for five photomultipliers. The light source was a modified pulsed argon- ion 

 laser and beam collimator in its own pressure housing and located at one end of 

 the main beam. At the other end, a separate pressure housing holds an image 

 dissector tube, focus and deflection coils. By sweeping the dissector at a 

 rate (4 Hz) much slower than the laser pulse rate (400 Hz) continuous sweeps of 

 the light flux distribution on a plane normal to the beam were obtained. 



The beam housing was in three parts with the electronic and optical components 

 housed in the transmitter or received subsections. The center section serves 

 as a spacer and was either 12", 6', or 3' in length. The instrument can be 

 assembled for measurement with beam lengths of from 3' (no spacer) to 24' (all 

 spacers) in 3' steps. All beam housing components were of 6061T6 aluminum 

 alloy, hard black anodized. The aluminum was chosen to optimize requirements 

 of weight, external pressure capability, stiffness, corrosion, and availability. 

 Final instrument weight with the 12' spacer was about 550 lbs. and the instru- 

 ment was capable of 500 ft depth. 



The final assembly is shown in Figure 3 where an assembled instrument is shown 

 as located on the boat used for the TEKTITE II experiments. The laser beam has 

 about 5 milliradian divergence. This was unacceptable for the measurements 

 planned and a beam collimator was added to provide a parallel beam. The final 

 beam output was through a flat window in the laser housing. 



VII-35 



