Gamma ray source

Cobalt-60, an artificial isotope, is an important gamma ray source, and is extensively used as a tracer and a radiotherapeutic agent. 

The density section of the tool, also seen in Figure 4-281, uses a 1.7 curie (Ci) of 137-cesium (Ce) gamma ray source in conjunction with two gain-stabilized scintillation detectors to provide a high-quality, borehole compensated density measurement. 

Due to the presence of the Belt the rate of SN around us (say in few hundred parsecs) during the last several tens of million years is higher, than it is in an average place at a solar distance from the galactic center. Because of that there should be a local overabundance of young NSs which can appear as hot cooling objects, as gamma-ray sources etc. 

Mirabal, N., Halpern, J.P. (2001), A neutron star identification for the high-energy gamma-ray source 3EG J1835+5918 detected in the ROSAT All-Sky Survey , ApJ 547, LI37. 

In the past, the extraction of Sr and Cs was investigated for some practical applications (heat and gamma ray sources) but the main interest today is for decreasing the thermal power and the potential hazard of nuclear waste in underground repositories. Results of extractions with some... 

The calibration is done by national or secondary standards laboratories. Calibration at the National Institute of Standards and Technology (NIST) involves exposure to either gamma ray source ( Co) over the dose range 10° to 10 Gy, or high-energy electron beam (1 to 28 MeV) combined with a graphite or water calorimeter. ... 

Figure 7. Flow and instrumentation diagram for high temperature, balanced pressure bench-scale unit. LR, level recorder LT, level transmitter TR, temperature recorder FR, pressure recorder FR, flow recording RD, densitometer PC, pressure controller TC, temperature controller GM, gas meter F, filter VSD, variable speed drive PCV, pressure regulator CV, control valve SV, solenoid valve S, gamma ray source.

The third analog experiment was performed in the presence of a cobalt-60 gamma ray source The average dose rate to experimental components was 1 x 105 rad/h ... 

Irradiation of the samples was performed at the Institut Armand-Frappier (IAF). Four irradiators with different dose rates were used. In all instances, Cobalt-60 ( Co, half-life 5.26 years, 1.25 MeV yray photon) was used as the gamma ray source. The GammaCell I, n, HI and the Calibrator emit y rays at 107,350,700 and 3000 krad/h respectively. At the end of the experimental runs, the 107 and 350 krad/h dose rates of the GammaCell I and n were down to 85 and 265 krad/h respectively, due to the Co half-life. The calibrator was kept constant at 3000 krad/h. The exact value of the various dose rates was constantly monitored during the experiments. 

Annihilation fluxes would be enhanced, to a level where such sources could possibly account for a subset of the unidentified EGRET gamma ray sources. 

Quality assurance (QA) measurements also are performed with a set of QA gamma-ray sources to confirm that the radiation detection instrument is functioning normally. The measurements are performed at regular intervals and the results are plotted to show the mean value and random deviations by 1 and 2 standard deviations (cr and 2cr). The factors that are considered include the count rate at characteristic control source peaks, the resolution of these peaks, and the background radiation shown by the detector. Any significant deviations beyond the 2-sigma values on the control charts require a repeated measurement and - if confirmed - corrective actions before further measurements are performed. 

Gamma-ray sources for activity calibration as standard sources are characterised in terms of activity, expressed in kBq. They can be used for the calibration of all gamma-ray detectors and spectrometers Nal(Tl) or Ge(Li) (see Table 4.13 for the list of radionuclides available and their characteristics). Four types of sources are available ... 

Gamma-ray sources for efficiency measurements as standard sources are characterised in terms of photon emission flux in 4tc sr, expressed in s, for each specified gamma-ray. The activity of the source is indicated. When an activity standard is used to determine the efficiency of a y-ray spectrometer as a function of photon energy, certain decay scheme parameters are required (gamma branching ratio, internal conversion coefficient, etc.). In this case, the calibration uncertainty is the combination of the uncertainty on the activity of the standard and of the uncertainties on the parameters of the decay scheme. 

Table 4.13 Gamma-ray sources for activity calibration Chapter 4... 

Gamma-rays follow the inverse square law over a wide range of exposure rate and distance. Suppose that a point gamma ray source is uniformly emitting S photons of energy E (MeV) per second in every direction. The photon fluence rate d> (photons/ cmVs) at a distance of d cm from the source is represented by... 

Now, suppose that n photons are emitted in a single disintegration. With the yield of photon i taken as P. and energy as E. (MeV), the exposure rate X(R/h dps) at a point 1 cm off a point gamma-ray source of 1 dps (Bq) is represented by... 

R-m7(h Ci)). Exposure rate X(R/h) at a distance d (m) from a gamma-ray source of radioactivity A (Ci) can be approximated by using this exposure rate constant T as follows ... 

We have carried out methane radiolysis experiments under widely varying conditions (9). The most important results are obtained either by homogeneous gamma ray irradiations with a Co source or by heterogeneous irradiations with this same gamma ray source or with fission fragments. Alumina (CAU), silica (CSU), and uranium impregnated charcoal (ECU) have been used as microporous solids. 

Ci of cesium-137 are used for the gamma ray source of an experimental food irradiation unit. What is the amount of activity remaining after 5 years The half-life of cesium-137 is 11,000 days. 

The optimal square bin size for detection of a point gamma-ray source with Milagro is 2.1° on a side corresponding to an angular resolution of 0.75 °. To search for diffuse gamma-ray sources with angular extent greater than or equal... 

A compelling motivation for the search of gamma ray sources in the energy range between 30 GeV and 300 GeV is the apparent discrepancy between the well populated sky-map of sources below 10 GeV observed by EGRET (more than half of them still unidentified) and the handful of sources discovered by... 

---