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Proton and ion beams are radiotherapy modalities of increasing importance and interest. Because of the different biological dose response of these radiations as compared with high-energy photon beams, the current approach of treatment prescription is based on the product of the absorbed dose to water and a biological weighting factor, but this is found to be insufficient for providing a generic method to quantify the biological outcome of radiation. It is therefore suggested to define new dosimetric quantities that allow a transparent separation of the physical processes from the biological ones. Given the complexity of the initiation and occurrence of biological processes on various time and length scales, and given that neither microdosimetry nor nanodosimetry on their own can fully describe the biological effects as a function of the distribution of energy deposition or ionization, a multiscale approach is needed to lay the foundation for the aforementioned new physical quantities relating track structure to relative biological effectiveness in proton and ion beam therapy. This article reviews the state-of-the-art microdosimetry, nanodosimetry, track structure simulations, quantification of reactive species, reference radiobiological data, cross-section data and multiscale models of biological response in the context of realizing the new quantities. It also introduces the European metrology project, Biologically Weighted Quantities in Radiotherapy, which aims to investigate the feasibility of establishing a multiscale model as the basis of the new quantities. A tentative generic expression of how the weighting of physical quantities at different length scales could be carried out is presented. [ABSTRACT FROM AUTHOR]

Background: Uncertainties in adopted models of particle + nucleus opücal-model potentials directly influence the accuracy in the theoretical predictions of reaction rates as they are needed for reaction-network calculations in, for instance, γ-process nucleosynthesis. The improvement of the α + nucleus optical-model potential is hampered by the lack of experimental data at astrophysically relevant energies especially for heavier nuclei. Purpose: Measuring the 187Re(α,n)190Ir reaction cross section at sub-Coulomb energies extends the scarce experimental data available in this mass region and helps understanding the energy dependence of the imaginary part of the α + nucleus optical-model potential at low energies. Method: Applying the activation method, after the irradiation of natural rhenium targets with α-particle energies of 12.4 to 14.1 MeV, the reaction yield and thus the reaction cross section were determined via γ-ray spectroscopy by using the Cologne Clover Counting Setup and the method of γ γ coincidences. Results: Cross-section values at five energies close to the astrophysically relevant energy region were measured. Statistical model calculations revealed discrepancies between the experimental values and predictions based on widely used α+nucleus optical-model potentials. However, an excellent reproduction of the measured crosssection values could be achieved from calculations based on the so-called Sauerwein-Rauscher α + nucleus optical-model potential. Conclusion: The results obtained indicate that the energy dependence of the imaginary part of the α + nucleus optical-model potential can be described by an exponential decrease. Successful reproductions of measured cross sections at low energies for a-induced reactions in the mass range 141 <= A <= 187 confirm the global character of the Sauerwein-Rauscher potential. [ABSTRACT FROM AUTHOR]

Abstract: Cross sections for the and 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 . 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 could be derived. [Copyright &y& Elsevier]

Abstract: A novel neutron spin-echo spectrometer with superconducting main coils enabling enclosure by a double walled -metal magnetic shielding chamber has been built and set into operation at the spallation neutron source in Oak Ridge. The layout of the spectrometer is described. Performance with emphasis on the superconducting main solenoids and the time-of-flight operation is described. Data on resolution, stability and first experiments are shown. [Copyright &y& Elsevier]

The quasistellar neutron spectrum for a thermal energy of kT = 25 keV that can be produced via the 7Li(p, n)7Be reaction at a proton energy of Ep = 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, γ) cross section of 197Au, where the averaged cross section for the spectrum defined in this work agrees perfectly with the result of a previous measurement. [ABSTRACT FROM AUTHOR]

The reaction 141Pr(α,n)144pm was investigated between Eα = 11 MeV and 15 MeV with the activation method using the γγ 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 γγ coincidence method is an excellent tool to investigate cross sections down to the microbam range. The (α,n) reaction at low energy is especially suited to test α + 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 (γ, α) rates for 145pm and 148Gd were explored. In summary, the data and further results underline the problems in global predictions of α + nucleus optical potentials at astrophysically relevant energies. [ABSTRACT FROM AUTHOR]

