Micro-structured electron accelerator for the mobile gas ionization sensor technology
Mobile and economically priced gas monitoring and warning systems will become increasingly important for civil security, such as in fire brigade operations in undefined hazardous environments (Daum et al., 2006). Normally, photoionization detectors (PIDs) are used for the detection of gases. Hereby,...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-04-01
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| Series: | Journal of Sensors and Sensor Systems |
| Online Access: | http://www.j-sens-sens-syst.net/4/151/2015/jsss-4-151-2015.pdf |
| Summary: | Mobile and economically priced gas monitoring and warning systems will become
increasingly important for civil security, such as in fire brigade operations
in undefined hazardous environments (Daum et al., 2006). Normally,
photoionization detectors (PIDs) are used for the detection of gases. Hereby,
the principle is based upon the ionization of the measured gas by photons,
which are generated by a high-energetic gas discharge lamp with energy of
10–11 eV. Besides the detrimental unspecific gas detection because of the
ionization of all gases with ionization potential (IP) below the provided
photon energy, sensors also have a short lifetime combined with a high cost
(<a href="http://www.intlsensor.com/pdf/photoionization.pdf"target="_blank">http://www.intlsensor.com/pdf/photoionization.pdf</a>).
<br><br>
This can be remedied by the concept of an electronic supported
photoionization detector (ePID; Zimmer et al., 2012) consisting of a durable
UV-LED with an above-positioned electron accelerator chip manufactured on a
glass substrate by planar technology. Photoelectrons are extracted by UV
illumination out of the bottom electrode and will be accelerated to an energy
matching the ionization potential of the gas by a downstream acceleration
grid. Thereby, the stable honeycomb-structured grid acts as a porous
separator between the evacuated electron acceleration path due to nm scaling
and the ionization area of the detector. To enhance the emitting area
yielding a higher photoelectron current, the grid structure almost levitates,
realized by the use of compatible planar technological processes such as
reactive ion etching (RIE) and isotropic wet etching of sacrificial layers,
which will be explained in detail in this paper. Furthermore, the tunability
of the grid's acceleration voltage would enable a substance-specific
determination of the gas composition, where the ionization of the analytes is
clearly performed by photoelectrons instead of photons. |
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| ISSN: | 2194-8771 2194-878X |