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For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The main acceleration of this room temperature linac will be provided by six CH cavities operated at 325 MHz. Each cavity will be powered by a 2.5 MW Klystron. For the second acceleration unit from 11.5 MeV to 24.2 MeV a 1:2 scaled model has been built. Low level RF measurements have been performed to determine the main parameters and to prove the concept of coupled CH cavities. For this second tank technical and mechanical investigations have been performed in 2010 to develop a complete technical concept for the manufacturing. In Spring 2011, the construction of the first power prototype has started. The main components of this cavity will be ready for measurements in summer 2011. At that time, the cavity will be tested with a preliminary aluminum drift tube structure, which will allow precise frequency and field tuning. This paper will report on the recent technical development and achievements. It will outline the main fabrication steps towards that novel type of proton DTL. Also first low level RF measurements are expected.
The MYRRHA Project (Multi Purpose Hybrid Reactor for High Tech Applications) at Mol/belgium will be a user facility with emphasis on research with neutron generated by a spallation source. One main aspect is the demonstration of nuclear waste technology using an accelerator driven system. A superconducting linac delivers a 4 mA, 600 MeV proton beam. The first accelerating section is covered by the 17 MeV injector. It consists of a proton source, an RFQ, two room temperature CH cavities and 4 superconducting CH-cavities. The initial design has used an RF frequency of 352 MHz. Recently the frequency of the injector has been set to 176 MHz. The main reason is the possible use of a 4-rod-RFQ with reduced power dissipation and energy, respectively. The status of the overall injector layout including cavity design is presented.
SIS100 is the main synchrotron of the FAIR project. It is designed to accelerate high intensity intermediate charge state uranium beams from 200 MeV/u up to 2.7 GeV/u. Intermediate charge state heavy ions are exposed to a high probability of charge exchange due to collisions with residual gas molecules. Since the charge exchange process changes the magnetic rigidity, the involved ions are lost behind dispersive elements, and an energy-dependent gas desorption takes place. The StrahlSim code has been used to predict the stability of the residual gas pressure in SIS100 under beam loss driven dynamic conditions. The results show, that a stable operation at highest U28+ intensities is possible, under the constraint that the vacuum chambers of the ion catcher system are cold enough to pump hydrogen. Furthermore, in order to determine the load to the cryogenic system, the average beam energy deposition onto the ion catcher system has been calculated.
The ARMADILLO bunch compressor currently being designed at IAP is capable of reaching a longitudinal pulse compression ratio of 45 for proton beams of 150 mA at 2 MeV. It will provide one nanosecond proton pulses with a peak current of 7.7 A. The system guides nine linacμbunches deflected by a 5 MHz rf kicker and uses four dipole magnets - two homogeneous and two with field gradients - to merge them on the target. For longitudinal focusing and an energy variation of ±200 keV two multitrack rf cavities are included. ARMADILLO will be installed at the end of the Frankfurt Neutron Source FRANZ making use of the unique 250 kHz time structure. This contribution will provide an overview of the layout of the system as well as recent advances in component design and beam dynamics of the compressor.
At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under development for future beam tests at GSI UNILAC, Darmstadt. The cavity with 7 accelerating cells has a geometrical beta of 0.15 corresponding to 11.4 AMeV. The design gradient is 5 MV/m. The geometry of this resonator was optimized with respect to a compact design, low peak fields, surface processing, power coupling and tuning. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper rf simulations, multipacting analysis as well as thermal calculations will be presented.
On the clay plains surrounding Lake Chad (West Africa: northern Sudanian and southern Sahelian zone), certain varieties of pearl millet (Sorghum bicolor), commonly referred to as Masakwa, are cultivated during the dry season. Recently fallowed Masakwa fields support a particular progression of pioneer vegetation. In the first year of fallow, the pioneer vegetation typically belongs to the class Echinochloetea colonae Wittig 2005 and can be classified as Hygrophiletum auriculatae sensu lato. Approximately half of the stands consist of the Hygrophiletum auriculatae Ataholo 2002 sensu stricto, whereas the other half is primarily composed of a Celosia argentea-Hibiscus trionum community. After two years of fallow, the vegetation is typically formed by the Sorghetum arundinacei Ataholo 2002, which, in a few cases, can also occur in the first fallow year.
