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Relative efficiency values are often used for germanium detectors, and compare the efficiency of the detector at 1332 keV to that of a 3 in × 3 in NaI detector (i.e., 1.2×10 −3 cps/Bq at 25 cm). Relative efficiency values greater than one hundred percent can therefore be encountered when working with very large germanium detectors.
The detector is a photodiode made of a 1.2 kg germanium crystal, reverse biased to about 3 kilovolts, mounted at the end of a six-meter boom to minimize interferences from the gamma radiation produced by the spacecraft itself. Its spatial resolution is about 300 km. [3] [4] The neutron spectrometer is 173 by 144 by 314 mm (6.8 by 5.7 by 12.4 in).
It has a half-life of 30 years, and decays by beta decay without gamma ray emission to a metastable state of barium-137 (137m Ba). Barium-137m has a half-life of a 2.6 minutes and is responsible for all of the gamma ray emission in this decay sequence. The ground state of barium-137 is stable. The photon energy (energy of a single gamma ray) of ...
Materials for shielding gamma rays are typically measured by the thickness required to reduce the intensity of the gamma rays by one half (the half-value layer or HVL). For example, gamma rays that require 1 cm (0.4 inch) of lead to reduce their intensity by 50% will also have their intensity reduced in half by 4.1 cm of granite rock, 6 cm (2.5 ...
[8] In its first year, a new stem, the primocane, reaches a full length of about 3–6 metres (9.8–19.7 feet) trailing on the ground and bearing large palmate compound leaves with 5–7 new leaves; it does not produce any flowers. [8] In its second year, the cane is a floricane with a non-growing stem. [8]
The source was detected in the ultraviolet (but not in X-rays) 15.3 hours after the event by the Swift Gamma-Ray Burst Mission. [4] [6] After initial lack of X-ray and radio detections, the source was detected in X-rays 9 days later [29] using the Chandra X-ray Observatory, [30] [31] and 16 days later in the radio [32] using the Karl G. Jansky ...