Since p isotopes cannot be produced in neutron-capture reaction networks, a production mechanism via photodisintegration reactions was proposed - the gamma process. The specific path of this reaction network, however, depends strongly on the statistically averaged ratios for proton-, neutron-, and alpha-decay widths. It was shown in the past, that the uncertainties in the cr-decay widths have an impact on the isotopic abundance of the gamma-process ashes. Besides systematic studies of the alpha+nucleus optical-model potential, direct measurements of (alpha,gamma) reaction are needed to reduce the unpredictability of (gamma, alpha) reaction rates. We present preliminary results from direct measurements of the Ru-98(alpha,gamma) and Sm-144(alpha,gamma) cross sections via in-beam measurements at the University of Cologne and the Ruhr-Universitat Bochum and activation experiments at the Physikalisch-Technische Bundesanstalt in Braunschweig and the Technische Universitat Dresden. The in-beam experiment might help to improve our understanding of the gamma-process contribution to the p nuclei in the A similar to 100 mass region, while the activation experiment is important for the determination of the initial isotopic abundance ratio of the Sm-146/Sm-144 chronometer.

The track structure of ionizing radiation predominantly determines the biological effects after irradiation. A new detector to register 3D track structure segments in low pressure gas was proposed in a previous work. The device combines the operational principle of thick gas electron multipliers (THGEM), working in reverse polarity, and resistive plate chambers.In this work, the detector was further developed. Optimization of THGEM thickness, hole pitch and cathode resistivity were studied. A new detector prototype was built and tested with a microbeam providing different radiation qualities. The detector rate capability and ion collection efficiency were also investigated.Results show that the detector efficiency increases with increasing THGEM thickness and decreasing cathode resistivity. Preliminary results show that the ion collection efficiency is low and that the detector performance is limited by a long dead time.The detector is able to register single ions with a low dark rate. However, further development is needed in order to obtain the efficiency necessary to reconstruct 3D track structure.

The aim of the 'BioQuaRT' (Biologically weighted Quantities in RadioTherapy) project is to develop measurement techniques for characterising charged particle track structure on different length scales, and to correlate at the cellular level the track structure properties with the biological effects of radiation. This multi-scale approach will allow characterisation of the radiation qualities used in radiotherapy and the related biological effects. Charged-particle microbeam facilities were chosen as the platforms for all radiobiology experiments in the 'BioQuaRT' project, because they allow targeting single cells (or compartments of a cell) with a predefined number of ionising particles and correlating the cell-by-cell induced damage with type and energy of the radiation and with the number of ions per cell. Within this project, a novel in situ protocol was developed for the analysis of the misrepaired and/or unrepaired chromosome damage induced by charged-particle irradiations at the Physikalisch-Technische Bundesanstalt (PTB) ion microbeam facility. Among the cytogenetic biomarkers to detect and estimate radiation-induced DNA damage in radiobiology, chromosomal aberrations and micronuclei were chosen. The characteristics of the PTB irradiation system required the design of a special in situ assay: specific irradiation dishes with a base made from a biofoil 25-µm thick and only 3000-4000 cells seeded and irradiated per dish. This method was developed on Chinese hamster ovary (CHO) cells, one of the most commonly used cell lines in radiobiology in vitro experiments. The present protocol allows the simultaneous scoring of chromosome aberrations and micronuclei on the same irradiated dish. Thanks to its versatility, this method could also be extended to other radiobiological applications besides the single-ion microbeam irradiations.

The gamma gamma coincidence method with a clover-type HPGe detector is used to investigate the reaction Pr-141(alpha,n)Pm-144 between E-alpha = 11 MeV and 15 MeV in an activation experiment. The experimentally determined cross sections were compared to Hauser-Feshbach statistical model calculations using different optical potentials. None of these optical-model potentials reproduces the data. Therefore, a local potential was constructed to improve the agreement with the data. The consequences of applying the same potential to calculations of the astrophysical (gamma,alpha) rates of Pm-145 and Gd-148 were explored.

