Detectors solid-state detector

Figure Bl.24.3. Layout of a scattering experiment. Only primary particles that are scattered within the solid angle O spaimed by the solid state detector are counted.

Ernest O. Lawrence, inventor of the cyclotron) This member of the 5f transition elements (actinide series) was discovered in March 1961 by A. Ghiorso, T. Sikkeland, A.E. Larsh, and R.M. Latimer. A 3-Mg californium target, consisting of a mixture of isotopes of mass number 249, 250, 251, and 252, was bombarded with either lOB or IIB. The electrically charged transmutation nuclei recoiled with an atmosphere of helium and were collected on a thin copper conveyor tape which was then moved to place collected atoms in front of a series of solid-state detectors. The isotope of element 103 produced in this way decayed by emitting an 8.6 MeV alpha particle with a half-life of 8 s. 

Fig. 4.6. Cross section of the front end of an SSD (solid-state detector), here Gold contact with a grooved Si(Li) crystal. Crystal and preamplifier are connected with a cooled copper rod and shielded by a case with an end cap and Be window [4.21, 4.29].

The energy-dispersive (EDX) solid state detector (SSD, Figs 4.6, 4.7) is made of lithium-drifted Si crystal (Si(Li)). Between a thin p-type and an n-type layer lies a high-resistivity Si crystal of centimeter dimensions. The front and end planes of the crystal are coated with Au and serve as electrodes. The crystal, cooled to 77 K by liquid nitrogen, represents a p-i-n diode (Fig. 4.7). An incident X-ray photon with... 

Tab. 4.1. Certain elements whose Ka peaks interfere with escape peaks of other elements using solid state detector SSD or silicon drift detector SDD [4.16].

Following a decay period of at least 15 hrs, the 1,524 MeV 7-photopeak of 42K is counted for 40 min with a Ge-U solid state detector and a 4096-channel analyzer. This more sophisticated counting system is necessary to obtain the required resolution, since with a Na iodide detector, the 1,524 MeV peak of 42 K overlaps with the 1.369 MeV 7-peak of the 24Na decay spectrum... 

The NAA measurements on the paper samples were made at the Breazeale Nuclear Reactor Facility at the Pennsylvania State University with a TRIGA Mark III reactor at a flux of about 1013 n/cm2-sec. Samples were irradiated from 2 to 20 min and counted for 2000 sec, after a 90 min decay time for Ba and a 60 hr decay for Sb, Analyses were performed instrumentally, without radiochemical separation, using a 35cm3 coaxial Ge-Li detector and a 4096-channel pulse height analyzer. With these procedures, detection limits for Ba and Sb were 0.02ug and 0.001 ug, respectively. These sensitivities are comparable to those obtained by GA s radiochemical separation procedure, and are made possible by the use of the higher neutron output from the more powerful reactor and in combination with the higher resolution solid state detector... 

Transmission spectroscopy offers two significant advantages over photoacoustic spectroscopy of powders. First, transmission spectroscopy is not susceotible to external acoustic disturbances. Commercial spectrometers must be modified for vibrational isolation in order to obtain good photoacoustic spectra. Secondly, transmission spectroscopy can use solid state detectors with very fast response times, whereas photoacoustic spectroscopy is much slower, with spectra taking a few minutes to collect as compared to a few seconds for transmission spectra when both are taken with an FTIR. 

Some properties of the detectors most commonly used for transmission experiments are summarized in Table 3.2. Alternative counters are scintillation detectors based on Nal or plastic material that is attached to a photomultiplier, and solid-state detectors using silicon- or germanium-diodes. 

Solid-state detectors based on silicon- or germanium-diodes possess better resolution than gas counters, particularly when cooled with liquid nitrogen, but they allow only very low count rates. PIN diodes have also recently become available and have been developed for the instruments used in the examination of Martian soils (Sects. 3.3 and 8.3). A very recent development is the so-called silicon-drift detector (SDD), which has very high energy resolution (up to ca. 130 eV) and large sensitive detection area (up to ca. 1 cm ). The SNR is improved by an order of magnitude compared to Si-PIN detectors. Silicon drift detectors may also be used in X-ray florescence spectroscopy, even in direct combination with Mossbauer spectroscopy (see Sects. 3.3 and 8.3). 

