E. Wisniewski ANL, Lemont, Illinois, USA B.T. Freemire, C.-J. Jing Euclid Beamlabs, Bolingbrook, USA
	Funding: Contract DE-SC0019864 to Euclid Beamlabs LLC. AWA work from U.S. DOE Office of Science under Contract DE-AC02-06CH11357. Chicagoland Accelerator Science Traineeship U.S. DOE award number DE-SC-0020379 A method of decreasing the required footprint of linear accelerators and improving their energy efficiency is to employ Dielectric Disk Accelerators (DDAs) with short RF pulses ( ∼ 9 ns). A DDA is an accelerating structure that utilizes dielectric disks to improve the shunt impedance. Two DDA structures have been designed and tested at the Argonne Wakefield Accelerator. A single cell clamped DDA structure recently achieved an accelerating gradient of 1{02} MV/m. A multi-cell clamped DDA structure has been designed and is being fabricated. Simulation results for this new structure show a 1{08} MV/m accelerating gradient with 400 MW of input power with a high shunt impedance and group velocity. The engineering design has been improved from the single cell structure to ensure consistent clamping over the entire structure.
	Slides MOZE5 [9.338 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE5
About •	Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 21 August 2022 — Issue date ※ 06 October 2022
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MOZE6	Fulfilling the Mission of Brookhaven ATF as a DOE Flagship User Facility in Accelerator Stewardship
	I. Pogorelsky, M. Babzien, M.G. Fedurin, R. Kupfer, M.A. Palmer, M.N. Polyanskiy BNL, Upton, New York, USA N. Vafaei-Najafabadi Stony Brook University, Stony Brook, USA
	Funding: This work is funded by the U.S. Department of Energy under contract DE-SC0012704 Over last three decades, BNL Accelerator Test Facility (ATF) pioneered the concept of a proposal-based user facility for lasers and electron beam-driven advanced accelerator research (AAR). This has made ATF an internationally recognized destination for researchers who benefit from access to unique scientific capabilities not otherwise available to individual institutions and businesses. Operating as an Office of Science National User Facility and a flagship DOE facility in Accelerator R&D Stewardship, ATF pursues an ambitious upgrade plan for its lasers and electron beam infrastructure to enable experiments at the forefront of the AAR. In this talk, we will present our path towards attaining a novel multi-terawatt sub-picosecond regime with a long-wave IR 9-um laser. Future enhancements to the electron beam and near-IR laser capabilities will also be presented. The combination of linac- and laser-driven e-beams will empower a unique state-of-the-art science program. This includes integrated multi-beam research in laser wakefield accelerators, such as the two-color ionization injection, with the promise of an all-optical scheme for generating collider-quality electrons beams.
	Slides MOZE6 [6.929 MB]
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MOPA74	Design of a W-Band Corrugated Waveguide for Structure Wakefield Acceleration	210
	B. Leung, X. Lu, C.L. Phillips, P. Piot Northern Illinois University, DeKalb, Illinois, USA D.S. Doran, X. Lu, P. Piot, J.G. Power ANL, Lemont, Illinois, USA
	Current research on structure wakefield acceleration aims to develop radio-frequency structures that can produce high gradients, with work in the sub-terahertz regime being particularly interesting because of the potential to create more compact and economical accelerators. Metallic corrugated waveguides at sub-terahertz frequencies are one such structure. We have designed a W-band corrugated waveguide for a collinear wakefield acceleration experiment at the Argonne Wakefield Accelerator (AWA). Using the CST Studio Suite, we have optimized the structure for the maximum achievable gradient in the wakefield from a nominal AWA electron bunch at 65 MeV. Simulation results from different solvers of CST were benchmarked with each other, with analytical models, and with another simulation code, ECHO. We are investigating the mechanical design, suitable fabrication technologies, and the possibility to apply advanced bunch shaping techniques to improve the structure performance.
	Poster MOPA74 [1.518 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA74
About •	Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 26 August 2022
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MOPA76	Wakefield Modeling in Sub-THz Dielectric-Lined Waveguides	218
	C.L. Phillips, B. Leung, X. Lu, P. Piot Northern Illinois University, DeKalb, Illinois, USA
	Dielectric-lined waveguides have been extensively studied to potentially support high-gradient acceleration in beam-driven dielectric wakefield acceleration (DWFA) and for beam manipulations. In this paper, we investigate the wakefield generated by a relativistic bunch passing through a dielectric waveguide with different transverse sections. We specifically consider the case of a structure consisting of two dielectric slabs, along with rectangular and square structures. Numerical simulations performed with the fine-difference time-domain of the WarpX program reveal some interesting features of the transverse wake and a possible experiment at the Argonne Wakefield Accelerator (AWA) is proposed.
	Poster MOPA76 [1.294 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA76
About •	Received ※ 12 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 12 September 2022
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TUPA75	High Gradient Testing Results of the Benchmark a/λ=0.105 Cavity at CERF-NM	505
	M.R.A. Zuboraj, D.V. Gorelov, T.W. Hall, M.E. Middendorf, D. Rai, E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA
	Funding: This work was supported by Los Alamos National Laboratory’s Laboratory Directed Research and Development (LDRD) Program. This presentation will report initial results of high gradient testing of two C-band accelerating cavities fabricated at Los Alamos National Laboratory (LANL). At LANL, we commissioned a C-band Engineering Research Facility of New Mexico (CERF-NM) which has unique capability of conditioning and testing accelerating cavities for operation at surface electric fields at the excess of 300 MV/m, powered by a 50 MW, 5.712 GHz Canon klystron. Recently, we fabricated and tested two benchmark copper cavities at CERF-NM. These cavities establish a benchmark for high gradient performance at C-band and the same geometry will be used to provide direct comparison between high gradient performance of cavities fabricated of different alloys and by different fabrication methods. The cavities consist of three cells with one high gradient central cell and two coupling cells on the sides. The ratio of the radius of the coupling iris to the wavelength is a/λ=0.105. This poster will report high gradient test results such as breakdown rates as function of peak surface electric and magnetic fields and pulse heating.
