• Supports gross-pulse and -current mode detectors and measurements as used in Safeguards monitoring and measurements
• Modular nature allows the MiniGRAND to be used in various configurations
• Supports a Flash-ROM based operating system that allows different application firmware to be loaded for different instrument functionality
• Various configurations are supported in the firmware
• Unattended and attended modes of operation possible
• May be used as a drop-in replacement for the GRAND3 in virtually all applications
• Capable of functioning autonomously in the event of a power loss (resident-battery operation) and/or communication outages (built-in battery-backed-up storage)
• Built in self-diagnostic capabilities
• Front-panel emulator program provides an easy to use User Interface
• Compatible with all LANL unattended monitoring collect software
• May be configured as a stand-alone instrument or integrated into a board stack for use in detectors
• With the optional Mini-Instrument Family Application-Board Suite, the following capabilities can be supported:
  • Ethernet communications
  • Authentication of Data Files
  • Encryption of Data Files

The Miniature Gamma Ray and Neutron Detector electronics package (MiniGRAND) is one of the latest developments in a new generation of the Mini-Instrument family that has evolved over the last several years. Originally developed by Los Alamos National Laboratory (LANL) Safeguards Science and Technology Group, the MiniGRAND is a compact, modular instrument intended primarily for measuring and monitoring gross gamma rays and neutrons. It was developed to duplicate and extend the capabilities of the Gamma Ray and Neutron Detector (GRAND3) electronics package previously used. In fact, the MiniGRAND can be used as a drop-in replacement for a GRAND3 in virtually all applications.

The MiniGRAND is the first LANL designed instrument designed specifically for unattended monitoring applications. It can also be used in attended mode using a terminal emulator (low-level interface) or a front panel emulator (high-level interface). The MiniGRAND may be configured as a benchtop instrument or as a board stack that can be built into integrated detectors. Its small size and low power allow the unit to be mounted close to the detector, preferably in a sealed boundary shared by the detector and MiniGRAND. This removes the problem of unauthenticated noise or ground loop pickup noise between the detector and the electronics; a problem frequently encountered with previous systems. The MiniGRAND can be coupled with an intelligent local node (ILON) or an application board suite, either of which can provide authenticated communication between the remotely located MiniGRAND and a collect computer that would reside within another sealed boundary. Thus, the data and communications are protected from the remote instrument to the collect computer or to other instruments.

The MiniGRAND is designed to function autonomously to survive power and communication outages and to adapt to changing conditions. It is powered from an external dc source or from an internal battery. An integrated battery permits operation for a significant amount of time if power is interrupted. A large local, battery backed-up memory permits storage of many hours of data if communication with the central computer is interrupted, and local decision-making allows the instrument to adapt to changing conditions. Front Panel Emulator software, which runs on a PC, provides an operator interface for configuration and attended operation of the unit. Communication with the MiniGRAND boardset is via one of the computer's serial ports.

The basic MiniGRAND boardset includes four electronics boards that may be configured as a stand-alone instrument contained in a compact enclosure or as an open frame board stack for use in detectors where an external box is not necessary. The basic boards include the Master Processor Board (MPB), a Low-voltage/BIAS board, and two personality boards; the Dual Current-Mode Board (DCM) and the Triple Pulse Counter Board (TPC).

The Master Processor Board (MPB) provides an embedded system to control the entire instrument for its setup, data communication, data acquisition, and data storage. The MPB provides the intelligence to control the operation of the personality boards, to adjust the parameters based on present conditions, to filter data, provide external triggers, store data and to pass data on to a central collect computer, when required. A bias is provided for a neutron type detector (e.g., ³He). The Dual Current-Mode (DCM) and Triple Pulse Counter (TPC) boards supply the hardware interface to the detectors. The MiniGRAND is capable of measuring the current generated from gamma rays interacting with an ionization chamber or other sensor that operates in the current mode. It features two current mode measurement channels; a single negative bias supply and output control signals for an external relay to open the current circuit at a remote location for diagnostic purposes.

The MiniGRAND embedded firmware allows the instrument to operate in one of two modes: Monitor or User. In Monitor mode, the system acquires data from the counters, stores it in the buffer to be transmitted to the Collect software and responds to the set of commands sent by the Collect software to retrieve stored information. User mode also allows the instrument to be operated interactively in attended mode, allowing the acquisition of data, calibration of the instrument, and general diagnostics. The firmware supports or can support a variety of configurations including:

• A single pulse channel input configuration is supported with only the MPB. Using the on-board +5 V dc supply of the master processor board, this configuration is used when the MiniGRAND is not required to supply bias or external pre-amp power to detectors.
• Three-channel pulse input configuration is possible by adding the TPC to the MPB.