Generation of ultrarelativistic electron bunches

One application of high-power laser systems is the generation of electron bunches and their acceleration to ultrarelativistic energies. Both experimental studies at the subpetawatt laser facility PEARL and theoretical investigations involving modern computational tools have been conducted at IAP RAS.
In experiment laser pulses of energy up to 10 J and duration 50—70 fs were focused onto a helium or nitrogen gas jet. An original spectrometer which ensured high-accurate measurements in a broad energy range was used to measure energy of electrons generated in the gas jet (A. A. Shaykin, A. A. Soloviev, M. V. Starodubtsev).

Diagram showing experimental setup used to study acceleration
of ultrarelativistic electron bunches by super-high-power radiation
from PEARL laser system

Electron bunches with energies up to 300 MeV were produced in experiment and accelerating electric fields in the plasma reached values of 0.5 GeV/cm, which is three orders of magnitude higher than the record values attainable with conventional linear accelerators. The result fits into the existing phenomenological theory of wake field electron acceleration and is confirmed by numerical modeling performed at IAP RAS on supercomputers using the particle-in-cell method.

Electron bunch images produced by scintillators after the bunches have passed through the magnetic field, depending on plasma concentration. The horizontal deflection of electrons to the left is determined by electron energy

Result of numerical simulation showing electron energy versus distance: laser pulse diameter is larger than diameter of the cavity structure (left) and is equal to diameter of the cavity structure (right). In the latter case, the formed electron bunch is much denser and the electrons are accelerated more effectively