The basic function of the spectrometer is to separate the polychromatic beam of radiation coming from the specimen in order that the intensities of each individual characteristic line can be measured. In principle, the wide variety of instruments (WDXRF and EDXRF types) differ only in the type of source used for excitation, the number of elements which they are able to measure at one time and the speed of data collection. Detectors commonly employed in X-ray spectrometers are usually either a gas-flow proportional counter for heavier elements/soft X-rays (useful range E < 6keV 1.5-50 A), a scintillation counter for lighter elements/hard X-rays (E > 6keV 0.2-2 A) or a solid-state detector (0.5-8 A). 

Scattering Cross Sections. Particles are scattered into the solid state detector that subtends a small solid angle Q (typically less than 10 2sr). The number of counts, H, registered by the detector, and thus the height of the spectrum, is... 

Scattering on the Triple-Axis-Diffractometer [1,2] at the HASYLAB high-energy beamline BW5 is performed in the horizontal plane using an Eulerian cradle as sample stage and a germanium solid-state detector. The beam is monochromatized by a singlecrystal monochromator (e.g. Si 111, FWHM 5.8 ), focused by various slit systems (Huber, Riso) and iron collimators and monitorized by a scintillation counter. The instrument is controlled by a p-VAX computer via CAMAC. 

As the anapole interaction is the candidate which directly breaks parity conservation in electromagnetic interaction [1], it is very desirable to test whether the anapole moment could couple to the p decay or not. This experiment can be performed by solid state detectors as well asby a magnetic spectrometer. There are also other choices for the crystal samples [3] and p sources. Since the anapole moment has the same intrinsic structure as for Majorana neutrinos, its coupling is valid to both p decay and p+ decay. 

The Compton profile measurements on Cu and Cu 953AI0047 were performed at ID 15b of the ESRF. Figure 1 shows the setup of the scanning-type Compton spectrometer used. It consists of a Si (311) monochromator (M), a Ge (440) analyzer (A) and a Nal detector (D). The signal of an additional Ge solid state detector (SSD) was used for normalization. ES, CS and DS denote the entrance slit, the collimator slit and the detector slit, respectively. For each sample 10 different directions were measured with approximately 1.5-2 x 103 7 total counts per direction. The incident energy was 57.68 keV for the Cu and 55.95 keV for the Cuo.953Alo.047 measurement. 

X-ray diffraction (XRD) patterns for the materials were recorded on a X-ray diffractometer using nickel-filtered CuKa (0.154 nm) radiation and a liquid nitrogen-cooled germanium solid-state detector. Thermal stability of the materials was performed using a thermogravimetric analyser. The acidity of calcined samples were determined... 

In this example, as in many facilities, the final detector is simply used to count the particles. When this is the case, solid state detectors, like silicon surface barrier ones, can also be used. 

The alternative approach to detection and analysis incorporates a solid state detector and a multichannel pulse height analysis system. The crystals used are of silicon (of the highly pure intrinsic type), or the lithium drift principle (p. 463 etseq.) is utilized. All emitted radiations are presented to the detector simultaneously and a spectrum is generated from an electronic analysis of the mixture of voltage pulses produced. Chapter 10 contains a more detailed account of pulse height analysis and solid state detectors. Production of an X-ray spectrum in this way is sometimes known as energy dispersive analysis ofX-rays (EDAX) and where an electron microscope is employed as SEM-EDAX. 

At ID18F beamline simultaneous p-XRF (excitation energy of 28 keV spectrum collection using a Si(Li) solid state detector with detection limits in the range 0.01 ppm for 3025) and p-XRD (monochromatic X-rays... 

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