Single-photon detection at 1550-nm with a high repetition rate was realized using an InGaAs/InP avalanche photodiode operated with a sine wave gating. Removing the AC noise due to the transferred gate signal usingband elimination filters, we have discriminated the avalanche signal which is much smaller than that in the conventional gating, which results in the suppression of the afterpulsing. At the repetition frequency of 800MHz, the overall afterpulsing probability was 6.0% with the detection efficiency of 8.5% and the dark count probability of 9.2X10(-6).

X-ray absorption near edge structure (XANES) analysis in combination with synchrotron radiation induced total reflection X-ray fluorescence (SR-TXRF) acquisition was used to determine the oxidation state of Fe in human cancer cells and simultaneously their elemental composition by applying a simple sample preparation procedure consisting of pipetting the cell suspension onto the quartz reflectors. XANES spectra of several inorganic and organic iron compounds were recorded and compared to that of different cell lines. The XANES spectra of cells, independently from the phase of cell growth and cell type were very similar to that of ferritin, the main Fe store within the cell. The spectra obtained after CoCl 2 or NiCl 2 treatment, which could mimic a hypoxic state of cells, did not differ noticeably from that of the ferritin standard. After 5-fluorouracil administration, which could also induce an oxidative-stress in cells, the absorption edge position was shifted toward higher energies representing a higher oxidation state of Fe. Intense treatment with antimycin A, which inhibits electron transfer in the respiratory chain, resulted in minor changes in the spectrum, resembling rather the N-donor Fe-α,α′-dipyridyl complex at the oxidation energy of Fe(III), than ferritin. The incorporation of Co and Ni in the cells was followed by SR-TXRF measurements.

Single-photon detection at 1550-nm using an InGaAs/lnP-avalanche photodiode operated with an 800MHz sinusoidal gating was reported. The quantum efficiency was 8.5% with the dark count probability of 9.2X10-6 and the overall afterpulsing probability of 6.0%. IntroductionA single-photon detector (SPD) at 1550-nm is an

The determination of light elements (Z<14) requires a set of precautions and experimental modifications in comparison to the analysis of higher Z elements. All measurements have to be performed in vacuum around 1mbar pressure as achieved from a membrane pump. A high resolution energy dispersive detector with ultra thin window and efficiency high enough from 200eV upward is required. The analysis is performed under x-ray total reflection conditions (TXRF) and mechanical components for translation and rotation have to be foreseen for the adjustment. The measurement set-up consisted of a modified vacuum chamber suitable to accommodate 6"- 8" wafers on a rotatable sample carrier and will be described. Droplets containing Mg and two types of elemental matrices consisting of a) medium Z elements (Ti-Zn) and b) light elements (Na, Mg, Al) were prepared on 6" Si wafers in the laboratory of Siltronic AG in Freiberg. For the low Z elements concentrations of 10ng, 100ng, and 1000ng were taken and for the medium Z elements a variable concentration range from 1ng to 100ng was chosen. It was assumed that the presence of medium Z elements causes a stronger absorption of the light elements' fluorescence, whereas light elements affect each other non-serious. The results with respect to the made assumptions and detection limits for the new set-up will be shown.

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