In the GDH sum rule measurement in JLab Hall-A, to obtain the cross section of electron scattering on polarized 3He and its asymmetry in different helicity states, the dilution effect from unpolarized nitrogen mixed in the polarized 3He target were calculated at different kinematic settings.
A precision measurment of inclusive electron scattering cross sections is carried out at Jefferson Lab in the quasi-elastic region for 4 He, 12 C, 56 Fe and 208 Pb targets. The longitudinal (R L ) and transverse (R T ) response functions of the nucleon need to be extracted precisely in the momentum transfer range 0.55 GeV/c≤ | q | ≤1.0 GeV/c. To achieve the above goal, a NaI (Tl) calorimeter is used to distinguish good electrons from background, including pions and low energy electrons rescattered from the walls of the spectrometer magnets. Due to a large set of kinematics and changes in HV settings, a number of calibrations are performed for the NaI (Tl) detector. Corrections for a few blocks of NaI (Tl) with bad or no signal are applied. The resolution of the NaI (Tl) detector after calibration reached δE/E^(1/2) ≈ 3% at E=1 GeV. The performance of the NaI (Tl) detector is compared with a simulation. The good calibration and background analysis for the NaI(Tl) detector are very important for the reduction of the systematic error of cross sections and the separation of R L and R T .
