BEBC

The Big European Bubble Chamber (BEBC) is a large size detector formerly used to study particle physics at CERN. The chamber body, a stainless-steel vessel, was filled with 35 cubic metres of superheated liquid hydrogen, liquid deuterium or a neon-hydrogen mixture, whose sensitivity was regulated by means of a movable piston weighing 2 tons. The liquids at typical operation temperatures around 27 K were placed under overpressure of about 5 atm. The piston expansion, synchronized with the charged particle beam crossing the chamber volume, caused a rapid pressure drop with in consequence the liquid reaching its boiling point During each expansion, charged particles ionized the atoms of the liquid as they passed through it and the energy deposited by them initiated boiling along their path leaving trails of tiny bubbles. These bubbles tracks were photographed by the five cameras mounted on top of the chamber. The stereo photographs were subsequently scanned and all events finally evaluated by a team of scientists. After each expansion, the pressure was increased again to stop the boiling. The bubble chamber was then ready again for a new cycle of particles beam exposure.

The conception and construction of giant bubble chambers such as Gargamelle and BEBC was based on the know-how acquired through the construction and operation of smaller bubble chambers such as the 30 cm hydrogen chamber, which came into operation at CERN in 1960, and followed four years later by the 2 m hydrogen chamber.

The BEBC project was launched in 1966 by CERN, France (Saclay) and Germany (DESY) and installed at CERN in the early 1970s. The chamber body was surrounded by the then largest superconducting solenoid magnet of two coils in Helmholtz arrangement. The magnet coils were fabricated at CERN using copper reinforced Niob-Titanium superconductor cable. The BEBC coils created a strong magnetic field of 3.5 T over the sensitive volume of the chamber. Thus, the fast charged particles passing through the chamber were bent in the magnetic field which provided information on their momentum.

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