	Poster TUPA75 [0.890 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA75
About •	Received ※ 05 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 01 October 2022
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TUPA81	Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure	516
	G.E. Lawler, A. Fukasawa, J.R. Parsons, J.B. Rosenzweig UCLA, Los Angeles, California, USA Z. Li, S.G. Tantawi SLAC, Menlo Park, California, USA A. Mostacci Sapienza University of Rome, Rome, Italy E.I. Simakov, T. Tajima LANL, Los Alamos, New Mexico, USA B. Spataro LNF-INFN, Frascati, Italy
	Funding: This work was supported by the DOE Contract DE-SC0020409. High-gradient RF structures capable of maintaining gradients in excess of 250 MV/m are critical in several concepts for future electron accelerators. Concepts such as the ultra-compact free electron laser (UC-XFEL) and the Cool Copper Collider (C3) plan to obtain these gradients through the cryogenic operation (<77K) of normal conducting copper cavities. Breakdown rates, the most significant gradient limitation, are significantly reduced at these low temperatures, but the precise physics is complex and involves many interacting effects. High-power RF breakdown measurements at cryogenic temperatures are needed at the less explored C-band frequency (5.712 GHz), which is of great interest for the aforementioned concepts. On behalf of a large collaboration of UCLA, SLAC, LANL, and INFN, the first C-band cryogenic breakdown measurements will be made using a LANL RF test infrastructure. The 2-cell geometry designed for testing will be modifications of the distributed coupled reentrant design used to efficiently power the cells while staying below the limiting values of peak surface electric and magnetic fields.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA81
About •	Received ※ 29 July 2022 — Accepted ※ 02 August 2022 — Issue date ※ 08 August 2022
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TUPA87	Simulations for the Space Plasma Experiments at the SAMURAI Lab	539
	P. Manwani, H.S. Ancelin, A. Fukasawa, G.E. Lawler, N. Majernik, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams UCLA, Los Angeles, California, USA G. Andonian RadiaBeam, Santa Monica, California, USA
	Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914, and the DARPA GRIT Contract 20204571 Plasma wakefield acceleration using the electron linear accelerator test facility, SAMURAI, can be used to study the Jovian electron spectrum due to the high energy spread of the beam after the plasma interaction. The SAMURAI RF facility which is currently being constructed and commissioned at UCLA, is is capable of producing beams with 10 MeV energy, 2 nC charge, and 200 fsec bunch lengths with a 4 um emittance. Particle-in-cell (PIC) simulations are used to study the beam spectrum that would be generated from plasma interaction. Experimental methods and diagnostics are discussed in this paper.
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA87
About •	Received ※ 04 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 06 September 2022
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WEYD1	Ultrahigh Energy Electrons From Laser Wakefield Accelerators
	B.M. Hegelich The University of Texas at Austin, Austin, Texas, USA
	We report peak electron energies well in excess of 10 GeV from a laser wakefield accelerator. Proof-of-principle experiment have been performed at the Texas Petawatt laser using a 10 cm long gas cell filled with helium gas and seeded by metallic nanoparticles. Greater than 10 GeV electron energies have been observed repeatedly in multiple independent experiments. This results fulfill a major milestones in DOE’s Advanced Accelerator Strategy Report from 2016 and open up the potential of laser wakefield accelerators as high energy machines or as drivers for laser-driven XFELs. Compared with other wakefield acceleration schemes, our scheme is straightforward since it requires only a gas cell and a source of nanoparticles for electron injection. No external guiding or heating mechanisms are employed. The nanoparticle-assisted laser wakefield acceleration can control all the electron beam parameters: charge, energy spread, energy, emittance, and the number of bunches in the beam. Bunch charges are on the order of a few nanocoulomb for the whole beam and in the 100s pC range in the high energy part, an order of magnitude increase over previous results at greater than 5 GeV.
	Slides WEYD1 [16.825 MB]
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WEYD2	First Lasing of a Free-Electron Laser With a Compact Beam-Driven Plasma Accelerator
	S. Romeo, M. Galletti, R. Pompili LNF-INFN, Frascati, Italy
	Plasma-based technology promises a revolution in the field of particle accelerators by pushing beams to GeV energies within centimeter distances and enabling the realization of ultra-compact facilities for user applications like Free-Electron Lasers (FEL). Here we report the first experimental evidence of FEL lasing by a compact (3 cm) particle beam-driven plasma accelerator. FEL radiation is observed in the infrared range with typical exponential growth of its intensity over six consecutive undulators. This achievement is based on the technique we recently developed for energy spread control during acceleration in plasma, generating electron bunches with high-quality, comparable with state-of-the-art accelerators. This proof-of-principle experiment represents an important milestone in the use of plasma-based accelerators contributing to the development of next-generation compact machines for user-oriented applications.
	Slides WEYD2 [3.894 MB]
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WEYD3	Positron Acceleration in Linear, Moderately Non-Linear and Non-Linear Plasma Wakefields	560