The use of woody species of rural populations in Northern Benin was investigated by semi-structured and open interviews. Of the 129 woody species found in the area, 124 (96%) were mentioned to be used as firewood, for house and furniture construction or preparation of tools, for alimentation, in traditional medicine and/or for other purposes. Our study confirms and underlines the high importance of non timber forest products (NTFPs) for the local population.
The SIS300 synchrotron, planned for the new Facility for Antiproton and Ion Research (FAIR) at GSI-Darmstadt, will become the first superconducting synchrotron worldwide using cos(θ) magnets for resonant slow extraction. A multi-objective optimization algorithm has been developed for the design of the non-linear magnet scheme. The optimization algorithm makes use of the analytical model for the slow extraction from Kobayashi, the analytical description of the resonance excitation and amplitude-dependent tune-shift from Bengtsson, and corrects the chromaticity in order to fulfill the Hardt condition. As a result, the placement of the chromatic and harmonic sextupole magnets in SIS300, the number of sextupole families and the gradients of these families have been optimized for a high efficiency slow extraction. The algorithm accounts also for the sextupole errors on the dipole magnets, compensating its effects. Furthermore, optimized time-dependent settings for the sextupole magnets are generated to compensate the persistent current decay occurring at slow extraction. Tolerances for the magnets are set for the limits where the compensation is no longer valid.
Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.
A modern linear accelerator of ions is a long chain of different accelerating-focusing structures. The design of new linacs, as well as an upgrade and optimization of operating facilities, requires precise and reliable beam matching with the subsequent sections. Proper matching of the beam to the channel allows to improve the performance of the whole linac and to reduce the specific costs. Additionally it helps to avoide particle loss in high energy high intensity linacs. Generally a matching algorithm combines precisely measured or calculated accelerating-focusing external fields and experimentally obtained details of the beam parameters with an advanced code for beam dynamics simulations including space charge effects. Experimental results are introduced into a code as input data. The described algorithm has already been successfully implemented for several GSI projects: an upgrade of the GSI heavy ion linac UNILAC, an ion linac for the cancer therapy, the proton linac for the FAIR facility, a facility for laser acceleration of ions and others. Measured data and results of beam dynamics simulations leading to an achieved improvement of the linac performance are presented.
At GSI a new, superconducting (sc) continuous wave (cw) LINAC is under design in cooperation with the Institute for Applied Physics (IAP) of Frankfurt University and the Helmholtz Institut Mainz (HIM). This proposed LINAC is highly requested by a broad community of future users to fulfill the requirements of nuclear chemistry, nuclear physics, and especially in the research field of Super Heavy Elements (SHE). In this context the preliminary layout of the LINAC has been carried out by IAP. The main acceleration of up to 7.3 AMeV will be provided by nine sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Currently, a prototype of the cw LINAC as a demonstrator is under development. The demonstrator comprises a sc CH-cavity embedded between two sc solenoids mounted in a horizontal cryomodule. A full performance test of the demonstrator in 2013/14 by injecting and accelerating a beam from the GSI High Charge Injector (HLI) is one important milestone of the project. The status of the demonstrator is presented.
The superconducting CH-structure (Crossbar-H-mode) is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode, which has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. With respect to different high power applications two types of superconducting CH-structures (f = 325 MHz, β = 0.16, seven cells and f = 217 MHz, β = 0.059, 15 cells) are presently under construction and accordingly under development. The structural mechanical simulation is a very important aspect of the cavity design. Furthermore, several simulations with ANSYS Workbench have been performed to predict the deformation of the cavity walls due to the cavity cool-down, pressure effects and mechanical vibrations. To readjust the fast frequency changes in consequence of the cavity shape deformation, a new concept for the dynamic frequency tuning has been investigated, including a novel type of bellow-tuner.