Abstract: Within the next decades, an increasing number of human beings will be brought into space to carry out technical and scientific tasks. There, they will be exposed simultaneously to combined stimuli, especially microgravity and radiation. In the endeavour to assess the risks for humans during long-duration space missions, it is necessary to understand already at the cellular level the complex interplay of these parameters. Cellular stress protection responses lead to an increased transcription of several genes via the modulation of transcription factors. The activation of the nuclear factor κB (NF-κB) pathway as a possible anti-apoptotic route represents such an important cellular stress response. It is hypothesized that the activation of NF-κB and the subsequent expression of NF-κB-dependent genes is involved in the cellular response to components of the cosmic radiation. Irradiation of human embryonic kidney cells (HEK/293) with α-particles (2.1MeV, LET ∼160keV/μm) was performed at the PTB, Braunschweig, Germany. Using the microbeam facility, cells were exposed to nuclear hits or, for the purpose of comparison, to a diffuse irradiation of the whole cell. After irradiation the following biological endpoints were determined: (i) cell survival (by means of the colony forming ability test), and (ii) quantitative RT-PCR analysis of selected NF-κB target genes (IκBα GADD45β, bcl-2, and bcl-XL). One nuclear α-particle traversal reduces the probability to survive to ∼75%. Exposure to two α-particles per nucleus resulted in an upregulation of the expression of the GADD45β gene. After exposure of HEK cells to five nuclear hits, about 43% of the irradiated cells survived, and the transcriptional response was not significant. Ten nuclear hits activated the IκBα expression, this increased IκBα production might be involved in the termination of the radiation-induced NF-κB activation. Diffuse irradiation increased the transcription of IκBα and GADD45β. Expression of the antiapoptotic genes bcl-2 and bcl-XL remained almost unchanged after α-particle irradiation. These findings suggest a role for GADD45β in the cellular radiation response to low fluences, while IκBα is enrolled at higher fluences. [Copyright &y& Elsevier]

Abstract: The release fraction of implanted 12keV K (=1.23s) ions from a variety of catcher foils was measured. The temperature dependence was measured for V, Fe, Ni, Y, Zr, Nb, Mo, Hf, Ta, W, Re, C, and Pt foils. The release fraction was found empirically to be a reasonably universal function of the ratio of temperature to catcher melting point. Limits on diffusion parameters (ignoring desorption) and on desorption (ignoring diffusion) were deduced. The results were used to find the optimal neutralizing catcher foil to load a neutral atom trap, and can be used to help choose ISOL target production materials. [Copyright &y& Elsevier]

The β-delayed particle decay of 17Ne has been studied via proton–γ coincidences, time-of-flight measurements and the “ratio-cut technique”, allowing cleanly-separated proton and α-particle spectra to be obtained. A complete set of proton and α branching ratios for the decay of 14 excited states in 17F to the ground and excited states of 16O and 13N has been determined and branching ratios for the β decay of 17Ne to these states have been deduced. From the branching ratios, fAt values and reduced Gamow–Teller matrix elements were calculated; no indication of isospin mixing in the isobaric analog state in 17F was observed. From the measurement of proton–γ angular correlations, combined with the selection rules for an allowed β decay, we obtain Jπ=12− for states at 8.436 and 9.450 MeV and 32− for the state at 10.030 MeV in 17F. Probabilities for the β-delayed pα decay to 12C through the tails of the subthreshold 7.117 and 6.917 MeV states in 16O have been calculated and the feasibility of using such decays to provide information about the rates for the E1 and E2 components of the 12C(α,γ)16O reaction is discussed. [Copyright &y& Elsevier]

The new DRAGON facility at TRIUMF is designed to measure alpha and proton capture reactions with radioactive ion beams in inverse kinematics. For nucleo-synthesis in astrophysical scenarios, the relevant energies lie in the 0.15–1 MeV/u range, where very low cross sections are expected. Therefore the separation of the recoil products from the beam particles will be a difficult task. This paper focuses on the end detectors, which will be used to distinguish recoils from beam particles at the end of the DRAGON separator. [Copyright &y& Elsevier]

The α-particle energy loss method (AEL) has been implemented in situ to monitor film thickness during growth by molecular beam epitaxy. For InP and GaAs substrates recoil implanted with α-particle emitters, we have been able to measure thickness and composition of deposited GaAs, AlGaAs and InGaAs in real time. The AEL method yields in situ real time results comparable in accuracy to those obtained by ex situ scanning electron microscope and high-resolution x-ray diffraction measurements. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]