Performance of a Rapid Cycling Hydrogen Bubble Chamber

A small hydrogen bubble chamber consisting of a convoluted bellows and driven by a loudspeaker-like coil expansion system was developed and tested to cycling rates of 90 Hz. (Submitted to Nucl. Instr . and Methods. ) * Work performed under the auspices of the U.S. Atomic Energy Commission. Present theory and research 192 indicate that under fairly conventional operating conditions in a hydrogen chamber, track bubbles can be grown to visibility in about 0.25 millisecond, and completely condensed in roughly 4 to 5 times the growth period. The only basic time limit on expansion and recompression is the time required for a pressure wave to cross the chamber at the velocity of sound, which is approximately 1 meter per millisecond in liquid hydrogen. Therefore based solely on these theoretical limitations even a large chamber should have an upper limit of several hundred cycles per second. Our approach was to investigate one class of rapid expansion system: the electromagnetic coil in a dc magnet, available commercially as a vibration table. All initial tests were made on a small cylindrical chamber 5 cm in diameter and 5 cm deep. The small volume effectively removes any refrigeration restrictions or limitations resulting from power requirements of the exL pansion system, and allowed us to concentrate on conditions specifically , associated with fast cycling rates. Figure 1 is an assembly drawing of the entire system. Pertinent details are : 1. The chamber body consists of a multiple convolution bellows3with a wall thickness of 0.04 cm, immersed in a bath of liquid hydrogen. This takes maximum advantage of the refrigeration system and reduces temperature variations to a minimum with the chamber. The original bellows has undergone several million cycles without failure.