Radiation damage of self-assembled monolayers, which are prototypes of thin organic layers and highly organized biological systems, shows a strong dependence on temperature. Two limiting cases could be identified. Reactions involving transport of single atoms and small fragments proceed nearly independent of temperature. Reactions requiring transport of heavy fragments are, however, efficiently quenched by cooling. We foresee the combined use of temperature and irradiation by electrons or photons for advanced tailoring of self-assembled monolayers on surfaces. In addition, our results have direct implications for cryogenic approaches in advanced electron and x-ray microscopy and spectroscopy of biological macromolecules and cells.

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First measurements with a prototype ionization chamber are described to be applied in online monitoring of modulated fields in radiation therapy. The liquids isooctane, isononane (TMP) and tetramethylsilane (TMS) are used in a high purity grade in order to realize high current signals for electronic read-out in parallel at frequencies exceeding 10 Hz. Signals of more than a factor 4 with respect to isooctane, analysis grade, are obtained. With an electrode structure of 400 pads, a uniformity in efficiency within 1.2% has been measured. The penumbra of a multileaf collimator could be resolved. Theoretical examination verifies that the free electrons in the liquids cause higher signals when the measured currents are compared with expectation for ion transport only.

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