	G.J. Cao, E. Adli University of Oslo, Oslo, Norway S. Corde LOA, Palaiseau, France S.J. Gessner SLAC, Menlo Park, California, USA
	Accelerating particles to high energies with high efficiency and beam quality is crucial in developing accelerator technologies. The plasma acceleration technique, providing unprecedented high gradients, is considered as a promising future technology. While important progress has been made in plasma-based electron acceleration in recent years, identifying a reliable acceleration technique for the positron counterpart would pave the way to a linear e⁺e⁻ collider for high-energy physics applications. In this work, we show further studies of positron beam quality in moderately non-linear (MNL)* plasma wakefields. With a positron bunch of initial energy 1 GeV, emittance preservation can be achieved in optimised scenarios at 2.38 mm’mrad. In parallel, asymmetric beam collisions at the interaction point (IP) are studied to evaluate the current luminosity reach and provide insight to improvements required for positron acceleration in plasma. It is necessary to scale down the emittance of the positron bunch. In the MNL regime, a positron beam with 238 ’m’mrad level emittance implies compromise in charge or necessity for ultra-short bunches. * "Efficiency and beam quality for positron acceleration in loaded plasma wakefields",C. S. Hue, G. J. Cao, et.al Phys. Rev. Research 3, 043063
	Slides WEYD3 [3.635 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYD3
About •	Received ※ 01 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 24 August 2022
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WEYD4	Design and Fabrication of a Metamaterial Wakefield Accelerating Structure	564
	D.C. Merenich, X. Lu Northern Illinois University, DeKalb, Illinois, USA D.S. Doran, X. Lu, J.G. Power ANL, Lemont, Illinois, USA
	Metamaterials (MTMs) are engineered materials that can show exotic electromagnetic properties such as simultaneously negative permittivity and permeability. MTMs are promising candidates for structure-based wakefield acceleration structures, which can mitigate the impact of radio frequency (RF) breakdown, thus achieving a high gradient. Previous experiments carried out at the Argonne Wakefield Accelerator (AWA) successfully demonstrated MTM structures as efficient power extraction and transfer structures (PETS) from a high-charge drive beam. Here we present the design, fabrication, and cold test of an X-band MTM accelerator structure for acceleration of the witness beam in the two-beam acceleration scheme. The MTM structure design was performed using the CST Studio Suite, with the unit cell and the complete multi-cell periodic structure both optimized for high gradient. Cold test of the fabricated structure shows good agreement with simulation results. Future work includes a beam test at AWA to study the short-pulse RF breakdown physics in the MTM structure, as an important component towards a future compact linear collider based on two-beam acceleration.
	Slides WEYD4 [2.322 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYD4
About •	Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 31 August 2022
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WEYD5	Highly Spin-Polarized Multi-GeV Sub-Femtosecond Electron Beams Generated From Single-Species Plasma Photocathodes
	Z. Nie, C. Joshi, F. Li, K.A. Marsh, D. Matteo, W.B. Mori, N. Nambu, F.S. Tsung, Y.P. Wu, C. Zhang UCLA, Los Angeles, California, USA W. An BNU, Haidian District Beijing, People’s Republic of China F. Morales, S. Patchkovskii, O. Smirnova MBI, Berlin, Germany
	Funding: DOE Grant No. DE-SC0010064; DOE through a SciDAC FNAL Subcontract No. 644405; NSF Grants No. 1734315, No. 1806046 and No. 2108970; ONR MURI (4-442521-JC-22891); and NSFC Grant No. 12075030 High-gradient and high-efficiency acceleration in plasma-based accelerators has been demonstrated, showing its potential as the building block for a future collider operating at the energy frontier of particle physics. However, generating and accelerating the required spin-polarized beams in such a collider using plasma-based accelerators has been a long-standing challenge. Here we show that the passage of a highly relativistic, high-current electron beam through a single-species (ytterbium) vapor excites a nonlinear plasma wake by primarily ionizing the two outer 6s electrons. Further photoionization of the resultant Yb²⁺ ions by a circularly polarized laser injects the 4f14 electrons into this wake generating a highly spin-polarized beam. Combining time-dependent Schrodinger equation simulations with particle-in-cell simulations, we show that a sub-femtosecond, high-current (4 kA) electron beam with up to 56% net spin polarization can be generated and accelerated to 15 GeV in just 41 cm. This relatively simple scheme solves the perplexing problem of producing spin-polarized relativistic electrons in plasma-based accelerators.
	Slides WEYD5 [2.323 MB]
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WEYD6	Design of a PIP-II Era Mu2e Experiment	568
	M.A. Cummings, R.J. Abrams, R.P. Johnson, T.J. Roberts Muons, Inc, Illinois, USA D.V. Neuffer Fermilab, Batavia, Illinois, USA
	We propose a design of an upgraded Mu2e experiment for the future Fermilab PIP-II era based on the muon collider front end. The consensus is that such an upgrade should provide a factor of 10 increase in the rate of stopping muons in the experimental target. The current Mu2e design is optimized for 8 kW of protons at 8 GeV. The PIP-II upgrade project is a 250-meter-long CW linac capable of accelerating a 2-mA proton beam to a kinetic energy of 800 MeV (total power 1.6 MW). This would significantly improve the Fermilab proton source to enable next-generation intensity frontier experiments. But using this 800 MeV beam poses challenges to the Mu2E experiment. Bright muon beams generated from sources designed for muon collider and neutrino factory facilities have been shown to generate two orders of magnitude more muons per proton than the current Mu2e production target and solenoid. In contrast to the current Mu2e, the muon collider design has forward-production of muons from the target.
	Slides WEYD6 [1.937 MB]
DOI •	reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYD6
About •	Received ※ 06 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 09 October 2022
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Paper

