Metal-dielectric structures for high charge state ion production in ECR plasma

Metal-dielectric (MD) structures of pure (99.999%) aluminum foils were previously studied [1, 2] in the National Institute for Physics and Nuclear Engineering (NIPNE), Bucharest, Romania showing high secondary electron emission properties. Consequently, 26 mm diameter disks of such structures (Al-Al2O3) were tested in the ECR ion source of the Institut fuer Kernphysik (IKF) der J. W. Goethe Universitat, Frankfurt/Main, Germany, allowing to demonstrate their ability to significantly increase the ECRIS performances in what concerns the production of high charge state ions [3]. New experiments carried on in Bucharest on a special facility [2] stressed out the possibility to develop high emissive MD structures starting from lower purity (99%) aluminum foils. This result allowed us to make a special cylinder of 1 mm wall thickness electrolytically treated so that only the inner face had a MD structure layer while the external surface remained metallic. Such a cylinder introduced in the plasma chamber of an ECR ion source provides a high rate of secondary electrons that enhance the ECR plasma electron density while its metallic external surface provides a good electric and thermal contact with the plasma chamber. The tests performed with such a MD aluminum cylinder in the IKF 14 GHz ECR ion source, successfully demonstrated the possibility to shift the ECRIS output toward very high charge states (Ar16+) due to the strong secondary electron emission of the MD inner surface of the cylinder

A multi-detector array for high energy nuclear e+e- pair spectrosocopy

A multi-detector array has been constructed for the simultaneous measurement of energy- and angular correlation of electron-positron pairs produced in internal pair conversion (IPC) of nuclear transitions up to 18 MeV. The response functions of the individual detectors have been measured with mono-energetic beams of electrons. Experimental results obtained with 1.6 MeV protons on targets containing $^{11}$B and $^{19}$F show clear IPC over a wide angular range. A comparison with GEANT simulations demonstrates that angular correlations of $e^+e^-$ pairs of transitions in the energy range between 6 and 18 MeV can be determined with sufficient resolution and efficiency to search for deviations from IPC due to the creation and subsequent decay into $e^+e^-$ of a hypothetical short-lived neutral boson.Comment: 20 pages, 8 figure

Time Resolved Experiments at the Frankfurt 14 GHz ECR Ion Source

To investigate the basic production processes of highly charged ions and combined phenomena of an ECRIS plasma (e. g. influence of secondary electrons and plasma instabilities) time resolved experiments have been carried out at the Frankfurt 14 GHz ECRIS [1] (see also the contributions to this workshop by O. Hohn et al. and V. Mironov et al.). We report time resolved measurements of the extracted ion currents by pulsing the biased disk voltage [2]. The measurements have shown that the extracted ion currents respond too fast to explain the "biased disk effect" (i. e. the intensity increase of highly charged ions) by enhanced ion breeding. Furthermore the influence of the pulsed biased disk on plasma instabilities has been investigated. It has also been shown that this method can be used to extract pulsed ion beams from an ECRIS

Further search for a neutral boson with a mass around 9 MeV/c2

Two dedicated experiments on internal pair conversion (IPC) of isoscalar M1 transitions were carried out in order to test a 9 MeV/c2 X-boson scenario. In the 7Li(p,e+e-)8Be reaction at 1.1 MeV proton energy to the predominantly T=0 level at 18.15 MeV, a significant deviation from IPC was observed at large pair correlation angles. In the 11B(d,n e+e-)12C reaction at 1.6 MeV, leading to the 12.71 MeV 1+ level with pure T=0 character, an anomaly was observed at 9 MeV/c2. The compatibility of the results with the scenario is discussed.Comment: 12 pages, 5 figures, 2 table

Status of the Frankfurt 14 GHz-ECRIS-(ve)RFQ Facility

The accelerator facility installed at the Institut fuer Kernphysik (IKF) combines a 14 GHz electron cyclotron resonance ion source (ECRIS) and a variable energy radio frequency quadrupole accelerator (ve-RFQ)[1,2]. The provided highly charged ions have an energy range between a few keV - using the beam delivered from the source - up to 200 keV/u by using the post acceleration of the ve-RFQ. The setup is designed to deliver a wide spectrum of ions in sufficiently high charged states for atomic physics and materials research. Besides this the ion source is used for studies of the production of highly charged ions with the intention to improve quality and intensity of ion beams. In addition to these activities there are some special topics which deal with the investigation of phenomena on the ECRIS plasma and the production of metal ions by laser ablation technique (see also contributions to this workshop S. Runkel et al. And V. Mironov et. al). The present status and further activities of the facility and a view of the different projects will be reported

