Defined charge distribution for SMPS measurements by means of X-ray ionization
** Regulations and requirements can vary depending on the state/country
The XRC 049 is a neutralizer on the basis of X-ray ionization. It can be used the same way as the Kr-85-370 (for example in SMPS systems), i.e. when the measurement task requires a reliable and defined charge distribution of the aerosol. The XRC 049 is especially suitable for mobile measurements performed at different locations, as there are no official requirements for the transport that need to be considered in most countries. The XRC 049 is a bipolar neutralizer generating positive and negative ions through ionization. If these ions are brought together with an aerosol, a defined equilibrium charge distribution is set, as it is necessary for measuring systems such as a scanning mobility particle sizer (e.g. Palas®U-SMPS*). Compared to an unipolar neutralization, a bipolar neutralization has a significant advantage: regardless of the initial state of charge of the particles, a reproducible equilibrium charge distribution is always set. This is why a bipolar neutralization is mandatory for a traceable calibration of a condensation particle counter (e.g. ISO/CD 27891). The XRC 049 can be integrated into the U-SMPS / DEMC control unit (figure 3). The full performance is immediately available after switching on the device, after switching off no ionization takes place and therefore no further radiation.
Function The soft X-rays ionize the carrier gas. As a first result of the ionization process, positively charged gas ions and free electrons are generated. Neutral gas molecules with a strong electron affinity (e.g. O2) collect the free electrons to build negatively charged ions. When, at this point, aerosol particles are exposed to this mixture of ions during a determined period of time, the charge level of the aerosol particles is set at a defined equilibrium charge distribution.
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