Revision 1

Accepted · first revision · record

Title: Multistage plasma acceleration with preserved beam quality
Plain: Each plasma stage can only add a limited energy, so a collider needs many stages in a row. Passing a beam from one stage to the next without losing particles or blurring it has not been demonstrated.
Precise: Between stages the strongly focused beam diverges and must be refocused, producing chromatic emittance growth $(\Delta \epsilon/\epsilon)^2 \sim (W \sigma_{\delta})^2$ with chromatic amplitude $W \sim \beta_{\mathrm{lens}}/f$. Demonstrate acceleration through at least two independently driven stages with charge coupling above 90 percent, normalized emittance growth below 10 percent and rms energy spread below 1 percent, or show it is impossible with known optics. An answer is an experiment or a proof of a fundamental limit.
Settled by: A two-stage experiment with independent drivers meeting the stated charge, emittance and energy-spread metrics.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: As of 2025 no staging of beam-driven plasma accelerators had been demonstrated; the only two-stage laser-driven test (2016) coupled about 3.5 percent of the charge.
Posed since: (empty)