• A typical bubble chamber is filled with liquid hydrogen (forming a very simple nuclear target) at a temperature above the normal boiling point but held under a pressure of about 10 atmospheres by a large piston to prevent boiling.

 
• When particles have passed, and possibly interacted in the chamber, the piston is moved to reduce the pressure, allowing bubbles to develop along particle tracks.

 
• After about 3 milliseconds have elapsed for bubbles to grow, the tracks are photographed using flash photography.  Several cameras provide stereo views of the tracks.

 
• The piston is then moved back to recompress the liquid and collapse the bubbles before boiling can occur.

Features of bubble chambers include

• this is a true 3-D detector, rather than one providing a set of projections;
• an extremely good spatial resolution (~0.1 mm in large chambers, even better in specialised small chambers);
• the bubble density is proportional to the primary ionisation
• this leads to a Poisson distribution, rather than a Landau distribution with its long tail,
• particle identification can thus be achieved, separating pions and kaons up to ~0.9 GeV/c, and pions and protons up to ~1.6 GeV/c;
• the chamber may be mounted in a magnetic field, allowing accurate momentum determination
At high momentum, the error is dominated by uncertainties in the optical constants, distortions, etc.;
At low momentum, it is dominated by multiple Coulomb scattering as the particle passes through the dense liquid.

Enhancements

• Holographic recording of the bubble chamber can lead to a resolution as good as 6 microns in small chambers (used for studying very short-lived particles such as B-mesons).
• Other liquids can also be used, to provide an alternative target.  E.g. if deuterium is used, interactions with both protons and neutrons are possible.
• Heavier liquids are useful for detecting photons, but may not be appropriate as the primary target.  With a "track sensitive target", a central region of liquid hydrogen in a transparent box or bag is surrounded by, for example, neon to convert photons into e⁺e⁻ pairs.  (In practice, a mixture of liquids may be required to maintain appropriate boiling temperatures and pressures in the two compartments.)
• Additional external detectors can be used to trigger the flash and film advance, to select particular types of events.

Drawbacks

• Film measurement and event reconstruction is slow, even with semi-automatic measuring machines (such as Sweepniks, spiral readers, etc.).
  (This typically limits experiments to 10⁵ to 10⁶ events.)
• The sensitive period is quite long, so the beam intensity must be limited.
• Though the camera can be triggered, the chamber itself cannot.  A typical cycling rate is about 10 Hz or less (though it can be faster for very small chambers), normally matched to the pulsed beam extraction rate from the accelerator.
• For the above reasons, it is difficult to search for and study very rare events.
• The liquid in the chamber acts as both target and detector, so bubble chambers cannot be used with modern colliding-beam machines.

A careful study of this photograph reveals the reaction to be  ,  where

the slow proton is identifed by its heavier ionisation,

the K⁰ subsequently decays into a pair of charged pions,

the antineutron annihilates with a proton a short distance downstream from the primary interaction, to produce three charged pions,

the neutral pion decays into two photons, which (unusually for a hydrogen chamber) both convert into e⁺e⁻ pairs,

(external particle detectors were used to identify the charged kaon).