Polarized proton beams from laser-induced plasmas

Anna Hützen,Ralf Engels,Johannes Thomas,Jürgen Böker,T Peter Rakitzis,Dimitris Sofikitis,Andreas Lehrach,Alexander Pukhov,Markus Büscher,Ralf Gebel

doi:10.1017/hpl.2018.73

Abstract

We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the particle-in-cell (PIC) simulation code VLPL (Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM, Shanghai.

Highlights

We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator
Spin effects have been implemented into the particle-in-cell (PIC) simulation code VLPL (Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas
A polarized hydrogen chloride (HCl) gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms

Summary

Introduction

Ion acceleration driven by super-intense laser pulses has undergone impressive advances in recent years. Increasing energies and repetition rates allow even higher ion energies and intensities, possibly even laser-induced nuclear fusion In this context, one important feature of modern accelerators is still missing, namely the production of highly polarized particle beams. With respect to gas targets it has been demonstrated that for nuclear and electron spin-polarized hydrogen at densities of at least ∼1019 cm−3 the polarization lifetime is ∼10 ns, which is sufficiently long to generate polarized hydrogen atoms on the timescale of our experiment[9] This density is large enough for laser-driven ion acceleration of spinpolarized protons. One conclusion from this experiment is that for measuring a proton polarization P = 0, both a stronger laser pulse with an intensity of about 1023 W · cm−2 and an extended gas instead of a thin foil target are needed

Proton-spin dynamics

Particle-in-cell simulations

Experimental realization

Discussion and conclusion