Speaker
Description
The time for a stationary plasma to recover its original state after a wake is excited determines the repetition rate and luminosity of plasma-based colliders. Recent measurements showed that, after exciting one wake with an impulse of $\sim 0.5$J energy in plasma of density $n_e\sim10^{16}\,$cm$^{-3}$, a second wake yielding indistinguishable beam properties could be excited at time delays ranging from 60ns to $<1$ns, depending on plasma species, suggesting a potential for repetition rates ranging from tens of MHz to $\sim 1$GHz.
Here, we report complementary experiments carried out at SLAC’s Facility for Advanced Accelerator Science and Experimental Tests (FACET-II) in which, instead of generating a second wake, we employed a sub-ps, time-delayed, grazing-incidence optical probe pulse to detect remnants of the original excitation. Moreover, we excited wakes with impulses up to 20 J energy, 40x more strongly than in previous experiments, and examined the response of plasmas of three different species (hydrogen, lithium, argon). The results show that wake remnants are detectable at time delays ranging from $\sim 0.1\,\mu$s in hydrogen to several tens of $\mu$s in argon. These long-lived structures will contribute to cumulative heating, and thus are likely to limit plasma accelerators to sub-MHz repetition rates.
| Working group | WG3 |
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