Speaker
Description
Future linear collider concepts often use "flat beams" with high emittance asymmetry to reduce bremsstrahlung, together with extreme beam focusing to achieve high luminosities. Although plasma lenses provide superior focusing gradients, existing designs are limited by the current-carrying capacity of active capillary-based lenses or the cylindrical symmetry of underdense lenses. This symmetry introduces transverse coupling and triggers resonant emittance mixing, which rapidly degrades the flat-beam phase space and reduces luminosity. In this talk, we present a novel 1D plasma lens that overcomes these challenges by operating in a previously unobserved, focusing-dominated wakefield regime at a low plasma density. By employing a 2-3 $TW$, 2 $ps$ long-wavelength IR CO2 laser pulse, we generate a highly elongated, electron-depleted ion cavity in a plasma density of $3 \times 10^{15} cm ^{-3}$. The regime was observed with a 50-60 $MeV$ electron beam probe at the Accelerator Test Facility in Brookhaven National Laboratory. This configuration produces strong, linear transverse focusing fields while nearly extinguishing longitudinal accelerating fields. The resulting cylindrical ion channel focuses exclusively in one transverse direction, providing a decoupled focusing geometry that preserves the phase space of highly asymmetric beams with minimal emittance degradation. This 1-D plasma lens represents a critical step toward the robust focusing geometry that produces a flat beam without requiring significant initial mismatch in emittance for next-generation high-energy physics colliders.
| Working group | WG5 |
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