NUCLEATION IN BUBBLE CHAMBERS
A new approach is presented to the creation of vapor bubbles in superheated liquids by high-energy charged particles. A compilation is given of the theoretical work done on both spontaneous nucleation and nuclcation under the influence of charged particles. The processes are compared with another nucleation process, the condensation of supersaturated vapors. Some striking differences are demonstrated. It is seen to be plausible that nucleation in liquids through the action of charged particles is a thermal process, for which the liquid must be heated locally. The amount of heat necessary to create a bubble that can grow to visible size was calculated for a number of practical cases. The energies are 8.2 ev for helium, 12.0 ev for hydrogen and 256 ev for propane. It is shown that this amount of heat must be concentrated in an area with a diameter of about 10 nm at the beginning of the nucleation process. The non-occurrence of a relativistic increase in the bubble density---velocity curve supports the assumption that, at least in hydrogen, the bubbles are created by delta -electrons. In the case of helium a detailed calculation is given of the way in which a delta -electron transfers its energy to the liquid. It can be shown that direct heating of the liquid by electrons is only a minor effect, but that excitation and ionization can produce the necessary heat for bubble formation by their subsequent processes, deexcitation and recombination. In the presented model the liquid is treated as gas-like, only those effects which are observed in gaseous helium are incorporated in the mechanism. It is made clear that a single deexcitation or recombination event is not sufficient to create a bubble, but that a number of them have to cooperate. A discussion about bubble creation in hydrogen and in more complex liquids is presented. The influence of molecular effects, the possibility of collective excitations and the consequences of complex chemical behavior are estimated. It is seen to be plausible that the nucleation process takes place more easily in more complex liquids, because of the greater variety of ways in which the charged particles can transfer their energy to the liquid. Mention is made of the possibility that, in complex liquids, bubbles can be created by an excitation of lower atomic levels rather than by the production of delta -electrons. This may explain the occurrence of a relativistic rise in the bubble density-- velocity curve in liquids like freon. (auth)
- Research Organization:
- Universiteit, Amsterdam
- NSA Number:
- NSA-17-023773
- OSTI ID:
- 4709107
- Journal Information:
- Nucl. Instr. Methods, Vol. Vol: 22; Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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