Gammasphere Detectors

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An outlined detector of Gammasphere and its different parts.

The detectors in Gammasphere are high purity germanium detectors sensitive to x- and gamma-rays from a few dozen keV to ~10MeV energy. All Gammasphere detectors are Compton shielded using bismuth germanate (BGO) shields. Six planar BGO detectors form a hexagonal shield array around the HPGe detector sides and a 7th BGO shield behind (at farther radius from the interaction point) is used as a "back plug". The germanium detector itself is of the coaxial type. Incident gamma-rays typically deposit charge in the germanium that is read out through the center contact. A detector in the upgraded Gammasphere system consists of Ge and BGO, a preamplifier, a nitrogen tank, a slope box, and an SBX. All the hardware is there to monitor or maintain the Ge and BGO.

The data that is collected in each detector occurs when gamma rays hit the Ge and BGO of the detector. Incident gamma-rays typically deposit charge in the germanium that is read out through the center contact, creating various signals. The signal is understood and conditioned through the DAQ system, the data acquisition system that presents human-readable results to the user. Detectors are the first components of Gammasphere to acquire any kind of data about gamma ray interaction. The data that is collected in each detector goes through the DAQ system, the data acquisition system which presents results to the user.

Segmented Detectors

Many of the Ge detectors in Gammasphere are segmented. In these the Ge portion of the detector is split in half resulting in three Ge contacts (Center, Side A, Side B). Only one of the side connections is brought out to the digitizers as the charge that would be in the other side is given by subtraction of the measured side from the center contact.

Non-Segmented Detectors

Non-Segmented detectors are the same as segmented ones, but the Ge inside of the detector isn't split, resulting in two Ge contacts instead of three. The hardware is nearly identical, and the main difference is in the signals that are sent.

Detector EPICS Screens

Gammasphere Detectors have multiple relevant screens. The primary ones used are the temperature screens of the detector and the relevant process variables (PVs).

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