Ce Scintillation Detectors Research Articles

Analytical expression to calculate total and full-energy peak efficiencies for cylindrical phoswich and lanthanum bromide scintillation detectors

Abstract An analytical expression for the total and full-energy peak efficiencies for cylindrical phoswich and lanthanum bromide (LaBr 3 :Ce) scintillation detectors is derived. This approach depends on the accurate analytical calculation of two important factors; the path length d , the photon traverses within the active volume of a gamma detector, and the geometrical solid angle Ω , subtended by the source to the detector at the point of entrance. In addition, the attenuation of photons by the detector housing materials is also treated by calculating the photon path length through these materials. The comparisons with the experimental and Monte Carlo method data reported in the literature indicate that the present method is useful in the efficiency calibration of the cylindrical phoswich and lanthanum bromide scintillation detectors.

The mirror symmetric centroid difference method for picosecond lifetime measurements via [formula omitted] coincidences using very fast LaBr3(Ce) scintillator detectors

The ultra-fast timing technique was introduced in the 1980s and is capable of measuring picosecond lifetimes of nuclear excited states with about 3ps accuracy. Very fast scintillator detectors are connected to an electronic timing circuit and detector vs. detector time spectra are analyzed by means of the centroid shift method. The very good 3% energy resolution of the nowadays available LaBr3(Ce) scintillator detectors for γ-rays has made possible an extension of the well-established fast timing technique. The energy dependent fast timing characteristics or the prompt curve, respectively, of the LaBr3(Ce) scintillator detector has been measured using a standard 152Eu γ-ray source. For any energy combination in the range of 200keV<Eγ<1500keV, the γ–γ fast timing characteristics is calibrated as a function of energy with an accuracy of 2–4ps. An extension of the centroid shift method providing very attractive features for picosecond lifetime measurements is presented. The mirror symmetric centroid difference method takes advantage of the symmetry obtained when performing γ–γ lifetime measurements using a pair of almost identical very fast scintillator detectors. In particular cases, the use of the mirror symmetric centroid difference method also allows the direct determination of picosecond lifetimes, hence without the need of calibrating the prompt curve.

A new analytical method to calibrate cylindrical phoswich and LaBr3(Ce) scintillation detectors

A new analytical method of efficiency calibration is proposed for cylindrical phoswich and lanthanum bromide (LaBr3:Ce) scintillation detectors. This method depends on the accurate analytical calculation of two important factors: the path length d, the photon traverses within the active volume of a gamma detector, and the geometrical solid angle Ω, subtended by the source to the detector at the point of entrance. In addition, the attenuation of photons by the detector housing materials is also treated by calculating the photon path length through these materials. The comparisons with the experimental and Monte Carlo method data reported in the literature indicate that the present method is useful in the efficiency calibration of the cylindrical phoswich and lanthanum bromide (LaBr3:Ce) scintillation detectors.

HPGe detectors timing using pulse shape analysis techniques

In this work the Pulse Shape Analysis has been used to improve the time resolution of High Purity Germanium (HPGe) detectors. A set of time aligned signals was acquired in a coincidence measurement using a coaxial HPGe and a cerium-doped lanthanum chloride (LaCl 3:Ce) scintillation detector. The analysis using a Constant Fraction Discriminator (CFD) time output versus the HPGe signal shape shows that time resolution ranges from 2 to 12 ns depending on the slope in the initial part of the signal. An optimization procedure of the CFD parameters gives the same final time resolution (8 ns) as the one achieved after a correction of the CFD output based on the current pulse maximum position. Finally, an algorithm based on Pulse Shape Analysis was applied to the experimental data and a time resolution between 3 and 4 ns was obtained, corresponding to a 50% improvement as compared with that given by standard CFDs.

Measurement of prompt gamma-ray emission in fission

In this work we present results from the characterization of both LaCl3:Ce scintillation and polycrystalline diamond detectors to be used for measurements of prompt gamma radiation emitted in fission. The properties of these new detector types, such as excellent timing resolution and improved energy resolution will allow to obtain fission data with higher accuracy than those available today.

