A long-lifetime and maintenance-free atomic cell for laser spectroscopy experiment of 6Li atoms

We report a hot pipe for a laser spectroscopy experiment of lithium atoms, which can work at a relatively low temperature of ∼280 °C for observing a nearly lifetime-limited laser spectrum of D2 line transitions of 6Li atoms. The spectrum has a high signal-to-noise ratio and serves as a stable reference for laser frequency stabilization. The main structure of the pipe includes an 80-cm-long stainless steel tube with a 19.05 mm inner diameter and several standard vacuum components, leading to an overall axial length of ∼1.1 m. Instead of filling noble atomic gas to protect the viewports from contamination, we find that the residual gas around both windows can act as buffer gas, and almost no contamination is discernible after over four years of operation. Furthermore, the pipe exhibits characteristics of free maintenance and simple operation, as no vacuum pumping process is needed after preparation. Even when being idle in a cold state for months, the vacuum can be recovered by heating the pipe to a higher temperature above the melting point (∼181 °C) of bulk lithium for a day.