Compact High-Flux X-Ray Source by Bursts of Femtosecond Laser Pulses
A collaborative effort by Light Conversion, Vilniaus universitetas (Vilnius University), and Center for Physical Sciences and Technology (FTMC) have demonstrated a compact high-flux X-ray source based on irradiation of solid targets by gigahertz and megahertz bursts of femtosecond laser pulses.
The simplicity and relative cost-effectiveness of the presented X-ray source makes it an attractive solution for future applications in ultrafast x-ray imaging and spectroscopy.
The paper documenting this research is entitled, “Compact high-flux X-ray source based on irradiation of solid targets by gigahertz and megahertz bursts of femtosecond laser pulses.”
Figure 1(a) shows the scheme of the experimental X-ray generation and detection setup. Laser radiation is delivered by solid-state femtosecond laser (Carbide, Light Conversion). Its average power output is 90 W, the minimum pulse duration is 240 fs (FWHM), a repetition rate can be adjusted from single-shot to 2 MHz (maximum average power and maximum pulse energy are achieved simultaneously at 100 kHz), and the central wavelength is 1030 nm. The laser beam quality parameter M2 was less than 1.2, and the focused laser beam spot size diameter was 25 µm (FWHM), resulting in ∼ 450 TW/cm2 driving intensity onto the target surface at 0.9 mJ pulse energy.
Figure 1(b) displays the schematic layout of pre-pulse generation with a variable delay time. BS: beam splitter; M: dielectric mirror; DL: delay line; λ/2: half-wave plate; BD: beam dump; PL: polarizer.
Figure 1(c) presents the typical spectrum of an X-ray radiation plasma source obtained d = 220 cm from the source for 60 seconds via Amptek X-123SDD spectrometer, with laser pulses of 100 kHz repetition rate and 0.9 mJ pulse packet energy (EPP = 0.08 mJ, EDR = 0.82 mJ and FPP = 11.8 J/cm2, FDR = 118 J/cm2 fluence on the target surface) using Fe, Cu, and Al targets and Al 22 µm foil before the spectrometer.
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