In Deutschland sind Paranüsse besonders in der Advents- und Weihnachtszeit als Knabberei und als Dekoartikel sehr beliebt. Der Paranussbaum, der seinen Namen nach dem brasilianischen Bundestaat Pará bzw. dem gleichnamigen Ausfuhrhafen erhielt, war ursprünglich in den tropischen Regenwäldern Südamerikas verbreitet; es wird jedoch mittlerweile auch versucht, ihn plantagenmäßig in Südostasien und im tropischen Afrika anzubauen. Die Biologie und Nutzung werden im vorliegenden Beitrag beschrieben.
The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum is driven by a 2 MeV proton linac consisting of a 4-rod-radio-frequency-quadrupol (RFQ) and an 8 gap IH-DTL structure. RFQ and IH cavity will be powered by only one radio frequency (RF) amplifier to reduce costs. The RF-amplifier of the RFQ-IH combination is coupled into the RFQ. Internal inductive coupling along the axis connects the RFQ with the IH cavity ensuring the required power transition as well as a fixed phase relation between the two structures. The main acceleration of 120 keV up to 2.03 MeV will be reached by the RFQ-IH combination with 175 MHz and at a total length of 2.3 m. The losses in the RFQ-IH combination are about 200 kW.
This novel kind of neutron beam facility will provide 1 ns short neutron pulses with an approximately thermal energy distribution around 30 keV. The pulse repetition rate will be up to 250 kHz, the total proton number per pulse will be up to 6×1010 in the final stage, starting with a p – source current of 200 mA. A second target station will allow n – activation experiments by cw beam operation. An intense 2 MeV proton beam will drive a neutron source by the 7 Li (p,n) 7 Be reaction. The facility is under construction at the physics experimental hall of the J.W. Goethe – University. The 1m thick concrete tunnel was installed in 2009. In 2011 all rf amplifiers will be delivered and installed. Successful 200 mA proton source experiments in 2010 at a test stand will be followed by experiments on the 120 kV FRANZ terminal in 2011. The 250 kHz, 100 ns chopper in front of the rf linac is under construction, while the 2 MeV bunch compressor design was finished and the technical design of all components has started. The main accelerator cavity is under construction. First 2 MeV beam tests are expected for end of 2012.
Mit dieser Arbeit konnte die Funktionsweise von gekoppelten Resonatoren erklärt werden. Das Verhalten von induktiv gekoppelten Beschleunigerkavitäten wurde näher studiert. Dabei wurde verstanden, wie sich Verstimmungen auf die Resonatoren auswirken und was zu tun ist um die Spannungsamplituden des gekoppelten Systems zu beeinflussen. Zudem wurden die Grundlagen für den gekoppelten Betrieb des FRANZ-Beschleunigers gelegt.
Als Adalbert Stifters Roman „Der Nachsommer“ 1857 erscheint, hat das Bild der klassischen Antike, wie es durch Winckelmann und Goethe einen hohen Grad der Verbindlichkeit erhalten hatte, längst an Faszination und normativer Kraft eingebüßt. Im Gefolge des Historismus, der jeder Epoche ihr Eigenrecht zuerkannte, waren historische Vorstellungen an die Stelle normativer getreten. In Stifters „Nachsommer“ ist davon freilich nur wenig zu spüren. Der Roman wendet sich ostentativ gegen aktuelle Zeittendenzen und scheint für ein Festhalten an einer zeitlos-idealen Antike einzutreten. Die ausführlichen Gespräche, die der Ich-Erzähler Heinrich Drendorf mit seinem Gastgeber Risach über antike Kunst führt, wiederholen und zementieren überkommene Auffassungen. In Superlativen beschwört Risach Größe und Einfachheit der antiken Kunst; er nennt die griechische Dichtung „das Höchste“ und „was die Griechen in der Bildnerei geschaffen haben, [...] das Schönste, welches auf der Welt“ überhaupt bestehe. Stifters Antike orientiert sich, wie in der Forschung einhellig anerkannt, an Leitvorstellungen Winckelmanns, und die im „Nachsommer“ geführten Kunstgespräche treten in die Spuren der ästhetischen Debatten des ausgehenden 18. Jahrhunderts.
