Passive integrated detector

In order to assess the accuracy of the present method, we compared it with two other methods. One was the Track Etch detector manufactured by the Terradex Corp. (type SF). Simultaneous measurements with our detectors and the Terradex detectors in 207 locations were made over 10 months. The correlation coefficient between radon concentrations derived from these methods was 0.875, but the mean value by the Terradex method was about twice that by our detectors. The other method used was the passive integrated detector using activated charcoal which is in a canister (Iwata, 1986). After 24 hour exposure, the amount of radon absorbed in the charcoal was measured with Nal (Tl) scintillation counter. The method was calibrated with the grab sampling method using activated charcoal in the coolant and cross-calibrated with other methods. Measurements for comparison with the bare track detector were made in 57 indoor locations. The correlation coefficient between the results by the two methods was 0.323. In the case of comparisons in five locations where frequent measurements with the charcoal method were made or where the radon concentration was approximately constant, the correlation coefficient was 0.996 and mean value by the charcoal method was higher by only 12% than that by the present method. 

Dual-technology sensors consist of two different sensor technologies incorporated together into one sensor unit. For example, a dual technology sensor could consist of a passive infrared detector and a monostatic microwave sensor integrated into the same sensor unit. 

The neutron bubble detector (trade name BD-IOOR) is a reusable, passive integrating dosimeter that allows instant, visible detection of neutron dose. The bubble detector consists of a glass tube filled with thousands of superheated liquid drops in a stabilizing matrix. When exposed to neutrons, these droplets vaporize, forming visible permanent bubbles in an elastic polymer. The total number of bubbles formed is proportional to the neutron dose equivalent H. The bubbles can be counted manually or by a machine. Figure 16.15 shows the response of the bubble detector as a function of neutron energy. 

Integrators methods—Usually passive type detectors that collect information about the average concentrations during periods of up to days, weeks or months, with three months as a typical value of integration period more commonly used. It is the most economic and the most widely used method since it is suitable for studies of inspection and recognizing. 

Integrating alpha track based passive detectors, which yield both a measurement of the mean radon concentration and of the radon daughter equilibrium (F) in each house, are being used in this national survey. 

With solid samples, the lower chamber always operates in a discrete manner since, as noted earlier, the sample is weighed in it. In this case, the separation module is also used as a leaching reaction vessel, which also can incorporate the detection step, thus operating as a mini-autoanalyser integrating all of the steps of the analytical process through an appropriate computer connected to the detector via a passive interface [165]. 

These detectors can be passive (like household smoke detectors) or active detectors (constant read-out to an integrated central security system). 

As in electronics in integrated optics, one has to distinguish between passive and active waveguiding components. A simple waveguide is a passive component. Active components enable controlled variations of the guided wave to be performed with respect to phase, amplitude, frequency, polarisation and direction of propagation. All these active components are either modulators or light emitters and amplifiers and detectors. 

Compared to conventional LoaC devices, the LoaD platform displays several intrinsic advantages regarding the integration of optical detection methods. The actuation and the detector as well as all moving parts can be entirely delegated to a robust macroscopic unit which resembles a conventional ODD, e.g., a CD or a DVD player. The LoaD device thus constitutes a fluidically and optically merely passive module. Also, the mechanical interface between the polymer disc and the optical detection module is usually made up by a simple, central clamp holder. Finally, the optical detection can be performed by conventional optical equipment with the disc either at rest or rotating a suitable frequency to match the acquisition rate capability of the detector. 

Activated charcoals Passive radon measurements can be achieved without a passive detector by absorbing radon with activated charcoal, which is analyzed by y-ray spectrometry at the end of the exposure. These charcoal-based radon monitors are sufficiently sensitive for the assessment of short-term integrated (less than 1 week) radon exposures. They have been widely applied for screening surveys. Unfortunately, because of the 3.825 day half-life of Rn, the exposure period cannot be longer than 1 week and the detector must be analyzed in the laboratory soon after the exposure. For the same reason, this technique does not provide a true integration, but a response more closely related to the last day or two of exposure. 

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