Refine
Document Type
- Article (3)
- Conference Proceeding (3)
- Diploma Thesis (1)
- Doctoral Thesis (1)
Has Fulltext
- yes (8) (remove)
Is part of the Bibliography
- no (8)
Keywords
- 325 MHz (1)
- Beschleuniger (1)
- CH-Struktur (1)
- Linac (1)
- supraleitend (1)
Institute
- Physik (8)
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.
Superconducting, energy variable heavy ion linac with constant
β, multicell cavities of CH-type
(2009)
An energy variable ion linac consisting of multigap, constant-β cavities was developed. The effect of phase sliding, unavoidable in any constant-β section, is leading to a coherent rf phase motion, which fits well to the H-type structures with their long π-mode sections and separated lenses. The exact periodicity of the cell lengths within each cavity results in technical advantages, such as higher calculation accuracy when only one single period can be simulated, simpler manufacturing, and tuning. This is most important in the case of superconducting cavities. By using this concept, an improved design for a 217 MHz cw superconducting heavy ion linac with energy variation has been worked out. The small output energy spread of ± 3 AkeV is provided over the whole range of energy variation from 3.5 to 7.3 AMeV. These capabilities would allow for a competitive research in the field of radiochemistry and for a production of super heavy elements (SHE), especially. A first 19-cell cavity of that type was designed, built, and rf tested successfully at the Institute for Applied Physics (IAP) Frankfurt. A 325.224 MHz, seven-cell cavity with constant β = 0.16 is under development and will be operated in a frequency controlled mode. It will be equipped with a power coupler and beam tests with Unilac beams at GSI are foreseen.
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.
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.
EUROTRANS is a European research program for the transmutation of high level nuclear waste in an accelerator-driven system (ADS). As proposed, the driver linac needs to deliver a 2.5–4 mA, 600 MeV continuous-wave (CW) proton beam and later a 20 mA, 800 MeV one to the spallation target in the prototype-scale and industrial-scale demonstration phases, respectively. This paper is focusing on the conceptual studies performed with respect to the 17 MeV injector. First, the special beam dynamics strategies and methods, which have been developed and applied to design a current-variable injector up to 30 mA for allowing an easy upgrade without additional R&D costs, will be introduced. Then the error study made for evaluating the tolerance limits of the designed injector will be presented as well.
The crossbar-H-mode (CH) structure is the first superconducting multicell drift tube cavity for the low and medium energy range operated in the H21 mode. Because of the large energy gain per cavity, which leads to high real estate gradients, it is an excellent candidate for the efficient acceleration in high power proton and ion accelerators with fixed velocity profile. A prototype cavity has been developed and tested successfully with a gradient of 7MV/m. A few new superconducting CH cavities with improved geometries for different high power applications are under development at present. One cavity (f=325 MHz, β=0.16, seven cells) is currently under construction and studied with respect to a possible upgrade option for the GSI UNILAC. Another cavity (f=217 MHz, β=0.059, 15 cells) is designed for a cw operated energy variable heavy ion linac application. Furthermore, the EUROTRANS project (European research program for the transmutation of high level nuclear waste in an accelerator driven system, 600 MeV protons, 352 MHz) is one of many possible applications for this kind of superconducting rf cavity. In this context a layout of the 17 MeV EUROTRANS injector containing four superconducting CH cavities was proposed by the Institute for Applied Physics (IAP) Frankfurt. The status of the cavity development related to the EUROTRANS injector is presented.
Die vorliegende Arbeit handelt von der Entwicklung, dem Bau, den Zwischenmessungen sowie den abschließenden Tests unter kryogenen Bedingungen einer neuartigen, supraleitenden CH-Struktur für Strahlbetrieb mit hoher Strahllast. Diese Struktur setzt das Konzept des erfolgreich getesteten 19-zelligen 360 MHz CH-Prototypen fort, der einen weltweiten Spitzenwert in Bezug auf Beschleunigungsspannung im Niederenergiesegment erreichte, jedoch wurden einige Aspekte weiterentwickelt bzw. den neuen Rahmenbedingungen angepasst. Bei dem neuen Resonator wurde der Schwerpunkt auf ein kompaktes Design, effektives Tuning, leichte Präparationsmöglichkeiten und auf den Einsatz eines Leistungskopplers für Strahlbetrieb gelegt. Die Resonatorgeometrie besteht aus sieben Beschleunigungszellen, wird bei 325 MHz betrieben und das Geschwindigkeitsprofil ist auf eine Teilcheneingangsenergie von 11.4 MeV/u ausgelegt. Veränderungen liegen in der um 90° gedrehten Stützengeometrie vor, um Platz für Tuner und Kopplerflansche zu gewährleisten, und in der Verwendung von schrägen Stützen am Resonatorein- und ausgang zur Verkürzung der Tanklänge und Erzielung eines flachen Feldverlaufs. Weiterhin wurden pro Tankdeckel zwei zusätzliche Spülflansche für die chemische Präparation sowie für die Hochdruckspüle mit hochreinem Wasser hinzugefügt. Das Tuning der Kavität erfolgt über einen neuartigen Ansatz, indem zwei bewegliche Balgtuner in das Resonatorvolumen eingebracht werden und extern über eine Tunerstange ausgelenkt werden können. Der Antrieb der Stange soll im späteren Betrieb wahlweise über einen Schrittmotor oder einen Piezoaktor stattfinden. Für ein langsames/ statisches Tuning kann der Schrittmotor den Tuner im Bereich +/- 1 mm auslenken, um größeren Frequenzabweichungen in der Größenordnung 100 kHz nach dem Abkühlen entgegenzuwirken. Das schnelle Tuning im niedrigen kHz-Bereich wird von einem Piezoaktor übernommen, welcher den Balg um einige µm bewegen kann, um Microphonics oder Lorentz-Force-Detuning zu kompensieren. Der Resonator wird von einem aus Titan bestehendem Heliummantel umgeben, wodurch ein geschlossener Heliumkreislauf gebildet wird.
Derzeit befinden sich mehrere Projekte in der Planung bzw. im Bau, welche auf eine derartige Resonatorgeometrie zurückgreifen könnten. An der GSI basiert der Hauptteil des zukünftigen cw LINAC auf supraleitenden CH-Strukturen, um einen Strahl für die Synthese neuer, superschwerer Elemente zu liefern. Weiterhin könnte ein Upgrade des vorhandenen GSI UNILAC durch den Einsatz von supraleitenden CH-Resonatoren gestaltet werden. Zudem besteht die Möglichkeit, die bisherige Alvarez-Sektion des UNILAC alternativ durch eine kompakte, supraleitende CH-Sektion zu realisieren. Ebenfalls sollen die beiden parallelbetriebenen Injektorsektionen des MYRRHA-Projektes durch den Einsatz von supraleitenden CH-Strukturen erfolgen.