Bose-Einstein condensation (BEC) is a powerful tool for a wide range of research activities, a large fraction of which are related to quantum simulations [1][2][3][4][5] . Various problems may benefit from different atomic species, but cooling down novel species interesting for quantum simulations to BEC temperatures requires a substantial amount of optimization and is usually considered as a hard experimental task [6][7][8][9][10][11][12] . In this work, we implemented the Bayesian machine learning technique 13 to optimize the evaporative cooling of thulium atoms and achieved BEC in an optical dipole trap operating near 532 nm. The developed approach could be used to cool down other novel atomic species to quantum degeneracy without additional studies of their properties.For a number of problems in quantum simulations, long-range interactions are of great interest 2 . To address this demand, lanthanide atoms such as erbium and dysprosium were cooled down to quantum degeneracy and successfully used for quantum simulations [3][4][5] . Thulium also belongs to the lanthanide series of chemical elements, but compared to previously cooled Er and Dy, it has only one hole in the fshell. This leads to a slightly smaller dipole moment in the ground state of B 4 , but thulium has a simpler level structure and a less dense Fano-Feshbach resonances spectrum, thus simplifying the control of the

Here, we report on the observation of a random to chaotic temperature transition in the spacing of Fano-Feshbach resonances in the ultracold polarized gas of thulium atoms. This transition is due to the appearance of so-called d -resonances, which are not accessible at low temperatures, in the spectra at high temperatures, which drastically changes thulium's overall resonance statistic. In addition to this statistical change, it has been observed that s -and d -resonances experience quite different temperature shifts: s -resonances experience almost no shift with the temperature, while d -resonances experience an obvious positive shift. In addition, careful analysis of the broad Fano-Feshbach resonances enabled the determination of the sign of thulium's background scattering length. A rethermalization experiment made it possible to estimate a length value of 144 38 a.u. bg a    . This proves