Back in the middle of the 20th century, a bubble chamber was invented - a device that was actively used to observe microparticles. For the most part, it was used by physicists who observed the microworld. Even today, despite the enormous development of technology and the presence of various electronic sensors, students are shown photographs of particles made using bubbles.
About how the camera appeared
As already noted above, in the middle of the 20th century this invention appeared. And all due to the fact that physicists could not in any way investigate charged particles with existing detectors. By that time, everyone already knew what a proton, neutron, electron and positron are. In 1950, D. Glaser took up this issue. The scientist tried to use both chemical and physical reactions, electric and liquid, as well as solid transformations. But he decided to dwell on the liquid phenomenon, or more precisely, on the principle of overheating of the working mixture. The main requirements that Donald put forward to his invention are a high response speed, which allows you to capture a particle in a photograph at the right time. Of course, the bubble chamber and Wilson's chamber are somewhat similar. But there are a number of differences, which we, in fact, will discuss further.
Bubble chamber: principle of operation
As the working fluid, diethyl ether was used, which possessed such an advantage as a low price. In addition, it could easily be obtained in pure form. The bottom line was to heat this liquid to a boiling point (1400 degrees Celsius), and then cool to room temperature. At this time, radioactive material, such as cobalt, is brought in, after which, with an interval of about 60 seconds, the working fluid boils. Once a minute it was possible to capture the movement of particles in a photograph.
To show everything clearly, Glaser used two chambers made of refractory glass and filled with diethyl ether. The heating was carried out in an oil bath, and the pressure could be lowered using the handle. At this time, the camera started. On average, the frame rate was about 3000 per second. This made it possible to capture the movement of particles in vessels. Further bubble chamber was a little automated, but the principle of operation remained the same. Most often, a Geiger counter was used , which made it possible to track the appearance of radiation.
Bubble chamber: device
Now let's talk a bit about what this invention is. In most cases, this is a vessel that has several small windows. The cameras were filled with special fluid and placed in a magnetic field. Above atmospheric pressure has always been used. Sometimes a cryostat was used, which was necessary to cool the working fluid (RH) boiling at low temperatures. Immediately before the release of the radioactive elements from the accelerator, the pressure in the chambers was released and an overheated liquid was obtained. Everything that has a charge leaves bubbles with boiling liquid in its path. To carry out the reaction, only a fraction of a microsecond is sufficient. Within an instant, the bubbles became an order of magnitude larger. For illumination, a lamp and three cameras were turned on, with the help of which a stereo image was obtained.
The final stage of the experiment
At the final stage, a complex analysis of the trajectory and nature of the movement of charged radioactive particles was carried out. There are cases when photographs were taken for processing for several days, but they were processed for whole months. When a spiral was obtained, this indicated the passage of an electron. The so-called “forks” spoke of the presence of neutral particles. In most cases, based on the data of the obtained 3 photos, the trajectory of the movement of the elements was carefully measured. If the picture was completely restored, then a spatial picture could be created. At first, scientists were engaged in this, but such a study could take years. The situation changed with the advent of computers, which significantly accelerated the process.
About the benefits of using this type of camera
As noted above, the device on the principle of action is a bit like Wilson’s invention. But there are a number of undeniable advantages. The most significant advantage is the response speed, which with a high probability allows you to capture a phenomenon worthy of attention in a photograph.
Another plus is that high-density fluids are used as the working fluid. This greatly increases the chance that an expected event will occur in a given environment. What is the advantage of the bubble chamber, is that the cycle of its operation takes quite a bit of time. This parameter is simply a prerequisite for using the device in accelerators of various types. Superheated liquid can be obtained quickly enough, for this you only need to reduce the pressure in the system. Here, in principle, all the main advantages of this device.
A bit about the flaws
As was noted at the very beginning of this article, currently there is simply a huge number of different electronic sensors that allow you to find the right objects with high accuracy, select the right elements with high speed, and determine their spatial picture. It is in the lack of controllability that the main disadvantages of the bubble chamber are. As a rule, most of the results obtained are of no scientific interest, but it can take quite a while to discard unnecessary photos. Another minus is that the device is simply impossible to instantly start, in particular, this is due to the inertia of the working fluid and other physical parameters. In principle, we figured out the shortcomings, let's move on.
About the technical side
During the use of this method for detecting charged particles, a little more than 100 instances of bubble chambers were recorded. During this time, a wide variety of liquids were used, such as helium, hydrogen, freon, xenon, propane and others. The same applies to temperatures that began with ultralow and ended with room for xenon. "Gargamel" is the last bubble chamber, the scheme of which is not fundamentally different from others. But about 18 tons of freon were poured into her cells. This device made it possible to make a great discovery for those times - the interaction between neutral points. The largest specimen had a diameter of 4.5 meters. The device was designed to work with hydrogen. But the whole problem was that new accelerators were invented, which produced beams of radioactive particles with great speed, so no bubble chambers could cope anymore.
A few important points
It is worth paying attention to the fact that currently these cameras are no longer in use. Almost everyone wrote them off, but as it turned out, it was a premature decision. In 2002, new particles called pentacquarts were discovered using bubbles. But again, this is not the result of studies of the same year, but an elementary verification of photographs taken many years ago. This suggests that you can find something worthwhile from what has been done in the past.
Moreover, the computing power of modern technology is so great that it will take very little time to process each image. In principle, the effectiveness of this kind of track detector is currently quite low, so it is no longer advisable to use them, however, once obtained experimental data can be useful today.
Conclusion
Well, that’s all that can be said about what a bubble chamber is. The device diagram is quite simple, like all ingenious. It is worth saying a few words that the effectiveness of such devices largely depends on their size. The larger the camera, the higher the chance to discover something useful. Nevertheless, with an increase in size, the price of materials and working fluid increases, which in large sizes has an impressive cost. Now you know what a bubble chamber is, the principle of operation of which is based on overheating of a liquid. This effect has been studied along and across, therefore, electronic sensors that win in all respects are considered more relevant at present.