Si-PIN detectors

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). 

Fig. 3.15 Left External view of the MIMOS II sensor head (SH) with pyramid structure and contact ring assembly In front of the Instrument detector system. The diameter of the one Euro coin is 23 mm the outer diameter of the contact-ring is 30 mm, the inner diameter is 16 mm defining the field of view of the Instrument. Right. Mimos II SH (without contact plate assembly) with dust cover taken off to show the SH Interior. At the front, the end of the cylindrical collimator (with 4.5 mm diameter bore hole) Is surrounded by the four SI-PIN detectors that detect the radiation re-emltted by the sample. The metal case of the upper detector is opened to show its associated electronics. The electronics for all four detectors Is the same. The Mossbauer drive is inside (in the center) of this arrangement (see also Fig. 3.16), and the reference channel is located on the back side In the metal box shown In the photograph...

Fig. 3.25 Left signal-to-noise ratio (SNR) of the Mbssbauer spectra of a basalt taken with MIMOS II (full SI-PIN detector system black data-points) and MIMOS IIA (1/4 of full SDD system red data-points) respectively. Right XRF spectra of low Z elements measured with MIMOS IIA (SDDs) at —20°C. The Compton scattered 14.4 keV line (at 13.8 keV) and the resonant 14.4 keV Mossbauer line are well separated...

Fig. 8.41 Left. Comparison of SNR of 14.4 keV Mossbauer spectra, taken with a Si-PIN detector system (MER instrument four diodes) and with a SDD detector system (advanced MIMOS instrument only one diode chip) Right. X-ray spectrum of a basalt (Ortenberg basalt see [366, 371], taken with a high resolution Si-drift detector system at ambient pressure (1 atm), demon-...

The Unisantis XMF-104 X-ray microanalyzer (Unisantis S.A., www.unisantis.com) was used by researchers at the Institute for Roentgen Optics, Moscow, Russian Federation, to examine nonde-structively the composition of ancient coins from the fourth century BC through the second century AD. The fourth century BC coins were found to be an alloy of 82% Ag/18% Cu, but areas of pure Ag showed the inhomogeneity of the alloy. A drachma coin depicting Alexander was composed of 99% Ag/1% Cu. The XMF-104 system had a 50 W Mo tube, a 2-stage Peltier-cooled compact Si-PIN detector and polycapillary focused X-ray beam with a 50-250 pm focal spot. Spectra, images of the coins, and details are available at www.unisantis.com, application note 605. 

Adjustable Workbench (PAW) instrument assembly. The SH shown in Figs. 3.15 and 3.16 contains the electromechanical transducer (mounted in the center), the main and reference Co/Rh sources, multilayered radiation shields, detectors and their preamplifiers and main (linear) amplifiers, and a contact plate and sensor. The contact plate and contact sensor are used in conjunction with the IDD to apply a small preload when it places the SH holding it firmly against the target. The electronics board contains power supplies/conditioners, the dedicated CPU, different kinds of memory, firmware, and associated circuitry for instrument control and data processing. The SH of the miniaturized Mossbauer spectrometer MIMOS II has the dimensions (5 x 5.5 x 9.5) cm and weighs only ca. 400 g. Both 14.4 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously by four Si-PIN diodes. The mass of the electronics board is about 90 g [36],... 

The light-weight Elva-X energy dispersive XRF spectrometer employed for this study has an air-cooled rhodium target anode X-ray tube with 140 micron Be window and a thermoelectrically cooled Si-PIN diode detector. The detector... 

Commercial systems consist of an optical microscope for observation of the sample area and an ED-based XRF systan with a low-power, microfocused X-ray source using Kumakhov optics, a filter wheel, and a detector (Si[Li], Si-PIN, SDD). The X-ray source is generally air-cooled, and... 

Modern WDXRF instruments permit the determination of all elements from fluorine (Z = 9) to uranium (Z = 92). Some WDXRF systems allow measurement of elements from Be to U. Benchtop EDXRF instruments can determine elements from sodium (Z = 11) to uranium (Z = 92) with a special SDD detector, it is possible to measure from fluorine to uranium. Handheld EDXRF units with SDD detectors can measure from magnesium (Z = 12) to uranium, and Si-PIN units can do the same with vacuum or He purge. 

The silicon-based solid-state detectors fall into three general categories surface barrier devices, PIN diodes, and Si(Li) (pronounced silly ) devices. These detectors are used to measure short-ranged radiation charged particles in the first two cases and low-energy 7 rays and X-rays in the third case. The detector... 

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). 

In energy dispersive analysis, semiconductor crystals such as the PIN-diode, Si(Li), Ge(Li), and silicon drift detector (SDD) are generally used as X-ray detectors. They allow the count of an amount of photons and determination of the energy of the photon. An introduction of recent progress in X-ray detection... 

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