In situdiagnostics of the crystal-growth process through neutron imaging: application to scintillators.
Neutrons are known to be unique probes in situations where other types of radiation fail to penetrate samples and their surrounding structures. In this paper it is demonstrated how thermal and cold neutron radiography can provide time-resolved imaging of materials while they are being processed (e.g.while growing single crystals). The processing equipment, in this case furnaces, and the scintillator materials are opaque to conventional X-ray interrogation techniques. The distribution of the europium activator within a BaBrCl:Eu scintillator (0.1 and 0.5% nominal doping concentrations per mole) is studiedin situduring the melting and solidification processes with a temporal resolution of 5-7 s. The strong tendency of the Eu dopant to segregate during the solidification process is observed in repeated cycles, with Eu forming clusters on multiple length scales (only for clusters larger than ∼50 µm, as limited by the resolution of the present experiments). It is also demonstrated that the dopant concentration can be quantified even for very low concentration levels (∼0.1%) in 10 mm thick samples. The interface between the solid and liquid phases can also be imaged, provided there is a sufficient change in concentration of one of the elements with a sufficient neutron attenuation cross section. Tomographic imaging of the BaBrCl:0.1%Eu sample reveals a strong correlation between crystal fractures and Eu-deficient clusters. The results of these experiments demonstrate the unique capabilities of neutron imaging forin situdiagnostics and the optimization of crystal-growth procedures.
Space Sciences Laboratory, University of California at Berkeley, Berkeley, CA 94720, USA.
Anton S
AS
Tremsin
Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, Roskilde 4000, Denmark; European Spallation Source ESS AB, PO Box 176, Lund SE-221 00, Sweden.
Małgorzata G
MG
Makowska
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Didier
D
Perrodin
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Tetiana
T
Shalapska
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Ivan V
IV
Khodyuk
Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
Pavel
P
Trtik
Paul Scherrer Institute, 5232 Villigen PSI, Switzerland.
Pierre
P
Boillat
Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Sven C
SC
Vogel
Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Adrian S
AS
Losko
European Spallation Source ESS AB, PO Box 176, Lund SE-221 00, Sweden.
Markus
M
Strobl
Department of Energy Conversion and Storage, Technical University of Denmark, Frederiksborgvej 399, Roskilde 4000, Denmark.
L Theil
LT
Kuhn
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Gregory A
GA
Bizarri
Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
Edith D
ED
Bourret-Courchesne
crystal growth; in situ diagnostics; neutron imaging; non-destructive testing; scintillators