Gamma detection with

After the end of the 4-day exposure, the detectors were returned to EML for analysis. The amount of radon adsorbed on the carbon device was determined by counting the gamma rays of radon progeny in equilibrium with radon. The concentrations of radon in the buildings were determined from the radioactivity in the device and the calibration factor, obtained in a radon chamber, that takes into consideration the length of exposure and a correction for the amount of water vapor adsorbed during the exposure. The lower limit of detection with this technique is 0.2 pCi/1 for a measurement period of 4 days when the test sample is counted for 10 min, 4 days after the end of exposure. More than 90% of the radon monitoring devices were analyzed successfully. Most of the unsuccessful measurements were due to delays or losses caused by the participants. 

Most radioactive nuclides employed in radiopharmaceuticals have a short half-life. This is beneficial to the patient as the total number of radioactive atoms given to the patient to produce an image is small when the half-life of the radioactive nuelide is short, as compared to longer half-life radioactive nuclides. Fewer total atoms reduce the radiation dose to the patient and thus the risk from a nuclear medi-eine procedure. However, the short half-life of the radioactive nuclide results in a short shelf-life for the radiopharmaeeutical. As a result, most radiopharmaceuticals are eompounded on a daily basis. The most common radioactive nuclide used for this purpose is technetium-99m (Te-99m) with a half-life of 6 hr, emiting only gamma radiation with an energy almost ideal for detection. 

Signal-to-noise considerations make most neutron-based explosive detection approaches very difficult to implement. The basis for combining multiple detection approaches (FNA, along with thermal gamma detection and neutron transmission spectroscopy) in a FNAP application that preserves the small volume advantage of a APSTNG remains to be established. There are distinct advantages associated with the API approach, but the concomitant reductions in available neutron flux, issues of tube lifetime, and the intrinsic poor spatial resolution must be taken into consideration for potential applications. 

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... 

Flaxseed oils contain much lower amounts of tocopherols, half of the amount present in sunflower and canola oils and one-third of that present in soybean oil (Table 2). A lower content of these antioxidants makes these oils even more susceptible to oxidation. Gamma-tocopherol was found as the main tocopherol in flax oils, with a contribution of about 80% to the total amount. This makes flax oil comparable with soybean oil. Among unique antioxidants detected in flax oils was plasto-chromanol-8. This compound is a derivative of gamma tocotrienol with twice as long unsaturated side chain. Plastochromanol-8 was found to be a more efficient antioxidant than any tocopherols isomer (15). A low content of tocopherols in flaxseed did not make them more susceptible to oxidation experiments showed that milled flaxseed could be stored for 28 months at ambient temperatures without measurable changes in oxidation products. This can be attributed to the presence of antioxidants other than tocopherols in the seeds (16). 

Milagro is a unique TeV gamma-ray observatory capable of continuously monitoring the overhead sky. The directions of gamma-rays impacting the earth s atmosphere are reconstructed through the detection of air-shower particles that reach the earth. The shower particles are detected with a 60m x 80m... 

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. 

Lamanna G. High-energy gamma-ray detection with the Alpha Magnetic Spectrometer on board the International Space Station . Nuclear Physics B (Proc. Suppl.) 113 (2002) 177-185. 

The ampoules were filled with the CRM solution and left in contact with the solution for at least 24 h. After the conditioning each ampoule was emptied, filled with the solution and immediately heat-sealed. The samples were sterilised by gamma-irradiation with a °Co source, dose 25 kGy. After irradiation the ampoules were stored at ambient temperature in the dark. Some differences were observed in the contents before and after irradiation, particularly in the CRM 408 for hydronium, ammonium and nitrate. It was suspected that nitrate could have been formed from ammonium upon irradiation. Nitrite was also detected immediately after irradiation but was probably rapidly oxidised. 

Check Sources. The following isotopes have been used by the military as check sources Cobalt-60, Krypton-85, Strontium-90, Barium-133, Cesium-137, Lead-210, Radium-226, Thorium-232, Uranium-238, and Plutonium-239. As such, they are normally found as sealed sources associated with radiation detection instrumentation or in a calibration lab, and would take some serious effort to release to the environment. Sealed sources represent an external exposure hazard only (unless they are physically destroyed). One other item that should be considered with respect to sealed source beta emitters is that they are often associated with lower energy. The other sources are gamma emitters, with the exception of the Am-Be source that produces neutrons. The gamma emitters will expose the whole body externally, as will the neutron source. The sealed sources will be detected in most cases using the AN/PDR-77 with the beta/gamma probe. 

Less common detection of electrons is by photons emitted during their deceleration in a medium. The two mechanisms are creation of bremsstrahlung (continuous X-ray spectrum) and Cherenkov radiation (visible light). Cherenkov radiation is detected with a PMT bremsstrahlung X rays are detected as discussed below for gamma rays. 

The radionuclides in this category that emit beta particles also emit gamma rays that can be detected by spectral analysis. Short-lived radionuclides that emit alpha particles occur in the natural decay chains and usually are identified by other members of the decay chain that emit gamma rays. One caution to consider is that air filters and other surfaces in the environment collect particulate progeny of °Rn and Rn that emit alpha particles, beta particles, and gamma rays with half-lives of minutes to hours. Observation of such emissions and decays has misled unprepared observers into attributing these radiations to man-made radionuclides. 

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. 

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... 

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