Title

Page

MOZE1

Demonstration of High-Gradient in a Cryo-Cooled X-Band Structure

M.H. Nasr
SLAC, Menlo Park, California, USA

We present an experimental demonstration of the high-gradient operation of an X-band, 11.424 GHz, 20-cells linear accelerator (linac) operating at a liquid nitrogen temperature of 77 K. The tested linac was previously processed and tested at room temperature. Low-temperature operation increases the yield strength of the accelerator material and reduces surface resistance, hence a great reduction in cyclic fatigue could be achieved resulting in a large reduction in breakdown rates compared to room- temperature operation. Furthermore, temperature reduction increases the intrinsic quality factor of the accelerating cavities, and consequently, the shunt impedance leading to increased RF-to-beam efficiency and beam loading capabilities. We verified the enhanced accelerating parameters of the tested accelerator at cryogenic temperature using different measurements including electron beam acceleration up to a gradient of 150 MV/m, corresponding to a peak surface electric field of 375 MV/m. We also measured the breakdown rates in the tested structure showing a reduction of 2 orders of magnitude compared to their values at room temperature for the same accelerating gradient.

Slides MOZE1 [6.217 MB]

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MOZE2

Results of Awake Run 1 and Plans for Run 2 Towards HEP Applications

M. Bergamaschi
CERN, Meyrin, Switzerland

The high accelerating gradient that plasma wakefield can produce make it a an interesting technology for next generation of particle accelerators. The AWAKE experi-ment at CERN demonstrated during Run1 that thanks to the process of self-modulation an high energy (400 GeV) long (10 cm) proton bunch drive intense wakefield in plasma. Externally injected electrons were successfully accelerated to 2 GeV in a 10m plasma. The main aims of the AWAKE Run 2 phase are to demonstrate that a con-trolled self-modulation process can lead to stable acceler-ating gradient up to 1 GV/m preserving the emittance of injected electron bunches and to be scalable to plasma sources of 100s of meters and beyond for high energy. The AWAKE scheme aim to provide electron beams for particle physics experiments by the end of the Run2 phase. This contribution reports the main achievement of Run1 and summarises the programme of AWAKE Run 2 including possible applications of the AWAKE scheme to novel particle physics experiments.

Slides MOZE2 [7.505 MB]

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MOZE3

Emittance Measurements and Simulations from an X-Band Short-Pulse Ultra-High Gradient Photoinjector

45

G. Chen, D.S. Doran, C.-J. Jing, S.Y. Kim, W. Liu, W. Liu, P. Piot, J.G. Power, C. Whiteford, E.E. Wisniewski
ANL, Lemont, Illinois, USA
C.-J. Jing, E.W. Knight, S.V. Kuzikov
Euclid TechLabs, Solon, Ohio, USA
C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA
X. Lu, P. Piot, W.H. Tan
Northern Illinois University, DeKalb, Illinois, USA

