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Mikroskopie und Tomographie Vortrag: Mi., 11:00–11:30 M-V1
Neutron Imaging Methods at FRM-II
Michael Schulz 1 , Thomas Bücherl 2 , Elbio Calzada 1 , Klaus Lorenz 1 , Martin
Mühlbauer 1 , Burkhard Schillinger 1
1 FRM-II, Munich and Physics E21, Munich – 2 Institut für Radiochemie, München
The research reactor FRM-II hosts two facilities for neutron imaging offering several
different spectra and radiations for different imaging methods.
The beam tube of the ANTARES facility faces the cold source and offers standard neutron
radiography as well as computed tomography with very high spatial resolution.
Using a Cd filter, the epithermal part of the spectrum can be used for better penetration.
A B4C filter blocks nearly all cold to epithermal neutrons. With a gamma scintillation
screen, the gamma radiation emitted from the reactor vessel and beam nozzle can be
used for high-energy gamma imaging. Several pin hole apertures can be used for phase
contrast imaging. Additional switchable lead filters and a monocrystalline Bismuth
filter serve as gamma filters to suppress the remaining gamma background that is still
detected by the neutron scintillation screen, a polycrytalline Bismuth filter can shift
the spectrum to cold neutrons around 6˚A.
When the neutron shutter is closed, a 300 kV X-ray tube can be rotated into the beam
close to the neurton shutter, rendering an X-ray beam with virtually the same geometry
as the neutron beam. X-ray and neutron images can be superimposed without a
registering process.
The NECTAR facility is the only neutron imaging facility world-wide situated at a
beam tube with a uranium converter plate inside the reactor vessel delivering an unmoderated
fission spectrum of fast neutrons. Thermal neutrons are suppressed with Cd
filters, fast neutron radiography and tomography can be performed on thick samples.
The talk will describe the setup of the facilities and show examples for each imaging
method available.
Fig. 1: Cold neutron
radiography of
an oil-filled pump
Fig. 2: The same
pump seen with reactor
gammas