Sub-nanosecond lifetime measurements using the Double Orange Spectrometer at the cologne 10 MV Tandem accelerator

Conversion electron spectroscopy constitutes an important tool in nuclear structure physics. A high efficiency iron-free Orange type electron spectrometer with an energy resolution of 1–2% has been installed at a beam line of the Cologne 10MV FN Tandem Van-de-Graaff accelerator for in-beam studies of conversion electrons. In combination with a γ-ray detector array, high efficiency e-–γ-coincidences can be performed. The newly developed very fast LaBr3(Ce) scintillator detector with an energy resolution of about 4% makes it also possible to use e-–γ-coincidences for lifetime measurements of nuclear excited states. A second iron-free Orange spectrometer can be connected to perform e-–e--coincidences. Because of the higher efficiency and the better energy resolution, the use of the Double Orange Spectrometer for lifetime measurements is more powerful. Lifetimes down to 100ps and even less can be determined with an accuracy of about 10ps. The working principle of the Orange spectrometer and the setup of the Double Orange Spectrometer are described. The performances are illustrated by examples of in-beam experiments with a main focus on high precision lifetime measurements.

Experimental feasibility studies on a SPECT tomograph for BNCT dosimetry

This article reports on the development of a prototype of a SPECT tomograph system for online dosimetry in BNCT based on LaBr 3(Ce) scintillation detectors. The setup shielding was optimized to be used in the accelerator based BNCT facility of the University of Birmingham. The system was designed and built. An image of a 241Am point source was reconstructed. A projection of a phantom with two tumors with 400 μg/g of 10B was measured at the BNCT facility.

Comparison of &lt;formula formulatype="inline"&gt;&lt;tex&gt;${\hbox {LaBr}}_{3}:{\hbox {Ce}}$&lt;/tex&gt;&lt;/formula&gt; and &lt;formula formulatype="inline"&gt; &lt;tex&gt;${\hbox {LaCl}}_{3}:{\hbox {Ce}}$&lt;/tex&gt;&lt;/formula&gt; With NaI(Tl) and Cadmium Zinc Telluride (CZT) Detectors

Energy resolution and detection efficiency were compared between new scintillators, lanthanum bromide (LaBr3:Ce) and lanthanum chloride (LaCl3:Ce) with conventional detectors, sodium iodide NaI(Tl) and cadmium zinc telluride (CdZnTe or CZT). The study has shown that LaBr3:Ce and LaCl3:Ce scintillator detectors provided by Saint-Gobain offer better resolution than NaI(Tl) detector. LaBr3:Ce and LaCl3:Ce detectors could resolve some closely spaced peaks from 133Ba and 152Eu, which Na(I) could not. LaBr3:Ce has slightly better resolution and higher efficiency than LaCl3:Ce. An overall advantage of LaBr3:Ce and LaCl3:Ce detectors over NaI(Tl) and CZT has been discussed. The intrinsic activity of LaBr3:Ce is also demonstrated in this study.

LaCl 3(Ce) scintillation detector applications for environmental gamma-ray measurements of low to high dose rates

A new cerium-doped LaCl 3(Ce) scintillator is evaluated with respect to the application in environmental gamma-ray dosimetry and spectrometry. The scintillator is very attractive for gamma-ray spectrometry in the case of high count rate, because it has excellent energy resolution and fast decay time. The performance characteristics of a scintillator with a 25.4 mm×25.4 mm LaCl 3(Ce) crystal are studied and compared to those of a NaI(Tl) scintillator with the same size crystal. Acquired pulse height spectra are converted to dose rates by using the G ( E ) function method. Though the LaCl 3(Ce) crystal itself produces a rather high background in the crystal itself, the scintillator provides good energy information and dose-rate readings from low to high-level (several mGy/h) by subtracting the self-background. The properties of LaCl 3(Ce) scintillator suggest that the scintillator could be a promising candidate for monitoring at high dose levels as in emergencies, as well as at ordinary levels of background radiation.