Funding: This work is supported by the U.S. DOE, under award No. DE-SC0018656 to NIU, DOE SBIR grant No. DE-SC0018709 to Euclid Techlabs LLC, and contract No. DE-AC02-06CH11357 with ANL.
A program is under way at the Argonne Wakefield Accelerator facility, in collaboration with the Euclid Techlabs and Northern Illinois University (NIU), to develop a GeV/m scale photocathode gun, with the ultimate goal of demonstrating a high-brightness photoinjector beamline. The novel X-band photoemission gun (Xgun) is powered by high-power, short RF pulses, 9-ns (FWHM), which, in turn, are generated by the AWA drive beam. In a previous proof-of-principle experiment, an unprecedented 400~MV/m gradient on the photocathode surface* was demonstrated. In the current version of the experiment, we added a linac to the beamline to increase the total energy and gain experience tuning the beamline. In this paper, we report on the very first result of emittance measurement as well as several other beam parameters. This preliminary investigation has identified several factors to be improved on in order to achieve one of the ultimate goals; low emittance.
* W. H. Tan et al., "Demonstration of sub-GV/m Accelerating Field in a Photoemission Electron Gun Powered by Nanosecond X-Band Radiofrequency Pulses", 2022. arXiv:2203.11598v1

Slides MOZE3 [5.565 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE3

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Received ※ 03 August 2022 — Revised ※ 05 August 2022 — Accepted ※ 11 August 2022 — Issue date ※ 14 August 2022

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MOZE4

Ceramic Enhanced Accelerator Structure Low Power Test and Designs of High Power and Beam Tests

49

H. Xu, M.R. Bradley, L.D. Duffy, M.A. Holloway, J. Upadhyay
LANL, Los Alamos, New Mexico, USA

Funding: Research was supported by the Laboratory Directed Research and Development program of Los Alamos National Laboratory, under project number 20210083ER.
A ceramic enhanced accelerator structure (CEAS) uses a concentric ceramic ring placed inside a metallic pillbox cavity to significantly increase the shunt impedance of the cavity. Single cell standing wave CEAS cavities are designed, built, and tested at low power at 5.1 GHz. The results indicate 40% increase in shunt impedance compared to that of a purely metallic pillbox cavity. A beam test setup has been designed to use a single cell CEAS cavity to modulate a 30-keV direct-current (DC) electron beam at an accelerating gradient of 1 to 2 MV/m to verify the beam acceleration capability of the CEAS concept and to study the potential charging effect on the ceramic component during the operation. Another single cell standing wave CEAS cavity has been designed for high power test at 5.7 GHz for the high accelerating gradient capability.

Slides MOZE4 [1.652 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE4

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Received ※ 01 August 2022 — Revised ※ 07 August 2022 — Accepted ※ 09 August 2022 — Issue date ※ 07 October 2022

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MOZE5

Simulation and Experimental Results of Dielectric Disk Accelerating Structures

52

S. Weatherly, E.E. Wisniewski
Illinois Institute of Technology, Chicago, Illinois, USA
D.S. Doran, C.-J. Jing, J.F. Power, E.E. Wisniewski
ANL, Lemont, Illinois, USA
B.T. Freemire, C.-J. Jing
Euclid Beamlabs, Bolingbrook, USA

Funding: Contract DE-SC0019864 to Euclid Beamlabs LLC. AWA work from U.S. DOE Office of Science under Contract DE-AC02-06CH11357. Chicagoland Accelerator Science Traineeship U.S. DOE award number DE-SC-0020379
A method of decreasing the required footprint of linear accelerators and improving their energy efficiency is to employ Dielectric Disk Accelerators (DDAs) with short RF pulses ( ∼ 9 ns). A DDA is an accelerating structure that utilizes dielectric disks to improve the shunt impedance. Two DDA structures have been designed and tested at the Argonne Wakefield Accelerator. A single cell clamped DDA structure recently achieved an accelerating gradient of 1{02} MV/m. A multi-cell clamped DDA structure has been designed and is being fabricated. Simulation results for this new structure show a 1{08} MV/m accelerating gradient with 400 MW of input power with a high shunt impedance and group velocity. The engineering design has been improved from the single cell structure to ensure consistent clamping over the entire structure.

Slides MOZE5 [9.338 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOZE5

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Received ※ 02 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 21 August 2022 — Issue date ※ 06 October 2022

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MOZE6

Fulfilling the Mission of Brookhaven ATF as a DOE Flagship User Facility in Accelerator Stewardship

I. Pogorelsky, M. Babzien, M.G. Fedurin, R. Kupfer, M.A. Palmer, M.N. Polyanskiy
BNL, Upton, New York, USA
N. Vafaei-Najafabadi
Stony Brook University, Stony Brook, USA

Funding: This work is funded by the U.S. Department of Energy under contract DE-SC0012704
Over last three decades, BNL Accelerator Test Facility (ATF) pioneered the concept of a proposal-based user facility for lasers and electron beam-driven advanced accelerator research (AAR). This has made ATF an internationally recognized destination for researchers who benefit from access to unique scientific capabilities not otherwise available to individual institutions and businesses. Operating as an Office of Science National User Facility and a flagship DOE facility in Accelerator R&D Stewardship, ATF pursues an ambitious upgrade plan for its lasers and electron beam infrastructure to enable experiments at the forefront of the AAR. In this talk, we will present our path towards attaining a novel multi-terawatt sub-picosecond regime with a long-wave IR 9-um laser. Future enhancements to the electron beam and near-IR laser capabilities will also be presented. The combination of linac- and laser-driven e-beams will empower a unique state-of-the-art science program. This includes integrated multi-beam research in laser wakefield accelerators, such as the two-color ionization injection, with the promise of an all-optical scheme for generating collider-quality electrons beams.

