FHT 762 Wide-Energy Neutron Detector

Overview

The FHT 762 Wide-Energy Neutron Detector is a field-deployable, high-fidelity instrument engineered for accurate ambient dose equivalent rate measurement, H*(10), across an exceptionally broad neutron energy spectrum—from thermal neutrons (0.025 eV) up to 5 GeV. Developed from foundational research conducted at Los Alamos National Laboratory and San Jose State University, the detector implements a large-volume ³He proportional counter embedded in a polyethylene–borated moderator assembly optimized per ICRP 74 (1996) fluence-to-H*(10) conversion coefficients. Its design addresses critical limitations of conventional neutron survey meters—particularly poor high-energy response and gamma-induced over-response—by integrating multi-layered neutron moderation, selective thermal neutron capture, and intrinsic gamma discrimination via pulse-height analysis. The result is a robust, metrologically traceable solution for neutron dosimetry in mixed-field environments, including particle accelerator facilities, nuclear medicine cyclotron vaults, spent fuel handling areas, and post-incident radiological assessment scenarios.

Key Features

• Wide-energy neutron response spanning six orders of magnitude: 0.025 eV (thermal) to 5 GeV (relativistic), fully compliant with ICRP 74 fluence-to-dose conversion functions
• High intrinsic sensitivity of 0.84 counts per second per µSv/h (referenced to ²⁵²Cf neutron source calibration)
• Exceptional gamma rejection: maintains dose accuracy with ≤5 µSv/h equivalent error under simultaneous 100 mSv/h ¹³⁷Cs gamma exposure
• Isotropic angular response within ±20% over full 4π solid angle—validated per ISO 8529-2:2000 requirements for reference neutron fields
• Portable, battery-operated architecture with IP65-rated enclosure; operational temperature range: −10 °C to +50 °C
• No external bias voltage or cryogenic cooling required—enables rapid deployment and long-duration unattended monitoring

Sample Compatibility & Compliance

The FHT 762 is designed for direct measurement of neutron ambient dose equivalent rate (H*(10)) in air without sample preparation or spectral unfolding. It meets the performance criteria outlined in IEC 61005:2021 (Radiation protection instrumentation — Neutron ambient dose equivalent (rate) meters) and conforms to ANSI N42.17A-1989 for neutron survey meter classification. Its response function has been experimentally verified against ISO/IEC 17025-accredited reference neutron fields—including ²⁵²Cf, ²⁴¹Am–Be, and monoenergetic neutron beams at PTB (Germany) and NIST (USA). The device supports GLP-compliant operation through audit-trail-capable firmware logging and is suitable for use in regulatory contexts requiring compliance with EURATOM Directive 2013/59, IAEA Safety Standards Series No. GSR Part 3, and US NRC Regulatory Guide 8.34.

Software & Data Management

Data acquisition and configuration are managed via the integrated FHT Control Suite (v3.2+), a Windows-based application supporting real-time dose rate visualization, time-stamped event logging, and configurable alarm thresholds (audio/visual/vibration). All measurements are timestamped with GPS-synchronized UTC and stored in IEEE 1588-compliant binary format (.fhtd), ensuring traceability and interoperability with laboratory information management systems (LIMS). Raw pulse-count data and processed H*(10) values are exportable as CSV or XML for third-party analysis. Firmware updates preserve full 21 CFR Part 11 compliance—supporting electronic signatures, role-based access control, and immutable audit trails for QA/QC documentation.

Applications

• Routine radiation protection surveys around proton therapy accelerators and spallation neutron sources
• Emergency response dosimetry following nuclear incidents involving fast neutron release (e.g., criticality accidents)
• Commissioning and periodic testing of neutron shielding integrity in radiotherapy bunkers
• Environmental neutron background monitoring near nuclear power plants and reprocessing facilities
• Calibration verification of secondary standard neutron dosimeters in accredited laboratories
• Research applications requiring high-statistics, time-resolved neutron flux characterization in pulsed beamlines

FAQ

Does the FHT 762 require annual recalibration?
Yes—annual calibration against a certified ²⁵²Cf neutron source is recommended per ISO/IEC 17025 and national metrology institute guidelines. Calibration certificates include uncertainty budgets traceable to PTB or NIST standards.
Can it be used underwater or in high-humidity environments?
The unit is rated IP65 and operates reliably at up to 95% relative humidity (non-condensing), but submersion is not permitted. Optional waterproof cable glands are available for extended outdoor deployment.
What is the minimum detectable dose rate at environmental levels?
At typical terrestrial neutron backgrounds (~0.01 µSv/h), the 10-minute integration mode achieves a detection limit of 0.003 µSv/h (3σ confidence) with statistical uncertainty <±15%.
Is firmware upgrade support included post-purchase?
Yes—lifetime firmware updates, including regulatory-compliance patches and enhanced spectral correction algorithms, are provided free of charge with valid service contract registration.
How does it handle pulsed neutron fields?
The detector’s dead-time-corrected counting electronics support pulse rates up to 10⁵ cps; integrated gating logic allows synchronization with accelerator RF cycles for time-of-flight–resolved dose assessment.