Defence Research Agency

About: Defence Research Agency is a based out in . It is known for research contribution in the topics: Synthetic aperture radar & Radar. The organization has 1211 authors who have published 1109 publications receiving 31542 citations.

A new approach to electron-gun design for high-performance cathode-ray tubes

Abstract: — A new cathode-ray tube electron-gun configuration is described and compared with alternative electron guns, both traditional designs and more recent high-performance types. Key features and advantages of the new approach are discussed. Three sample designs are outlined, with more detailed consideration of one typical example.

Assessment of electrical inhomogeneity of undoped and doped Hg 1− x Cd x Te MOVPE (IMP) layers by variable magnetic field Hall profile measurements

Abstract: A Hall profiling technique in which measurements are made at 77K as a function of magnetic field (0.01–1T) and layer thickness (by chemical thinning) has been developed for the characterization of Hg1−xCdxTe epitaxial layers. The technique has been applied to undoped and lightly In doped MOVPE interdiffusion multilayer process (IMP) layers grown on (100) GaAs and CdTe with x values between 0.19 and 0.30 in order to investigate the parameters controlling the electrical homogeneity. Results show unpassivated layers with x>0.25 are uniformly p-type with 77K hole concentrations consistent with Hg vacancy concentrations for the growth conditions while layers with x<0.25 are anomalous, being either inhomogeneous or uniformly n-type depending on x. The inhomogeneous layers are mainly n on p layer structures, in which the junction depth, Xj, but not the carrier concentration is found to be a function of x and can be comparable to layer thickness at x=0.20. Carrier levels in the n and p-type regions are consistent with the net background impurity donor and Hg vacancy concentrations respectively, suggesting that the n-type properties occur through post growth Hg in-diffusion filling in the vacancies. This model was partly confirmed by capping layers with CdTe, which significantly reduced the extent of the n-type region, and by ex-situ annealing experiments to simulate the inhomogeneity. Results show the low temperature process responsible for the type conversion in MOVPE CMT is highly x dependent, suggesting a variation in the electrical “Hg diffusion coefficient” of over an order of magnitude between 0.20 and 0.30 at 200°C. Carrier and mobility profiles of both as-grown and annealed n-p structures are abrupt and consistent with an interstitial Hg diffusion mechanism.

Nitration by Oxides of Nitrogen. Part 4. Unexpected Behaviour of Certain Aziridines and Azetidines Upon Reaction with Dinitrogen Pentoxide.

Abstract: Seven aziridines and azetidines, either unsubstituted on ring nitrogen or bearing N-acyl (N,N-dimethylcarbamyl or propionyl) groups, were reacted with N2O5 in halogenated solvents with the following results:- the behaviour of the aziridines was highly dependent on the N-substituent, giving respectively dinitrate esters, nitramine-nitrate or predominantly uncharacterisable products, whereas the azetidines gave in all cases N-nitroazetidine. The different behaviour is believed to result from ring strain effects.