Our experiments combine high-power lasers, vacuum systems, and in-situ diagnostics to study vaporization and reduction of lunar regolith simulants and aluminum-oxide.
The continuous-wave fiber laser MFSC 1500 CW by Maxphotonics (up to 1.5 kW) is used to perform regolith vaporization and alumina reduction experiments. The beam diameter and intensity can be adjusted to study different processing regimes from melting to explosive boiling and ablation.
The continuous-wave fiber laser DLM 200 by IPG (up to 200 W) is used to heat additional equipment inside the vacuum chamber such as the condensation plate to study temperature dependent aluminum condensation.
The main vacuum chamber (20 L) hosts our regolith simulants and alumina samples. It allows experiments both in high vacuum and in controlled background gases such as argon, nitrogen, as well as hydrogen. The vacuum is created by an oil rotary vacuum pump (ULVAC VD401).
We apply radiometric thermometry, a contactless temperature measurement method, to estimate the sample temperature inside the chamber. We collect the continuum spectrum through a lens system, couple into optical fibers and feed it into the spectrometer EPP2000 by StellarNet Inc. at band of 200 nm to 1000 nm with a spectral resolution of 0.5 nm. We apply Blackbody Fit, Ratio Pyrometry, and Multiwavelength Pyrometry to estimate the sample temperature. Furthermore, we capture the optical emission spectrum of laser ablation plumes to identify the vapor composition.
Laser power, sample temperature, chamber pressure, cooling water, and diagnostics are monitored and recorded during each experiment. This enables reproducible operation and detailed post-processing. We have developed a code in LabVIEW that enables the automatic adjustment of the laser power to achieve a constant surface temperature on the sample using a PID mechanism.