Bubble chamber facts
- Invented when: 1952
- Invented by: Donald A. Glaser
- What it does: detects charged particles moving through the detector
Bubble chambers are a really cool piece of technology. They allow us to observe elementary particles by eye (size of proton is about 1e-15 m). Even though we can’t actually see the particle, we can see its trajectory. Bubble chamber (used in a magnetic field) can measure the particle’s speed, mass and charge.
Apparently, some of the earliest prototypes used beer as a medium which might have given the bubble chamber its name. I would like to know what prompted Donald A. Glaser to pour some beer into his newly constructed detector. Did he really just not want to share it with some colleagues? Anyway, he soon realised that liquid hydrogen will do much better and his lab could stop smelling like a pub.
The basic principle of bubble chamber is a container filled with a liquid at high pressure above its usual boiling temperature (most commonly used liquid hydrogen). When an electrically charged particle enters the detector, the detector volume is quickly increased, decreasing the pressure at the same time which leads to the liquid entering a superheated stage. A charged particle ionises the superheated liquid (separates the positive and negative charges of an atom) and the ionisation boils off some of the liquid, bubbles appear. Because the detector container is still expanding, the bubbles also increase in size and can be photographed from a camera facing the detector.
Bubble chambers were the successors of the cloud chambers. They were used in the discovery of weak neutral currents (ref) which confirmed the electroweak theory and later led to the discovery of the W and Z bosons. There are some more recent experiment using this technology such as COUPP, PICASSO and PICO. These are all used for detecting dark matter, the mysterious part of our universe that we know exists but cannot seem to find what it is composed of. There are different detector technologies also hoping to discover dark matter. We can just wait and see which detector will be the one.
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