Particle X-ray

Fig. 8.28 External view of the MIMOS II sensor head without contact plate assembly (left) MIMOS II sensor head mounted on the robotic arm (IDD) of the Mars Exploration Rover. The IDD also carries the a-Particle-X-ray Spectrometer APXS, also from Mainz, Germany, for elemental analysis, the Microscope Imager MI for high resolution microscopic pictures ( 30 pm per pixel), and the RAT for sample preparation (brushing grinding drilling (< 1 cm depth)). Picture taken at Kennedy-Space-Center KSC, Florida, USA...

Thermal Emission Spectrometer) instrument indicated the metallic nature of the rock [340]. Observations made with the panoramic camera and the microscopic image revealed that the surface of the rock is covered with pits interpreted as regmaglypts and indicate the presence of a coating on the surface. The a-Particle-X-ray spectrometer (APXS) and the Mossbauer spectrometer were used to investigate the undisturbed and the brushed surface of the rock. Based on the Ni and Ge... 

MIMOS lla is an advanced version of the MER instruments (Klingelhofer et al. 2003) operating continuously since landing in January 2004. A new detector system has been implemented, inherited from the Alpha Particle X-ray Spectrometer (APXS), also part of the MER payload. This Si Drift Detector system provides higher energy resolution and increased... 

Ming, D.W. et al. 2008. Geochemical Properties of Rocks and Soils in Gusev crater, Mars Results of the Alpha Particle X-ray Spectrometer from Cumberland Ridge to Home Plate. Journal of Geophysical Research, 113, E12S39,... 

Andreev Belyaev (Ref 8) describe action on various explosives of ions, electrons, U28S fragments, alpha particles, X-rays and of supersonic waves, but it is not stated how this action affects the deton velocity... 

The Mars Pathfinder rover carried an Alpha Proton X-ray Spectrometer (APXS), and the two Mars Exploration Rovers (MER - Spirit and Opportunity) carried Alpha Particle X-ray Spectrometers (also called APXS, but in this case more precise versions of the Pathfinder instrument, though without the ability to monitor protons for light element analyses). These instruments contained radioactive curium sources (Fig. 13.16) whose decay produced a-particles, which irradiated target rocks and soils. The resulting characteristic X-rays provided measurements of major and minor element abundances. The MER rovers also carried Mossbauer spectrometers, which yielded information on iron oxidation state. 

Gellert, R., Rieder, R., Briickner, J. et al. (2006) The Alpha Particle X-Ray Spectrometer (APXS) results from Gusev crater and calibration report. Journal of Geophysical Research, 111, E02S05, doi 10.1029/2005JE002555. 

Rieder, R., Gellert, R., Anderson, R. C. et al. (2004) Chemistry of rocks and soils at Meridiani Planum from the alpha particle X-ray spectrometer. Science, 306, 1746-1749. 

All Mars rovers to date have carried alpha-particle X-ray spectrometer (APXS) instruments for chemical analyses of rocks and soils (see Fig. 13.16). The source consists of radioactive curium, which decays with a short half-life to produce a-particles, which then irradiate the sample. Secondary X-rays characteristic of specific elements are then released and measured by a silicon drift detector. The Mars Pathfinder APXS also measured the backscattered a-particles, for detection of light elements, but the Mars Exploration Rovers measured only the X-rays. 

As shown by the investigations of a number of authors, irradiation of lead azide (and other azides) with a-particles, X-rays and y-rays does not cause explosion (Ha issinsky and Walden [89] Gunther, Lepin and Andreyev [90]). However, it produces a slow decomposition of lead azide, according to Kaufman [91]. 

A theory was applied to these curves known as hit theory. This purported to describe the physical action of the radiation, whatever its type—y, a-particles, X-rays—in terms of quantum hits on a target in the cell such that after n or... 

Neutron activation analysis is based upon the production of radioisotopes by nuclear reactions resulting from neutron bombardment, followed by identification and measurement of the different radioisotopes formed. Element activation can also be carried out by bombardment with high-energy charged particles, X-rays or gamma rays (5). 

The choice of the nondestructive technique used in the examination of the sample on hand also depends upon the complexity of the shape of the sample. The following order of the methods is in progressively increasing complexity of the shape of the sample to be examined acoustic microscopy, microwave method, eddy current, magnetic particle, X-ray radiography, ultrasonics, liquid penetrant and visual methods. 

Electron paramagnetic resonance experiments also support the existence of ferromagnetic iron particles. X-ray powder diffraction experiments, electron microscopy, and surface analysis measurements show the existence of both metals on the surface before and after reduction. We know the particle size again is quite large, although there is a wide digtribution in these samples, ranging from 30 A to about 150 A. 

Radiation hardness Detectors for neutrons and a particles. X-ray lithography masks... 

Figure 12.16 Alpha particle X-ray spectrometer (APXS). To determine the elemental composition of rocks and soils of Martian surface, the rovers, which landed in 2004 on Mars, carry a deployment device that could be in contact with the rocks. The sensor head contains six Cm radioactive sources, six alpha detectors and one X-ray detector in the centre. The accumulation time is a few hours per sample analysed.

For each absorbed x-ray photon or neutron, the proportional or scintillation counter produces a discrete electric pulse. The flux J of the beam of x-rays or neutrons is measured as the number of counts of such pulses observed per second. If measurements are made repeatedly with a beam of constant flux, the number of counts observed during a fixed time period is not exactly the same, but is rather subject to statistical fluctuations. The arrival time of any one particle (x-ray photon or neutron) is totally uncorrelated with the arrival time of the next particle. The flux J of the particles,... 

An analogous synthetic approach has been used by Fox et al. [SO] for the preparation of CdSe/ZnSe core-shell particles. X-ray photoelectron and Auger and absorption spectroscopies were applied to demonstrate the assumed structure of both composites, CdSe on ZnSe and ZnSe on CdSe. It is found that the shell material dominates the optical properties of the particles, even when the narrower bandgap material was used for the core. This apparent contradiction to the above-mentioned statement of Brus et al. on the composite ZnS on CdSe is probably due to different sizes and different core-to-shell ratios in the two studies. 

In this introductory chapter, we present the types and main properties of ionizing radiation and general description of its interaction with matter. In addition, taking into account that some other chapters of the present book are dedicated, in particular, to the synthesis of materials using P-particles and y-irradiation, here in the present chapter we will carry out the analysis of examples of more rare application of a-particles, x-rays, neutrons, protons, and ion beams for obtaining various materials, composites, and chemical compounds. 

Among the characterization techniques, the primary one is particle X-ray diffraction (PXRD) analysis, which is essential to determine if the material retained the crystal structure following the postmodification steps. Nevertheless, this technique suffers from the inability to detect amorphous by-products, if any, and by the sometimes weak response due to the presence of crystalline impurities and/or structural distortions [85]. Measurement of the BET surface area gives evidence whether species, Unked or not, are trapped inside the pores and the accessible volume is reduced. In addition, elemental analysis of the modified MOFs is essential to determine the exact formula of the material. However, the framework often contains an undetermined number of solvent molecules that could lead to difficulty in interpreting the data. 

---