Absolutely calibrated scintillator stack spectrometer for high-intensity laser-plasma experiments

Real-time online diagnostics are essential for high-repetition-rate laser-plasma experiments, offering clear advantages over traditional, manually exchanged offline detectors, such as imaging plates, by eliminating the shot-to-shot processing time. Scintillator based detectors are widely used to measure bremsstrahlung radiation from laser-matter interactions, enabling the characterization of hot-electron distributions. In this study, we present absolute calibration of a lutetium-yttrium oxyorthosilicate crystal-based multilayer scintillator stack spectrometer performed at the MT25 microtron facility in Prague. Bremsstrahlung radiation was generated by irradiating a tungsten converter with monoenergetic electron beams in the energy range between 5 MeV and 22 MeV. The response of the individual crystal was measured and compared with the energy deposition calculated using the Fluktuierende Kaskade (FLUKA) Monte Carlo simulation. A linear correlation between signal response and energy deposition was obtained for all crystals within the experimental uncertainty, confirming detector linearity with the calibration factor 0.014 ± 0.002 ADU/keV (where ADU denotes the analog-to-digital unit). This calibration enables quantitative, real-time measurement of bremsstrahlung spectra and is valuable for particle acceleration, high-intensity laser-plasma experiments, laboratory astrophysics, warm dense matter, and inertial confinement fusion studies.