A design of a velocimeter using a radioactive positron emitting source without lead collimators

A possible method of eliminating lead collimators without loss of spatial accuracy in the velocity or position measurement of a positron active source is described here, and the accuracies of this and the lead collimator method are calculated and compared. The theoretical calculations have been tested by laboratory measurements, It is shown that at low source activities the method described is superior to the conventional lead collimator method. (Auth.)