What is the limitation of ionization chamber?

Detectors in the ionization region operate at a low electric field strength, so gas multiplication does not occur. The collected load (output signal) is independent of the applied voltage. Ion chambers have a good, uniform response to radiation over a wide range of energies and are the preferred medium for measuring high levels of gamma radiation. They are widely used in the nuclear power industry, research laboratories, radiography, radiobiology and environmental monitoring.

Multi-cavity ionization chambers can measure the intensity of the radiation beam in several different regions, providing information on the symmetry and flatness of the beam. Ionization chambers are widely used in the nuclear industry, as they provide an output proportional to the radiation dose. They find wide use in situations where a constant high dose rate is measured, as they have a longer service life than standard Geiger-Müller tubes, which suffer from gas breakage. and are generally limited to a lifetime of approximately 1011 counting events.

This study is a systematic investigation that explores the feasibility of employing currently available ionization chambers for future FLASH and VHEE radiation therapy in a wide range of high dose per pulse values. Proportional meters are more sensitive than ionization chambers and are suitable for measurements in low-intensity radiation fields. Small ventilated air ionization chambers with a volume of 0.01 to 0.3 cm3 are considered suitable for measuring field parameters up to 2 cm × 2 cm. An ionization chamber and an electrometer require calibration before use and, with a triaxial connection cable, tools are required for calibration of the radiation beam.

They act as solid-state ionization chambers when exposed to radiation and, like scintillation detectors, belong to the class of solid-state detectors. After exposure to radiation for a period of time, the ionization produced in the chamber discharges the condenser; the exposure (or air kerma) is proportional to the discharge, which can be read directly against the light through a built-in eyepiece. The transmission ionization chamber generally consists of layers of PMMA coated with conductive material. Ionization chambers with transparent X-ray plates made of aluminized plastic or thin metal mesh are used for the detection of fluorescent radiation.

In medical physics and radiation therapy, ionization chambers are used to ensure that the dose delivered from a therapy unit or radiopharmaceutical is as intended. The radiobiological data available so far on the FLASH effect indicate that better preservation of normal tissues is obtained by administering a lower number of pulses and, therefore, a higher dose per pulse, which would lower the collection efficiency in the ionization chambers. Proportional counters work on successive ionization by collision between ions and gas molecules (charge multiplication); in the proportional region, amplification occurs (approximately 103-104 times) so that the primary ions obtain enough energy in the vicinity of the thin central electrode to cause additional ionization in the detector. Multi-channel xenon ionization chambers pressurized to 20 bar were developed in the 1970s and 1980s (Drost and Fenster, 1982, 198) and were successfully used in several clinical computed tomography (CT) scanners, such as the Philips 768-channel LX CT, the General Electric Model CT 90000 Series II, and the Siemens Model Somatom CR.

When ionization chambers are not the most appropriate detectors for side profile measurements, an alternative is to use 2D detectors such as scintillation detectors14,15 and Gafchromic films. Radiation indicators are considered, whereas ionization chambers are used for more quantitative measurements. .

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