לוח שנה משולב

Laser-wakefield accelerators (LWFAs) have demonstrated the ability to generate high-quality, monoenergetic electron beams. Yet, efforts to achieve higher electron energies and improved accelerator efficiency remain limited by several fundamental constraints, most notably electron dephasing and beam diffraction. One promising approach to mitigating these limitations is the use of structured light to control the on-axis propagation velocity within LWFAs. By combining the diffraction-resistant characteristics of Bessel beams with spatiotemporal pulse shaping, this method promises an improved balance of extended acceleration distances and strong accelerating gradients.In this talk, we report the first experimental observation of wakefields driven by such structured-light beams as well as the first experimental evidence of the mitigation of dephasing in electron acceleration. Spatiotemporally engineered laser pulses are focused using a specialized mirror to produce a quasi-Bessel beam, and the resulting wakefields are directly measured using femtosecond relativistic electron microscopy. Numerical simulations support the experimental observations and provide new insight into this largely unexplored regime. We experimentally demonstrate control over the on-axis propagation velocity of the wakefield and follow its evolution throughout the focal region. Furthermore, we investigate how targeted spatiotemporal modifications affect both the wakefield structure and its propagation velocity. Finally, we present the first successful acceleration of electrons using these wakefields. We compare the electron profiles obtained by wakefields traveling at different velocities, demonstrating that the faster wakefield is able to achieve a higher electron cutoff energy. By combing our data with insights from simulations, we suggest the first successful partial mitigation of dephasing with such techniques. Together, these results lay the groundwork for leveraging structured-light-based techniques to overcome dephasing limitations in LWFA systems.

Aging is characterized by several quantitative regularities: mortality and disease incidence rise exponentially with age, organ function declines linearly, and species with very different lifespans exhibit similarly shaped survival curves. I will present recent developments that unify these quantitative phenomena within the framework of the Saturating Removal (SR) model. The SR model is a biologically motivated stochastic differential equation that describes aging as a damage accumulation process with linearly increasing production with time and saturating removal, with death and disease modeled as first-passage-time processes. I will discuss the statistical properties of the model, including how the exponential mortality increase emerges from a Kramers escape rate over a barrier. I will then present recent results showing how the model organizes aging across species into two distinct aging regimes- ballistic and quasi steady state. Comparing the model to human data, indicates that late-life survival and the extreme-value tail of exceptionally long-lived individuals constrain damage production and removal parameters in human populations. This model can help prioritize longevity interventions. I will discuss future directions and open questions. FOR THE LATEST UPDATES AND CONTENT ON SOFT MATTER AND BIOLOGICAL PHYSICS AT THE WEIZMANN, VISIT OUR WEBSITE: https://www.bio