Gamma-rays with detector

Findings with PDU. Work with the PDU largely paralleled the bench-scale reactor tests there was one important addition—extensive three-phase fluidization studies. As was mentioned, the PDU is equipped with a traversing gamma-ray density detector that is capable of measuring bed density to within dbO.Ol specific gravity units. Thus, we could measure and correlate fluidized bed expansion as a function of liquid and gas velocities and physical properties, and could also determine the... 

Gas-filled detectors are used, for the most part, to measure alpha and beta particles, neutrons, and gamma rays. The detectors operate in the ionization, proportional, and G-M regions with an arrangement most sensitive to the type of radiation being measured. Neutron detectors utilize ionization chambers or proportional counters of appropriate design. Compensated ion chambers, BF3 counters, fission counters, and proton recoil counters are examples of neutron detectors. 

These have been used for detecting gamma rays with high positional resolution in 2D-ACAR experiments (see 7.2) [20], although—principally for reasons of availability, lower complexity and more straightforward maintenance—scintillation detectors are more common. Very briefly, a spark chamber is modified to detect gamma radiation with positional... 

The Milagro detector s large field of view and continuous duty cycle make it an ideal instrument for the discovery of previously unknown sources. Recent publications cover topics including detection of the Crab Nebula[l], limits on TeV emission from GRB [2] and a TeV all-sky survey of the northern celestial hemisphere[3]. Recently we have presented papers on the detection of diffuse TeV emission from the Galactic plane[4], limits on TeV emission from satellite detected GRB[5], a study of nearby AGN[6] and limits on relic neutralino annihilation derived from TeV flux limits from the sun[7]. The focus of this paper is the search for extended sources of TeV gamma rays with the Milagro detector. 

Many factors affect a gamma radiation measurement (Knoll, 1979 Tsoulfanidis, 1983). The most important factors relevant to the CAPTF are the characteristics of the radioactive source, the interaction of gamma rays with matter, the position of the source relative to that of the detector, the efficiency of the scintillation detector, and the dead-time behavior of the whole measurement system. These factors are separately discussed in the following subsections. 

Radioactive tracer techniques have long been used to study particle motion in solids fluidization systems. The advantage of this technique is that the flow field is not disturbed by the measurement facility and, therefore, the measurement of the motion of the tracers represents the actual movement of particles in the system. The tracer particles are usually made of gamma-emitting radioisotopes, and their gamma radiation is measured directly by scintillation detectors. Factors that affect gamma radiation measurement were identified as the characteristics of the radiation source, interactions of gamma rays with matter, the tracer s position relative to the detector, detector efficiency, and dead time of the measurement system. 

Counting Gamma Rays with a Germanium Detector and Spectrometer... 

Photoelectric interaction in materials surrounding the detector can result in characteristic X rays in the lower energy region of the gamma-ray spectrum. For example, the Ka (72 keV) and Kp (85 keV) X rays are almost always part of the background in a spectrum of a detector shielded with lead. Commercially available lead shields for gamma-ray-spectrometer detectors are lined with thin cadmium and copper layers to attenuate these lead X rays. 

The G-M counter is a simple and relatively inexpensive gas-filled tube with a count-rate meter an amplifier may also be present. The G-M detector counts alpha particles, beta particles, and gamma rays with a very thin window, counts beta particles and gamma rays with a thicker window, and counts gamma rays only with a thick shield. Alpha and beta particles interact in the gas gamma rays interact mostly in the walls, from which electrons enter the gas. The intrinsic efficiency for counting gamma rays relative to beta particles depends on the amount and type of solids surrounding the detection gas. 

All of these interactions by gamma rays with the detector can be modeled by a gamma-ray simulation program such as the previously cited Monte Carlo n-particle code, version 4. Modeling requires precise information on the location and material of the source, detector, and surroundings. A description of the detector such as that shown in Fig. 8.9 must be obtained from the supplier because the detector container is sealed. 

Thin Ge detectors with spectrometer systems are designed to detect gamma rays with energies as low as a few kiloelectron volts to measure K X rays of lighter elements and L X rays of heavier elements. Peaks are resolved for energy... 

Bertrand GHV, Hamel M, Normand S, Sguerra F (2015) Pulse shape discrimination between (fast or thermal) neutrons and gamma rays with plastic scintillators state of the art. Nucl Instmm Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip 776 114-128... 

The abundance of LEU products is determined with a total uncertainty of 0.13% (Is) by measuring the 186 keV gamma rays with a Nal or GeLi well detector on 5 ml solutions containing a well-known amount of uranium, close to 0.5 g. The volume of the sample and synthetic calibration test solutions, their acid and U concentrations are kept in a very narrow range so that the self-absorption and coimting geometry be constant factors or minor variations be accurately... 

In an earlier section, I briefly mentioned the collection of the charge carriers produced by interaction of the gamma-ray with the detector crystal. If we are to understand some of the problems in gamma spectrometry, it is necessary to discuss charge collection and the mobility of the charge carriers in more detail. 

The list now represents what is likely to be observed in a 200 000 s background spectrum measured by a 50 % detector housed in a typical commercial shield in a routine ground-level counting room in an unremarkable geological area of the UK. Ac and Bi emit hundreds of gamma-rays with low emission probability not included in the hst. From time to time, particular with very long counts, some of these may be detected. 

CHARGE CARRIERS Collectively electrons and holes created by the interaction of the gamma-ray with the detector that comprise the detector signal. 

Break foam with hot pipes Water shots in hot oil Rapid depressurization Gamma-ray foam detectors Defoaming chemicals Split liquid levels... 

One commercially proven method to follow foam levels in difficult services is with a gamma-ray level detector. This device, in effect, looks through the vessel wall and finds the foam level by detecting changes in density inside the vessel. Gamma-ray level detection has proven to be quite valuable in black-oil services. 

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