Pulse-height measurements with a cooled avalanche-photodiode detector

1998 ◽  
Vol 5 (3) ◽  
pp. 883-885 ◽  
Author(s):  
Shunji Kishimoto
Keyword(s):  
Energy Resolution ◽  
Pulse Height ◽  
Threshold Level ◽  
Avalanche Photodiode ◽  
X Ray Diffraction ◽  
Counting System ◽  
Internal Gain ◽  
Discriminator Threshold ◽  
A Charge ◽  
Charge Sensitive Preamplifier

A cooled avalanche-photodiode (APD) detector has been developed for X-ray diffraction experiments. Although an APD is normally used at room temperature and a high internal gain, the energy resolution can be improved by decreasing temperature and gain. The APD device was cooled to 253 K by a thermoelectric cooler. When the gain was M = 13, the energy resolution was 5% (FWHM) at 16.53 keV with a charge-sensitive preamplifier. By scanning the discriminator threshold level of a fast-counting system, energy spectra were obtained at M ≃ 50 and count rates of up to 4.7 × 107 s−1.

scholarly journals Small All-Range Lidar for Asteroid and Comet Core Missions

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3081
Author(s):  
Xiaoli Sun ◽  
Daniel R. Cremons ◽  
Erwan Mazarico ◽  
Guangning Yang ◽  
James B. Abshire ◽  
...  
Keyword(s):  
Fiber Lasers ◽  
Dynamic Range ◽  
Photon Counting ◽  
Avalanche Photodiode ◽  
Integration Time ◽  
Sample Collection ◽  
Long Distance ◽  
Linear Mode ◽  
Internal Gain ◽  
Pseudo Noise

We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber laser that is intensity modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver detects the coded pulse-train by correlating the detected signal with the RZPN kernel. Unlike regular pseudo noise (PN) lidars, the RZPN kernel is set to zero outside laser firing windows, which removes most of the background noise over the receiver integration time. This technique enables the use of low peak-power but high pulse-rate lasers, such as fiber lasers, for long-distance ranging without aliasing. The laser power and the internal gain of the detector can both be adjusted to give a wide measurement dynamic range. The laser modulation code pattern can also be reconfigured in orbit to optimize measurements to different measurement environments. The receiver uses a multi-pixel linear mode photon-counting HgCdTe avalanche photodiode (APD) array with near quantum limited sensitivity at near to mid infrared wavelengths where many fiber lasers and diode lasers operate. The instrument is modular and versatile and can be built mostly with components developed by the optical communication industry.

Modulated vacancy ordering in SrGe6−x (x≈0.45)

2019 ◽  
Vol 74 (1) ◽  
pp. 137-145 ◽  
Author(s):  
Ulrich Schwarz ◽  
Rodrigo Castillo ◽  
Aron Wosylus ◽  
Lev Akselrud ◽  
Yurii Prots ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ambient Pressure ◽  
Stoichiometric Composition ◽  
Binary Compound ◽  
Crystal Structure Analysis ◽  
Local Defect ◽  
X Ray Diffraction ◽  
Vacancy Ordering ◽  
Metal Type ◽  
A Charge

AbstractThe structural properties of modulated SrGe6−x (x≈0.45) were investigated by means of single-crystal and powder X-ray diffraction combined with quantum chemical calculations. The framework compound SrGe6−x adopts a defect variant of the EuGa2Ge4-type crystal structure. Samples of the binary compound with nominal compositions 0≤x≤0.5 were synthesized at pressures from 5 to 6 GPa and a temperature of typically 1400 K. The product reveals diffraction peaks of the EuGa2Ge4-type subcell plus additional reflections indicating an ordered superstructure. Detailed crystal structure analysis evidences the incommensurate nature of the superstructure and a modulation of the vacancy ordering in the germanium network. The computations have shown that the non-stoichiometric composition of the framework with its local defect organization affects the calculated charge of the strontium anions. Although the chemical composition is close to a charge-balanced situation, temperature-dependent resistivity measurements showed metal-type conductivity. At ambient pressure SrGe6−x decomposes exothermally and irreversibly at T=680(10) K into SrGe2 and germanium, indicating its metastable nature at ambient pressure.

