Alterations Indicated by Test 



Since sand transport is rapid in the surf area, the surveys need to be 

 done in the shortest time period possible. Data will be useful only if 

 the data collection period is short compared with the time required for 

 the tracer pattern to develop. Our present accumulation period is 10 sec. 

 Since the detector surveys a strip 2 ft wide, at a tow speed of 3 "to 5 

 fps the radiation data are averaged over an area of 60 to 100 ft . We 

 believe that this area is too large and are therefore modifying the sys- 

 tem to print out every second. This will permit a larger survey in a 

 much shorter time span. Models of experiments indicate that this survey 

 time will be a definite improvement. 



The photomultiplier tubes will be changed to high-shock-resistant tubes. 

 An electromechanical cable will be purchased and adapted to the survey 

 system. This cable will make it possible to use a power winch and drum 

 to raise and lower the detector assembly. Slight modifications and ad- 

 ditions will be made to accommodate multiple photopeaks . 



C- 19 



