X-Ray Proportional Counters

Jun 21

A proportional counter is a gaseous ionization detector that measures ionizing radiation particles. The detector's main characteristic is its capacity to quantify the energy of incoming radiation by creating a proportionate detector output; thus the name. It is extensively utilized in situations where the energy levels of incoming radiation must be determined, such as in the distinction of alpha and beta particles or precise X-ray dosage monitoring.

A proportional counter combines the mechanics of a Geiger–Müller tube and an ionization chamber, operating at a voltage range in between. The x-ray proportional counters operating voltage can be shown in graphs.

In a proportional counter, the fill gas is an inert gas that is ionized by incoming radiation, and the quench gas is a combination of 90% argon and 10% methane known as P-10. An ionizing particle enters the gas and ionizes an inert gas atom, producing an electron and a positively charged ion known as a "ion pair." The number of ion pairs left behind by the charged particle as it goes through the chamber is proportional to the particle's energy if it is totally halted inside the gas. 30,000 ion pairs are produced by a 1 MeV halted particle on average.

Detector Construction

The proportional counter we chose is the Russian-made SI-6R type, as shown in the side picture. Technically, it has the following features:

182 mm long
37mm in diameter
1700 To 1900 V (working voltage)

The counter is widely accessible on the internet, however there are no more technical information or application examples.
Because it operates in the proportional zone rather than the discharge zone, the proportional counter has a functional scheme that is very similar to that of a standard Geiger tube. However, the operating voltage is lower.
The pulse is extracted with the help of a high-voltage generator, a bias resistor, and a coupling capacitor. The pulse may then be read out on a load resistor or transmitted via a chain of amplification and comparison to improve the S/N ratio and allow for digital counting system acquisition. High-value bias resistors, such as 100 M, are recommended for the corona tube's properties.

Conclusions

The energy resolution of our proposed counter is rather inadequate, as shown by the tests conducted. Instead, it has a great sensitivity; in fact, the modest tritium emission still registers a stunning 77 CPS. As a result, the detector is especially well suited to detecting low-energy X-rays.