STUDY RESULTS FROM A.G. PETROSYAN ET AL PROVIDE NEW INSIGHTS INTO NUCLEAR SCIENCE

Science Letter
November 24, 2009

"Scintillation properties of LuAP:Ce and LuAP:Ce,Sc crystal series
were studied under excitation by gamma-rays from a (CS)-C-137 source.

Both series demonstrated comparable optical quality in terms of
underlying absorption at 260 nm, slope of the optical edge and
transmission in the range of emission," researchers in Armenia report
(see also Nuclear Science).

"The light yield of LuAP:Ce crystals measured in 0.2 cm x 0.2 cm x
0.8 cm pixels increases linearly with the Ce concentration reaching at
0.58 at. % 6448 +/- 322 ph/MeV and 9911 +/- 496 ph/MeV in the long and
in the short directions respectively (the light yield ratio is 65%)
and shows no sign of fight saturation. The energy resolution is found
to depend, among other factors, on the uniformity of Ce concentration
within the pixels and is improved to 7.1 +/- 0.4% (1 = 0.2 cm), 9.5
+/- 0.5% (l = 0.8 cm). Intentional co-doping with Sc3+ ions was tested
and resulted in increase of the Ce distribution coefficient to about
0.3. This enabled to increase the concentration of Ce in LuAP:Ce,Sc
crystals up to 0.7 at. %, while conserving high optical quality. In
contrast to LuAP:Ce, the light yield in LuAP:Ce.Sc crystals does
not increase with Ce concentration, the photo peak being gradually
suppressed," wrote A.G. Petrosyan and colleagues.

The researchers concluded: "The involved mechanisms are discussed
basing on measurements of the unit cell volumes, Ce concentration
uniformity, x-ray rocking spectra, absorption spectra of pure and
variously doped LuAP crystals, and emission spectra under different
excitations."

Petrosyan and colleagues published their study in IEEE Transactions on
Nuclear Science (Comparison of Spectral and Scintillation Properties of
LuAP:Ce and LuAP:Ce,Sc Single Crystals. IEEE Transactions on Nuclear
Science, 2009;56(5 Part 1):2574-2579).

For additional information, contact A.G. Petrosyan, Institute Physics
Research, Laboratory Crystal Growth Luminescent Materials, Ashtarak
0203 2, Armenia.

Publisher contact information for the journal IEEE Transactions on
Nuclear Science is: IEEE-Institute Electrical Electronics Engineers
Inc., 445 Hoes Lane, Piscataway, NJ 08855, USA.