primary rays

pri·mar·y rays

1. cosmic rays in the form in which they first strike the atmosphere;
2. x-rays generated at the focal spot of the tube. Synonym(s): direct rays
References in periodicals archive ?
The Philippine flag has two horizontal bands of blue and red with a white equilateral triangle based at the hoist side and a golden yellow sun in the centre of the triangle with eight primary rays - each containing three individual rays.
2I) with smooth primary rays and micro-rough secondary rays numbering 1-4, often with branching retricted to one axis; discohexaster (or tylohexasters) with short smooth primary rays, each bearing 5 rough secondary rays terminating in a small cap with 4-6 marginal spines (Fig.