F.Z. Khiari

Response-function measurement of an NE213 scintillator using the 2H(d, n)3He reaction

The response function of a 12.5 cm diameter NE213 scintillator detector has been measured over neutron energies ranging from 4.9 to 16.6 MeV. Beams of monoenergetic neutrons were produced using the 2H(d, n)3He reaction. The response function is about 12% lower than previously reported values for a similar detector obtained using a continuous spectrum of neutrons from a 252Cf fission source. However, the present response function agrees with portions of data sets obtained in published work that used monoenergetic neutron source reactions.

Response function measurements of an NE102A organic scintillator using an 241Am-Be source

The response function of a 125 mm diameter NE102A organic scintillation detector has been measured over the 2.7–14.8 MeV neutron energy range. The detector response function was derived from the light output for monoenergetic neutrons and gamma rays. The light output of the detector for monoenergetic neutrons was measured by selecting narrowgates in the time-of-flight (TOF) spectrum for a 241Am-Be neutron source. In order to provide check points on the data, the detector light output was also measured for monoenergetic neutrons from the D(d, n) and T(d, n) reactions. The response function of the NE102A detector is in good agreement (within 1–5%) with the published data of Cecil et al. [Nucl. Instr. and Meth. 161 (1979) 439].

Large angle scattering of α-particles from 32S

Abstract The elastic scattering of α-particles from 32 S was studied in the incident energy range between 4 and 8.9 MeV. In order to ascertain whether quasi-molecular states exist, as predicted in the α- 32 S system, excitation functions were measured, and angular distribution measurements were carried out using targets with different thicknesses in the angular range from θ lab = 30° to 175° at each extreme in the excitation functions. The analysis of the angular distribution data at back angles was performed using the Regge-pole method. A resonance with J = 3 was observed at 7.7 MeV in the α- 32 S system. Evidence was also found for both a broad resonance which can be characterized by an angular momentum J = 1, and for a narrow J = 2 resonance.

Pulse height tests of a large diameter fast LaBr3:Ce scintillation detector

The pulse height response of a large diameter fast 100 mm × 100 mm LaBr3:Ce detector was measured for 0.1-10 MeV gamma-rays. The detector has a claimed time resolution of 608 ps for 511 keV gamma rays, but has relatively poor energy resolution due to the characteristics of its fast photomultiplier. The detector pulse height response was measured for gamma rays from cobalt, cesium, and bismuth radioisotope sources as well as prompt gamma rays from thermal neutron capture in water samples contaminated with mercury (3.1 wt%), boron (2.5 wt%), cadmium (0.25 wt%), chromium (52 wt%), and nickel (22 wt%) compounds. The energy resolution of the detector was determined from full width at half maximum (FWHM) of element-characteristic gamma ray peaks in the pulse height spectrum associated with the element present in the contaminated water sample. The measured energy resolution of the 100 mm × 100 mm detector varies from 12.7±0.2% to 1.9±0.1% for 0.1 to 10 MeV gamma rays, respectively. The graph showing the energy resolution ΔE/E(%) versus 1/√Eγ was fitted with a linear function to study the detector light collection from the slope of the curve. The slope of the present 100 mm × 100 mm detector is almost twice as large as the slope of a similar curve of previously published data for a 89 mm × 203 mm LaBr3:Ce detector. This indicates almost two times poorer light collection in the 100 mm × 100 mm detector as compared to the other detector.

Energy resolution of NE102A and NE230 scintillators for monoenergetic gamma rays

Abstract The energy resolution of 125 and 50 mm diameter cylindrical NE102A detectors and 25 mm × 19 mm (height × diameter) NE230(C 6 D 6 ) deuterated scintillator has been measured for monoenergetic gamma rays with an energy of 0.5–1.3 MeV. Over this energy range, the energy resolution of 125 mm NE102A detector varies from 22.8 to 13.2% and from 19.6 to 11.5% for the 50 mm NE102A detector. The measured energy resolution of the NE230 scintillator varies from 12.9 to 7.0% over the same energy range. The energy resolution of NE102A detectors and C 6 D 6 scintillator is in good agreement with the energy resolution of NE213 detectors with comparable size.

KFUPM fast neutron activation analysis facility

Abstract A newly established Fast Neutron Activation Analysis facility at the Energy Research Laboratory is described. The facility mainly consists of a fast ne

Hydrogen, carbon and oxygen determination in proxy material samples using a LaBr3:Ce detector.

