September 30, 1882 – Birth of Hans Geiger, German physicist who developed the counter that bears his name

Hans Geiger

PhD in physics and mathematics from the University of Erlangen (Germany), collaborated with Ernest Rutherford at the University of Manchester (England).

In 1908, he built the first version of the particle detector and counter that bears his name together, indispensable in the identification of the nature of alpha particles as helium nuclei by Rutherford and himself.

This first Geiger counter consisted of a cylinder filled with gas at reduced pressure and an insulated wire through its axis, establishing a high potential difference between them. When an ion or an electron penetrates the tube, electrons are released from the atoms of the gas that fills the tube. Due to the positive voltage of the central wire, they are attracted to it, and in doing so they gain energy, collide with the atoms in the gas and release more electrons, until the process continues and a detectable current pulse is produced. With the right gas, the flow of electricity stops by itself or even the electrical circuit can help stop it.

Why is it called an accountant? This is because each particle that passes through it produces an identical pulse, allowing the particles to be counted. In the case of the Geiger counter, it only detected alpha particles.

In 1911, Geiger and Jon Mitchell Nuttall developed the Geiger-Nuttall Law and carried out a series of experiments that led to Rutherford's model of the atom. This law establishes the relationship between the decay constant of a radioactive isotope and the energy of the alpha particles they emit, that is, it is established that short-lived isotopes emit more energetic alpha particles than long-lived ones.

In 1912, already in Germany, he held the position of director of the Physics Research Laboratory in Berlin, and between 1925 and 1929, he became a professor at the University of Kiel (Germany), where his first graduating student was precisely Walther Muller. It is in 1928, when both developed a counter that allowed the detection of various types of ionizing radiation. It was a practical and relatively cheap instrument, the output signal from the tube required very little electronic processing (an advantage over other devices) and it became very popular as a portable radiation detector.

The current version of the counter was developed by physicist Sidney H. Liebson in 1947. This device lasts longer than the original Geiger instruments and requires a lower voltage.

If you want to know more about this scientist, click on the following link: Johannes (Hans) Geiger

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