In the realm of energy research, understanding the behavior of radiation detectors is crucial for various applications, including nuclear power and radiation therapy. A team of researchers from the National Metrology Institute of Germany (PTB) and other institutions has delved into the performance of commercially available ionization chambers (ICs) when exposed to ultra-high dose per pulse (DPP) radiation. The researchers—José Paz-Martín, Andreas Schüller, Araceli Gago-Arias, Juan Pardo-Montero, and Faustino Gómez—have published their findings in a study that sheds light on the charge collection efficiency (CCE) of these devices under extreme conditions.
Ionization chambers are essential tools for measuring radiation dose, but their accuracy can be compromised when exposed to ultra-high DPP. The researchers investigated two types of PinPoint ionization chambers, the PP3D and PP models, using an ultra-high-DPP reference electron beam with an energy of 20 MeV and DPPs ranging from 0.1 Gy to 9.3 Gy. They varied the bias voltage supplied to the ICs between +/- 200 V and +/- 500 V and recorded the time-resolved signal of the ICs using an oscilloscope. To simulate the response of the chambers, the team developed a novel finite element code capable of simulating 1D and 2D geometries.
The study revealed that thimble ICs exposed to ultra-high-DPP exhibit a significant polarity effect due to the different distribution and recombination of charge carriers. The PP model, despite having a similar sensitive volume to the PP3D, showed a greater CCE due to its smaller external radius. The researchers found that a numerical model based on the finite element method could accurately reproduce the actual CCE for these chambers. For the PP3D, including the guard ring in the simulation geometry was mandatory to obtain accurate results. The findings suggest that thimble ICs should be used with caution at large DPPs due to their substantial polarity effect.
This research, published in the journal “Physics in Medicine & Biology,” provides valuable insights into the behavior of ionization chambers under extreme radiation conditions. For the energy sector, particularly in nuclear power plants and radiation therapy, understanding these behaviors is crucial for ensuring accurate dose measurements and maintaining safety standards. The developed numerical model offers a powerful tool for simulating and predicting the performance of ionization chambers, thereby enhancing their reliability in high-dose applications.
This article is based on research available at arXiv.