Detective-200 in Wide Area Search Applications (Land and Air)
In these non-maritime applications, Detective-200s are easily installed into unmodified vehicles, cars, vans, and aircraft for mobile detection applications at higher speeds and larger distances. Additional Detective-200s are easily added into the system for increased sensitivity. The data can be combined by the Detective-Remote software utility. Multiple Detective-200s are easily stacked vertically.
In another class of application the instrument system is stationary and the potential source is moving, such as traffic choke point monitors (toll booths, bridges, tunnels), monitoring entry to a public event, monitoring road traffic or ships passing beneath a bridge structure. The measurement is essentially the same.
The configurability of the Detective-200 solution in both mobile and static applications is a practical benefit which cannot be over-emphasized as requirements constantly change.
Detective-200 in Maritime applications
- “Slow Pass” Materials interdiction
Detective-200 is very well suited for mounting on naval vessels. The IP67 packaging is immune to salt spray. The tough fold-flat handles make it easy to lift and mount aboard a vessel, or transport from vessel to vessel.
A ship-borne Detective-200 system consisting of one or more instruments, controlled through wired or wireless networking via Detective-Remote, is capable of reliably detecting illicit materials on a nearby vessel in a slow “sail by” measurement. Figure 1 shows an example of sensitivity for unshielded HEU at representative speeds and distances for multiple units of Detective-200s.
Choke Point Monitoring
Because of the lack of 100% coverage with fixed traffic portal monitors, it is desirable to be able to quickly setup and configure temporary or "ad-hoc" portal systems capable of monitoring for nuclear devices, dirty bombs, or contaminated materials in pass-through traffic. One or more Detective-200s can be placed inconspicuously at a roadside, pedestrian entryway, vendor services entrance, warehouse dock, or parking garage. The Detective-200 internal battery power and “Auto Identification” reporting provides simple deployment and operation.
Figure 2 provides estimated performance of multiple units of land-based Detective-200s at 10 MPH and distances, up to 40 meters with the same alarm conditions as figure 1.
Detective-200 Hardware Features
Standoff detection is the problem of correctly identifying a distant stationary or near stationary radioactive source. The standoff detection limit is essentially a question of signal-to-noise ratio in the detection system. As distance increases, gamma rays are attenuated by air and a fixed field of view means at further distances more background is in the field of view of the source. Both of these affects reduce the signal-to-noise ratio. As with other applications in low resolution systems, background variation is problematic. The high resolution of the Detective-200 and its large area detector make it an ideal standoff tool either alone or in an array. Figure 3 shows the time to identify 2.5 kg of Bare HEU with a >95% probability of detection and <1 false alarm per 20 hrs. (Note that a critical mass of HEU is approximately 50 kg.)
IMPORTANT NOTE: The effect of Collimation on System Performance
In all of the applications discussed, the time-to-detect or limit-of-identification may be adversely affected by radiation background, which degrades counting statistics and therefore degrades (raises) the minimum detectable (identifiable) nuclide activity. Background can be reduced by restricting the field-of-view (FOV) of the detection system by the use of a shielding collimator. The example data presented in figures 1, 2 and 3 above assume a collimated FOV of 120°. The optimum collimation depends on the measurement speed, distance and then radioactivity of the environment to be encountered. The overall effectiveness of the system depends on the number of Detective-200s and the choice of collimation. ORTEC scientists are happy to provide advice on the most effective configurations.
Detective-200 is fully supported by the latest versions of the Detective-Remote software. Detective-Remote is a Windows-based application which “combines” the identification capabilities of multiple Detective-200s and controls them remotely over direct-connect USB or remotely over wireless LAN. Detective-Remote supports one or more Detectives as participants in a multi-detector system, providing the ability to combine multiple instruments into a composite system, based on multiple “nodes.” By sophisticated techniques (NOT simple spectral summing) the composite system can operate as if it was a single large detector with some positional sensitivity. In contrast to an actual single large detector, contributing Detective-200s which “see” no nuclide ID signal can be temporarily ignored, along with their background contribution, thereby enhancing signal-to-noise in the composite signal compared to a single large detector (as is the case in the NaI “LOGS” often deployed in scintillation detector mobile systems). Detective-Remote software also supports not just Detective-200s, but Detectives of any size or model, and any combination can be used. Data are gathered by Detective-Remote in LIST mode and individual spectra are stored in the localized database and can be exported into other applications such as spreadsheets, GIS applications, or reporting software.
“No other nuclide identification instrument provides such sensitivity and accuracy in such a rugged and flexible package.”
Since the first model was introduced in 2004, all ORTEC Detective identifiers have incorporated the same principle technologies and features, namely:
- High-resolution, high-purity germanium (HPGe) detector.
- Mechanically cooled by miniature Stirling-cycle refrigerator.
- Internal high range GM tube provides gamma dose rate.
- Fast, Simple and ULTRA-Reliable Classification of NORM, Medical, Industrial, SNM and Natural Isotopes, shielded and unshielded.
- Touch Screen or Remote Software Operation.
- ANSI N42.34 and ANSI N42.42 compliant.
- Battery/AC/DC powered, highly stable digital electronics.
- Wired USB, 802.11 wireless communications.
- Local storage of spectra.