Allein in einer entlegenen Klassikerausgabe des Jahres 1921 findet man, was man in der Forschungsliteratur vergeblich sucht: den Versuch, Friedrich Hölderlins „Hyperion“ und Carl Rottmanns griechische Landschaftsbilder einander anzunähern oder zumindest zu vergleichen. Rottmanns Gemälde und Hölderlins Roman werden zu Recht zu den eigenwilligsten und produktivsten Schöpfungen des deutschen Philhellenismus gezählt, und doch ist – soweit ich sehe – in der literaturwissenschaftlichen und kunsthistorischen Forschung noch nie nach einem engeren Zusammenhang zwischen beiden Werken gefragt worden. Trennt Hölderlins Roman, der in zwei Teilen 1797 und 1799 erschien, und Rottmanns Gemäldezyklus, der in den Jahren 1838 bis 1850 entstand, tatsächlich ein allzu großer zeitlicher Abstand? Zeichnen beide Werke gänzlich verschiedene Bilder Griechenlands, sodass sich jeder Vergleich verbietet?
Das christliche Bild im 19. Jahrhundert zeigt, so die These dieses Aufsatzes, dass Verwissenschaftlichung nicht notwendigerweise historistische Entidealisierung bedeuten musste – wie eben auch die Lektion der historisch-kritischen Bibelforschung nicht unweigerlich zu einer Relativierung der Heiligen Schrift führen musste. In der ästhetischen Konstruktion der biblischen Antiken wurden Evidenz und Imagination zu komplementären Repräsentationsstrategien, die einen gemeinsamen Ursprung jenseits der Unterscheidung zwischen geschichtlicher Wahrheit und archäologischem Wissen hatten. Eine christliche Kunst musste diese historische Wahrheit, die eben keine wissenschaftlich positivistische sein sollte, sichtbar machen. „Das Göttliche kann sich in der Knechtsgestalt begränzter Zeit und Körperlichkeit nicht völlig offenbaren“, formulierte Karl Schnaase im Jahre 1862 diesen Grundsatz eindringlich, „es will mehr geahnt und geglaubt als gesehen sein“. Zwischen archäologischer Treue und kunsthistorischer Tradition, mimetischer Sinnlichkeit und abstrakter Idee erfüllt die Kunst ihre ureigene Aufgabe des Sichtbarmachens im Bewusstsein einer eingeborenen Unmöglichkeit. Die Welt der biblischen Antike wird so zum experimentellen Feld eines erfolgreichen Scheiterns.
Im Spektrum der Epochen, von denen der Historienroman im 19. Jahrhundert erzählt, spielt die Antike eine untergeordnete Rolle. Ihr vorgezogen werden die großen Zeitalter der nachantiken europäischen Geschichte: das hohe Mittelalter, die Renaissance, die Frühe Neuzeit und die Revolutionsepoche um und nach 1800. Erst gegen Ende des 19. Jahrhunderts, lange nach der sogenannten „Scott-Ära“ in den 1820er Jahren, in denen sich der historische Roman in ganz Europa zur beliebtesten Erzählform entwickelt, wird häufiger über die Antike erzählt. So steigt die Zahl der Romane, welche die antike Geschichte thematisieren, gegen Ende der sechziger Jahre des 19. Jahrhunderts langsam und kontinuierlich an bis zu einem Höhepunkt in den 1880er Jahren, um danach wieder leicht zurückzufallen. Auch in den 1880er Jahren bleibt die jährliche Publikationsrate von Romanen über das Altertum freilich im einstelligen Bereich und damit deutlich unterhalb der Quote je- ner Texte, die sich späteren historischen Zeiträumen widmen. Themen aus der Phase zwischen Barockzeitalter und beginnendem 19. Jahrhundert dominieren die gesamte Epoche; bestimmend ist die Tendenz zu jüngeren Zeitabschnitten, zur modernen Geschichte.