Hardware
There are two models of Micro-Detective available:
- Micro-Detective: Lightweight, Portable HPGe Identifier with Gamma and Neutron detection.
- Micro-Detective-DX: “Gamma only” version of the Micro-Detective.
Both models of the Micro-Detective feature the same compact, light weight and rugged hardware. A 50 mm diameter HPGe crystal in a “hardened” cryostat is cooled by an integrated low-power Stirling-cycle cryocooler. The latest revision Micro-Detective features a new cooler offering reduced levels of acoustic noise and vibration, and longer operation life. The hardened cryostat is entirely free of conventional molecular sieve allowing the instrument to be turned off or on at any point in the detector cool-down or warm-up cycle without risk. This is impossible with conventional HPGe cryostat systems which require careful temperature cycling procedures to avoid damage.
A built-in digital MCA system and powerful data processor are included. All models feature the same bright and clear VGA resolution display, readable in direct sunlight, with a touch sensitive operator screen. 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.
Gamma and neutron count rate and gamma dose rate are displayed continuously both numerically and in bar graph form.
In the latest version, the Micro-Detective internal battery provides enough power for up to 5 hours of operation and is easily replaced in seconds, allowing continuous in-field operation.
At just under 16 lbs. in weight, the Micro-Detective sets a world record for portable, high resolution nuclide identifiers, by a wide margin.
Analysis Capabilities
Since initial introduction of the first Detective instruments, identification performance capabilities have iteratively been improved through taking part in many independent performance testing programs. These programs are sponsored by governmental and international organizations, such as the US DTRA, the IAEA, and most recently the on-going international ITRAP-plus 10 testing program.
Micro-Detective performance has continued to advance as a result of these rigorous test programs. As the needs and best practices of deploying organizations have also evolved, Detective software features have expanded to meet these new requirements.
Summary of Operational Features
(refer to Technical Specifications for more detail)
- Three “Search Modes”:
Gamma/neutron total count rate
SNM Search mode
Sliding average “monitor” mode
- User choice of identification schemes:
“Classify Mode” (by nuclide type: “nuclear, natural, medical, industrial, etc.”)
“ANSI mode”
Time preset or continuous count selectable to match CONOPS
Suspected Nuclides (not in preset mode)
More sensitive LCX mode for SNM detection
- Background collect feature eliminates reporting of background nuclides.
- “Smart” spectrum stabilizer ensures optimum results, even with hard-to-analyze spectra.
- ANSI N42.42 format storage of spectra.
Calibration and Stabilization
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 a required part of calibration. By allowing for activities already in the background, the system will not report nuclides detected in the background. The background must be updated on a schedule which is chosen by the privileged user.
SMART Stabilizer The “smart stabilizer” stabilizes the gain very precisely on the 1460 keV peak of K-40, if present. 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.
Optional Software for the Micro-Detective
The Micro-Detective is fully supported by the latest versions of the highly successful MAESTRO MCA Emulator as well as ORTEC Gamma Spectroscopy Packages such as GammaVision for generalized HPGe spectrum analysis, FRAM and MGAHI for Pu and U isotopic ratio analysis and ISOPlus for in-situ waste assay analysis. The integral USB connection in the instrument hardware provides full PC control, real-time live MCA display, fast data transfer of single and multiple spectra to the PC, and full ORTEC Connections network support. Separate brochures are available on request. PLEASE NOTE: MAESTRO is supplied as part of packages containing "PKG" in the model number, or it can be purchased separately at a later date.
The Micro-Detective is a member of the ORTEC Connections family. Remote MCA control and individual spectrum download, even over a network, is achieved simply, by the use of ORTEC Connections products such as MAESTRO MCA Emulation software. Multiple spectra may be block-transferred from the instrument controller to an external PC by the use of Microsoft ActiveSync. Third party products such SOTI “Pocket Controller Enterprise” may be used to implement the 802.11 wireless feature to provide remote wireless control of the complete instrument.
Mobile MCB Server
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.
Operation Modes
SEARCH
Scanning mode for location of radioactive sources, with audio alert using an external ear piece. Both neutron and gamma search is simultaneous; speed settings 0.1 to 50 seconds/point: Neutron counts are displayed in red and gamma counts in blue.