First (3 + 2)-dimensional superspace approach to the structure of levyclaudite-(Sb), a member of the cylindrite-type minerals

2006 ◽  
Vol 62 (5) ◽  
pp. 775-789 ◽  
Author(s):  
Michel Evain ◽  
Vaclav Petricek ◽  
Yves Moëlo ◽  
Colette Maurel
Keyword(s):  
Energy Minimization ◽  
Inorganic Compounds ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Layer Compound ◽  
X Ray ◽  
Density Modulation ◽  
Wavelength Control ◽  
A Charge ◽  
Positively Charged

The structure of synthetic levyclaudite-(Sb), approximately (Pb1 − y Sb y S)1.357[Sn1 − x (Cu2) x S2], has been determined by single-crystal X-ray diffraction on the basis of the (3 + 2)-dimensional superspace approach. This misfit-layer compound, of the cylindrite type, results from the combination of two heavily modulated triclinic Q and H subsystems with a common q wavevector and only one shared reciprocal axis (stacking direction). The Q pseudo-tetragonal layer, ∼(Pb0.70Sb0.30S), derived from the NaCl archetype, is positively charged; the H pseudo-hexagonal layer, ∼(Sn0.85Cu0.30S2), derived from the CdI2 archetype, is negatively charged, owing to the replacement of Sn4+ in an octahedral coordination by Cu+ pairs in an opposite triangular coordination. The analysis shows a strong transverse displacive modulation of the two layers, referred to as a `mondulation', correlated to a maximal Sb site occupation factor in the concavity of the Q layer undulation. The wavelength control of the `mondulation' obeys the vernier principle (14cQ ≅ 13cH ), which would correspond to an energy minimization through a charge transfer density modulation wave, common to all two-dimensional misfit-layer inorganic compounds.

Event-Driven 2D Detector for Digital Electron Imaging

1997 ◽  
Vol 3 (S2) ◽  
pp. 1089-1090
Author(s):  
G. Y. Fan ◽  
E. Beuville ◽  
P. Datte ◽  
J-F. Beche ◽  
J. Millaud ◽  
...  
Keyword(s):  
Integrated Circuit ◽  
Pulse Height ◽  
Array Detector ◽  
Diode Array ◽  
Signal Pulse ◽  
Discriminator Threshold ◽  
Pixel Array ◽  
Event Driven ◽  
Application Specific Integrated Circuit ◽  
Electron Imaging

An event-driven 2D pixel array detector designed for protein crystallography is being tested to determine its suitability as a direct electron detector for digital imaging in electron microscopy. The detector prototype consists of an 8×8 pixel array with an 150 μm pitch. The device configuration is illustrated in Fig. 1. The detector module consists of a reverse-biased 300 μm thick monolithic silicon diode array which is bump-bonded to an Application Specific Integrated Circuit (ASIC) which instruments each diode in the array. Each pixel cell of the ASIC forms a pixel processor which consists of an amplifier, discriminator, prescalar and readout circuit.When an incident electron enters the detector, a group of electron-hole pairs is created in the silicon. The detector bias of the diode array is such that holes are collected at the input to the amplifier where the signal is then amplified and shaped. When the output signal pulse height is greater than the discriminator threshold, the event is then registered in the prescalar, causing one count to be accumulated.

Cation and vacancy distribution in an artificially oxidized natural spinel

1997 ◽  
Vol 61 (406) ◽  
pp. 411-421 ◽  
Author(s):  
Giorgio Menegazzo ◽  
Susanna Carbonin ◽  
Antonio Della Giusta
Keyword(s):  
Single Crystal ◽  
Tetrahedral Site ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
Reflected Light ◽  
Marginal Part ◽  
Influence Of Temperature On ◽  
Vacancy Distribution ◽  
Crystal Structural ◽  
A Charge

AbstractDuring research on the influence of temperature on cation partitioning in natural Mg-Al-Fe2+-Fe3+ spinels, some crystals were accidentally oxidized during heat treatment. The oxidation product, studied by means of single-crystal X-ray diffraction, turned out to be a phase retaining the Fd3m parent spinel structure, but with cell edge a and oxygen coordinate u considerably smaller than the parent ones (a ∼ 8.087 as compared with ∼ 8.111 Å; u ∼ 0.2609 vs. 0.2617–0.2636) and with vacant sites due to oxidation.Assuming that the oxidation process must occur due to the addition of oxygen to the crystal boundary as cations are being preserved and rising in total valence, the site population was determined and compared with that of untreated and heated samples. It was found that, on oxidation, a charge enrichment in the tetrahedral site T had occurred, this phenomenon following that observed during heating at increasing temperatures also in other spinel series. This continuity was always in the direction of an increase in random charge distribution. Cation vacancies produced during oxidation were restricted to the octahedral site M.Examination of bulk sections by reflected light microscopy showed a few hematite lamellae as inclusions in the oxidized samples, not detectable by microprobe analysis or single-crystal structural refinement. However, hematite played a marginal part in oxidation. Vacancy-oxygen distances in oxidized spinels were determined from experimental data in the literature.

scholarly journals Synchrotron x-ray diffraction study of a charge stripe order in18-dopedLa1.875Ba0.125−xSrxCuO4

2003 ◽  
Vol 67 (14) ◽  
Author(s):  
H. Kimura ◽  
H. Goka ◽  
M. Fujita ◽  
Y. Noda ◽  
K. Yamada ◽  
...  
Keyword(s):  
Diffraction Study ◽  
X Ray Diffraction ◽  
X Ray ◽  
Stripe Order ◽  
Charge Stripe ◽  
A Charge

