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Neutrinos exist in one of three types or ‘flavours’—electron, muon and tau neutrinos—and oscillate from one flavour to another when propagating through space. This phenomena is one of the few that cannot be described using the standard model of particle physics (reviewed in ref. 1), and so its experimental study can provide new insight into the nature of our Universe (reviewed in ref. 2). Neutrinos oscillate as a function of their propagation distance (L) divided by their energy (E). Therefore, experiments extract oscillation parameters by measuring their energy distribution at different locations. As accelerator-based oscillation experiments cannot directly measure E, the interpretation of these experiments relies heavily on phenomenological models of neutrino–nucleus interactions to infer E. Here we exploit the similarity of electron–nucleus and neutrino–nucleus interactions, and use electron scattering data with known beam energies to test energy reconstruction methods and interaction models. We find that even in simple interactions where no pions are detected, only a small fraction of events reconstruct to the correct incident energy. More importantly, widely used interaction models reproduce the reconstructed energy distribution only qualitatively and the quality of the reproduction varies strongly with beam energy. This shows both the need and the pathway to improve current models to meet the requirements of next-generation, high-precision experiments such as Hyper-Kamiokande (Japan)3 and DUNE (USA)4. Electron scattering measurements are shown to reproduce only qualitatively state-of-the-art lepton–nucleus energy reconstruction models, indicating that improvements to these particle-interaction models are required to ensure the accuracy of future high-precision neutrino oscillation experiments.

Measurements of elastic electron scattering data within the past decade have highlighted two-photon exchange contributions as a necessary ingredient in theoretical calculations to precisely evaluate hydrogen elastic scattering cross sections. This correction can modify the cross section at the few percent level. In contrast, dispersive effects can cause significantly larger changes from the Born approximation. The purpose of this experiment is to extract the carbon-12 elastic cross section around the first diffraction minimum, where the Born term contributions to the cross section are small to maximize the sensitivity to dispersive effects. The analysis uses the LEDEX data from the high resolution Jefferson Lab Hall A spectrometers to extract the cross sections near the first diffraction minimum of 12C at beam energies of 362 MeV and 685 MeV. The results are in very good agreement with previous world data, although with less precision. The average deviation from a static nuclear charge distribution expected from linear and quadratic fits indicate a 30.6% contribution of dispersive effects to the cross section at 1 GeV. The magnitude of the dispersive effects near the first diffraction minimum of 12C has been confirmed to be large with a strong energy dependence and could account for a large fraction of the magnitude for the observed quenching of the longitudinal nuclear response. These effects could also be important for nuclei radii extracted from parity-violating asymmetries measured near a diffraction minimum., Comment: 14 pages, 10 figures

The atomic nucleus is composed of two different kinds of fermions: protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority of fermions (usually neutrons) to have a higher average momentum. Our high-energy electron-scattering measurements using (12)C, (27)Al, (56)Fe, and (208)Pb targets show that even in heavy, neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few-body systems to neutron stars and may also be observable experimentally in two-spin-state, ultracold atomic gas systems.

There has been an increased interest in defects within structural materials motivated by future fission and fusion reactor needs. While reactor steels are extensively studied, much more research effort is needed in order to understand radiation damage in ceramic materials and its effect on their macroscopic characteristics (1). Sapphire – the single crystal of Al2O3, is a candidate material to serve in diagnostic systems for burning plasma experiments (2), due to its transparency to a wide range of wavelengths (200-5000 nm), high melting temperature (~2300K) and hardness close to that of a diamond. Its optical and electronic properties are expected to be affected by the harsh radiation environment. The family of ceramics that contains Boron is another interesting group of materials for the nuclear industry, mainly due to high cross sections for thermal neutron capture in Boron, which produce helium inside the material. The much higher neutron flux expected in future reactors can cause swelling of materials and macroscopic cracks formation. Helium is also considered to be one of the most interesting challenges for fusion reactors, due to alpha particles production in the D-T reaction. Materials that will be used as first wall, matrices for Li, or coating materials, will suffer from high radiation damage. The sensitivity of Positron Annihilation Spectroscopy (PAS) methods to point defects makes them perfect tools to study radiation damage in its first stages of creation. Especially, Positron Annihilation Lifetime Spectroscopy (PALS) is sensitive to size and concentration of the point defects and Coincidence Doppler Broadening (CDB) can probe changes in defect characteristics as well as in electron momenta in the lattice We present first results of Sapphire and Boron Carbide (B4C) samples investigated at the Gamma Induced Positron Spectroscopy (GiPS) facility at the HZDR (3). Unirradiated Sapphire and B4C samples were measured, as well as neutron irradiated samples, to a fluence of 6x10E18 n/cm2 and ~10E15 n/cm2 for the Sapphire and B4C samples, respectively. In the GiPS facility, four pairs of detectors, each consisting of BaF2 and HPGe detectors, allow to measure PALS, DB and to use the correlated information to measure also CDB and Age-Momentum Correlation (AMOC). Results from these measurements will be discussed. References [1] Workshop on Advanced Computational Materials Science: Application to Fusion and Generation IV Fission Reactors, Washington, D.C. 31 March – 2 April 2004. [2] D.M. Duffy, Phil. Trans. R. Soc. A 368 (2010) 3315-3328. [3] M. Butterling et al., Phys. Status Solidi A 207 (2010) 334-337.

