Neutron Imaging Facility (NIF)

Summary

The NIST Neutron Imaging Facility provides users with a unique “plug and play” approach to imaging operating fuel cells, electrolyzers, and lithium-ion batteries. The first NIST-NeXT system was first installed at BT2, allowing simultaneous neutron/X-ray tomography of complex materials and systems such as batteries, concrete, shales, and two-phase flow in granular media. The neutron beam characteristics of the facility are detailed below.

Beamline Description

The NIST Neutron Imaging Facility (NNIF) is located at Beam Tube 2 (BT-2) at the NIST Center for Neutron Research (NCNR) which provides an extremely intense source of thermal neutrons. The NNIF offers multiple sample positions from 2 m to 6 m distances from the beam defining aperture. The 2 m location offers the highest intensity while the 6 m location offers the largest beam diameter and the simultaneous neutron/X-ray tomography capability. The sample distance along with the aperture diameter define the image sharpness (L/D ratio) as neutron optics follow pinhole optics. The higher the L/D ratio the sharper the image is at the expense of image acquisition time. Table 1 gives the full range of beam parameters. Apertures listed are the typically installed sizes but can be changed to better match an experiment upon special request.

Table 1. General beam characteristics are described here. The last column shows the values for no filter for the sake of comparison to other neutron radiography facilities.

Detector Specifications

The NNIF offers multiple detectors to tailor spatial and temporal resolution to experimental requirements. Details of how the NIST Neutron Imaging Team has pushed image resolution can be found on the spatial resolution project page.  The most common detector system is the lens-couple CMOS camera viewing a scintillator, but all NIST imaging detectors [link to detector suite] can be used at the facility.  

Sample Interfacing with the Instrument

The NNIF uses imperial fasteners to mount samples usually with optical breadboards and optical posts that use ¼”-20 or #8-32 threads. 

Sample sizes supported:

• Typical high-resolution tomography with height translation
  • Max weight: 23 kg (50 lbs)
  • Sample size: determined by resolution requirements and transmission, typically 1-3 cm diameter
  • Vertical translation of up to 25 cm (10 in)
• Tomography of larger objects
  • Max weight: 90 kg (200lbs)
  • Sample size: determined by resolution requirements and transmission
• Neutron radiography
  • With translation stages
    • Max weight with X-Y translation stages: 90 kg (200 lbs)
      • Max weight depends on exact stages selected
    • Distance below beam center: 58 cm (23 in)
    • Distance above beam center: 106 cm (42 in)
  • No translation stages
    • Max weight: 230 kg (500 lbs)
    • Distance below beam center: 71 cm (28 in)
    • Distance above beam center: 106 cm (42 in)
  • Max field-of-view limited by beam diameter of 26 cm

There is room inside and outside the shielded instrument enclosure for user supplied ancillary equipment with pass-throughs in the shielding to allow for cabling and fluid connections to be run.

Low and high experimental temperatures are supported on the beamline. The NCNR orange cryostats are typically used for cryogenic temperatures.  

Flammable gases other than hydrogen and corrosive liquids can be supported upon safety review.

Facility Infrastructure and equipment 

• Hydrogen infrastructure 
  • Please see the fuel cell project page
• Gamry Reference 3000 
  • Single channel 
  • +/- 15 V @ +/- 3 A 
  • Electrochemical Impedance Spectroscopy from 10 µHz to 1 MHz 
  • 2, 3, 4 electrode measurements 
  • Reference 30K booster provide +20 V, - 2.5V @ +/-30 A 
• Battery infrastructure
  • Please see the lithium-ion battery project page
• Pressure cell for geology experiments 
  • Core size 1.5 inch diameter, length 5.5 inch to 6.5 inch, other lengths possible 
  • 1600 psi confining pressure 
  • PEEK and PFA wetted components for acid compatibility 
  • Aluminum pressure vessel is compatible with X-ray system for simultaneous neutron and X-ray tomography 
• Humidity control cell for high resolution tomography 
  • Sample diameters up to 15 mm 
  • Gases supplied from small scale test stand 
  • Air or nitrogen flow up to 10 lpm 
  • Dry or fully humidified gases at room temperature 
  • Subsaturated gas streams possible with special request 
  • Gas pressure controllable to 400 kpa 
  • Beam window materials are aluminum or quartz 
  • Beam windows are compatible with X-ray system 
• ISCO 260D syringe pumps 
  • 266 ml capacity 
  • 0.001 mL/min to 107 mL/min flow rate 
  • 10 psi to 7500 psi pressure range 
  • 4 pumps with two controllers available, each controller can operate two pumps 
  • Pumps can be set up in pairs for continuous flow beyond syringe capacity 
• Circulators 
  • Huber Unistat Petit Fleur 
    • -40 to 200°C with ±0.01°C temperature stability 
    • Typically used for D2O sample coolant 
  • Huber Unistat 405 
    • -45-250°C with ±0.01°C temperature stability 
    • Typically used with Fluorinert coolants

Data Acquisition

Data acquisition is fully automated through using a software package written by the Neutron Imaging Team called DataScripting.

Data Analysis

Users of the facility have access to both the source code and compiled data analysis packages written in Matlab by members of the Neutron Imaging Team.