The increasing importance of ion beams in cancer therapy and the lack of experimental data for W-values for protons and heavy ions in air require new measurements. A new experimental set-up was developed at PTB and consistent measurements of W-values in argon, nitrogen and air for protons and alpha particles with energies from 0.7 to 3.5 MeV u(-1) at PTB, and for carbon ions between 3.6 and 7.0 MeV u(-1) at GSI were carried out. This publication concentrates on the measurements with protons and alpha particles at PTB. The experimental methods and the determination of corrections for recombination effects, beam-induced background radiation and additional effects are presented.

Cross sections for the Yb168(α,γ)Hf172 and Yb168(α,n)Hf171 reactions were measured by means of the activation method using α particles with energies between 12.9 MeV and 15.1 MeV. The spectroscopy of the γ rays emitted by the reaction products was performed using three different HPGe detector types, namely clover-type high-purity germanium detectors, a low-energy photon spectrometer detector, and a coaxial high-purity germanium detector. The results were compared to Hauser–Feshbach statistical model calculations. Within certain assumptions, astrophysical conclusions could be drawn concerning the production of the p nucleus Yb168. The data in this work can serve as a contribution to the current very fragmentary experimental data base for charged-particle induced reactions. In addition, the absolute intensity for nine γ-ray transitions following the electron capture decay of Hf171 could be derived.

Two experiments were performed to resolve a discrepancy of the 197Au(n, γ) cross section between the IAEA standard evaluation and the reference cross section for astrophysical experiments in the lower keV energy region. We measured the 197Au(n, γ) reaction by means of the time-of-flight technique with n_TOF at CERN and extracted the cross section in the unresolved resonance region between 5-400 keV with an overall uncertainty from 3.9-6.7% for a resolution of 20 bins per energy decade. Additionally, we remeasured the neutron spectrum of the 7Li(p, n)7Be reaction with Ep = 1912 keV, which was used as a neutron source for determining the astrophysical reference cross section. The n_TOF data are already fully analyzed and published. The results are in good agreement with the ENDF standard evaluation, but uncertainties don't allow to draw definite conclusions. The analysis of the neutron spectrum of 7Li(p, n)7Be is underway, preliminary results will be reported here.

The quasistellar neutron spectrum for a thermal energy of kT = 25 keV that can be produced via the Li-7(p, n)Be-7 reaction at a proton energy of E-p = 1912 keV has been measured using the dedicated setup for the definition of neutron fields at Physikalisch-Technische Bundesanstalt Braunschweig. The results confirm previous work with improved accuracy and resolution. Small variations in proton energy leave the spectrum essentially unchanged. This is illustrated by the example of the (n, gamma) cross section of Au-197, where the averaged cross section for the spectrum defined in this work agrees perfectly with the result of a previous measurement.

Proton-activation reactions on natural and enriched palladium samples were investigated via the activation technique in the energy range of E-p = 2.75-9 MeV, close to the upper end of the respective Gamow window of the. process. We have determined cross sections for Pd-102(p,gamma)Ag-103, Pd-104(p,gamma)Ag-105, and Pd-105(p,n)Ag-105, as well as partial cross sections of Pd-104(p,n)Ag-104(g), Pd-105(p,gamma)Ag-106(m), Pd-106(p,n)Ag-106(m), and Pd-110(p,n)Ag-110(m) with uncertainties between 3% and 15% for constraining theoretical Hauser-Feshbach rates and for direct use in gamma-process calculations.

The reaction Pr-141(alpha, n)Pm-144 was investigated between E-alpha = 11 MeV and 15 MeV with the activation method using the gamma gamma coincidence method with a segmented clover-type high-purity Germanium (HPGe) detector. Measurements with four other HPGe detectors were additionally made. The comparison proves that the gamma gamma coincidence method is an excellent tool to investigate cross sections down to the microbarn range. The (alpha, n) reaction at low energy is especially suited to test alpha + nucleus optical-model potentials for application in the astrophysical p process. The experimentally determined cross sections were compared to Hauser-Feshbach statistical model calculations using different optical potentials and generally an unsatisfactory reproduction of the data was found. A local potential was constructed to improve the description of the data. The consequences of applying the same potential to calculate astrophysical (gamma, alpha) rates for Pm-145 and Gd-148 were explored. In summary, the data and further results underline the problems in global predictions of alpha + nucleus optical potentials at astrophysically relevant energies.