Slides MOZE6 [6.929 MB]

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MOPA74

Design of a W-Band Corrugated Waveguide for Structure Wakefield Acceleration

210

B. Leung, X. Lu, C.L. Phillips, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
D.S. Doran, X. Lu, P. Piot, J.G. Power
ANL, Lemont, Illinois, USA

Current research on structure wakefield acceleration aims to develop radio-frequency structures that can produce high gradients, with work in the sub-terahertz regime being particularly interesting because of the potential to create more compact and economical accelerators. Metallic corrugated waveguides at sub-terahertz frequencies are one such structure. We have designed a W-band corrugated waveguide for a collinear wakefield acceleration experiment at the Argonne Wakefield Accelerator (AWA). Using the CST Studio Suite, we have optimized the structure for the maximum achievable gradient in the wakefield from a nominal AWA electron bunch at 65 MeV. Simulation results from different solvers of CST were benchmarked with each other, with analytical models, and with another simulation code, ECHO. We are investigating the mechanical design, suitable fabrication technologies, and the possibility to apply advanced bunch shaping techniques to improve the structure performance.

Poster MOPA74 [1.518 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA74

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Received ※ 30 July 2022 — Revised ※ 03 August 2022 — Accepted ※ 07 August 2022 — Issue date ※ 26 August 2022

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MOPA76

Wakefield Modeling in Sub-THz Dielectric-Lined Waveguides

218

C.L. Phillips, B. Leung, X. Lu, P. Piot
Northern Illinois University, DeKalb, Illinois, USA

Dielectric-lined waveguides have been extensively studied to potentially support high-gradient acceleration in beam-driven dielectric wakefield acceleration (DWFA) and for beam manipulations. In this paper, we investigate the wakefield generated by a relativistic bunch passing through a dielectric waveguide with different transverse sections. We specifically consider the case of a structure consisting of two dielectric slabs, along with rectangular and square structures. Numerical simulations performed with the fine-difference time-domain of the WarpX program reveal some interesting features of the transverse wake and a possible experiment at the Argonne Wakefield Accelerator (AWA) is proposed.

Poster MOPA76 [1.294 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-MOPA76

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Received ※ 12 August 2022 — Accepted ※ 13 August 2022 — Issue date ※ 12 September 2022

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TUPA75

High Gradient Testing Results of the Benchmark a/λ=0.105 Cavity at CERF-NM

505

M.R.A. Zuboraj, D.V. Gorelov, T.W. Hall, M.E. Middendorf, D. Rai, E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA

Funding: This work was supported by Los Alamos National Laboratory’s Laboratory Directed Research and Development (LDRD) Program.
This presentation will report initial results of high gradient testing of two C-band accelerating cavities fabricated at Los Alamos National Laboratory (LANL). At LANL, we commissioned a C-band Engineering Research Facility of New Mexico (CERF-NM) which has unique capability of conditioning and testing accelerating cavities for operation at surface electric fields at the excess of 300 MV/m, powered by a 50 MW, 5.712 GHz Canon klystron. Recently, we fabricated and tested two benchmark copper cavities at CERF-NM. These cavities establish a benchmark for high gradient performance at C-band and the same geometry will be used to provide direct comparison between high gradient performance of cavities fabricated of different alloys and by different fabrication methods. The cavities consist of three cells with one high gradient central cell and two coupling cells on the sides. The ratio of the radius of the coupling iris to the wavelength is a/λ=0.105. This poster will report high gradient test results such as breakdown rates as function of peak surface electric and magnetic fields and pulse heating.

Poster TUPA75 [0.890 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA75

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Received ※ 05 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 01 October 2022

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TUPA81

Design of a High-Power RF Breakdown Test for a Cryocooled C-Band Copper Structure

516

G.E. Lawler, A. Fukasawa, J.R. Parsons, J.B. Rosenzweig
UCLA, Los Angeles, California, USA
Z. Li, S.G. Tantawi
SLAC, Menlo Park, California, USA
A. Mostacci
Sapienza University of Rome, Rome, Italy
E.I. Simakov, T. Tajima
LANL, Los Alamos, New Mexico, USA
B. Spataro
LNF-INFN, Frascati, Italy

Funding: This work was supported by the DOE Contract DE-SC0020409.
High-gradient RF structures capable of maintaining gradients in excess of 250 MV/m are critical in several concepts for future electron accelerators. Concepts such as the ultra-compact free electron laser (UC-XFEL) and the Cool Copper Collider (C3) plan to obtain these gradients through the cryogenic operation (<77K) of normal conducting copper cavities. Breakdown rates, the most significant gradient limitation, are significantly reduced at these low temperatures, but the precise physics is complex and involves many interacting effects. High-power RF breakdown measurements at cryogenic temperatures are needed at the less explored C-band frequency (5.712 GHz), which is of great interest for the aforementioned concepts. On behalf of a large collaboration of UCLA, SLAC, LANL, and INFN, the first C-band cryogenic breakdown measurements will be made using a LANL RF test infrastructure. The 2-cell geometry designed for testing will be modifications of the distributed coupled reentrant design used to efficiently power the cells while staying below the limiting values of peak surface electric and magnetic fields.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA81

