- Bubble chamber
A bubble chamber is a vessel filled with a superheated transparent
liquid (most oftenliquid hydrogen ) used to detect electrically charged particles moving through it. It was invented in1952 byDonald A. Glaser , for which he was awarded the 1960Nobel Prize in Physics .Anecdotally, Glaser was inspired by the bubbles in a glass of
beer . He also did experiments using beer to fill earlyprototype s.Function and use
The bubble chamber is similar to a
cloud chamber in application and basic principle. It is normally made by filling a large cylinder with a liquid heated to just below itsboiling point . As particles enter the chamber, apiston suddenly decreases its pressure, and the liquid enters into a superheated,metastable phase. Charged particles create an ionization track, around which the liquid vaporizes, forming microscopicbubble s. Bubble density around a track is proportional to a particle's energy loss.Bubbles grow in size as the chamber expands, until they are large enough to be seen or photographed. Several cameras are mounted around it, allowing a three-dimensional image of an event to be captured. Bubble chambers with resolutions down to a few μm have been operated.
The whole chamber is subject to a constant magnetic field, which causes charged particles to travel in helical paths whose radius is determined by their
charge-to-mass ratio s. Given that for all known charged long-lived subatomic particles, the magnitude of their charge is that of anelectron , their radius of curvature is thus proportional to theirmomentum .Recently, bubble chambers have been used in research on
WIMP s. [ [http://www-coupp.fnal.gov/ COUPP web site] ]Drawbacks
Although bubble chambers were very successful in the past, they are of only limited use in current very-high-energy experiments, for a variety of reasons:
* The need for a photographic readout rather than three-dimensional electronic data makes it less convenient, especially in experiments which must be reset, repeated and analyzed many times.
* The superheated phase must be ready at the precise moment of collision, which complicates the detection of short-lived particles.
* Bubble chambers are neither large nor massive enough to analyze high-energy collisions, where all products should be contained inside the detector.
* The high-energy particles' path radii may be too large to allow the precise estimation of momentum in a relatively small chamber.Due to these issues, bubble chambers have largely been replaced by
wire chamber s, which allow particle energies to be measured at the same time. Another alternative technique is thespark chamber .Notes
External articles and references
* [http://teachers.web.cern.ch/teachers/archiv/HST2005/bubble_chambers/BCwebsite/index.htm General Information]
* cite journal
author = Donald A. Glaser
title = Some Effects of Ionizing Radiation on the Formation of Bubbles in Liquids
journal = Phys. Rev.
volume = 87
issue = 4
pages = 665–665
year = 1952
url = http://link.aps.org/abstract/PR/v87/p665
doi = 10.1103/PhysRev.87.665
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