PIN -diode

Fig. 4.7. A semiconductor detector operated as a pin diode with a reverse voltage or bias. An incident X-ray photon ultimately produces a series of electron-hole pairs. They are "swept out" by the bias field of-500 V- electrons in the direction ofthe n-layer holes in the direction ofthe p-layer. Thus, a small charge pulse is produced after [4.21],...

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). 

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],... 

Fig. 3.18 Pulse-height analysis (PHA) spectrum (or energy spectrum) for Co/Rh Mossbauer source radiation backscattered nonresonantly and/or resonantly from aluminum and stainless steel plates. Data were obtained with Si-PIN diodes with sensitive area of 1 cm per diode and a thickness of 400 pm (from [36, 46])...

Energy-dispersive spectrometry (EDS) is a technique of X-ray spectroscopy that is based on the simultaneous collection and energy dispersion of characteristic X-rays. Typical ED detectors are thermoelectrically cooled semiconductors (usually operated at 77 K), PIN diodes,... 

Figure 4.1. Typical X-ray setup with 2D detector in normal-transmission geometry. The intensity of the incident X-ray beam is measured in an ionization chamber (a). Thereafter it penetrates the sample which is subjected to some process. At a distance R (cf. Table 2.1 on p. 7) behind the sample the detector is recording the scattering pattern. In its center (b) the detector is protected by a beam stop. It is equipped with a pin-diode which records the intensity of the attenuated beam...

The intensity of the X-ray beam is measured by ionization chambers or pin-diodes13. Pin-diodes can only be operated in the beam stop. The variation of the beam intensity during the experiment should be measured both before and after the sample. If the beam intensity monitors are set up properly, the absorption of the primary beam by the sample can be computed for each scattering pattern. The placement of the first ionization chamber in or after the X-ray guide tube to the sample is uncritical. 

The design and placement of the second beam intensity monitor demands more attention. The definition of X-ray absorption does not discriminate between primary beam, USAXS and SAXS. So the second beam intensity monitor should guide primary beam, USAXS and SAXS through its volume, whereas the WAXS should pass outside the monitor. The optimum setup for SAXS and USAXS measurements is a narrow ionization chamber directly behind the sample. For WAXS measurement a pin-diode in the beam stop is a good solution for WAXS. For USAXS and SAXS it may be acceptable, as long as the relevant part of the primary beam is caught, the optical system is in thermal equilibrium and the synchrotron beam does not jump (cf. Sect. 4.2.3.5). 

A pin-diode has three layers p-doted layer, i intrinsic interaction layer, n-doted layer. The outer layers provide the electrical field. In the inner layer photons generate electron-hole-pairs which result in a current, although the diode is operated in reverse-biasing mode. 

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... 

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... 

The alignment of discrete detectors for each input is no less a difficult task than the source assembly problem. The extra traces associated with connecting discrete field effect transistors (FETs), PIN diodes, or avalanche photodiodes leads to degradation of signal, lower reliability, and greater cost. The integration of photo FETs onto the IC does provide a way to simplify the detector side of the problem, unfortunately at the... 

Figure 3-42 Initial apparatus for measuring anti-Stokes emission using a frequency-doubled Nd YAG pumped dye laser. L is a short focal lens (3-4 cm) S is the sample I is an iris for spatially filtering the two exciting beams F is a wideband interference filter D is the detector (usually a PIN diode) M is a monochromator (not usually necessary). Not shown are the PAR-160 box car integrator, chart recorder, and dye laser scan drive used to record spectra. (Reproduced with permission from Ref. 104.)...

In the actual Hs experiment [30] an improved version namely the ryo On-Line Detector (COLD) was used. This detector was constructed at PSI and consisted of 2 times 36 PIN diodes. A schematic of the COLD is shown in Figure 13. 

An essential requirement is that the characteristic time, T2, for the decay of the macroscopic polarisation must be much longer than the time taken for the polarising radiation pulse to dissipate. This requirement is readily satisfied the pin-diode S2 is held closed until the pulsed radiation has dissipated, and is then opened to capture the coherent radiation emitted by the polarised gas, due to one or more rotational transitions producing spontaneous emission. If all is well, the emission is detected against a near-zero radiation background. 

The first two components in the detection assembly, a high-power PIN diode and a single-pole switch are required to protect later circuit elements from the high-power microwave polarizing pulse. The leakage peak power from the diode is still too high for the low noise amplifier used to amplify the rotational FID, so the microwave switch is placed after the diode. This switch is controlled by the same pulse that activates the TWTA pulse output. 

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