jiaweic

• Zhang, Chaojie; Storey, Douglas; Knetsch, Alexander; O’Shea, Brendan D.; Ariniello, Robert & Cao, Jiawei [Vis alle 22 forfattere av denne artikkelen] (2025). Plasma-wakefield accelerator simultaneously boosts electron beam energy and brightness. Nature Communications. 16(1). doi: 10.1038/s41467-025-65742-8. Fulltekst i vitenarkiv Vis sammendrag

  High-energy particle colliders and X-ray free-electron lasers demand electron beams with qualities currently achieved only in kilometer-scale radio-frequency accelerators. Plasma accelerators promise a compact alternative but have faced challenges in delivering the needed beam quality at relevant energies. Here, we demonstrate that a plasma-wakefield accelerator operating in the nonlinear regime acts as a transformer to simultaneously boost the energy and brightness of an electron bunch injected from the plasma. Using a 10-GeV drive bunch and a three-stage meter-scale plasma source, we generated electron bunches exceeding 20 GeV with sub-percent energy spread, 2 mm·mrad normalized emittance, and multi-kA peak current. A significant number of drive-bunch electrons lost over 90% of their energy, a prerequisite for high energy-conversion efficiency. This demonstration of an energy transformer ratio exceeding two and a brightness enhancement over an order of magnitude opens a path towards cost-effective accelerators for future colliders and light sources.

• Cao, Jiawei; Lindstrøm, Carl A.; Adli, Erik; Corde, Sébastien & Gessner, Spencer (2024). Positron acceleration in plasma wakefields. Physical Review Accelerators and Beams. ISSN 2469-9888. 27(3). doi: 10.1103/PhysRevAccelBeams.27.034801. Fulltekst i vitenarkiv Vis sammendrag

  Plasma acceleration has emerged as a promising technology for future particle accelerators, particularly linear colliders. Significant progress has been made in recent decades toward high-efficiency and high-quality acceleration of electrons in plasmas. However, this progress does not generalize to the acceleration of positrons, as plasmas are inherently charge asymmetric. Here, we present a comprehensive review of historical and current efforts to accelerate positrons using plasma wakefields. Proposed schemes that aim to increase energy efficiency and beam quality are summarized and quantitatively compared. A dimensionless metric that scales with the luminosity-per-beam power is introduced, indicating that positron-acceleration schemes are currently below the ultimate requirement for colliders. The primary issue is electron motion; the high mobility of plasma electrons compared to plasma ions, which leads to nonuniform accelerating and focusing fields that degrade the beam quality of the positron bunch, particularly for high efficiency acceleration. Finally, we discuss possible mitigation strategies and directions for future research.

• Storey, D.; Zhang, C.; Claveria, Miguel San Miguel; Cao, Jiawei; Adli, Erik & Alsberg, L. [Vis alle 32 forfattere av denne artikkelen] (2024). Wakefield generation in hydrogen and lithium plasmas at FACET-II: Diagnostics and first beam-plasma interaction results. Physical Review Accelerators and Beams. ISSN 2469-9888. 27(5). doi: 10.1103/PhysRevAccelBeams.27.051302. Fulltekst i vitenarkiv Vis sammendrag

  Plasma wakefield acceleration provides ultrahigh acceleration gradients of tens of GeV/m, providing a novel path toward efficient, compact, TeV-scale linear colliders, and high brightness free electron lasers. Critical to the success of these applications is demonstrating simultaneously high gradient acceleration, high energy transfer efficiency, and preservation of emittance, charge, and energy spread. Experiments at the FACET-II National User Facility at SLAC National Accelerator Laboratory aim to achieve all of these milestones in a single-stage plasma wakefield accelerator, providing a 10 GeV energy gain in a <1  m plasma with high energy transfer efficiency. Such a demonstration depends critically on diagnostics able to measure emittance with mm mrad accuracy, energy spectra to determine both percent level energy spread, and broadband energy gain and loss, incoming longitudinal phase space, and matching dynamics. This paper discusses the experimental setup at FACET-II, including the incoming beam parameters from the FACET-II linac, plasma sources, and diagnostics developed to meet this challenge. Initial progress on the generation of beam ionized wakes in meter-scale hydrogen gas is discussed as well as commissioning of the plasma sources and diagnostics.

• Zhang, Chaojie; Storey, Doug; Claveria, Pablo San Miguel; Nie, Zan; Marsh, Ken A. & Mori, Warren B. [Vis alle 29 forfattere av denne artikkelen] (2024). Correlations between X-rays, visible light and drive-beam energy loss observed in plasma wakefield acceleration experiments at FACET-II. Journal of Plasma Physics. ISSN 0022-3778. 90(4). doi: 10.1017/S0022377824000734. Fulltekst i vitenarkiv Vis sammendrag

  This study documents several correlations observed during the first run of the plasma wakefield acceleration experiment E300 conducted at FACET-II, using a single drive electron bunch. The established correlations include those between the measured maximum energy loss of the drive electron beam and the integrated betatron X-ray signal, the calculated total beam energy deposited in the plasma and the integrated X-ray signal, among three visible light emission measuring cameras and between the visible plasma light and X-ray signal. The integrated X-ray signal correlates almost linearly with both the maximum energy loss of the drive beam and the energy deposited into the plasma, demonstrating its usability as a measure of energy transfer from the drive beam to the plasma. Visible plasma light is found to be a useful indicator of the presence of a wake at three locations that overall are two metres apart. Despite the complex dynamics and vastly different time scales, the X-ray radiation from the drive bunch and visible light emission from the plasma may prove to be effective non-invasive diagnostics for monitoring the energy transfer from the beam to the plasma in future high-repetition-rate experiments.

