6TiSCH is an emerging networking technology proposed by IETF for the Industrial Internet of Things. As a result of its standardization effort, IETF has proposed the so-called minimal 6TiSCH configuration, which sets the minimal requirements for building functional 6TiSCH networks. However, this minimal configuration provably leads to large synchronization times and, consequently, to a waste of energy every time a node desires to join the network. In this paper, in order to optimize this initial synchronization process, we study the effect of the channel scan period on the initial synchronization time and on the energy consumption. The scan period is the time a node spends on listening for network advertisements on a specific channel as it scans the available channels in the network. Our study includes the mathematical modeling and analysis of the initial synchronization process, its algorithmic representation as well as experiments in a 12-node testbed. The theoretical results demonstrate that by optimally setting the scan period, we can achieve an up to 48.37percent and 47.10percent reduction in the average initial synchronization time compared to the default scan periods of Contiki-NG and OpenWSN respectively. Both the algorithmic approach and the experiments exhibit almost identical results, thus, confirming the performance improvement. Furthermore, our experiments demonstrate an almost linear relation between the average initial synchronization time and the average energy consumption.