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Received ※ 29 July 2022 — Accepted ※ 02 August 2022 — Issue date ※ 08 August 2022

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TUPA87

Simulations for the Space Plasma Experiments at the SAMURAI Lab

539

P. Manwani, H.S. Ancelin, A. Fukasawa, G.E. Lawler, N. Majernik, B. Naranjo, J.B. Rosenzweig, Y. Sakai, O. Williams
UCLA, Los Angeles, California, USA
G. Andonian
RadiaBeam, Santa Monica, California, USA

Funding: This work was performed with support of the US Department of Energy under Contract No. DE-SC0017648 and DESC0009914, and the DARPA GRIT Contract 20204571
Plasma wakefield acceleration using the electron linear accelerator test facility, SAMURAI, can be used to study the Jovian electron spectrum due to the high energy spread of the beam after the plasma interaction. The SAMURAI RF facility which is currently being constructed and commissioned at UCLA, is is capable of producing beams with 10 MeV energy, 2 nC charge, and 200 fsec bunch lengths with a 4 um emittance. Particle-in-cell (PIC) simulations are used to study the beam spectrum that would be generated from plasma interaction. Experimental methods and diagnostics are discussed in this paper.

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-TUPA87

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Received ※ 04 August 2022 — Revised ※ 08 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 06 September 2022

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WEYD1

Ultrahigh Energy Electrons From Laser Wakefield Accelerators

B.M. Hegelich
The University of Texas at Austin, Austin, Texas, USA

We report peak electron energies well in excess of 10 GeV from a laser wakefield accelerator. Proof-of-principle experiment have been performed at the Texas Petawatt laser using a 10 cm long gas cell filled with helium gas and seeded by metallic nanoparticles. Greater than 10 GeV electron energies have been observed repeatedly in multiple independent experiments. This results fulfill a major milestones in DOE’s Advanced Accelerator Strategy Report from 2016 and open up the potential of laser wakefield accelerators as high energy machines or as drivers for laser-driven XFELs. Compared with other wakefield acceleration schemes, our scheme is straightforward since it requires only a gas cell and a source of nanoparticles for electron injection. No external guiding or heating mechanisms are employed. The nanoparticle-assisted laser wakefield acceleration can control all the electron beam parameters: charge, energy spread, energy, emittance, and the number of bunches in the beam. Bunch charges are on the order of a few nanocoulomb for the whole beam and in the 100s pC range in the high energy part, an order of magnitude increase over previous results at greater than 5 GeV.

Slides WEYD1 [16.825 MB]

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WEYD2

First Lasing of a Free-Electron Laser With a Compact Beam-Driven Plasma Accelerator

S. Romeo, M. Galletti, R. Pompili
LNF-INFN, Frascati, Italy

Plasma-based technology promises a revolution in the field of particle accelerators by pushing beams to GeV energies within centimeter distances and enabling the realization of ultra-compact facilities for user applications like Free-Electron Lasers (FEL). Here we report the first experimental evidence of FEL lasing by a compact (3 cm) particle beam-driven plasma accelerator. FEL radiation is observed in the infrared range with typical exponential growth of its intensity over six consecutive undulators. This achievement is based on the technique we recently developed for energy spread control during acceleration in plasma, generating electron bunches with high-quality, comparable with state-of-the-art accelerators. This proof-of-principle experiment represents an important milestone in the use of plasma-based accelerators contributing to the development of next-generation compact machines for user-oriented applications.

Slides WEYD2 [3.894 MB]

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WEYD3

Positron Acceleration in Linear, Moderately Non-Linear and Non-Linear Plasma Wakefields

560

G.J. Cao, E. Adli
University of Oslo, Oslo, Norway
S. Corde
LOA, Palaiseau, France
S.J. Gessner
SLAC, Menlo Park, California, USA

Accelerating particles to high energies with high efficiency and beam quality is crucial in developing accelerator technologies. The plasma acceleration technique, providing unprecedented high gradients, is considered as a promising future technology. While important progress has been made in plasma-based electron acceleration in recent years, identifying a reliable acceleration technique for the positron counterpart would pave the way to a linear e⁺e⁻ collider for high-energy physics applications. In this work, we show further studies of positron beam quality in moderately non-linear (MNL)* plasma wakefields. With a positron bunch of initial energy 1 GeV, emittance preservation can be achieved in optimised scenarios at 2.38 mm’mrad. In parallel, asymmetric beam collisions at the interaction point (IP) are studied to evaluate the current luminosity reach and provide insight to improvements required for positron acceleration in plasma. It is necessary to scale down the emittance of the positron bunch. In the MNL regime, a positron beam with 238 ’m’mrad level emittance implies compromise in charge or necessity for ultra-short bunches.
* "Efficiency and beam quality for positron acceleration in loaded plasma wakefields",C. S. Hue, G. J. Cao, et.al Phys. Rev. Research 3, 043063