An introductory view on archaeoastronomy

Archaeoastronomy is still a marginalised topic in academia and is described by the Sophia Centre, the only UK institution offering a broader MA containing this field, as ‘the study of the incorporation of celestial orientation, alignments or symbolism in human monuments and architecture’. By many it is associated with investigating prehistoric monuments such as Stonehenge and combining astronomy and archaeology. The following will show that archaeoastronomy is far more than just an interdisciplinary field linking archaeology and astronomy. It merges aspects of anthropology, ethno-astronomy and even educational research, and is possibly better described as cultural astronomy. In the past decades it has stepped away from its quite speculative beginnings that have led to its complete rejection by the archaeology community. Overcoming these challenges it embraced full heartedly solid scientific and statistical methodology and achieved more credibility. However, in recent times the humanistic influences of a cultural context motivate a new generation of archaeoastronomers that are modernising this subject; and humanists might find it better described as post-modern archaeoastronomy embracing the pluralism of today’s academic approach to landscape and ancient people

Nothing Lasts Forever: Environmental Discourses on the Collapse of Past Societies

The study of the collapse of past societies raises many questions for the theory and practice of archaeology. Interest in collapse extends as well into the natural sciences and environmental and sustainability policy. Despite a range of approaches to collapse, the predominant paradigm is environmental collapse, which I argue obscures recognition of the dynamic role of social processes that lie at the heart of human communities. These environmental discourses, together with confusion over terminology and the concepts of collapse, have created widespread aporia about collapse and resulted in the creation of mixed messages about complex historical and social processes

Comparability of Raman Spectroscopic Configurations: A Large Scale Cross-Laboratory Study

This is the final version. Available on open access from the American Chemical Society via the DOI in this recordThe variable configuration of Raman spectroscopic platforms is one of the major obstacles in establishing Raman spectroscopy as a valuable physicochemical method within real-world scenarios such as clinical diagnostics. For such real world applications like diagnostic classification, the models should ideally be usable to predict data from different setups. Whether it is done by training a rugged model with data from many setups or by a primary-replica strategy where models are developed on a 'primary' setup and the test data are generated on 'replicate' setups, this is only possible if the Raman spectra from different setups are consistent, reproducible, and comparable. However, Raman spectra can be highly sensitive to the measurement conditions, and they change from setup to setup even if the same samples are measured. Although increasingly recognized as an issue, the dependence of the Raman spectra on the instrumental configuration is far from being fully understood and great effort is needed to address the resulting spectral variations and to correct for them. To make the severity of the situation clear, we present a round robin experiment investigating the comparability of 35 Raman spectroscopic devices with different configurations in 15 institutes within seven European countries from the COST (European Cooperation in Science and Technology) action Raman4clinics. The experiment was developed in a fashion that allows various instrumental configurations ranging from highly confocal setups to fibre-optic based systems with different excitation wavelengths. We illustrate the spectral variations caused by the instrumental configurations from the perspectives of peak shifts, intensity variations, peak widths, and noise levels. We conclude this contribution with recommendations that may help to improve the inter-laboratory studies.COST (European Cooperation in Science and Technology)Portuguese Foundation for Science and TechnologyNational Research Fund of Luxembourg (FNR)China Scholarship Council (CSC)BOKU Core Facilities Multiscale ImagingDeutsche Forschungsgemeinschaft (DFG, German Research Foundation

OPTIMIZED EXTRACTION CONDITIONS FROM HIGH POWER-ECRIS BY DEDICATED DIELECTRIC STRUCTURES

Abstract The MD-method of enhancing the ion output from ECR ion sources is well established and basically works via two mechanisms, the regenerative injection of cold electrons from an emissive dielectric layer on the plasma chamber walls and via the cutting of compensating wall currents, which results in an improved ion extraction from the plasma. As this extraction from the plasma becomes a more and more challenging issue for modern ECRIS installations with high microwave power input, a series of experiments was carried out at the 14 GHz ECRIS of the Institut für Kernphysik in Frankfurt/Main, Germany (IKF). In contrast to our earlier work, in these experiments emphasis was put on the second of the above mechanisms namely to influence the sheath potential at the extraction by structures with special dielectric properties. Two different types of dielectric structures, Tantalum-oxide and Aluminium oxide (the latter also being used for the MD-method) with contrastingly different electrical properties were mounted on the extraction electrode of the IKF-ECRIS, facing the plasma. For both structures an increase of the extracted ion beam currents for middle and high charge states by 60-80 % was observed. The method is able to be applied also to other ECR ion sources for increasing the extracted ion beam performances