Hydrogen, carbon and oxygen concentrations were measured in caffeine, urea, ammonium acetate and melamine bulk samples via 14 MeV neutron inelastic scattering using a LaBr3:Ce detector. The samples tested herein represent drugs, explosives and benign materials, respectively. Despite its intrinsic activity, the LaBr3:Ce detector performed well in detecting the hydrogen, carbon and oxygen elements. Because 5.1 MeV nitrogen gamma rays interfere with silicon and calcium prompt gamma rays from the room background, the nitrogen peak was not detected in the samples. An excellent agreement was observed between the experimental and theoretical yields of 2.22, 4.43 and 6.13 MeV gamma rays from the analyzed samples as a function of H, C and O concentrations, respectively. Within statistical errors, the minimum detectable concentration (MDC) of hydrogen, carbon and oxygen elements in the tested materials were consistent with previously reported MDC values for these elements measured in hydrocarbon samples.

Backangle anomaly in scattering of α -particles from 28 Si at low energies

Abstract In order to resolve the differences in the literature on the existence of quasi-molecular states in the α - 28 Si system, excitation functions were measured for the scattering of α -particles from 28 Si in the incident energy range E lab =3 –7.8 MeV. An angular distribution measurement was carried out in the angular range θ lab =30° –174.5 ° for every potential resonance observed in the excitation functions. Data was analysed using a Regge-pole formalism by coherently adding specific resonances to an underlying diffraction term calculated by a strong absorption model. Furthermore, the usual compound elastic contribution was incoherently added to the direct interaction part of the cross section. The 6.8 MeV resonance was confirmed with J=3 and some evidence was observed for a J=1 resonance around 6.0 MeV.

Elemental analysis using natural gamma-ray spectroscopy

A gamma-ray spectroscopy setup has been recently established to measure the natural gamma-ray activity from potassium (40K), uranium (238U), and thorium (232Th) isotopes in rock samples of oil well-logs. The setup mainly consists of a shielded 135 cm3 Hyper Pure Germanium (HPGe) detector, a 5 in. × 5 in. NaT(Tl) detector and a PC based data acquisition system. The core samples, with 70–100 g weight, have cylindrical geometry and are sealed such that radon gas from 238U decay would not escape from the sample. For room background subtraction, pure quartz samples identical to core samples were used. The sample is first counted with the HPGe detector to identify the elements through its characteristics gamma rays. Then the elemental concentration is determined by counting the sample with a NaI detector. In order to determine the absolute concentrations, the sample activity is compared with the activities of standards supplied by NIST and IAEA. The concentration of 238U and 232Th has been determined in ppm range with that of 40K in wt.%.

Performance tests of a large volume cerium tribromide (CeBr3) scintillation detector.

The response of a large cylindrical 76mm×76mm (height×diameter) cerium tribromide (CeBr3) detector was measured for prompt gamma rays. The total intrinsic activity of the CeBr3 detector, which was measured over 0.33-3.33MeV range, was found to be 0.022±0.001 counts/s/cm(3). The partial intrinsic activity ( due to (227)Ac contamination), was measured over a energy range of 1.22-2.20MeV energy, was found to be 0.007±0.001 counts/s/cm(3). Compared to intrinsic activities of LaBr3:Ce and LaCl3:Ce detectors of equivalent volume, the CeBr3 detector has 7-8 times less total intrinsic activity. The detector response for low energy prompt gamma rays was measured over 0.3-0.6MeVgamma energy range using a portable neutron generator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup. The experimental yield of boron, cadmium and mercury prompt gamma-rays was measured from water samples contaminated with 0.75-2.5wt% mercury, 0.31-2.50wt% boron, and 0.0625-0.500wt% cadmium, respectively. An excellent agreement has been observed between the calculated and experimental yields of the gamma rays. Also minimum detection limit (MDC) of the CeBr3 detector was measured for boron, cadmium and mercury samples. The CeBr3 detector has 23% smaller value of MDCB and 18% larger value of MDCCd than those of a LaBr3:Ce detector of equivalent size. This study has shown that CeBr3 detector has an excellent response for the low energy prompt gamma-rays with almost an order of magnitude low intrinsic activity as compared to LaCl3:Ce and LaBr3:Ce detectors of equivalent volume.