Test:Fox; Date:February 6 1951; Fox was a concept proof test. Test device code named Freddie used composite core in D type core. Predicted yield was 34 kt. As you can see the actual
yield fell quite short of the prediction. At the time of this test the cores used in Freddie wre already being delpoyed in US armed forces.
My sincere gratitude to Los Alamos National Laboratory guys who finally identified this photo as Fox. The reason this picture looks so unusual is double exposure. According to LANL folks:
Evidently the camera first took a "snap" of the fireball, and then a second frame with a much longer exposure which depicts the rising fireball as a streak image.
If you have something interesting regarding this test please Contact me.