Liquid Hydrogen Bubble Chambers

After the first hydrocarbon bubble chambers were built by Donald Glaser in 1952, work was started at Chicago and Berkeley to find if liquid hydrogen could be used as the working fluid in a bubble chamber. In the fall of 1953, it was found by the Chicago group that superheated liquid hydrogen could be made to boil under the influence of ionizing radiation, but no tracks were observed. The observation of tracks at Berkeley a few months later completed the proof that hydrogen was a usable bubble chamber liquid. (Irradiated liquid nitrogen boils when superheated, but as of spring 1956 no one has seen tracks in liquid nitrogen.) In the past two years, the Chicago group has built several all-glass hydrogen chambers, the most recent of which is approximately 5.5 by 5.5 by 20 cm inside dimensions. Their chambers have been of the so-called clean variety (like Glaser's eariy ones), in which no boiling takes place unless ionizing particles aze present. They have used their latest chamber in an extensive study of the scattering of low-energy pions by protons.