Measurement of radon daughters in water and in air using the detection unit “YAPMARE” with a YAP:Ce scintillation detector

With a focus on the detection of the Rn concentration in water in extreme conditions, the detection unit YAPMARE was developed by the company CRYTUR. The main part of the detection unit is a detection probe based on the Ø25×100 mm YAP:Ce detector. The measured water covers approximately 95% of the crystal surface (the detection volume is 12 ml). Measurements of 222Rn and 220Rn standards for determination of individual peaks in the spectra were conducted, including an observation of the 222Rn (and its daughters) behavior. For YAPMARE calibration, fresh water was taken from a drilled well in the Lounovice area (biotitic granodiorite–adamellite). The calibration was carried out with the assistance of radon in water monitor RADIM 4. The results of the water measurements in Lounovice were as follows: detection limit was about 50 Bq/l, and calibration coefficient was 0.0011 imp/s per 1 Bq/l. The results of the fresh water and air sample measurements have demonstrated the main advantages (spectrometric results of the measurement, possibility for water or air samples evaluation) and disadvantages (large size of scintillation crystal increases gamma ray background, calibration for each water with particular composition, and detector cleaning using HCl acid).

05/00115 Developments to supplant CAMAC with industry standard technology at NSTX: Sichta, P. et al. Fusion Engineering and Design, 2004, 71, (1–4), 129–133

The neutron sensitivity of a cylindrical ⊘1.5 in.×1.5 in. LaBr3:Ce scintillation detector was measured using quasi-monoenergetic neutron beams in the energy range from 40 keV to 2.5 MeV. In this energy range the detector is sensitive to γ-rays generated in neutron inelastic and capture processes. The experimental energy response was compared with Monte Carlo simulations performed with the Geant4 simulation toolkit using the so-called High Precision Neutron Models. These models rely on relevant information stored in evaluated nuclear data libraries. The performance of the Geant4 Neutron Data Library as well as several standard nuclear data libraries was investigated. In the latter case this was made possible by the use of a conversion tool that allowed the direct use of the data from other libraries in Geant4. Overall it was found that there was good agreement with experiment for some of the neutron data bases like ENDF/B-VII.0 or JENDL-3.3 but not with the others such as ENDF/B-VI.8 or JEFF-3.1.

Performance of a tagged neutron inspection system (TNIS) based on portable sealed generators

A portable sealed neutron generator has been modified to produce 14 MeV tagged neutron beams with an embedded YAP:Ce scintillation detector. The system has been tested by detecting the coincident gamma-rays produced in the irradiation of a graphite sample by means of a standard NaI(Tl) scintillator . Time resolution of about δ t = 4 – 5 ns (FWHM) has been measured. The sealed neutron tube has been operated up to 10 7 neutron/s. Possible applications in non-destructive assays and future developments of the Tagged Neutron Inspection System concept are discussed.

Performance of a tagged neutron inspection system (TNIS) based on portable sealed generators

A portable sealed neutron generator has been modified to produce 14MeV tagged neutron beams with an embedded YAP:Ce scintillation detector. The system has been tested by detecting the coincident gamma-rays produced in the irradiation of a graphite sample by means of a standard NaI(Tl) scintillator. Time resolution of about δt=4–5ns (FWHM) has been measured. The sealed neutron tube has been operated up to 107neutron/s. Possible applications in non-destructive assays and future developments of the Tagged Neutron Inspection System concept are discussed.

Properties of a YAP:Ce detector for high-energy X-ray counting experiments

We designed a YAP:Ce scintillation detector for high-energy and high-rate X-ray experiments. The energy spectra and count-rate behavior were measured for 50.0, 28.0 and 16.5-keV synchrotron X-rays. Using a scintillator crystal 25 mm in diameter and 1 mm thick, an energy resolution of 24% (FWHM) was obtained at 7×10 5 counts/s for 50 keV X-rays. The intrinsic efficiency was 79%. A maximum count rate of 5.25×10 6 s −1 was observed and the dead time corresponded to 72 ns, according to a counting model for pulsed X-rays. The results for a 5-mm thick crystal are also described.