Ideal Scintillator Research Articles

Fast-response, Low-Afterglow 4,4'''-Bis[(2-butyloctyl)oxy]-1,1':4',1'':4'',1'''-quarterphenyl Dye-Based Liquid Scintillator for High-Contrast Detection of Laser Fusion-Generated Neutrons

4,4'''-Bis[(2-butyloctyl)oxy]-1,1':4',1'':4'',1'''-quaterphenyl (BBQ) dye dissolved in xylene and enriched with oxygen is shown to exhibit the characteristics of an ideal neutron scintillator for time-of-flight (TOF) measurement in a laser fusion experiment. Initial results from excitation with 290-nm pulses show that it has a 0.76-ns fast decay component and a negligible slow decay component or afterglow. By using this scintillator for TOF measurement, we have successfully discriminated between nuclear fusion-generated neutrons and X-rays. This would dramatically improve neutron diagnostics in fast ignition experiments where neutrons have to be detected in the presence of an intense X-ray burst.

Inorganic Scintillators—A Never Ending Story

For decades, scintillation detectors based on inorganic materials have become one of the most widely applied instrumentation techniques in physics—in particular in the fields of nuclear and high-energy physics. Their discovery and development are strongly correlated with the experimental needs in basic research and technology in physics. Visual counting of the discovered X-rays or natural radioactivity became possible with CaWO4 or ZnS at the end of the 19th century. The first construction of scintillation detectors, made possible by the development of the photomultiplier tube, started with the discovery of activated and pure alkali halide crystals. NaI(Tl) and CsI(Tl), introduced by Hofstadter [1, 2], have provided for 60 years efficient photon and particle detection. The continuous increase of the energy range of the probes to be detected directed crystal development toward faster response, shorter decay times, and higher compactness implementing high-Z ions. In particular, the discovery of the fast core-valence luminescence in BaF2 [3, 4], the allowed electric dipole transitions in Ce3+, and the short radiation lengths of BGO [5] or PbWO4 [6] set important milestones in the last decades of the 20th century to find or even engineer the ideal scintillator.

An approximation of the ideal scintillation detector line shape with a generalized gamma distribution

An approximation of the real line shape of a scintillation detector with a generalized gamma distribution is proposed. The approximation describes the ideal scintillation line shape better than the conventional normal distribution. Two parameters of the proposed function are uniquely defined by the first two moments of the detector response.

LaBr 3:Ce scintillators for in-beam gamma-ray spectroscopy with fast beams of rare isotopes

The scintillator material LaBr 3:Ce, which was discovered in 2001, has grown in popularity for a variety of applications in homeland security and nuclear medicine. In this paper we investigate its use for nuclear science spectroscopy applications in the context of in-beam gamma-ray spectroscopy with fast ion beams. In such experiments, the Doppler broadening of the gamma-ray line measured with a finite-size detector in the laboratory fundamentally limits the achievable energy resolution. For a typical experiment this effect is of the order of 3%. With the intrinsic energy resolution of LaBr 3:Ce better than 3% FWHM at 662 keV, and its favorable stopping power, it could be a nearly ideal scintillator for gamma-ray spectroscopy applications with fast beams. Results from in-beam gamma-ray spectroscopy measurements using two LaBr 3:Ce scintillators are presented and compared to results from segmented germanium detectors. Results from these measurements suggest that LaBr 3:Ce based scintillation arrays can provide a viable tool for many experiments. Additionally, we show that the excellent timing properties of LaBr 3:Ce can significantly reduce background events in the gamma-ray spectra.

High-light-output scintillator for photodiode readout: LuI3:Ce3+

In this paper, we investigated the scintillation properties of LuI3:Ce3+. Radioluminescence, light output, energy resolution, and γ-scintillation decay are reported. We find an extremely high light output of 98000±10000photons∕MeV. LuI3:Ce3+ also gives a very high electron-hole (e-h) pair response when it is coupled with an avalanche photodiode (APD) (92000±9000e-hpairs∕MeV). With an APD, a best energy resolution (full width at half maximum over the peak position) of 3.3%±0.3% for 662keV γ quanta is observed. A combination of an extremely high light output and a good energy resolution makes LuI3:Ce3+ an ideal scintillator for radiation sensor applications. Some drawbacks due to the hygroscopicity and the difficult growth of LuI3:Ce3+ crystals are also discussed.

Cesium Fluoride: A New Detector for Positron Emission Tomography

The ideal scintillation detector for positron tomography would be a very high Z material, nonhygroscopic, have a fast decay time, and copious light output. NaI(Tl) has good light output, and even though it is hygroscopic has found acceptance as a good scintillator. Recently BGO has been shown to satisfy the first two requirements for tomography, and has replaced NaI(Tl) as the detector of choice in tomography. However, its low light yield and poor coincidence timing make it unsuitable for fast scanners. Cesium fluoride (CsF) has been investigated by us as a possible scintillation detector for positron tomography, and shows great promise even though it is extremely hygroscopic and exhibits low scintillation efficiency as compared to NaI(Tl). Its very fast decay time, good detection efficiency, and fast coincidence timing make it an ideal detector for tomographs designed for fast dynamic studies. Moreover, it permits the incorporation of time of flight information with conventional tomography for improved signal to noise ratio in the image.

Photomultiplier single-electron statistics and the shape of the ideal scintillation line

A study has been made of the particular role of the photomultiplier in determining pulse-height resolution in a scintillation counter assembly. The contribution to photomultiplier noise of single electrons from the photocathode is discussed. It is shown that although the overall resolution depends sensitively on the frequency distribution of single-electron pulses, a statistical model can be formulated which leads to an expression for the shape of the ideal scintillation line, which adequately represents actual line-shapes and which is not itself sensitive to the details of the single-electron distribution. It is suggested that the same expression may be appropriate for describing the line-shape in proportional counters.

Energy Resolution Correction for Scintillation Spectrometers

A computational scheme is presented for correcting the energy resolution of scintillation spectrometers. This scheme, unlike others previously published, appertains only to experimental data and does not rely on theoretical considerations of energy absorption within the scintillator. Applications to beta spectroscopy and analysis are included and a derivation of the ideal scintillation line and the various factors which in practice statistically modify the ideal shape is given in the Appendix.