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Die Wirkungsweise des Protonen-Wendellinearbeschleunigers und sein prinzipieller Aufbau werden kurz beschrieben und Angaben über die erreichbare Parallelimpedanz gemacht. Es wird gezeigt, wie durch sektionsweisen Aufbau eine variable Endenergie erzielt und die Kühl- und Fokussierprobleme gelöst werden können. Zwei Konstruktionsbeispiele für kontinuierlichen und gepulsten Betrieb werden näher ausgeführt.
Determination of field strength and quality factor of heavily HOM damped accelerator cavities
(1992)
Two methods of of measuring field strength in accelerator cavities, heavily damped with respect to higher order modes (HOM), are presented. From the results of the field measurements the coupling (damping) factor and thus the quality factor of the damped resonator can be derived. Measurements of a pillbox resonator with heavily damped TM110-mode (Q < 20) demonstrate the usefulness of the techniques presented, even in this extreme range.
By replacing the irises in an electron linac by a slit one gets a structure capable of focussing/defocussing an electron beam (rf-quadrupoles). Therefore one can think of a combination of rf- and conventional magnetic quadrupoles for transversal focussing in linear-colliders. Furthermore they can meet the demands of BNS-damping without initial energy spread. Considering multibunch-operation of a collider, the long-range wake behaviour of this kind of structure has to be investigated. A three-cell structure has been built and investigated for dipole-type transversal long-range wakes. The experimental results are compared to numerical simulations done with MAFIA.
To reach high luminosities in future linear colliders short range wakes havea to be controlled in the range of X-band frequencies or higher. Rectangular irises can be used to introduce strong focusing quadrupole-like rf-fields. Even circular irises in iris-loaded accelarator structures have the capability of focusing if the particle velocity differs from phase velocity. Theoretical investigations concerning the focusing strength to be expected are presented. Their applicability for linear colliders is discussed.
A new method of measuring quality factors in cavities is presented. This method is well suited to measure quality factors in undamped cavities as well as in heavily damped cavities, and in addition this method provides a possibility of separating modes and measuring quality factors especially in cases of overlapping modes. Measurements have been carried out on HOM-damped cavities for the DESY/THD linear collider project. Results are presented.
Damping cells for the higher order modes are necessary for the S-band linear collider to minimize BBU (Beam-Break-Up). The construction of the damper cells has to take into account the different field geometries of the higher order modes. So two different types of dampers have been designed: a wall slotted an an iris slotted cell. In order to optimize the two types of damping cells with respect to damping strength, impedance matching between coupling system and waveguide dampers and between damping cell and undamped cells and the tuning system, damping cells of both types have been built and examinated.
The effect of a single HOM-damper cell within a channel of undamped cells is described theoretically using an equivalent circuit model. From this a simple equation can be derived which relates the Q-value of the single damping-cell, the bandwidth of the passband under consideration, and the additional phase shift which is introduced by the damper cell to provide energy flow into the damper cell. This equation immediately shows the limitations of such single cell damping systems. Comparisons with experimental results are shown.
Mode propagation in an iris type accelerator section loaded with single heavily HOM-damped cells
(1994)
The wakefield effects in accelerator sections for future linear colliders will be reduced either by damping by detuning or by a combination of both. For the DESY/THD linac [1] it is forseen to employ heavily HOM-damped cells to provide a strong coupling to the TE/TM11-dipole passband as well as to the TM/TE11-dipole passband. For our experiments we have used wall-slotted damping cells. This leads to several problems concerning the propagation of fundamental and HOM-modes. Experimental investigations have been done. Results are presented.
A new method for measuring quality factors in cavities is presented. This method is capable of measuring Q-factors in heavily damped as well as in undamped cavities. In addition, the possibility of separating overlapping modes and measuring their Q-factors is provided. Measurements on HOM (higher order mode) damped cavities for the DESY/THD linear collider project are presented
A new method for the determination of S-matrices of devices in multimoded waveguides and first experimental experiences are presented. The theoretical foundations are given. The scattering matrix of a TESLA copper cavity at a frequency above the cut-off of the second waveguide mode has been measured.
