High-energy differential-filtering photon spectrometer for ultraintense laser-matter interactions

Area of Science:

• High energy density physics
• Laser-driven X-ray generation
• Plasma physics

Background:

• Petawatt-class lasers produce abundant ultrahigh-energy X-rays (0.1-1 MeV).
• Spectroscopy in this range is challenging due to the long photon mean free path.
• Existing methods struggle with accurate spectral reconstruction in laser-matter interactions.

Purpose of the Study:

• To develop a novel spectrometer for measuring high-energy bremsstrahlung emission tails.
• To enable accurate X-ray spectroscopy in high energy density, short-pulse laser-matter interaction experiments.
• To reduce systematic errors in spectral reconstruction using a unique filter design.

Main Methods:

• Development of a novel geometry step filter with a grid design.
• Utilizing the filter for independent determination of local background.
• Application of the spectrometer to measure X-ray spectra under various laser and target conditions near 1 × 10^18 W/cm^2.
• Fitting single-exponential bremsstrahlung spectra to the measured data.

Main Results:

• Successfully measured high-energy bremsstrahlung emission tails.
• Demonstrated reduction of systematic errors through local background determination.
• Observed that photon temperature increases with laser pulse duration for a fixed laser intensity.
• Characterized X-ray spectra for different laser and target parameters.

Conclusions:

• The novel step filter spectrometer is effective for ultrahigh-energy X-ray measurements.
• The independent background determination significantly improves spectral accuracy.
• Laser pulse duration is a key parameter influencing photon temperature in these interactions.
• The findings advance diagnostics for high energy density physics experiments.