In an inter-disciplinary collaboration of Physikalisch-Technische Bundesanstalt (PTB), German Collection of Microorganisms and Cell Cultures (DSMZ) and Heinrich-Heine University, live-cell imaging has been established at the charged-particle microbeam facility of PTB. Candidate genes participating in DNA strand-break repair pathways such as PARP-1, MRE11, MSH2, MDC1 and p53BP1 have been modified to generate fluorescent fusion proteins. Using multi-cistronic expression vectors, stable genomic integration was achieved in HT-1080 fibroblasts. The aim of this study is to characterise and use these highly reliable cell lines for studying initial steps of DNA damage responses and kinetics of repair after microbeam irradiation with high- and low-linear energy transfer (LET) particles in living cells at physiological conditions.

The reaction 141Pr(alpha,n)144Pm was investigated between E_alpha=11 MeV and 15 MeV with the activation method using the gamma-gamma coincidence method with a segmented clover-type high-purity Germanium (HPGe) detector. Measurements with four other HPGe detectors were additionally made. The comparison proves that the gamma-gamma coincidence method is an excellent tool to investigate cross sections down to the microbarn range. The (alpha,n) reaction at low energy is especially suited to test alpha+nucleus optical-model potentials for application in the astrophysical p-process. The experimentally determined cross sections were compared to Hauser-Feshbach statistical model calculations using different optical potentials and generally an unsatisfactory reproduction of the data was found. A local potential was constructed to improve the description of the data. The consequences of applying the same potential to calculate astrophysical (gamma,alpha) rates for 145Pm and 148Gd were explored. In summary, the data and further results underline the problems in global predictions of alpha+nucleus optical potentials at astrophysically relevant energies.

The ambient dose equivalent from the secondary radiation produced during irradiation of a cylindrical water phantom with 200 MeV/u (12)C-ions was investigated at the biophysics cave at GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Pencil-like ion beams were delivered by the heavy-ion synchrotron SIS18 using the slow extraction mode. Since the secondary radiation field outside the phantom is complex in its particle composition and particle energy distribution, microdosimetric methods developed for the dosimetry of the cosmic radiation field at flight altitudes, which is similar in terms of complexity, were applied. Lineal energy distributions and the ambient dose equivalent were measured with a tissue-equivalent proportional counter at different particle emission angles. An additional veto counter allowed the identification of the different contributions of charged and neutral particles. A significant increase in the mean quality factor was observed at large emission angles which could be attributed to the decreasing contributions of charged particles compared to the (relative) contributions from neutrons.

The neoplastic transformation of human hybrid CGL1 cells is affected by perturbations from external influences such as serum batch and concentration, the number of medium changes during the 21-day expression period and cell seeding density. Nevertheless, for doses up to 1.5 Gy, published transformation frequencies for low linear energy transfer (LET) radiations (gamma-rays, MeV electrons or photons) are in good agreement, whereas for higher doses larger variations are reported. The (60)Co gamma-ray data here for doses up to 1.5 Gy, using a low-yield serum batch and only one medium change, are in agreement with published frequencies of neoplastic transformation of human hybrid cells. For 3.4 MeV alpha-particles (LET = 124 keV/mum) and 0.565 MeV monoenergetic neutrons relative to low doses of (60)Co gamma-rays, a maximum relative biological effectiveness (RBE(M)) of 2.8 +/- 0.2 and 1.5 +/- 0.2, respectively, was calculated. Surprisingly, at higher doses of (60)Co gamma-rays lower frequencies of neoplastic transformation were observed. This non-monotonic dose relationship for neoplastic transformation by (60)Co gamma-rays is likely due to the lack of a G2/M arrest observed at low doses resulting in higher transformation frequencies per dose, whereas the lower frequencies per dose observed for higher doses are likely related to the induction of a G2/M arrest.

