Magnetic field generation in multipetawatt laser-solid interactions

Magnetic field generation in ultraintense laser-solid interactions is studied over a range of laser intensities relevant to next-generation laser facilities <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mo>(</a:mo><a:msub><a:mi>a</a:mi><a:mn>0</a:mn></a:msub><a:mo>=</a:mo><a:mn>50</a:mn><a:mo>–</a:mo><a:mn>500</a:mn><a:mo>)</a:mo></a:mrow></a:math> using two-dimensional (2D) particle-in-cell simulations including strong-field quantum electrodynamic effects. It is found that fields <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi>O</b:mi><b:mo>(</b:mo><b:mn>0.1</b:mn><b:mo>)</b:mo></b:mrow></b:math> MT (1 GG) may be generated by relativistic electrons traveling along the surface of the target. However, a significant fraction of the energy budget is converted to high-energy photons, approximately <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mn>38</c:mn><c:mo>%</c:mo></c:mrow></c:math> at <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:msub><d:mi>a</d:mi><d:mn>0</d:mn></d:msub><d:mo>=</d:mo><d:mn>500</d:mn></d:mrow></d:math>, greatly reducing the available energy for field generation. A model for the evolution of the target-surface fields is created and the scaling of the field strength with <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:msub><e:mi>a</e:mi><e:mn>0</e:mn></e:msub></e:math> is extracted from a set of 2D simulations. The simulated scaling allows for the estimation of field strengths and the model gives insight into the evolution of the fields on the next generation of laser facilities, a necessary component to the proposal of any future magnetized experiment.