• Zhang, C.; Storey, D.; Claveria, Miguel San Miguel; Nie, Z.; Marsh, K.A. & Hogan, M. [Vis alle 29 forfattere av denne artikkelen] (2024). Generation of meter-scale hydrogen plasmas and efficient, pump-depletion-limited wakefield excitation using 10 GeV electron bunches. Plasma Physics and Controlled Fusion. ISSN 0741-3335. 66(2). doi: 10.1088/1361-6587/ad1ae4. Fulltekst i vitenarkiv Vis sammendrag

  High repetition rates and efficient energy transfer to the accelerating beam are important for a future linear collider based on the beam-driven plasma wakefield acceleration scheme (PWFA-LC). This paper reports the first results from the Plasma Wakefield Acceleration Collaboration (E300) that are beginning to address both of these issues using the recently commissioned FACET-II facility at SLAC national accelerator laboratory. We have generated meter-scale hydrogen plasmas using time-structured 10 GeV electron bunches from FACET-II, which hold the promise of dramatically increasing the repetition rate of PWFA by rapidly replenishing the gas between each shot compared to the hitherto used lithium plasmas that operate at 1–10 Hz. Furthermore, we have excited wakes in such plasmas that are suitable for high gradient particle acceleration with high drive-bunch to wake energy transfer efficiency- a first step in achieving a high overall energy transfer efficiency. We have done this by using time-structured electron drive bunches that typically have one or more ultra-high current (>30 kA) femtosecond spike(s) superimposed on a longer (∼0.4 ps) lower current (<10 kA) bunch structure. The first spike effectively field-ionizes the gas and produces a meter-scale (30–160 cm) plasma, whereas the subsequent beam charge creates a wake. The length and amplitude of the wake depends on the longitudinal current profile of the bunch and plasma density. We find that the onset of pump depletion, when some of the drive beam electrons are nearly fully depleted of their energy, occurs for hydrogen pressure ≥1.5 Torr. We also show that some electrons in the rear of the bunch can gain several GeV energies from the wake. These results are reproduced by particle-in-cell simulations using the QPAD code. At a pressure of ∼2 Torr, simulation results and experimental data show that the beam transfers about 60% of its energy to the wake.

• Cao, Jiawei (2023). Effects of Plasma Temperature in the Blowout Regime for Plasma Accelerators. Instruments. 7(4). doi: 10.3390/instruments7040037. Fulltekst i vitenarkiv
• Barklow, Tim; Gessner, Spencer; Hogan, Mark; Ng, Cho-Kuen; Peskin, Michael & Raubenheimer, Tor [Vis alle 30 forfattere av denne artikkelen] (2023). Beam delivery and beamstrahlung considerations for ultra-high energy linear colliders. Journal of Instrumentation (JINST). 18(9). doi: 10.1088/1748-0221/18/09/P09022. Fulltekst i vitenarkiv
• White, G.; Gessner, S.; Adli, Erik; Cao, Jiawei; Sjobak, Kyrre Ness & Barber, S. [Vis alle 15 forfattere av denne artikkelen] (2022). Beam delivery and final focus systems for multi-TeV advanced linear colliders. Journal of Instrumentation (JINST). 17(5). doi: 10.1088/1748-0221/17/05/P05042. Fulltekst i vitenarkiv Vis sammendrag

  The Beam Delivery System (BDS) is a critical component of a high-energy linear collider. It transports the beam from the accelerator and brings it to a focus at the Interaction Point. The BDS system includes diagnostic sections for measuring the beam energy, emittance, and polarization, as well as collimators for machine protection. The length of the BDS increases with collision energy. Higher collision energies also require higher luminosities, and this is a significant constraint on the design for energy-frontier machines. Here, we review BDS designs based on traditional quadrupole magnets and examine the challenges involved in extending these to the Multi-TeV regime consistent with requirements for advanced accelerator concepts.

• Hue, C.S.; Cao, Jiawei; Andriyash, I.A.; Knetsch, A.; Hogan, M.J. & Adli, Erik [Vis alle 8 forfattere av denne artikkelen] (2021). Efficiency and beam quality for positron acceleration in loaded plasma wakefields. Physical Review Research (PRResearch). 3(4). doi: 10.1103/PhysRevResearch.3.043063. Fulltekst i vitenarkiv Vis sammendrag

  Accelerating particles to high energies in plasma wakefields is considered to be a promising technique with good energy efficiency and high gradient. While important progress has been made in plasma-based electron acceleration, positron acceleration in plasma has been scarcely studied and a fully self-consistent and optimal scenario has not yet been identified. For high energy physics applications where an electron-positron collider would be desired, the ability to accelerate positrons in plasma wakefields is, however, paramount. Here we show that the preservation of beam quality can be compromised in a plasma wakefield loaded with a positron beam, and a tradeoff between energy efficiency and beam quality needs to be found. For electron beams driving linear plasma wakefields, we have found that despite the transversely nonlinear focusing force induced by positron beam loading, the bunch quickly evolves toward an equilibrium distribution with limited emittance growth. Particle-in-cell simulations show that for μm-scale normalized emittance, the growth of uncorrelated energy spread sets an important limit. Our results demonstrate that the linear or moderately nonlinear regimes with Gaussian drivers provide a good tradeoff, achieving simultaneously energy-transfer efficiencies exceeding 30% and uncorrelated energy spread below 1%, while donut-shaped drivers in the nonlinear regime are more appropriate to accelerate high-charge bunches at higher gradients, at the cost of a degraded tradeoff between efficiency and beam quality.

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