3Heproportionalrör

3Heproportionalrör, also known as 3He proportional counters, are gas-filled radiation detectors. They are specifically designed to detect and measure neutrons. The key component is a tube filled with a mixture of helium-3 (³He) gas and a counting gas, typically a noble gas like argon, often with a small amount of a quencher like methane. When a neutron enters the proportional counter, it interacts with a helium-3 nucleus. This interaction results in a nuclear reaction where the neutron is absorbed by the helium-3 nucleus, producing a proton and a tritium nucleus. This charged particle pair then ionizes the counting gas within the tube. An electric field is applied between a central anode wire and the outer cathode wall of the tube. The ionization electrons are accelerated towards the anode, causing further ionization in a process called gas amplification. This creates a measurable electrical pulse. The size of this pulse is proportional to the energy deposited by the initial interaction, allowing for energy spectrometry. The efficiency of 3Heproportionalrör for detecting neutrons is high due to the large neutron capture cross-section of helium-3. These detectors find applications in various fields, including nuclear physics research, security screening for illicit nuclear materials, and neutron radiography. Their ability to detect neutrons with high efficiency and provide some energy information makes them valuable tools in scientific and industrial settings.