ElseNuclear SP2 Single-Sphere Neutron Spectrometer

Overview

The ElseNuclear SP2 Single-Sphere Neutron Spectrometer is a compact, laboratory-grade passive neutron spectrometry system engineered for high-fidelity characterization of neutron energy distributions across an exceptionally broad range—from thermal energies (0.025 eV) up to 20 MeV, with validated extension capability to 5 GeV under moderated configurations compliant with ISO 8529-1 and IEC 61000-4-21 standards. Based on the Bonner Sphere Spectrometer (BSS) principle, the SP2 employs a single spherical polyethylene moderator surrounding a centrally mounted ⁶Li-loaded proportional counter (LI6 detector), enabling depth-dependent neutron thermalization and subsequent spectral unfolding via response matrix deconvolution. Unlike multi-sphere systems requiring sequential measurements, the SP2’s integrated circuit architecture performs real-time pulse-height analysis and spectrum reconstruction—eliminating manual reconfiguration and reducing measurement uncertainty associated with inter-sphere normalization. Its design prioritizes metrological traceability, mechanical stability, and immunity to gamma interference, making it suitable for reference-level neutron field characterization in accredited calibration laboratories and regulatory compliance environments.

Key Features

• Single-sphere geometry with optimized 12-inch diameter HDPE moderator and centrally positioned ⁶Li proportional counter for reproducible thermal neutron capture response
• Fully integrated digital signal processing unit performing pulse-height-to-energy mapping, dead-time correction, and iterative spectrum unfolding (MAXED/FRUIT algorithms supported)
• Extended energy coverage: validated 0.025 eV–20 MeV; extended response to 5 GeV achievable using validated response matrices and auxiliary moderation layers per ISO/IEC 17025-compliant procedures
• Gamma-insensitive detection: ⁶Li-based detector exhibits <10⁻⁴ gamma rejection ratio above 100 keV, ensuring reliable operation in mixed-field environments (e.g., nuclear facilities, cargo screening portals)
• Factory-calibrated with NIST-traceable neutron sources (Am-Be, Cf-252, ²⁵²Cf + D₂O) and supplied with full uncertainty budget documentation per ISO/IEC Guide 98-3 (GUM)
• Includes comprehensive software suite: SP2-Spectrum v3.x with built-in response libraries (MCNPX-derived), ISO 8529-2 compliant unfolding tools, and audit-ready export formats (CSV, XML, .n42)

Sample Compatibility & Compliance

The SP2 operates exclusively in gaseous media—primarily ambient air or sealed He-3 fill gas—and does not require sample introduction or containment vessels. It is designed for fixed-location deployment in controlled laboratory settings where environmental temperature (15–30 °C) and humidity (<70% RH non-condensing) are maintained. The system complies with IEC 61526 Ed. 4 (2021) for neutron dose equivalent rate meters, meets electromagnetic compatibility requirements per IEC 61326-1:2021, and supports GLP/GMP-aligned data integrity through 21 CFR Part 11-compliant electronic signatures and audit trails within its software platform. All calibration certificates are issued by an ILAC-MRA accredited provider and include measurement uncertainty statements referenced to primary standards at PTB (Germany) or NPL (UK).

Software & Data Management

SP2-Spectrum software provides end-to-end spectral analysis workflows—from raw pulse-height histogram acquisition to fully unfolded neutron fluence spectra (dΦ/dE) and derived quantities including H*(10), H'(0.07), and average neutron energy. Raw data files retain full timestamping, detector bias voltage logs, and environmental sensor inputs (temperature, pressure). Export modules generate ANSI N42.42-compliant files for inter-laboratory comparison and regulatory submission. Version-controlled firmware updates are delivered via secure HTTPS portal; all software binaries undergo annual penetration testing and vulnerability scanning in accordance with ISO/IEC 27001 Annex A.8.2.3.

Applications

• Reference neutron field characterization in national metrology institutes and secondary standard laboratories
• Radiation protection surveys in nuclear power plants, research reactors, and accelerator facilities—particularly for scattered neutron fields behind shielding
• Border security and customs inspection: identification of neutron-emitting special nuclear materials (SNM) via spectral signature discrimination (e.g., ²⁵²Cf vs. Am-Be vs. spontaneous fission backgrounds)
• Validation of Monte Carlo transport models (MCNP, GEANT4) against experimental spectral benchmarks
• Development and verification of neutron dosimetry algorithms for operational health physics programs
• Supporting ISO/IEC 17025 accreditation scope expansion for neutron spectrometry testing capabilities

FAQ

What neutron energy ranges are directly measured without extrapolation?
The SP2 provides direct spectral sensitivity from 0.025 eV (thermal) to 20 MeV using its standard configuration and factory-measured response matrix. Energies beyond 20 MeV up to 5 GeV rely on validated MCNPX-derived response extensions and require documented justification per ISO/IEC 17025 clause 7.2.2.
Is the LI6 detector replaceable in the field?
No—the ⁶Li proportional counter is hermetically sealed and pre-aligned within the moderator sphere. Replacement requires return to ElseNuclear’s authorized service center and recalibration against primary neutron standards.
Does the system support automated long-term unattended monitoring?
Yes—when connected to a dedicated industrial PC with UPS backup, SP2-Spectrum supports scheduled acquisition cycles (1 min to 24 h intervals), automatic file archiving, and SNMP-based alarm triggering upon dose rate threshold exceedance.
Can SP2 data be imported into third-party spectral analysis tools like GRAVEL or STAYSL?
Yes—raw pulse-height histograms and unfolded spectra are exportable in ASCII and N42.42 formats, both natively readable by GRAVEL, STAYSL, and MCNP input preprocessors.
What documentation accompanies delivery?
Each unit ships with a Certificate of Calibration (traceable to PTB/NPL), Uncertainty Budget Report, ISO 8529-2 Conformance Statement, Electrical Safety Test Report (IEC 61010-1), and Software Validation Summary per GAMP 5 Category 3.