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When a moderately intense, few-picosecond-long laser pulse ionizes gas to produce an underdense plasma column, a linear relativistic plasma wave or wake can be excited by the self-modulation instability that may prove useful for multi-bunch acceleration of externally injected electrons or positrons to high energies in a short distance. At the same time, due to the anisotropic temperature distributions of the ionized plasma electrons, the Weibel instability can self-generate magnetic fields throughout such a plasma on a few picoseconds timescale that can persist even longer than the lifetime of the wake. In the present paper, we first show using simulations that both these effects do indeed co-exist in space and time in the plasma. Using our simulations, we make preliminary estimates of the contribution to the transverse emittance growth of an externally injected beam due to the Weibel magnetic fields in a few-millimeter-long plasma. We then present the results of an experiment that has allowed us to measure the spatiotemporal evolution of the magnetic fields using an ultrashort relativistic electron probe beam. Both the topology and the lifetime of the Weibel instability induced magnetic fields in the experiment are in reasonable agreement with the fields induced by the Weibel instability in the simulations.
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This content will become publicly available on December 1, 2026
Characterization of spatiotemporal overlap of femtosecond lasers and electron beam with Ce:YAG screens
Interactions between short laser pulses and electron bunches determine a wide range of accelerator applications. Finding spatiotemporal overlap between few-micron-sized optical and electron beams is critical, yet there are few routine diagnostics for this purpose. We present a method for achieving spatiotemporal overlap between a picosecond laser pulse and a relativistic sub-ps electron bunch. The method uses the transient change in optical transmission of a Ce:YAG screen upon irradiation with a short electron bunch to co-time the electron and laser beams. We demonstrate and quantify the performance of this method using an inverse Compton source comprised of a 30 MeV electron beam from an X-band linac focused to a 10 μm spot, overlapped with a joule-class picosecond Yb:YAG laser system. This method is applicable to electron beams with few-microjoule bunch energies and uses standard scintillator screens common in electron accelerators.
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- PAR ID:
- 10658742
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Review of Scientific Instruments
- Volume:
- 96
- Issue:
- 12
- ISSN:
- 0034-6748
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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