Ionization chamber method

Ionization Chamber Method DSC directly sampled to an evacuated chamber, current measurement... 

Ionization Chamber Method (DSC), The ionization chamber is one of the most common instruments for measuring radon gas. The chmaber was cylindrically shaped and had a 1.5 liter volume. Air samples were drawn through a dryer filled with CaCl and a filter to remove... 

Flow-Type Ionization Chamber (PFC). The Flow -Type Ionization Chamber Method (PFC) has been developed for continuously measuring radon gas in the atmospheric air. The detail of the device has been described elsewhere (Shimo, 1985). Briefly, measurements are continuously carried out by drawing air through the detector at 1.0 2.0 /min. The ionization currentdue to alpha particles from radon and its daughters is detected with a vibrating reed electrometer (VRE) in the same manner as the DSC. The sensitivity... 

Double Ionization-Chamber Method (Real-Photon Method)... 

The double ionization-chamber method [19] provides an excellent means of measuring the photoabsorption cross sections of atoms and molecules in the range of the incident photon... 

In brief, the method consists of introducing small amounts (partial pressures of 10 3-10 4 torr) of the substance to be investigated into the ionization chamber of a mass spectrometer which contains a high pressure (1 torr) of methane, the reactant gas. Ionization is effected by electron impact, and because the methane is present in such an overwhelming preponderance, all but a negligibly small amount of the initial ionization occurs in the methane. The methane ions then undergo ion-molecule reactions to produce a set of ions which serve as reactant ions in the chemical ionization process. The important reactant ions formed from... 

There are several other methods which have been used in the experimental determination of electron impact ionization cross sections. Nottingham and Bell76,77 developed a method specifically for the purpose of accurately determining the absolute electron impact ionization cross section of mercury. A semicircular electron velocity analyzer included in their design ensured that very high energy resolution was possible since only electrons of the required velocity emerged from the analyzer into the ionization chamber. Other aspects of the experiment are similar to the condenser plate method. 

The instruments include an ionization chamber, the charcoal-trap technique, a flow-type ionization chamber (pulse-counting technique), a two-filter method, an electrostatic collection method and a passive integrating radon monitor. All instruments except for the passive radon monitor have been calibrated independently. Measurements were performed... 

Activated Charcoal Method ACC charcoals 5g, flow rate 5 /min, sampled temp.s -73°C, sampling time lhr.,transfered into ionization chamber... 

Another method for detecting neutrons using an ionization chamber is to use the gas boron trifluoride (BF3) instead of air in the chamber. The incoming neutrons produce alpha particles when they react with the boron atoms in the detector gas. Either method may be used to detect neutrons in nuclear reactor neutron detectors. 

Radiation detection circuit currents or pulse rates vary over a wide range of values. The current output of an ionization chamber may vary by 8 orders of magnitude. For example, the range may be from 10"13 amps to 10"5 amps. The most accurate method to display this range would be to utilize a linear current meter with several scales, and the capability to switch those scales. This is not practical. A single scale which covers the entire range of values is used. This scale is referred to as logarithmic. 

The El source has been the most widely used ion source over the past 60 years and continues to be the method of choice for the analysis (either qualitative or quantitative) of small- to medium-sized volatile organic compounds. The inherent reproducibility of the mass spectra has enabled the assembly of large spectral libraries. Computers associated with current generation instruments can efficiently (in a few seconds) search an unknown mass spectrum against tens of thousands of reference spectra in order to aid in the identification of an analyte. The general scheme of an El source includes the introduction of the vaporized analyte molecules into the ionization chamber, exposure of those molecules... 

Detailed Description of the Apparatus and the Method Employed.— After several trials the apparatus finally adopted is the one shown in Fig. 1. The gas enters the apparatus at A, passing into the ionization chamber if, through the slit at jS, into the magnetic chamber C, through Dy and im-... 

Figure 2 The photoabsorption (c), photoionization (o-,-), and photodissociation (cr

The first conventional mode of MS involves El ionization, in which the neutral flavonoid is impacted in the gas phase with an electron beam of 70 to 100 eV. Resulting mass spectra of the flavonoid aglycones are characterized by molecular ion peaks (M ), and fragment ions from both the A and B rings. The use of a reactant gas in the ionization chamber. Cl, normally results in the production of a more abundant molecular ion and simpler fragmentation patterns. General information about mass spectra of flavonoids recorded by these methods has been published by several authors. More specific mass spectra analyses... 

Neutral species are best sampled using molecular beam methods in which the neutral beam is modulated between the sampling orifice and the ionization chamber of the mass spectrometer and only the modulated component of the mass spectrometer output is recorded. This approach enables all neutral species, including radicals to be detected with a comparable sensitivity. If modulation techniques are not used, the sensitivity for detecting condensible or reactive species is much less than for non-condensible, non-reactive neutral molecules because of the much larger effective pumping speed for the former in the mass spectrometer chamber. However, the ease of installation of non-line-of-sight non-modulated... 

In the following year Miles. Curie and C. Chamie measured the half-life period of radon by a method which is very simple in principle. If a single tube of radon placed in the ionization chamber yields at time t a... 

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