Optical Measurements of the thickness of the Gallium Indium free surface jet for the SARAF beam dump and neutron source

The Soreq Applied Research Accelerator Facility (SARAF) is a proton/deuteron RF superconducting linear accelerator. Phase II of the project is underway and includes the development of the accelerator to its final specifications: energy of 40 MeV proton/deuteron, and a current of up to 5 mA. A beam dump and a neutron source will be required for the commissioning stage, daily operation, and basic physics experiments. A liquid metal target based on a high-velocity windowless gallium–indium jet has been designed to absorb a beam of 200 kW by generating a stable 6 mm-thick film flowing at a velocity of up to 5 m/s into a concave supporting wall (nozzle). The main goal of the present research was to demonstrate that the thickness and variations of the Ga–In flow satisfy the design requirement in the area corresponding to the beam footprint. This research also presents a novel method for optical non-contact measurements of the liquid Ga–In thickness by using a chromatic confocal sensor. The advantage of our system is that it uses an “off the shelf” non-expensive product, non-contact, very accurate, and with very high resolution. The results show that the average Ga–In thickness was 5.6 ± 0.3 mm at a flow speed of 5 m/s. These results are in agreement with the expected thickness of the nozzle.