A Structural Study of Ag-Rich Ag–As–S Glasses

Abstract

The γ /hadron separation in the imaging air Cherenkov telescope technique is based on differences between images of a hadronic shower and a γ induced electromagnetic cascade. One may expect for a large telescope that a detection of hadronic events containing Cherenkov light from one γ subcascade only is possible. In fact, simulations show that for the MAGIC telescope their fraction in the total protonic background is about 1.5% to 5.2% depending on the trigger threshold. It has been found that such images have small sizes (mainly below 400 photoelectrons) which correspond to the low energy primary γ 's (below 100 GeV). It is shown that parameters describing shapes of images from one subcascade have similar distributions to primary γ events, so those parameters are not efficient in all methods of γ selection. Similar studies based on MC simulations are presented also for the images from 2γ subcascades which are products of the same π 0 decay. The ratio of the number of the expected background from false γ and one π 0 to the number of the triggered high energy photons from the Crab direction has been estimated for images with a small alpha parameter to show that the occurrence of this type of protonic shower is the reason for the difficulties with true γ selection at low energies. Communicated by Professor M Giller

An XPS study of the early stages of silver photodiffusion in Ag/a-As2S3 films

“…Therefore, one might anticipate that X-rays would not cause significant changes in the electronic structure of the Ag/As 2 S 3 films either; for the same reason one may expect negligible effect of X-ray irradiation on silver diffusion. Numerous previous XPS studies of photo and thermally induced silver diffusion in chalcogenide glasses did not take into consideration of any X-ray induced effects [11,[22][23][24][25][26][27]. So contrary to general expectation, we have observed significant and very interesting X-ray induced changes in the As3d and S2p core level spectra of the Ag/As 2 S 3 samples.…”

“…Once inside the film, the silver ions may react to form again Ag 2 S by reaction (1). It is plausible that when the concentration of both Ag 2 S and As 2 S 3 is high, as would be the case if silver diffusion rates were high, stable ternary phases of Ag, As and S are formed as below [16,27]:…”

In Situ Measurements of X‐Ray‐Induced Silver Diffusion into a Ge30Se70 Thin Film

“…The existence of such silver species in a Se‐rich metastable composition based on Ag +δ –Se interactions very close to the surface is supported by the significant variation of the Se/Ge ratio with the irradiation time (2.8 and 2.5 at the beginning of irradiation and in the equilibrium state, respectively). This agrees with the earlier conclusions that Ag in ChG exists as Ag + ions incorporated into the glass matrix 20,28 . The significant decrease in the FWHM of the 368.3 eV component from 0.81 to 0.61 eV after prolonged irradiation may be an evidence of the stabilization of the Ag +δ –Se interactions as silver diffuses into the ChG film.…”

“…This agrees with the earlier conclusions that Ag in ChG exists as Ag 1 ions incorporated into the glass matrix. 20,28 The significant decrease in the FWHM of the 368.3 eV component from 0.81 to 0.61 eV after prolonged irradiation may be an evidence of the stabilization of the Ag 1d -Se interactions as silver diffuses into the ChG film. Both Ag 3d 5/2 components at lower BE can be linked only with some Ag-containing phases.…”

Comparison between blue lasers and light‐emitting diodes for future solid‐state lighting

“…Assuming light randomization, a simplified model can be derived for the extraction efficiency. Precise numerical modeling such as ray tracing [38,39] could have been used, but it will be shown below that this simple model does an excellent job of fitting to theoretical and experimental data. Moreover, this model gives physical intuition into the key thin-film design challenges associated with high extraction efficiency, and can easily incorporate improvements, leading to higher extraction efficiency.…”