(MSc. Thesis)
2008

Student: Ala’ Thawabteh
Supervisor: Dr. Adnan Lahham
Jerusalem – Palestine

Abstract

This study deals with a nuclear method of Gamma- Ray Backscattering Spectroscopy as a method that could be applied in measuring material bulk density specially soil density. The detection system consists of a 3” × 3” inch NaI(Tl) detector connected to multichannel analyzer Inspector 2000 from Canberra instruments and lap top computer. 137Cs is used as a Gamma-Ray emitter with energy of 662 KeV. Different soil types with different bulk densities are used in the calibration process. Before applying this technology in the field, calibration process took place in order to find a relationship between material bulk density and the collected count rate for that material. Calibration measurements are performed using three different materials with three different bulk densities filled in wooden boxes constructed specially for this purpose with dimensions of 59×42×34 cm. Gamma ray source is shielded to prevent direct gamma photons from reaching the detector in direct way. The detector and shielded gamma-ray source are placed on the top of the material’s surface, and gamma ray spectrum for 137Cs is collected for measuring times of 60 seconds. Collected spectra are analyzed using Genie 2000 software. Count rates are calculated for each spectrum, then a calibration curve was used to find the relation between the gamma count rate and the bulk density of material being investigated. Field measurements of bulk density (BD) are performed to check the validity of the system calibration. Results of Terra Rossa soil were in very good agreement with the measured density Measurement of bulk density are conducted in five different locations at Al-Quds University Main-Campus site. Results of these measurements are consistent in relation to the type of soil and other materials present at the investigated locations. It was found that the best results can be achieved with source to detector distance of about 20 cm.