This study investigates electron emission from copper broad-area emitters (CBAEs) and copper broad-area composite emitters (CBACEs) based on the principles of trapping and conductive pathways. Emission current measurements were conducted on two CBACEs, which consisted of copper coated with a 300–400 μm epoxy resin and subjected to high voltages up to 15 kV. The research specifically examines the ‘switch-on’ and collapse phenomena occurring within the epoxy layer. Field emission microscopy (FEM) was utilized in a high-vacuum environment ( 10 − 6 mbar) to observe these effects. A comprehensive model is developed to explain the formation of conductive pathways within the epoxy layer, allowing electrons transfer from traps to the surface. This model treats the composite emitter as a trap-rich capacitor. The study also clarifies the effects of trap density and epoxy layer thickness on the collapse process. To gain a deeper understanding of the model, changes in the I-V curve were examined. Simulations, scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDX) images, and Fourier transform infrared spectroscopy (FTIR) analysis were employed to understand the collapse mechanism of the epoxy collapse. Additionally, Nyquist and Cole–Cole plots were analyzed across frequencies ranging from 1 to 10 6 Hz before and after applying a high electric field on the samples, revealing changes in the capacitive component and the role of diodes in the formation of conductive channels.

Radioluminescence at room temperature and thermoluminescence (TL) measurements of single-doped and codoped LiNaSO₄ above room temperature are reported here. The codoped samples were studied to investigate the possibility of enhancing the TL sensitivity of LiNaSO₄:Eu. This objective was not satisfied and the codopants (Ce, Sm, Ho and Er) decrease the TL sensitivity and slightly shift the dosimetric peak to lower temperatures. Samples doped with Mg, K, Bi and Tl were used with the hope that they may alter the trapping centers stability and introduce new peaks in the temperature range 430–500 K to observe any TL discontinuity or wavelength shift in their spectra as observed in CL measurements. This objective was fulfilled with Tl and Bi, where there is a discontinuity and/or wavelength shift at about 460 K. Such intensity and/or wavelength variations are ascribed to microstructural phase changes within the LiNaSO₄ crystals that may result from twin boundaries behaving like Na₂SO₄.

It is generally observed that the various heating rates (VHR) method overestimates the activation energy ( E ) when applied to quenched thermoluminescence (TL) peaks. Based on the analysis of numerically computed quenched TL peaks, we introduced an empirical expression that estimates the error in E . The expression correlates the error in E with the width of the peak, the luminescence efficiency and its first derivative at the lowest heating rate evaluated at the temperature of peak maximum. In addition, the expression accurately predicts the temperature shift of the peak maximum as a function of the heating rate. The VHR-based methods used to evaluate the quenching parameters ( W and C ) result in erroneous values. The source of error in the peak area-based method is the replacement of the unquenched peak area by the quenched peak area at the lowest heating rate as usually practiced in the literature. Accurate values of W and C were obtained when we modified the basic equation to include the luminescence efficiency at the lowest heating rate. On the other hand, we explicitly showed that the maximum intensity-based method used to evaluate these parameters is not suitable due to the lack of a reference point.