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Four radiation detectors have been simulated in VIRTUS. Handheld systems include the Canberra UltraRadiac™ (AN/UDR-13/14/15) and the Thermo Scientific RadEye™ PRD-ER. These two hip-mounted devices are used by military, first-responder, and industry personnel worldwide.
The Thermo Scientific PackEye™ is a backpack system, and the handheld indicator module (left) has been integrated. The PackEye can detect both γ-rays and neutrons, and the two functionalities are simulated in VIRTUS.
VIRTUS simulates a vehicle-mounted detection system called the Thermo Scientific Mobile Detection System (MDS). The real MDS is housed within a large case, and it includes approximately five liters of scintillating crystals for γ-ray detection, as well as He-3 neutron detector. The system is very sensitive, and it can be mounted within land vehicles and helicopters. The user connects a laptop to the MDS on which a software application called MAPTRACK is used. In addition to displaying the exposure and count rates of the detectors in the MDS, MAPTRACK also creates a color-coordinated path onto a map of the local area. The colors of the dots along the path correspond to the levels of radiation detected, helping the user to determine geographic "hot zones." The MAPTRACK interface is simulated within VIRTUS, facilitating vehicle operations training.
The VIRTUS developers used pictures of the detectors as a foundation, linking the button locations on the Android device display with the corresponding physical behavior of the actual detector. Note that, although the manufacturers are aware of the VIRTUS project, they were not involved in this development. The detector behaviors and efficiencies were observed and emulated by the VIRTUS team, and the detectors are simulated only in an approximate way for training purposes. VIRTUS should never be used to evaluate the performance or the capabilities of the detectors that were simulated.
The Map App allows the user to place point sources on the map by touching the screen. A number of different sources approved by the Department of Energy have been modeled, including special nuclear material, medical patients, and industrial sources. The Map App also includes a "fingerpainted rad-map" capability, which allows the user, by rubbing his or her finger on the screen, to specify regions of elevated radiation emission. The longer the finger is held on a spot, the greater the magnitude of the radiation at that spot will be. The user can then define the radiation emissions to which the colors correspond. The user can also change between linear and logarithmic scaling. These fingerpainted rad-maps can be used to approximate heterogeneous radiation background regions and radioactive plumes.
Background maps and imagery data are used in both the Map Tool app and the MDS portion of the detector app. Map and imagery data from live streams, including Google Maps, Mapquest, and theUS Geological Survey, can be cached for offline use.
GPS positioning provides a baseline capability for VIRTUS, but GPS isn't effective indoors. For indoor operations, Bluetooth beacons can be used. The beacons utilize a relatively new Bluetooth standard called Bluetooth Low Energy (BLE), also known as Bluetooth 4.0 and Bluetooth Smart. The BLE standard has been adopted by a number of smartphone and tablet manufacturers. BLE devices require very little energy—a single beacon can have a battery life greater than a month, even with continuous use. Each beacon is about the size of a coin, similar to check sources used in the radiation detector industry. The beacons are set to emit data packets at 10 Hz
Each beacon always emits its signals at the same intensity. A VIRTUS device determines its approximate distance from a given beacon by measuring the strength of the signal received. Like with γ-rays, the RF signal intensity from a beacon drops off according to the squared inverse of the distance. The attenuation properties of RF are different than those of γ-rays, but the behaviors are similar enough for reasonably effective training.
Several beacon types are being integrated, including the StickNFind and the Nordic Semiconductor nRF51822 Kit.
Calculations for static sources and fingerpainted rad-maps are performed on each device regardless of wireless connectivity. A WiFi connection is necessary to push scenarios from device to device.