Calibrated reference source

Each calibrated reference source is supplied with a calibration certificate listing ... 

Many researchers have used this technique, originally suggested by Fery [83], to measure flame temperatures. The flame is commonly seeded with sodium salt. The salt vaporizes in the flame and dissociates into sodium atoms and other products. These excited atoms emit at a specific wavelength. This radiation is then compared to a calibrated reference source, such as a tungsten filament lamp. The temperature of this source is adjusted, until it matches the seed radiation. To the naked eye, the background source appears to disappear when it is at... 

The radionuclides come in the form of calibration/reference sources, and as inorganic compounds and labeled organic compounds. They are packed in various ways, most commonly in a glass ampoule packed in a small aluminum can. To reduce the surface radiation dose rate (cf. Ch. 18) for high intensity radiation sources (usually > 10 MBq) the can is put in a lead block which is packed in a wooden crate for shipment. Opening of the aluminum can and glass ampoule may require remote control and should be done only by experienced, licensed personnel. 

When we consider the efficiency, e, we find we have a separate uncertainty budget to consider taking into account all of the factors involved in preparing the efficiency calibration reference source and the measurement of the cahbration data. This would take into account the uncertainty of the certified source from which the calibration source was prepared aud the uncertainty of interpolation of the cahbration curve. 

Determine the efficiencies with which the calibrated reference sources were measured at Vq. Efficiencies. 

Most instruments of this type incorporate built-in selfchecking facilities but the check can only be as accurate as the internal reference which, itself, will only be accurate over a specific range. The instrument should be calibrated against a reference source at periodic intervals. 

Some of the intended categories of use of radioisotopic reference material have been reviewed recently by Fajgelj et al. (1999). They include assignment of property values, establishing the traceability of a measurement result, determining the uncertainty of a measurement result, calibration of an apparatus, assessment of a measurement method, use for recovery studies and use for quality control purposes. It should be noted however that, in general, natural matrix reference materials are not recommended for calibration purposes. This should preferably be done with pure chemical forms of the element labelled with the isotope of interest. Calibrated isotopic sources of this kind are available from a number of commercial suppliers and are not the subject of this review. 

Calibration or reference sources—shall not possess at any one time, at any one location of storage or use of241 Am 5 pCi NRC 2001d 10CFR31.8... 

Emission measuring sensors also need an internal calibration source. In the case of absorption sensors, the external source most often served as the standard. In the case of emission, a reference source is usually incorporated in the instrument to certify instrument performance and provide an absolute reference. 

The most accurate measurements of the CMB spectrum to date have come from the Far InfraRed Absolute Spectrophotometer (FIRAS) on the COsmic Background Explorer (COBE) (Boggess et al., 1992). In contradiction to its name, FIRAS was a fully differential spectrograph that only measured the difference between the sky and an internal reference source that was very nearly a blackbody. Figure 9.2 shows the interferograms observed by FIRAS for the sky and for the external calibrator (XC) at three different temperatures, all taken with the internal calibrator (IC) at 2.759 K. Data from the entire FIRAS dataset show that the rms deviation from a blackbody is only 50 parts per million of the peak Iv of the blackbody (Fixsen et al., 1996) and a recalibration of the thermometers on the external calibrator yield a blackbody temperature of... 

Calibrated beta reference sources. Individual beta reference sources calibrated with an accuracy of 3 to 5% (at 99% confidence). 

The list of calibrated beta reference sources is shown in Table 4.16, while calibrated gamma reference sources are shown in Table 4.17. 

This method is only slightly intrusive, due to the seeding. It is of relatively low cost. It may be effectively used for very high temperatures. However, the seeded field must be uniform. This may require the addition of a carrier gas to transport the seeds into the flame. Only an average gas temperature, across the flame, is measured. A calibrated reference light source is required and the adjustment for the source to vanish is somewhat subjective. 

We have defined in-house calibrations of source roek maturity from various petroleum systems, assessed as source roek vitrinite reflectance equivalent as a proxy for maximum source rock temperature. The molecular parameter versus Ro% calibrations referred to below are either based on published source rock parameters we have validated to our satisfaction (e.g. Schaefer Littke 1988) or from in-house work on source rock maturity sequences. Inevitably, as all oils are mixtures we cannot accurately define point maturities for reservoired oils but by judicious choice of calibrant source-rock samples we feel the calibrations referred to are as robust as is possible in dealing with spatially and temporally complex entities such as source basins. The oil maturities we report are those interpreted classically based on correlations between measured oil molecular ratios and the... 

Where available, reference materials need to be used for calibration or quality control. The National Institute of Standards and Technology (NIST) and many commercial sources supply such materials. Many high performing technology laboratories are capable of preparing their own reference materials using the same approach used by NIST in certifying their Standard Reference Materials (SRM). The calibration reference materials (RM) should be traceable to national standards, and the traceability must be preserved in the laboratory s documentation system. 

The radiant sensitivity of a detector - or its quantum efficiency - is one of the most important parameters for TCSPC application. Unfortunately absolute measurements of the radiant sensitivity or the quantum efficiency are extremely difficult. The problem is not only that a calibrated light source or a calibrated reference detector are required but also that extremely low light intensities have to be used. However, accurate attenuation of light by many orders of magnitude is difficult. 

Efficiency calibration in a laboratory environment is straightforward take a reference source, or sources, containing known activities of nuclides for which well-defined nuclear data are available, measure a spectrum and, from the individual peak areas, calculate efficiencies over a range of gamma-ray energies. Such simplicity is not achievable when one needs a calibration relevant to measurement of a 220 L waste disposal drum, a transport... 

Figure 8.6 Close geometry efficiency calibration using the QCYK reference source...

It is important to note that, if the final result is to be based upon more than one gamma-ray, it will be necessary to make a correction to the result from each individual gamma-ray before combining to achieve the final corrected result. If standardized reference sources are not available for a particular nuclide that must be measured, a direct measurement of the correction factor is not possible. In that case, it would be necessary to perform measurements at a large source-to-detector distance using an appropriate TCS-free calibration curve and compare these with the close geometry measurements. 

Use spectra of reference sources to generate energy, width and efficiency calibration data files. 

The potentiometer, used for accurate determinations of voltage in standards laboratories, has various applications in biological research. One, of course, is the accurate determination of various bioelectric potentials. In addition, many instruments can be constructed about the potentiometer as a central core. Figure 5.10 illustrates the basic potentiometer circuit. The instrument consists of two batteries, a standard reference cell and a working battery. In some instrumentation systems, the working battery is replaced by a regulated power supply, and a zener diode reference source is used in place of the standard cell. The heart of the instrument is a very accurately calibrated resistance, which is called a slide wire. It is usually in the form of a helix wrapped about a solid core. In operation, switch 1 is connected to the standard cell. The key (switch 2) is tapped at intervals... 

There are a number of techniques for meastuing subcritical reactivity relative to a calibrated reference control rod, in addition to soxuce multiplication. These include rod drop, rod jerk, source jerk, pulsed source and reactor power noise. Account must be taken of spatial flux transients (either by calculating them or measuring them with arrays of covmters) and of the spatial distribution of natural neutron sources due to spontaneous fission and (a,n) reactions and any fixed sources introduced to increase the subcritical flux level. The different methods have been reviewed and intercompared, for example, at the 1976 Specialists Meeting [4.87]. 

FIGURE 8.25 General form of the calibration curve used for calibrating post-source decay mass spectra on a curved-field reflectron TOR (Reprinted with permission from reference 15). 

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