Slides WEYD3 [3.635 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYD3

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Received ※ 01 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 24 August 2022

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WEYD4

Design and Fabrication of a Metamaterial Wakefield Accelerating Structure

564

D.C. Merenich, X. Lu
Northern Illinois University, DeKalb, Illinois, USA
D.S. Doran, X. Lu, J.G. Power
ANL, Lemont, Illinois, USA

Metamaterials (MTMs) are engineered materials that can show exotic electromagnetic properties such as simultaneously negative permittivity and permeability. MTMs are promising candidates for structure-based wakefield acceleration structures, which can mitigate the impact of radio frequency (RF) breakdown, thus achieving a high gradient. Previous experiments carried out at the Argonne Wakefield Accelerator (AWA) successfully demonstrated MTM structures as efficient power extraction and transfer structures (PETS) from a high-charge drive beam. Here we present the design, fabrication, and cold test of an X-band MTM accelerator structure for acceleration of the witness beam in the two-beam acceleration scheme. The MTM structure design was performed using the CST Studio Suite, with the unit cell and the complete multi-cell periodic structure both optimized for high gradient. Cold test of the fabricated structure shows good agreement with simulation results. Future work includes a beam test at AWA to study the short-pulse RF breakdown physics in the MTM structure, as an important component towards a future compact linear collider based on two-beam acceleration.

Slides WEYD4 [2.322 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYD4

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Received ※ 03 August 2022 — Revised ※ 09 August 2022 — Accepted ※ 10 August 2022 — Issue date ※ 31 August 2022

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WEYD5

Highly Spin-Polarized Multi-GeV Sub-Femtosecond Electron Beams Generated From Single-Species Plasma Photocathodes

Z. Nie, C. Joshi, F. Li, K.A. Marsh, D. Matteo, W.B. Mori, N. Nambu, F.S. Tsung, Y.P. Wu, C. Zhang
UCLA, Los Angeles, California, USA
W. An
BNU, Haidian District Beijing, People’s Republic of China
F. Morales, S. Patchkovskii, O. Smirnova
MBI, Berlin, Germany

Funding: DOE Grant No. DE-SC0010064; DOE through a SciDAC FNAL Subcontract No. 644405; NSF Grants No. 1734315, No. 1806046 and No. 2108970; ONR MURI (4-442521-JC-22891); and NSFC Grant No. 12075030
High-gradient and high-efficiency acceleration in plasma-based accelerators has been demonstrated, showing its potential as the building block for a future collider operating at the energy frontier of particle physics. However, generating and accelerating the required spin-polarized beams in such a collider using plasma-based accelerators has been a long-standing challenge. Here we show that the passage of a highly relativistic, high-current electron beam through a single-species (ytterbium) vapor excites a nonlinear plasma wake by primarily ionizing the two outer 6s electrons. Further photoionization of the resultant Yb²⁺ ions by a circularly polarized laser injects the 4f14 electrons into this wake generating a highly spin-polarized beam. Combining time-dependent Schrodinger equation simulations with particle-in-cell simulations, we show that a sub-femtosecond, high-current (4 kA) electron beam with up to 56% net spin polarization can be generated and accelerated to 15 GeV in just 41 cm. This relatively simple scheme solves the perplexing problem of producing spin-polarized relativistic electrons in plasma-based accelerators.

Slides WEYD5 [2.323 MB]

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WEYD6

Design of a PIP-II Era Mu2e Experiment

568

M.A. Cummings, R.J. Abrams, R.P. Johnson, T.J. Roberts
Muons, Inc, Illinois, USA
D.V. Neuffer
Fermilab, Batavia, Illinois, USA

We propose a design of an upgraded Mu2e experiment for the future Fermilab PIP-II era based on the muon collider front end. The consensus is that such an upgrade should provide a factor of 10 increase in the rate of stopping muons in the experimental target. The current Mu2e design is optimized for 8 kW of protons at 8 GeV. The PIP-II upgrade project is a 250-meter-long CW linac capable of accelerating a 2-mA proton beam to a kinetic energy of 800 MeV (total power 1.6 MW). This would significantly improve the Fermilab proton source to enable next-generation intensity frontier experiments. But using this 800 MeV beam poses challenges to the Mu2E experiment. Bright muon beams generated from sources designed for muon collider and neutrino factory facilities have been shown to generate two orders of magnitude more muons per proton than the current Mu2e production target and solenoid. In contrast to the current Mu2e, the muon collider design has forward-production of muons from the target.

Slides WEYD6 [1.937 MB]

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reference for this paper ※ doi:10.18429/JACoW-NAPAC2022-WEYD6

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Received ※ 06 August 2022 — Revised ※ 11 August 2022 — Accepted ※ 12 August 2022 — Issue date ※ 09 October 2022

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