Neutron Radiography Facility (NRF)

Description

Completed in 2004, the Neutron Radiography Facility (NRF) at the Oregon State TRIGA® Reactor (OSTR) represents a significant expansion of the reactor's capabilities. Utilizing beam port #3, the NRF takes advantage of its tangential orientation to provide a predominantly thermal neutron beam with minimal gamma contamination. The facility features a precision-engineered collimator with a bismuth filter, cadmium, boral, and lead components to ensure optimal beam quality. The emitted beam, shaped by a rectangular boral aperture, meets ASTM E545 Category 1 standards, with an L/D ratio ranging from 86 ± 4 to 117 ± 4. 

The NRF blockhouse was designed for safety and operational reliability. It includes a pneumatically operated lead shutter with fail-safe interlocks, lead-lined doors, and a beam stop composed of lithium-saturated polyethylene and lead bricks to minimize residual radiation. These engineered controls, complemented by constant communication protocols, prioritize user safety and facility longevity. 

This robust system supports a variety of neutron imaging applications, offering high-quality radiographs and dynamic imaging capabilities. Active imaging systems for acquisition of neutron radiographs include: 

1. FUJI Neutron-Sensitive Imaging System 

The FUJI Bio-Imaging Analyzer (BAS-2500) and its neutron-sensitive imaging plates remain a cornerstone of neutron radiography at the Oregon State TRIGA® Reactor (OSTR). Despite being out of production, the system offers exceptional versatility and resolution (~40 μm/pixel), making it an invaluable tool for high-resolution imaging and education. 

The BAS-2500 scanner, operated via dedicated software on a legacy Windows 98 platform, exemplifies durability and reliability. Its reusable BAS-ND2025 imaging plates, featuring a Gd₂O₃ converter in their photostimulable layer, are specifically designed for neutron detection. These 20 cm x 25 cm plates can capture fine details in both wet and dry samples, enabling diverse applications in research and training. 

Due to the discontinuation of these plates, usage is carefully managed to preserve them for critical applications, including external user projects requiring precision imaging. With well-documented operational procedures, the FUJI system continues to provide cutting-edge imaging capabilities while fostering the development of future nuclear scientists and radiographers.  

2. ANTARES Neutron Imaging System 

The ANTARES system, donated by Idaho National Laboratory (INL), has enhanced digital neutron radiography (NR) capabilities at the Oregon State University TRIGA Reactor (OSTR). Designed for compact fields of view (FOVs) and efficient neutron tomography (nCT), it supports detailed sample characterization with a square FOV of 114 mm × 114 mm, well-suited for high-resolution imaging. The system’s modular design prioritizes portability, enabling researchers to reposition it for various applications or educational purposes. 

The detection scheme integrates a custom-machined 6LiF/ZnS:Ag scintillator (1:2 ratio) adhered to the camera box with optical tape to ensure minimal light leakage. Photon emissions are directed via a high-precision, first-surface mirror to an ASI178MM-Cool ZWO monochrome camera, with a 3096 × 2080-pixel resolution and peak quantum efficiency of 81%. The use of first-surface mirrors, coated with a durable dielectric layer, minimizes optical distortions and oxidation over time, critical for maintaining image fidelity. Its innovative design, operational flexibility, and adaptability for educational purposes make it a cornerstone of neutron imaging at OSTR.  

3. DIANA (Dynamic Imaging Apparatus For Neutronic Analysis) 

The Dynamic Imaging Apparatus for Neutronic Analyses (DIANA) is a versatile, large-field-of-view (FOV) imaging system designed to support advanced neutron radiography and dynamic studies. 

DIANA's unique capabilities are achieved through its integrated telescopic lens and optional linear translational stage, allowing users to adjust focal distances and field sizes (ranging from 380 mm × 280 mm to 38 mm × 50 mm) without compromising image quality. The system is robustly constructed to withstand neutron environments, with features like overlapping seams to mitigate light leakage. Its adaptable design also facilitates vertical or horizontal orientation, maximizing its utility in confined research environments. DIANA's components include scintillator screens tailored to neutron wavelengths, a ZWO ASI294MM PRO CMOS camera with a Sony IMX492CJK sensor [array size: 8288 x 5644-pixels], and Nikkor telescopic lens. These components communicate with modern imaging software for a wide array of applications. 

Manufactured by King Machine Products INC. in Corvallis, OR, and modeled using NX CAD software, DIANA represents the culmination of collaborative design and engineering. For researchers and professionals interested in reproducing or customizing this system, the full CAD package is available for download on GrabCAD for personal and professional use. 

4. Coupled-Camera & Image Intensifier Detector 

An image intensifier coupled with a CCD camera via a light-tight right-angle adapter, providing a versatile detection scheme for neutron imaging applications. Utilizing a 50 mm f/1.2 lens, the camera achieves a theoretical spatial resolution of approximately 90 µm (3.54 × 10⁻³ in.). However, the system's effective resolution, determined through experimental measurements using precision aperture strips, is approximately 250 µm (9.84 × 10⁻³ in.).

This configuration offers a field of view (FOV) of approximately 150 mm (5.9 in.), making it suitable for capturing high-contrast neutron radiographs of moderately sized samples. The coupled-camera and image intensifier system balances resolution and field coverage, supporting both research and educational objectives at the NRF. 

Additional Equipment Information