The JSR-15 Handheld Multiplicity Register (HHMR) is a handheld shift register/multiplicity circuit intended for neutron counting applications. As a shift register the instrument counts and records total number of pulses and the time correlation of the pulses to provide coincidence timing. Multiplicity distributions of the coincident events are recorded as well. The JSR-15 device has an internal clock rate of 50 MHz and is therefore capable of handling high count-rate applications in nuclear safeguards, nuclear waste assay, and process monitoring. The JSR-15 instrument has been tested up to a count rate of 20 MHz using the NDA 2000 software, ensuring that the shift register will not be the limiting factor in any current or near-term practical counting situations.
The JSR-15 unit has built-in batteries, a built-in charging circuit, and a battery monitoring circuit. The instrument can run for up to eight hours on a single charge, when operated in battery-save mode with a single JAB-01 charge amplifier/discriminator. The battery capability, along with the compact size and lightweight make the instrument extremely portable.
Two interface mechanisms are available on the JSR-15 instrument. In addition to the typical software interface through a notebook or suitable computer, the unit has a front panel push-button LCD display. Through the front panel interface the user may change the setup parameters (count time, high voltage, gate width, pre-delay, etc.), start and stop acquisitions, and view the measurement results. An estimate of the battery level is displayed on the LCD display, and a separate menu option allows for checking battery diagnostics. The LCD display can be controlled for efficient use of the battery.
The software interface is compatible with the INCC (IAEA Neutron Coincidence Counting) and NDA 2000 software packages. The JSR-15 device utilizes a USB pipeline for communication with a computer, in place of the older RS-232 serial port. (The USB port also supplies power, thereby reducing the drain on the battery.)
The signal input to the JSR-15 instrument can be in the form of TTL pulses via coaxial cable or differential pulses via a twisted pair cable. The instrument also has two auxiliary scaler inputs which are available as either TTL or differential inputs. In addition the unit supports fast accidentals. The JSR-15 unit contains a user-programmable High Voltage (HV) power supply and a 5 V supply that can provide bias and power to the pre-amplifier/ discriminator boards.