Practical primary thermometry via alkali-metal-vapour Doppler broadening

Doppler-broadening thermometry (DBT) can be used as a calibration-free primary reference suitable for practical applications, e.g. reliably measuring temperatures over long periods of time in environments where sensor retrieval is impractical. We report on our proof-of-concept investigations into DBT with alkali metal vapour cells, with a particular focus on both absorption and frequency accuracy during scans. We reach sub-kelvin temperature accuracy, and experimental absorption fit residuals below $0.05\mathrm{\%}$, in a simple setup. The outlook for portable, practical devices is bright, with clear prospects for future improvement.