Relativistic positron creation using ultraintense short pulse lasers.

Area of Science:

• Plasma Physics
• High-Energy Physics
• Particle Acceleration

Background:

• Positron production is crucial for various scientific applications.
• Previous methods have limitations in achievable densities.
• Understanding positron generation mechanisms is an ongoing research area.

Purpose of the Study:

• To measure positron production yields and characteristics from gold targets irradiated by ultraintense lasers.
• To determine the positron density achieved in laboratory conditions.
• To investigate the dominant positron production mechanisms.

Main Methods:

• Irradiating gold targets (approximately mm thick) with short (approximately 1 ps), ultraintense (approximately 1x10^20 W/cm^2) laser pulses.
• Measuring the ejected positrons per steradian using specialized detectors.
• Analyzing the energy distribution and angular distribution of the produced positrons.
• Employing modeling to estimate the positron density.

Main Results:

• Up to 2x10^10 positrons per steradian were measured.
• Positrons were predominantly produced via the Bethe-Heitler process.
• The effective positron temperature ranged from 2-4 MeV, with a peak distribution at 4-7 MeV.
• Anisotropic angular distribution of positrons was observed.
• The estimated positron density reached approximately 10^16 positrons/cm^3, a record high.

Conclusions:

• Ultraintense lasers interacting with gold targets are an effective method for generating high-density positron beams.
• The Bethe-Heitler process is the primary mechanism for positron production in this setup.
• The achieved positron density represents a significant advancement in laboratory-based particle generation.