Suppression of X-Ray Fluorescence Background in X-Ray Powder Diffraction by a Mercuric Iodide Spectrometer

1983 ◽  
Vol 27 ◽  
pp. 307-316
Author(s):  
J. Nissenbaum ◽  
A. Levi ◽  
A. Burger ◽  
M. Schieber ◽  
Z. Burshtein
Keyword(s):  
Powder Diffraction ◽  
Energy Resolution ◽  
Scintillation Counter ◽  
Peak Height ◽  
Maximum Energy ◽  
Mercuric Iodide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Order Of Magnitude ◽  
Diffraction Patterns

AbstractWe have explored the merits of using a Hgl2 spectrometer as a detector in x-ray diffraction systems instead of a proportional gas counter, or a scintillation counter. The full width at half maximum energy resolution of the HgI2 spectrometer used was about 1.1 keV for the CuKα line (8.1 keV), and about 1.5 keV for the MoKα line (17.4 keV), The energy resolution was utilised to eliminate x-ray fluorescence background from powder diffraction spectra. We demonstrate the suppression of Fe x-ray fluorescence in diffraction patterns of ErFe03 obtained with a Cu x-ray tube, and of Y x-ray fluorescence in diffraction patterns of Y2O3 obtained with a Mo x-ray tube. The peak height to background ratios were improved by about an order of magnitude in both cases.

A High-Speed Signal Processor Using a Digital Divider for Position Sensitive Proportional Counters

1980 ◽  
Vol 24 ◽  
pp. 173-176
Author(s):  
S. Kobashi ◽  
K. Mochiki ◽  
K. Hasegawa ◽  
A. Sekiguchi ◽  
H. Hashizume ◽  
...  
Keyword(s):  
High Speed ◽  
Dead Time ◽  
Present System ◽  
X Ray Diffraction ◽  
Analog To Digital ◽  
X Ray ◽  
System A ◽  
Proportional Counters ◽  
Position Sensitive ◽  
A Charge

Most position sensitive proportional counters (PSPCs) currently used in X-ray diffraction experiments have a dead time longer than 5 μs. Though such PSPCs are useful in measuring weak diffraction diagrams, a faster counter is needed to detect strong X-ray diagrams produced with synchrotron radiation sources. The long dead time of PSPCs using a charge division position read-out is due to the slow analog division circuit plus analog-to-digital converter employed in the present system. A fast processor can be built utilising two high-speed ADCs to digitize voltage signals from the detector, followed by a digital divider to compute position of detected photons. The present paper describes the design of such a processor and some preliminary testings of its performances.

A Technique for Studying Coprecipitated Chromia-Alumina Catalysts by X-Ray Diffraction

1960 ◽  
Vol 4 ◽  
pp. 117-129
Author(s):  
W. L. Kehl
Keyword(s):  
Background Radiation ◽  
Pulse Height ◽  
Chromium Concentration ◽  
White Background ◽  
X Ray Diffraction ◽  
Pulse Height Analyzer ◽  
X Ray ◽  
Gas Proportional Counter ◽  
Diffraction Patterns ◽  
Alumina Catalysts

AbstractA diffractometer equipped with a gas proportional counter and pulse-height analyzer provides a very satisfactory means of recording the X-ray diffraction patterns of chromium-containing materials with Cu Kα radiation. The fluorescent chromium K radiation can be rejected along with much of the white background radiation without appreciable loss of Cu Kα intensity, and the advantages of copper over chromium or molybdenum radiation can be fully utilized. This is illustrated by an X-ray diffraction study of coprecipitated chromia-alumina catalysts, in which the chromium concentration varies between 0 and 37 w, %. At each chromium concentration the precipitate was studied in the washed and dried state, as well as after calcination at 500, 750, and 1400°C. X-ray diffraction patterns are presented to show the phase transformations and sample inhomogenelties that were observed.

Instrumentation for X-Ray Diffraction Studies of Highly Radioactive Samples

1958 ◽  
Vol 2 ◽  
pp. 107-115
Author(s):  
Vincent G. Scotti ◽  
James I. Mueller ◽  
John J. Little
Keyword(s):  
Radiation Damage ◽  
Gamma Ray ◽  
Pulse Height ◽  
Fission Products ◽  
Analytical Tool ◽  
Nuclear Engineering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Background Ratio ◽  
Gamma Ray Irradiation

AbstractWith the advent of nuclear engineering, x-ray diffraction has become an important analytical tool in the study of radiation damage due to neutron and gamma-ray irradiation. The materials under study in this work have rdioactive levels up to 40 R/hr. at 17 centimeters combined β and γ. The activity of the various samples under study may be due to (n, γ) reactions or fission products or both.Data are presented to illustrate the use of sample shielding, detector shielding pulse height discrimination and the combination of all three aids in an effort to attain the most favorable peak to background ratio.

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