Detector pressure

Figure 8.7 Detector pressure for limit charged valve...

The FEE (analogue, e.g. pre-amplifiers etc.) reside in the base of the detector pressure vessel. FEE are devoted to the processing of signals generated by the absorption of X-Rays in the active volume of the MWPC. They comprise a fast spectroscopic amplifier connected in unison to anode wires, together with four cathode pre-amplifiers (Two for each cathode plane). The FEE extract the requisite positional, spectral and temporal information from the MWPC readout system. Moreover, implementation of the fast delay-line readout concept enables a nanosecond discrimination capability. 

The HVU reside in the base of the detector pressure vessel. They comprise three digitally programmable power supplies which are used to power the anodes, drift region and anticoincidence region of the detector, respectively. 

On some NPP units I C have exhausted its term resources (have been working longer than projected lifetime). Such Systems have 20 years project lifetime but some of their separate components haven t more than 10 years (ionizing chambers, neutron detectors, pressure and temperature transducers, etc ). The Control and Protection Systems (CPS) exhausted their... 

The simplest application of a piezoelectric transducer is its use as a strain indicator, since the strains applied to a piezoelectric element can be quantified simply by measuring the electrical field which is created across the boundaries of that element. In the case of photoacoustic detectors, pressure pulses, created by the absorption of light from a chopped beam, deform a thin plate and are transformed into a series of voltage pulses. In such applications the electrical signals created are either dc or low-frequency, so that the design of the device and interface electronics is straightforward. 

The critical parameters are a constant and accurately measured gas flow rate, temperature, and injection and detector pressures. A small injection volume of the probe molecule is required, to ensure that the conditions of the thermodynamic treatment are met. 

The variation of Bq causes all ions to pass sequentially in front of the exit slit behind which is positioned the photomultiplier detector. The pressure in the apparatus is held at 10 torr in order to achieve mean free paths of ions sufficiently high that all ions emitted from the source are collected. 

During the attenuation measurements. Transducer 1 was excited with a narrowband tone burst with center frequency 18 MHz, see Figure 1 for a schematic setup. The amplitude of the sound pressure was measured at Tranducer 2 by means of an amplitude peak detector. A reference amplitude, Are/, was measured outside the object as shown at the right hand side of Figure 1. The object was scanned in the j y-plane and for every position, (x, y), the attenuation, a x, y), was calculated as the quotient (in db) between the amplitude at Transducer 2, A[x, y), and Are/, i.e., a(x,y) = lOlogm Pulse echo measurements and preprocessing... 

A connnon approach has been to measure the equilibrium constant, K, for these reactions as a fiinction of temperature with the use of a variable temperature high pressure ion source (see section (Bl.7.2)1. The ion concentrations are approximated by their abundance in the mass spectrum, while the neutral concentrations are known from the sample mlet pressure. A van t Hoff plot of In K versus /T should yield a straight Ime with slope equal to the reaction enthalpy (figure B1.7.11). Combining the PA with a value for basicityG at one temperature yields a value for A.S for the half-reaction involving addition of a proton to a species. While quadnipoles have been tire instruments of choice for many of these studies, other mass spectrometers can act as suitable detectors [19, 20]. 

Alternatively, ions of any one selected m/z value can be chosen by holding the magnetic field steady at the correct strength required to pass only the desired ions any other ions are lost to the walls of the instrument. The selected ions pass through the gas cell and are detected in the singlepoint ion collector. If there is a pressure of a neutral gas such as argon or helium in the gas cell, then ion-molecule collisions occur, with decomposition of some of the selected incident ions. This is the MS/MS mode. However, without the orthogonal TOF section, since there is no further separation by m/z value, the new ions produced in the gas cell would not be separated into individual m/z values before they reached the detector. Before the MS/MS mode can be used, the instrument must be operated in its hybrid state, as discussed below. 

In one instrument, ions produced from an atmospheric-pressure ion source can be measured. If these are molecular ions, their relative molecular mass is obtained and often their elemental compositions. Fragment ions can be produced by suitable operation of an APCI inlet to obtain a full mass spectrum for each eluting substrate. The system can be used with the effluent from an LC column or with a solution from a static solution supply. When used with an LC column, any detectors generally used with the LC instrument itself can still be included, as with a UV/visible diode array detector sited in front of the mass spectrometer inlet. 

A gas ionization detector consists of a tube filled with a high pressure gas and two electrodes. A tube filled with 2 MPa (20 atm) of xenon is common. The gas in the tube ionizes when x-rays pass through the tube causing a current to flow between a high voltage potential placed across the electrodes. This concept is similar to that used in a Geiger tube detector. Gas ionization detectors are utilized in some CT scanners. 

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