- Advanced analysis algorithms developed over thousands of real-world identification situations:
- Low levels of false alarms in the presence of NORM
- High-fidelity identification of mixture constituents
- Resistance to “spoofing” by masking sources
- Immunity to variation in background radiation
- Easy-to-use through intuitive, touch-sensitive screen GUI with operational modes configurable according to individual CONOPS, including long count mode for weak/distant sources.
- Neutron detecting models.
Detective-200 Operational Capabilities
Gamma count rates are presented as a time tracking strip chart.
Detective collects one spectrum per second and runs the ID algorithm against an eight second sliding average. More sensitive to sources which move relative to the instrument. Monitor mode is a valuable search method, but is also useful in ad-hoc portal monitoring applications.
SNM Search Mode
SNM Search mode is designed to help avoid false negatives when determining SNM. It helps in finding the point of maximum count rate which COULD be consistent with SNM.
Key regions of the spectrum are monitored which are critical to the determination of both U-235 (the key constituent of HEU) and Pu-239. The peak region confidence level is displayed in the form of a bar graph. A high and steady reading indicates that "something" is present which is worthy of more investigation. Once the maximum reading has been located, the "confirm" key initiates the full identification algorithm.
SNM Search mode is an INDICATOR of SNM but should always be followed by the confirmatory ID to avoid false positives. In combination, SNM Search and ID modes minimize BOTH false negatives and false positives.
GAMMA DOSE RATE
Gamma Dose Rate is monitored by the HPGe detector and by an internal compensated GM tube. The dose rate is displayed at all times. Dose rate units may be chosen as µSv/hr or mR/hr.
Mobile MCB Server
GPS Position Information
An internal GPS receiver displays GPS coordinates which may be saved along with spectrum data for future use.
Storage of Data (spectrum, search data, ID results)
To internal RAM and removable SD card.
USB connection to laptop. Spectral transfer by Microsoft® ActiveSync. Remote control via Microsoft “remotedsp.exe” (supplied). WiFi (802.11) communication. Wireless Mobile MCB Server software.
Features a large, bright and clear LCD display with touch-sensitive screen. Gamma count rate and gamma dose rate are displayed continuously both numerically and in bar graph form. Menu navigation is highly intuitive. The radionuclide gamma-ray spectrum may be displayed and manipulated (e.g., vertical scale, zoom) like a conventional multichannel analyzer. Y-axis units are now displayed.
In response to customer requests, Detective instruments can now operate in two modes “Classify” and “ANSI”.
The user presses the Identify button and the instrument gathers data until manually stopped, without preset. During the acquisition, suspected nuclide classification messages appear, such as “Suspect Industrial 1”, meaning the presence of one industrial nuclide is suspected. As the count continues and confidence levels increase, this might change to “Found Industrial 1” or disappear as better statistics determine the previously suspected nuclide was not, in fact, present. Clicking on the “Found” or “Suspect” message gives a listing of which nuclides were actually found (or suspected) by name.
This mode is similar to classify mode, but dispenses with the classification, and presents nuclide names directly, both suspect and found.
This is to allow for CONOPS in which it is required to count for a preset time, for example 60 seconds. At the end of the preset period, only what has been found is reported, no suspects are reported. The operator can request a count time extension, if desired, adding multiples of the original preset period.
LCX (Low-Confidence Expert) ID Mode
LCX mode is password protected. LCX denotes “Low Confidence-Expert,” and is intended for expert users. This identification mode displays suspected threat alarms and identifications at a lower confidence level than the normal mode. This results in more hits on suspected threat nuclides.
The instrument is calibrated prior to shipment from the factory. The energy calibration may be checked and adjusted with any known source with a clean gamma ray between 0 and 3 MeV. A higher energy is recommended. Cs-137 is often used. Calibration can be manual or automatic. Background collection is now a required part of calibration. By allowing for activities already in the background, the system will no longer report nuclides detected in the background. These IDs on former versions sometimes lead to user-confusion. The background must be updated on a schedule which is chosen by the privileged user.
The “smart stabilizer” stabilizes the gain very precisely on the 1460 keV peak of K-40, if present. The smart part is that if there is no K-40 present or if Eu-152 is detected, which could interfere with the K-40 peak, the stabilizer setting is held but not adjusted until “normal” conditions return. Even though the Detective is a highly stable instrument, the smart stabilizer allows accurate determination of more complicated mixed spectra.
The Mobile MCB Server software application enables any ORTEC portable instrument installed with a PDA to communicate wirelessly with ORTEC software applications such as MAESTRO, GammaVision, and Detective-Remote. The Mobile MCB Server acts like a wireless version of the USB connection, allowing users to control and monitor any portable spectrometer through a wireless network.
Users can develop their own applications through the use of the optional A11 tool kit.
Detective-200 Mobile Detection System Rack Kit
The rack kit provides a simple, transportable solution for creating “Ad-Hoc” mobile detection systems without the need for permanent vehicle installation.
- Supports up to four Detective-200s in varying configurations.
- Portable, light weight, and collapsible.
- Easy to install and remove.
- Rugged frame for mobile applications.
- Can be configured for multiple vehicle types.
- Transportable case for rack and two Detective-200s.
- Vehicle laptop mounting kit.