Experimental result of the laser in vessel viewing and ranging system (IVVS) for ITER

A prototype of laser in vessel viewing and ranging system (IVVS) was developed at ENEA laboratories. It is based on an amplitude modulated (AM) laser radar specifically designed to withstand the severe ITER conditions. The system is able to perform viewing and ranging of in-vessel surfaces at the same time. The most critical part part of the system, the fiber optic optical encoder, has been successfully tested by SCK-CEN laboratories in Mol under radiation at 15 KGy/h up to a dose of 2.47 MGy. The 15 KGy/h was estimated as a likely condition to be faced by the probe for unscheduled inspection (starting only a few hours after plasma). A series of viewing and ranging tests has been performed with the system to evaluate its main characteristics which comprise auto-illumination, large field of view, zoom capability, range measurement capability and high dynamic range. A test has been performed to determine the ranging capability of the system using a testing sample made of three groups of staircases of 10,5 and 1 mm of step. A standard deviation of the range measurement of 320 µm with a 3 ms stay time of the laser beam was reached comparing the measurement with the CAD representation of the sample.