Ge semiconductor detector

The calculated quantity is considerably higher as the NEP of a modem Ge semiconductor detector which is cooled with liquid nitrogen. Its NEP is about 10 W, thus even weak Raman lines may be recorded with a large signal-to-noise ratio. 

Figure 5.4 Portions of the spectrum of Co gamma-rays measured on (a) Nal(TI) scintillation, and (b) Ge semiconductor detectors (the dotted lines represent the underlying Gaussian distribution of counts)...

Interferometers work with single detectors. For the NIR range InGaAs or Ge semiconductor detectors are used. They have to be extremely sensitive, since the intensity of the Raman lines decreases with the fourth power of its absolute frequency (the factor). In order to reduce their thermal noise they are cooled by Peltier elements or liquid nitrogen. 

Ionization in a Solid (Semiconductor Detectors) In a semiconductor radiation detector, incident radiation interacts with the detector material, a semiconductor such as Si or Ge, to create hole-electron pairs. These hole-electron pairs are collected by charged electrodes with the electrons migrating to the positive electrode... 

Figure 7.16. y-ray spectra of Co taken with a Nal (Tl) scintillation detector and a Ge (Li) semiconductor detector. 

Determination of radioactivity is by counting emitted beta or gamma radiation with beta or gamma counters. Most INAA determinations are by gamma spectrometry using Ge(Li) semiconductor detectors, multichannel analyzers and associated dedicated computers. 

The characteristics of a semiconductor detector depend not only on the type of materia] used—e.g.. Si or Ge—but also on the way the semiconductor is... 

For a good measurement, the amplifier should satisfy many requirements. Not all types of measurements, however, require the same level of performance. For example, if one measures only the number of particles and not their energy, the precision and stability of the amplification process can be relatively poor. It is in spectroscopy measurements, particularly measurements using semiconductor detectors, that the requirements for precision and stability are extremely stringent. Since the energy resolution of Ge detectors is of the order of 0.1 percent, the dispersion of the pulses due to the amplification process should be much less, about 0.01 percent. 

For Ge detectors other than the well-type, the efficiency is low, relative to Na(Tl) scintillation counters. This statement holds true for Si(Li) detectors as well (see Sec. 12.9). Lower efficiency, however, is more than compensated for by the better energy resolution of the semiconductor detector. Figure 12.32 illustrates the outstanding resolution characteristics of a semiconductor detector by showing the same spectrum obtained with a Nal(Tl) and a Ge(Li) detector. Notice the tremendous difference in the FWHM. The Ge(Li) gives a FWHM =... 

For truly multielement determinations, increased selectivity is required. It is offered by semiconductor detectors, e.g., by lithium-drifted germanium [Ge(Li)] or intrinsic germanium (high-purity) [HP-Ge] types with a resolution - full width at half maximum or FWHM... 

The excellent resolution provided by the more recently developed lithium-drifted silicon [Si(Li)] and germanium [Ge(Li)] semiconductor detectors (see Chap. 

The detectors used in the various forms of EDXRF are semiconductor detectors Conventionally, two types, i. e. lithium drifted silicon (Si(Li)) and hyperpure germa nium (HP-Ge) detectors are used. Their main advantages are their compact size the non-moving system components, and relatively good energy resolution which optimally is of the order of 120 eV at 5.9 keV. Because of their operation prin... 

Ions, in particular protons from a particle accelerator, in the energy range 1 —4 MeV, are used with beam spots 1 pm—10 mm in diameter. a-Particles from some radioactive sources ( " Am) can also be used for excitation. The energy of emitted photons is measured by a wavelength dispersive Bragg spectrometer or by an energy-dispersive spectrometer with semiconductor Si(Li) or Ge(Li) detectors. 

Two type of detectors are used in commercially available units proportional detectors and semiconductor detectors such as silicon PIN, Si(Li), Ge(Li), and silicon drift detectors. The detectors used in EDXRF have very high intrinsic energy resolution. In these systems, the detector resolves the spectrum. The signal pulses are collected, integrated, and displayed by a multichannel analyzer (MCA). 

The demand for high purity metals has tremendously increased due to needs in the information technology and telecommunications industries. High purity Al is used in various microelectronic devices and semiconductor detectors are made of hyperpure Ge and Si, etc. Impurity levels depend upon both the raw material and the purification method and may influence the function of the device. For example, in semiconductor materials, alpha particle emission creates damage causing the so-called soft error effect. For this reason, U and Th levels are strictly limited in these applications. 

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