The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n, gamma) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on Fe-60, Ni-62 and Ni-64 are reported. Fe-60 is mostly produced during the short convective C shell burning phase, where peak densities of similar to 10(11) cm(-3) are reached, prior to the SN explosion. The stellar (n, gamma) cross section of Fe-60 could be measured with a 1 mu g sample obtained at PSI (Switzerland), which was sufficient for an activation measurement using the intense, quasi-stellar neutron field for a thermal energy of 25 keV at the Karlsruhe Van de Graaff accelerator. The FZK accelerator was also used for an activation of Ni-62, whereas in this case, the number of Ni-63 nuclei produced were determined via accelerator mass spectroscopy at the Maier-Leibnitz-Laboratorium in Garching/Munich. The (n, gamma) cross section of Ni-64 at a stellar temperature equivalent to 50 keV has been measured in a collaboration between FZK Karlsruhe and PTB Braunschweig. Finally, complementary time of flight measurements on the Fe and Ni isotopes over a broad energy range are planned at the white neutron source n_TOF of CERN for the future campaign in 2009.

The s process synthesizes the elements between Fe and Sr in massive stars during two major evolutionary stages, convective core He burning and C shell burning. This scenario implies fascinating consequences for the chemical evolution of the star. For instance, the neutron capture rate at each isotope can have a big influence on the production of many of the subsequent higher mass isotopes. Correspondingly, one needs to know the (n,γ) cross sections of the involved isotopes with high accuracy in order to determine the abundance pattern reliably and to obtain a consistent picture of this stage. This contribution gives an overview on recent and future experiments for the Fe/Ni nucleosynthesis in massive stars. New results on 60Fe, 62Ni and 64Ni are reported. 60Fe is mostly produced during the short convective C shell burning phase, where peak densities of ∼1011 cm−3 are reached, prior to the SN explosion. The stellar (n,γ) cross section of 60Fe could be measured with a 1 μg sample obtained at PSI (Switzerland), which was sufficient for an activation measurement using the intense, quasi‐stellar neutron field for a thermal energy of 25 keV at the Karlsruhe Van de Graaff accelerator. The FZK accelerator was also used for an activation of 62Ni, whereas in this case, the number of 63Ni nuclei produced were determined via accelerator mass spectroscopy at the Maier‐Leibnitz‐Laboratorium in Garching/Munich. The (n,γ) cross section of 64Ni at a stellar temperature equivalent to 50 keV has been measured in a collaboration between FZK Karlsruhe and PTB Braunschweig. Finally, complementary time of flight measurements on the Fe and Ni isotopes over a broad energy range are planned at the white neutron source n_TOF of CERN for the future campaign in 2009.

The $^{92}\mathrm{Mo}$($\ensuremath{\alpha},n$)$^{95}\mathrm{Ru}$, $^{94}\mathrm{Mo}$($\ensuremath{\alpha},n$)$^{97}\mathrm{Ru}$, and $^{112}\mathrm{Sn}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{116}\mathrm{Te}$ cross sections were measured at the upper end of the $p$-process Gamow window between 8.2 and 11.1 MeV. Our results are slightly lower than global Hauser-Feshbach calculations from the code NON-SMOKER, but still within the uncertainty of the prediction. The $^{112}\mathrm{Sn}$($\ensuremath{\alpha},\ensuremath{\gamma}$)$^{116}\mathrm{Te}$ cross section agrees well with a recently measured thick-target cross section in the same energy range. For the $^{92,94}\mathrm{Mo}$($\ensuremath{\alpha},n$) reactions the present data close to the reaction thresholds could eliminate previous uncertainties within a factor of 20, and we can present now useful comparisons to statistical model calculations with different optical potentials.