Liquid-Filled Ionization Chambers


Combining the advantages of air-filled ion chambers and
solid state detectors


How they work

Liquid-filled ionization chambers work according to the same principles as conventional air-filled ionization chambers: They consist basically of two conducting electrodes in a sealed container filled with a suitable liquid. Ionizing radiation creates positive and negative charge carriers which move in opposite directions, thereby producing a current which can be measured by an electrometer (see Fig. 2).

The liquid filling has a density roughly 1000 times greater than air as used in air-filled ion chambers (Fig. 1). It must be highly insultating to avoid leakage currents. Typical polarizing voltages are in the range of  400 - 1000 V.

 

The advantages they offer for use in high-radiation dosimetry   

  • High spatial resolution and strong signal
    Due to the higher ionization density of liquids compared to air, liquid ion chambers have a very small sensitive volume and still yield a high response.

  • Good energy response in the keV-range
    The response to low energy scattered photons is almost as water equivalent as for diamond detectors.

  • Very good energy response in the MeV-range
    The ratio of the mass stopping power to water varies only by 4.5 % in the range from 0.1 to 20 MeV whereas diamond and air vary by 2 % and 16 % respectively.

  • No air-density correction needed
    Liquids can be considered as incompressible compared to air.

  • Almost negligible directional dependence
    Contrary to diodes,  liquid-filled ion chambers show a very low directional dependence.

  • Long-term stability
    Ionization chambers are known to be stable over a long period of time. Compared to diodes, the liquid filling is less prone to ageing or degradation (see publication on long-term stability of liquid ionization chambers by Jalil Bahar-Gogani et al. listed on the right).

  • Made of water equivalent materials
Klicken um Bild zu vergrößern
Fig. 1: Basic principle of operation of an air-filled ion chamber
Klicken um Bild zu vergrößern
Fig. 2: Basic principle of operation of a liquid-filled ion chamber

Cookies at PTW websites

At our websites we use cookies to collect statistic information in order to optimise the use of our website. By proceeding further into our website, you accept our use of cookies. Read more about our cookie policy and instructions on how to delete cookies.
Accept cookies