A study of irradiation-induced damage in HAVAR® foils was initiated in order to extract the highest proton dose the foils can sustain. The lattice structure of HAVAR® foils in different metallurgic conditions is presented, as well as visible internal structure, measured by Transmission Electron Microscopy (TEM). Positron Annihilation Spectroscopy (PAS) techniques were used to investigate these foils, and another foil that had been irradiated to the maximal proton dose limit, set by the manufacturer, of 1 mAh. PAS techniques included Doppler Broadening (DB) measurement in the SPONSOR beam and Lifetime (LT) measurements, both carried at Helmholtz Zentrum Dresden-Rossendorf (HZDR). Both positron spectroscopy methods show clear differences between the investigated foils, with distinguished characteristics for annealed, cold-rolled and irradiated foils. The advantages of using a slow positron beam to study thin foils and defect profiles, over a table-top LT spectrometer, are discussed and demonstrated by the HAVAR® measurements.

HAVAR ist ein sehr festes, nicht magnetisches und korrosionsbeständiges Material. In der Medizintechnik wird es als Fenster für Targetkammern zur Produktion von Fluordesoxyglucose (FDG) benutzt. Das in der FDG enthaltene 18F findet Verwendung in der Positronen-Emissions-Tomographie als beta+-Strahler. Die Herstellung des 18F erfolgt dabei durch Protonenbestrahlung von 18O angereicherten Wassertargets entsprechend der Reaktion 18O(p,n)18F. Der wachsende Bedarf an 18FDG erfordert eine intensivere Protonenbestrahlung und damit eine höhere Beanspruchung der HAVAR-Folie als Targetfenster. Für eine Prognose der Beständigkeit der HAVAR-Folien gegenüber Protonenbestrahlung sind Informationen über die Defektstruktur innerhalb der Folien und deren strahlungsinduzierte Veränderungen erforderlich. Deshalb wurden 25 µm dicke HAVAR-Folien sowohl im Ausgangszustand, nach Wärmebehandlung und nach Protonenbestrahlung hinsichtlich der Ausbildung von leerstellenartigen Defekten mittels konventioneller Positronen-Lebensdauermessungen untersucht. Oberflächennahe Untersuchungen bis in Tiefen von ca. 3 µm erfolgten mit einer mono-energetischen Positronenstrahlapparatur durch Messung der Doppler-Verbreiterung der Annihilationslinie. Unterschiede in der Ausbildung der Defekte in Abhängigkeit von der Probenpräparation und –beanspruchung werden dargestellt und mit Ergebnissen, erhalten aus der Transmissions-Elektronenmikroskopie, verglichen.

The HAVAR alloy was originally developed in the late 1940. It is a high strength, nonmagnetic and corrosion resistant material. One of its applications is in the medical industry, in the process of fluorodeoxyglucose (FDG) production for Positron Emission Tomography (PET). The 18F positron emitting isotope is produced by the reaction 18O(p,n)18F in proton cyclotrons. In Soreq NRC, 25 µm foils of HAVAR are used as a window material for the 18O enriched water targets, contained in Al vessels. With the increasing demand for 18F-FDG, an accelerated production rate is planned, with much higher intense proton beam from the new SARAF accelerator at Soreq NRC [1]. This initiated a research effort to study radiation damage in HAVAR that can predict its radiation hardness in the ~2-4 mA SARAF proton beam. We measured four 25 µm thick HAVAR samples: cold rolled (CR), cold rolled and heat treated (HT), annealed (AN) and CR irradiated (IR). The latter was a window taken apart from the target 7 years ago after irradiation in the cyclotron to 10MeV protons of total charge 1mA-h. The first three samples were metallurgically characterized by means of Transmission Electron Microscope (TEM). Positron Annihilation Spectroscopy (PAS) measurements were preformed on all four samples. These included Doppler Broadening (DB) and Positron Annihilation Lifetime ( PAL) measurements in the slow positron beam and in the table top lifetime spectrometer at HZDR [2]. We present preliminary results from these PAS measurements, that show clear differences between the four samples. Positron lifetimes of the HAVAR types change between ~80ps for the annealed sample to ~175ps for the irradiated sample. The positron diffusion length changes from (8 ± 1) nm (CR) to (66 ± 1) nm (AN) in these samples. We also compare between the metallurgical characteristics of the different types of HAVAR measured with TEM to PAS results. The PAS measurements show a clear increase of the mean lifetime with the increase of the density of dislocations in the CR sample compared to that of AN HAVAR foils. [1] L. Weissman et al., "The Status of the SARAF Linac Project", WE102 in Proceedings of Linac 2010, Tsukuba, September 12-17, 2010 [2] W. Anwand, H. - R. Kissener, and G. Brauer, Acta Phys. Pol. A 88, 7 (1995).

A positron lifetime spectrometer for defect studies in bulk, with time resolution of 185 +-7 ps, is described. Its reliability, tested on 4N Fe samples in various states, is demonstrated. For comparison, the same samples are studied also by Slow Positron Implantation Spectroscopy.

We report a new, high-precision measurement of the proton elastic form factor ratio μpGE/GM for the four-momentum transfer squared Q2=0.3–0.7(GeV/c)2. The measurement was performed at Jefferson Lab (JLab) in Hall A using recoil polarimetry. With a total uncertainty of approximately 1%, the new data clearly show that the deviation of the ratio μpGE/GM from unity observed in previous polarization measurements at high Q2 continues down to the lowest Q2 value of this measurement. The updated global fit that includes the new results yields an electric (magnetic) form factor roughly 2% smaller (1% larger) than the previous global fit in this Q2 range. We obtain new extractions of the proton electric and magnetic radii, which are 〈rE2〉1/2=0.875±0.010 fm and 〈rM2〉1/2=0.867±0.020 fm. The charge radius is consistent with other recent extractions based on the electron–proton interaction, including the atomic hydrogen Lamb shift measurements, which suggests a missing correction in the comparison of measurements of the proton charge radius using electron probes and the recent extraction from the muonic hydrogen Lamb shift.