RAD

RAD – Static/dynamic thermal-neutron and X-ray imaging station

Instrument responsible: Zoltán Kis

Radiography utilizes transmission of photons or neutrons to obtain information on the structure and/or inner processes of a given object. The thermal neutron imaging facility, RAD is served by an in-pile, Cd-covered pin-hole-type collimator for neutron and gamma radiation. The facility offers two measurement positions along the neutron beam path with a beam diameter of ~200 mm, used for dynamic (DNR) and for static (SNR) imaging with a measured L/D ratio of ~250. Options are provided to use beam filters made of boron-containing rubber and lead bricks, resulting in a significant modification of the beam energy distribution, giving a fast/thermal neutron flux ratio of 77 instead of 0.6. The RAD facility is also equipped with an optional X‑ray tube, allowing dual-modality imaging. Two motorized sample stages, one for small and one for large samples (with a maximum load up to 250 kg) are available to support the investigated objects. A sapphire-crystal-based filter is under installation to suppress fast neutrons.

The image detection of the RAD station now comprises a new digital imaging equipment being able to carry out 2D and 3D imaging using suitable scintillation screens. The spatial resolutions of the available screens are as follows: scintillation screens for neutron radiography with resolution between 70-250 μm; intensifying screens for X-ray radiography with a resolution of 100-200 μm. For better flexibility, an option is provided to apply larger or smaller fields of views (FOV) with lower and higher spatial resolution, respectively. The static radiography and tomography is accomplished by a new, large area sCMOS camera. Here altogether three different optical systems can be setup using the available lenses with 50 mm, 105 mm and 300 mm fixed focal lengths, interchangeably coupled to the digital camera, giving the different FOVs.

For the manipulation, reconstruction and visualization of the 3D neutron and X-ray datasets (i.e. the tomographic images), the latest Fiji-ImageJ, Octopus 8.9 and VG Studio 2.1 software packages are used.

Dynamic radiography is performed by means of a low-light-level TV camera with a fast imaging cycle, making possible real-time imaging. The zoom optics coupled to the camera provides a variable field of view. The two cameras can be used interchangeably in a light-tight camera box equipped with a rail system providing the necessary optical path lengths.

In addition to the cameras, photo-luminescent imaging plate (IP) technique is also available for high-resolution X-ray and neutron radiation detection with transfer method using In and Dy (100 μm) foils. The exposed IP-s are read out by a BAS 2500 image plate reader equipped with the AIDA image processing software. 

 

Beam energy distribution:

      radial thermal-neutron channel

Thermal-equivalent flux at target:
  • 4.64×107cm-2s-1 at 209 cm (DNR)
  • 3.38×107cm-2s-1 at 282 cm (SNR)

Thermal-to-epithermal flux ratio Fth/Fepi 

      51
Fast neutron flux (E>2.1MeV, measured with the Ni-58(n,p)Co-58 reaction)
  • 2.7×107cm-2s-1 at 209 cm (DNR)

Collimator ratio (L/D) :

      250

Gamma dose rate:

      8.5 Gy/h

X-ray sources:

      5-300 keV; 5-10 mA

Field of view (useful):

     41×34 mm2, 110×93 mm2 or Ø200 mm

Scintillator screens (thickness):
  • Li6F/ZnS (100, 200, 225 and 450 mm)
  • Gadox P43 (10 and 20 mm)

Mirror:

      Al coated quartz mirror set in 45° to the beam

Optics:
  • Sigma 50 mm f/1.4 DG HSM ART;
  • Nikon-Nikkor 105 mm f/1.8
  • Nikon AF-S 300 mm f/2.8 G ED VR II

Imaging detectors :
  • Andor Neo 5.5 sCMOS camera with 2560×2160 pixels and 16-bit pixel depth
  • low-light-level TV camera (640×480 px) with a light sensitivity of 10‑4 lux and imaging cycle of 40 msec
  • BAS 2500 image plate reader

Spatial resolution:

      70‑250 μm depending on the FOV and scintillators

Exposure times:
  • 1-35 s per image
  • 601 – 1001 projections for a tomogram
  • 25 fps for dynamic measurements

Sample stages:
  • motorized sample manipulator for heavy objects up to 250 kg
  • ω turntable for 3D imaging up to 5 kg

Table 1. Specifications of the RAD facility

 

Figure 1. The 3D layout of the RAD facility

    

Figure 2. The optics of the detector system

 

Figure 3. The digital imaging system of RAD

 

RAD turntable Concrete bar porosity

Figure 4. The turntable for small objects with concrete test bars (left). Porosity analysis with VG Studio MAX (right) 

References:

Z Kis, L Szentmiklósi, T Belgya, M Balaskó, LZ Horváth, B Maróti. Neutron based imaging and element-mapping at the Budapest Neutron Centre, Physics Procedia. 69 (2015) 40 – 47. DOI: 10.1016/j.phpro.2015.07.005

Szentmiklósi László, Kis Zoltán, Belgya Tamás, Maróti Boglárka, Horváth László Zoltán, Papp Mariann: Roncsolásmentes képalkotás neutronokkal és röntgensugárzással a Budapesti Neutron Centrumban, Fizikai Szemle 67/7-8 (2017) 240-244.

V. Szilágyi, Z. Kis, L. Szentmiklósi: Neutron Imaging for Archaeometry / A neutronos képalkotás archeometriai alkalmazása, Archeometriai Műhely 2016/XIII./3. (2017) 157-172

R. Zboray, R. Adams, Z. Kis: Scintillator screen development for fast neutron tomography and its application at the beamline of the 10 MW BNC research reactor, Appl Radiat Isot. 2018 Oct;140:215-223. doi: 10.1016/j.apradiso.2018.07.016