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LULI2000 - High-resolution measurements of laser-driven magnetic fields with application to isochoric heating and ion acceleration (J. Santos)

This proposal builds upon the successful previous access to LULI’s pico2000 laser facility where we have reproducibly generated strong magnetic pulses (>500 T, a few ns duration) out of capacitor-coil targets driven by 500 J, 1 ns-long laser pulses focused to intensities ~ 1017 W/cm2. Such B-fields were successfully used to guide relativistic electron beams (REB), with about 30 MA current intensity, improving the energy-density flux into solid-density matter by an unprecedented factor 5.

Here we propose the use of such laser-driven B-fields:

i) to test novel atomic physics calculations in magnetized conditions, where the coupling of an external B-field to the atomic magnetic moment dominates the spin-orbit interaction. We will perform measurements of Zeeman-splitting in the UV emission lines from a low Z highly-ionized gas;

ii) to broad the scope of the magnetized electron transport experiments by directly characterizing the REB isochoric heating. The radially confined REB propagation assures a more homogenous target heating along the target depth compared to unmagnetized transport conditions, and this enables efficiently driving laboratory samples to exotic plasma states relevant to planetary or stellar science. The temperature at the rear side of foil targets of variable thickness will be inferred from spectral measurements of shifted Ka-fluorescence lines;

iii) to enhance the proton acceleration from the sheath field at the targets’ rear surface. Our preliminary PIC simulations in magnetized conditions for LULI parameters predict a >35% enhancement on the proton cutoff energy.

The driven B-fields will be characterized by the usual techniques of B-dot probing and backlighting proton-deflectometry. Yet, we will now specifically focus on characterizing the laser-plasma interactions (LPI) in the capacitor-coil, underlying to the intense current discharges and strong magnetic pulses production. Along with multiple x-ray spectrometers and streaked optical pyrometry, we will in particular focus on novel complex interferometry techniques allowing to simultaneously extract the plasma density and the self-generated B-field distributions. The understanding of the LPI mechanisms is essential to consolidate our modelling efforts in predicting the B-field production for any laser and capacitor-coil target parameters, namely for its future use in larger-scale laser facilities such as Omega, LMJ or NIF.

 

LULI2000 - S37-S39/2019