Development of a Motorized Telescope for the Pulse-Burst Laser System

The Pulse-Burst Laser System (PBLS) has been installed and commissioned on NSTX-U to measure the temperature and density of particles in the plasma. This system is part of the NSTX-U Thomson scattering system and will be operated at 30 Hz continuously, and 1 kHz and 10 kHz in burst mode. To control the beam divergence, a telescope is used after the oscillator in the laser cavity. Here, we develop and model a motorized telescope to enable the control of the beam divergence between plasma discharges. The design constraints are minimal footprint (12 cm by 8 cm), reduction of friction on the collar where the lens translates, and the accuracy of the positioning of lens (sub-millimeter over 25-30 mm travel) by the motorized system. In this presentation we will discuss the design parameters, the methodology used in developing the motorized system and the results from testing the prototype.