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The development of a few-cycle optical probe-pulse for the investigation of laser-plasma interactions driven by a Ti:sapphire, 30 Terawatt (TW) laser system is described. The probe is seeded by a fraction of the driving laser's energy and is spectrally broadened via self-phase modulation in a hollow core fiber filled with a rare gas, then temporally compressed to a few optical cycles via chirped mirrors. Shadowgrams of the laser-driven plasma wave created in relativistic electron acceleration experiments are presented with few-fs temporal resolution, which is shown to be independent of post-interaction spectral filtering of the probe-beam.

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Contains fulltext : 111457.pdf (publisher's version ) (Open Access)

Contains fulltext : 111435.pdf (publisher's version ) (Closed access)

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Contains fulltext : 99023.pdf (preprint version ) (Open Access)

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In recent years, the new technology of laser based particle acceleration was developed at such a rate that medical application for cancer therapy could become feasible. Promising more compact and economic proton and ion accelerators the laser technology however results in specific properties, like ultra-short (~ps) and ultra-intensive particle beam pulses. The clinical applicability of such new beam qualities requires comprehensive translational research from basic investigations to cell and animal experiments, finally followed by clinical trials. For the first time, the new laser based irradiation technology was established for animal experiments by the German joint research project “onCOOPtics”. A complete irradiation facility for laser accelerated electrons was developed, set up, commissioned, tested and applied for radiobiological tumour irradiation experiments under usage of a mouse model at the high intensity laser system JETI. The integration of a magnet and a collimator system resulted in an optimized beam transport and efficient electron energy filtration. Moreover, a specific irradiation and dosimetry setup was integrated allowing for the formation of irradiation fields, the real-time control of beam parameters and dose delivery to the tumour. For an accurate and reproducible positioning of the tumour in the irradiation field the mice were fixed in a movable box and the tumour position was online verified by means of a CCD camera system. The combination of both, the advanced laser accelerator system and the newly implemented irradiation and dosimetry setup allowed the successful performance of systematic radiobiological studies over months. Moreover, the practicability and easy handling of the system results in a reasonable duration of about 15 min for the whole procedure of mouse preparation, positioning and irradiation. In conclusion, the successful establishment of all technical requirements for and the performance of systematic animal studies with lase

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We have developed a novel laboratory instrument for studying gas phase, anion-neutral chemistry. To the best of our knowledge, this is the first such apparatus which uses fast merged beams to investigate anion-neutral chemical reactions. As proof-of-principle we have detected the associative detachment reaction H-+H -> H-2+e(-). Here we describe the apparatus in detail and discuss related technical and experimental issues.

Contains fulltext : 99094.pdf (preprint version ) (Open Access)

We have measured electron-ion recombination for Fe$^{9+}$ forming Fe$^{8+}$ and for Fe$^{10+}$ forming Fe$^{9+}$ using merged beams at the TSR heavy-ion storage-ring in Heidelberg. The measured merged beams recombination rate coefficients (MBRRC) for relative energies from 0 to 75 eV are presented, covering all dielectronic recombination (DR) resonances associated with 3s->3p and 3p->3d core transitions in the spectroscopic species Fe X and Fe XI, respectively. We compare our experimental results to multi-configuration Breit-Pauli (MCBP) calculations and find significant differences. From the measured MBRRC we have extracted the DR contributions and transform them into plasma recombination rate coefficients (PRRC) for astrophysical plasmas with temperatures from 10^2 to 10^7 K. This spans across the regimes where each ion forms in photoionized or in collisionally ionized plasmas. For both temperature regimes the experimental uncertainties are 25% at a 90% confidence level. The formerly recommended DR data severely underestimated the rate coefficient at temperatures relevant for photoionized gas. At the temperatures relevant for photoionized gas, we find agreement between our experimental results and MCBP theory. At the higher temperatures relevant for collisionally ionized gas, the MCBP calculations yield a Fe XI DR rate coefficent which is significantly larger than the experimentally derived one. We present parameterized fits to our experimentally derived DR PRRC., Comment: 44 Pages, 5 Figures. Accepted for publication in Astrophys. J

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Contains fulltext : 99118_pub.pdf (publisher's version ) (Open Access) Contains fulltext : 99118_pre.pdf (preprint version ) (Open Access)