The following is an archive film from British Pathé:
According to description by British Pathé, the video starts with Hungarian title. The next scene depicts people walking past GV Academy of Science building in Debrecen, Hungary. This is followed by various shots of Professor Alexander Szalay and his colleague Julius Csiky working on experiments in laboratory. They were working on the existence of the neutrino within the atom (sic.). They are creating atomic explosions in the Wilson fog (sic.) chamber.
(Lav.) Old record suggests that material dates from around 29/03/1957.
The information was cross-checked with the webpage by Hungarian Academy of Science; It turns out Alaxander Szalay was the founding director of the institute for nuclear research in Hungary. His studies in neutrino experiments laid groundwork in modern physics. Full note on professor Alaxander Szalay's work are available on the webpage.
Consider a pure beta decay; conversation of momentum should result in recoil nucleus and the emitted particle part ways linearly at 180 degrees. If neutrinos exist with non-zero mass and carries some of the energy from the radioactive decay, then both recoil nucleus and the beta particle must part ways at angle less than 180 degrees to preserve the conservation.
To prove neutrinos exist during beta decay, they chose to observe the radioisotope helium-6 in a cloud chamber because:
1. It is a pure (99.99 %) beta emitter with relatively long half-life of 807 ms. (less contamination, last longer)
2. It is gaseous. (Tracks of recoil atom can be seen and not "hidden" in solid sources.)
3. It has a large decay energy of 3.6 MeV. (plenty of energy for neutrinos to "carry away" if it exists)
The following stereo photographs seems to be the outcome of the experiment as was authored by J. Csikai:
The shorter track is the recoil nucleus (after He-6 has decayed). The beta track, energy, and parting angle are indicated. The stereoscopic photos (24° angle setup as shown in the British Pathé video) clearly shows the "missing impulse" carried away by the neutrino.
REFERENCE
J. Csikai, "Photographic Evidence for the Existence of Neutrino", Il Nuovo Cimento, 5(4), 1957
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