MONITOR Mode
The instrument collects one spectrum per second and runs the ID algorithm against an 8 second sliding average. This mode is more sensitive to sources which move relative to the instrument.
SNM Search Mode™
Nuclide-specific search mode for U-235, Pu-239 and neutron counts. Ba-133 surrogate detection may be turned on for training purposes. Bar graph display of nuclide confidence level. An aid to Identify mode.
LCX (Low Confidence Expert) ID Mode
Intended for expert users. Displays suspected threat alarms and identifications at a lower confidence level than ANSI and Classify modes. Results in more hits on suspected threat nuclides. Password protected.
IDENTIFY
Gamma Proprietary scheme for identification and classification of radionuclides. Background subtraction.
ANSI Mode
See following nuclide list. Preset Time counting allows for CONOPS* in which it is required to count for a preset time, e.g., 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.
Classify Mode
Nuclides classified according to: Industrial, Medical, Natural (NORM), and Nuclear. Classifications are based on an internal, fixed library according to ANSI N42.34. Customized libraries for specific applications can be supplied by special order.
Dose Rate
Visual over range indication and continuous audible alarm, user settable. Over-ride alarm at dose rates >10,000 µSv/hr.
Neutron Count Rate (if applicable)
Displayed continuously. Data can be quickly saved and transmitted for further off site analysis.
GPS Position Information
Internal GPS receiver displays GPS coordinates which may be saved along with spectrum data for future use.
Gamma-Ray Identification Performance Data for Uranium and Plutonium
(Typical values based on data obtained from actual measurements by ORTEC personnel.)
Single Sources
Unless otherwise stated, these data were taken at a standard dose rate from the source of 500 nSv/h measured with a calibrated dose rate meter at the instrument detector face according to ANSI N42.34. When an absorber was present, the dose rate at the detector was measured THROUGH the absorber.
Unshielded and Shielded Uranium: DU, U-NAT, LEU, HEU
The time to identify as uranium, either unshielded or shielded by up to 5 mm steel, is <2.5 sec. For LEU and HEU samples, the type ("LEU" or "HEU") is also reported in <2.5 sec. LEU and HEU samples shielded by 1.6 mm lead are identified as Uranium in <2.5 sec.
Unshielded and Shielded Plutonium: Weapons Grade (WG), Reactor Grade (RG) (~60–93% 239Pu)
Time to identify as Pu, unshielded or shielded by up to 5 mm steel or 10 mm lead: <13 seconds for all types of Pu (with Cd filter if high Am content). For WG Pu the type "WG Pu" is also reported in less than <35 sec.
Mixtures
In all cases, the mixture consists of 500 nSv/h of the "mask" nuclide, added to the specified quantity of uranium or plutonium. The "dose ratio threshold" is defined to be the standard 500 nSv/h dose rate from the mask in ratio to the smallest dose rate from U or Pu detectable in the time stated.
Uranium at 500 nSv/h in the presence of Cs-137 or Co-57 mask (unshielded)
Time to identify as uranium <2.5 sec. For LEU and HEU, the type ("LEU" or "HEU") is also reported in <2.5 sec.
Uranium Dose ratio threshold for 60 second measurement in the presence of Cs-137 or Co-57 mask (Dose from mask: Dose from uranium)
>7:1 for identification as uranium unshielded
>3:1 shielded 5 mm steel.
>2:1 for reporting as LEU or HEU unshielded
>1.5:1 shielded 5 mm steel.
Plutonium at 500 nSv/h in the presence of Ba-133 mask
Time to identify as Pu <20 sec, unshielded or shielded by 5 mm steel or 10 mm lead. Identified type as RG Pu or WG Pu in <100 sec.
Plutonium Dose ratio threshold for 5 minute measurement in the presence of Ba-133 mask
>6:1 for identification as Pu unshielded, >4:1 shielded by 5 mm steel or 10 mm lead.
>1:1 for reporting as WG Pu or RG Pu unshielded or shielded by 5 mm steel or 10 mm steel (with Cd filter if high Am content).