After three years of disappointment, the staff of the Cambridge Electron Accelerator is close to winning funds for what could be the most significant physics research ever done there.

A $650,000 grant for the research has been approved by the U.S. Atomic Energy Commission, it was reported in Washington last weekend. President Johnson will probably include it in the new Federal budget he presents to Congress today.

The grant would support attempts by Harvard and M.I.T. scientists to test the basic laws of physics by determining, for example, the actual structure of a sub-atomic particle.

If the request wins quick Congressional approval the powerful new equipment needed for the study could be set up by the spring of 1967, Robert Cummings, CEA assistant director, said yesterday.

The equipment was designed by CEA staff members last year, after three earlier designs had been rejected as too costly by the Atomic Energy Commission, which funds all CEA projects.

All the designs were attempts to produce the raw materials of the study -- the photographed tracks of thousands of collisions between two moving particles, an electron and an positron. Normal accelerator experiments send one particle into a stationary target.

Last year, the CEA turned to planning a cheaper alternative -- converting its present accelerator, with its one stream of electrons, into a tool for high-energy physics.

The result was a proposal last summer for a $650,000 "positron injector" which would send a stream of positrons into the accelerator in the opposite direction. The two streams could be made to collide at a given point.

Although the Atomic Energy Commission is believed to have approved the injector proposal, lit is reported to have cut $350,000 that the CEA requested for other improvements.