Detectors cross calibration

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. 

This sample preparation method is not instrument specific but was developed using a Thermo Fisher Element 2 MS-ICP-MS. Whatever instrument is used, the instrument should be mass calibrated. Although it is preferable for the sake of accuracy that all uranium isotopes be acquired in the same detector mode, cross-calibration should be up to date for single collector instruments, as should detector dead time. Since the Thermo Fisher magnetic sector instrument with a low-resolution ion slit in good condition produces data with flat top peaks, and automatically updates detector crosscalibration after acquisition of peak data with sufficient intensity, frequent recalibrations will not be necessary on this instrument or on the Thermo Fisher multicollector instruments. Detector dead time is relatively stable on this instrument but should be up to date. 

Although it is preferable for the sake of accuracy that all uranium isotopes be acquired in the same detector mode, cross-calibration should be up to date, as should detector dead time. Mass calibration should be performed every 2-3 days for accurate isotope ratio determination. 

Since the insertion and withdrawn of control rods on top of the core changes the shape of the neutron flux, care must be taken in selecting the right position for the neutron detectors. Periodic calibration and cross checking of neutron detectors is highly recommended. 

Two factors determine the intensity of the scattered beam the scattering cross section for the incident ion-target atom combination and the neutralization probability of the ion in its interaction with the solid. It is the latter quantity that makes LEIS surface sensitive 1 keV He ions have a neutralization probability of about 99 % on passing through one layer of substrate atoms. Hence, the majority of ions that reach the detector must have scattered off the outermost layer. At present, there is no simple theory to adequately describe the scattering cross section and the neutralization probability. However, satisfactory calibration procedures by use of reference samples exist. The fact that LEIS provides quantitative information on the... 

Relative measurements are considerably easier to make and are the type most commonly reported. However, absolute measurements are of importance, for example, in comparing measured scattering cross sections of nonspherical particles with calculations for equivalent spheres. Note that absolute as we are using the term here means that scattering is not normalized to some arbitrary reference angle it does not mean that absolute irradiances are measured, as with calibrated detectors. In both relative and absolute measurements, it is relative (i.e., dimensionless) irradiances that are determined. 

Acetylcholineesterase and choline oxidase The detector consisted of two Pt electrodes (6 mm x 3 mm) sandwiched between Perspex sheets and separated by a 1 mm thick sheet of silicone rubber, and the carrier stream (0.5 mL/min) was 0.1 M phosphate buffer (pH 8.2). AChE and ChO were immobilized by glutraldehyde cross-linking to controlled-pore glass and packed into columns (3 cm x 2.5 mm) that were operated at 25° C. Rectilinear calibration graphs for 10-100 pM choline and acetylcholine were obtained. [104]... 

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