A. Aksoy

Efficiency calibration of HPGe detector in far and close geometries

The absolute total and full-energy peak (FEP) efficiencies of a high purity germanium (HPGe) photon detector are measured in the energy range from 40 keV to 1500 keV. The functional parameters are fitted to the calibration points from 14 long-lived standard sources (129I,241Am,109Cd,57Co,139Ce,137Cs,54Mn,65Zn,60Co,22Na,133Ba,152Eu,154Eu and166mHo) within an accuracy better than the quoted uncertainty of the calibration sources. The efficiencies in far and close geometries are compared.

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].

Light yield measurements of a NE213 detector for 2.8–14.8 MeV neutrons

Abstract The light yield of a 125 mm diameter NE213 detector was measured over the neutron energy ranging from 2.8 to 14.5 MeV to resolve the discrepancy between the previously reported light yield of an identical NE213 detector using a 252 Cf source [K. Gul, A.A. Naqvi and H.A. Al Juwair, Nucl. Instr. and Meth. A278 (1989) 470] and 5.5-16.5 MeV monoenergetic neutrons from the D(d,n) reaction [A. Aksoy et al., to be published]. The new light yield measurements were carried out for 3.5–6.1 MeV neutrons using an 241 Am-Be neutron source while the detectors light yield for 14.8, 9.7 and 2.8 MeV neutrons were measured using the T(d,n) and D(d,n) source neutrons. The light yield data measured in this experiment is consistently 2–19% lower than that of Gul et al. [Nucl. Instr. and Meth. A278 (1989) 470]. Within the experimental uncertainties, the present data agrees well with that of Aksoy et al. [to be published] and with that of Verbinski et al. [V.V. Verbinski, W.R. Burrus, T.A. Love, W. Zobel and N.W. Hill, Nucl. Instr. and Meth. 65 (1968) 8]. These measurements have shown that the light yield of the NE213 detectors is smaller than that reported by Gul et al. The reason for this discrepancy might be the uncertainty involved in the technique used by Gul et al. to determine the proton energy.

Natural radioactivity in the scale of water well pipes

The natural radioactivity of 226Ra and 228Ra in scale samples taken from pipes used in several local water wells was investigated. The results showed 226Ra activities to be varying from 1284 to 3613 Bq/kg whereas, the 228Ra concentrations did not show any significant variation, all being low, below 30 Bq/kg. The 222Rn exhalations from these scale samples were also measured and compared with the 226Ra contents. The average ratio of 222Rn/226Ra was 31%. Chemical analyses showed that the main constituent of the scale samples was iron. The radiation dose rates from the pipes and scale were up to 100nSv/h. Although not a major hazard this could present a long-term risk if the scale materials were handled indiscriminately.

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.

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

Determination of the neutron detection efficiency of an NE213 scintillator for En = 2.5 to 16 MeV using the 2H(d, n)3He reaction

Abstract The absolute efficiency of an NE213 liquid scintillator of 12.7 cm diameter and 5.08 cm thickness was measured in the neutron energy range 2.5–16 MeV using the 2 H(d, n) 3 He reaction as a source of monoenergetic neutrons. The efficiencies were measured at the time-of-flight facility of Triangle Universities Nuclear Laboratory (TUNL). The experimental data are compared to calculations from the Monte Carlo code NEFF of Physikalisch-Technische Bundesanstalt, Braunschweig, Germany (PTB).

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.%.