Plus de la moitié des Européens de l’U.E. parlent une langue romane comme langue maternelle. Parmi les autres Européens, l’apprentissage de langues romanes comme langue étrangère est très fréquent, il n’est dépassé que par l’anglais: Une «Romanophonie» pourrait s’appuyer donc sur une base large, tandis que ses valeurs intercompréhensives ne sont pas encore suffisamment mises à la disposition d’un publique européen. Au contraire: les nations créent de plus en plus des barrières entre les langues romanes en institutionnalisant les différences et non pas ce qu’elles ont en commun. En Allemagne où l’on trouve encore la philologie romane (Romanische Philologie) comme unité d’études on peut observer en même temps une tendance vers une spécialisation en études unilingues (Einzelphilologien). Un tel séparatisme linguistique à l’intérieur d’une seule famille renonce aux avantages intercommunicatifs et intercompréhensifs offerts par les langues romanes. Le phénomène de l’intercompréhension est largement connu, pas seulement parmi les romanistes. C’est le résultat d’une tradition de l’écrit et d’un héritage culturel - une partie importante de l’unité intellectuelle du continent européen - qui rend les langues romanes si accessibles. ...
Das Neldophon gehört mittlerweile zum internationalen Wortschatz Europas. Neldophonieren ist heute alltägliche Praxis. Die Globalisierung des ausgehenden zweiten Jahrtausends setzt die Entwicklung der Neldophonie voraus, um idealtypisch in naher Zukunft von jedem Punkt der Erde aus mit jedem beliebigen anderen Punkt in neldophonischer Verbindung zu sein. Eurosemantische Gemeinsamkeiten des Neldophonierens und die außersprachliche Partizipiation an der entsprechenden Technologie erleichterten die Akzeptanz des Terminus in den romanischen (und anderen) Sprachen Europas und der Welt trotz des Unikalmorphems Neldo-(vergleichbar mit Him- und Brom- in Him-, bzw. Brombeere) in Verbindung mit dem ansonsten global in verschiedenen Graphien verbreiteten Restmorphem -phon. Wörter haben ihre Geschichte. Der Ausdruck läßt sich auf seinen etymologischen Entstehungsort, den Congrés Europeu sobre Planificació Lingüística (Barcelona 9.-10. November 1995) zurückführen, andem auch der Gründer der FFM teilnahm. Offensichtlich wurde der Terminus hier in internationaler Umgebung erstmalig geprägt und sogleich panromanisch umgesetzt. Die barceloniner Gastgeber sprachen von neldòfon, während hingegen die wenigen Hispanophonen neldófono bevorzugten. Das Verbum neldofonar ist in der Zwischenzeit auch im Portugiesischen belegt, die Académie française wird sich kaum einer Äußerung enthalten können, ob neldophoner oder neldofoner (da offensichtlich im katalanischen Sprachbereich entstanden) die normgerechte Graphie repräsentiere, während Italien den europäischen Neologismus seit dem Herbst 1995 bereits kennt (chiamami più tardi al neldefono) und - zu Recht? - das etymologische ius primi loci beansprucht. In Rumänien erhielt das Verb eine systemimanente Stammerweiterung (Petre neldofoneazã mult) seit 1996. Nach zuverlässigen Quellen (Jernudd 1995) trat der Terminus Ende 1995 in seiner englischen Variante in Honkong in Kontakt mit dem Kantonesischen. Sein Überleben scheint jedoch hier (nach 1997) insbesondere wegen der phonologischen Problematik des liquiden Auslauts der Silbe nel- und diverser noch zu erwartender sprachpolitischer Konflikte nicht gesichert. Da die europäischen Neldophone in USA noch nicht funktionieren, ist eine gewisse Skepsis für den terminologischen Siegeszug der Neldophonie im Amerikanischen Englisch nicht unangebracht. ...
Due to the additional need of very short bunches for the FEL operation with the TESLA-machine strong wakefield effects are expected. One third of the total wakefield energy per bunch is radiated into the frequency region above the energy gap of Cooper pairs in superconducting niobium. The energy of the cooper pairs in superconducting niobium at 2 K corresponds to a frequency of 700 GHz. An analytical and experimental estimation for the overall energy loss of the FEL bunch above energy gap is presented. The analytical method is based on a study from R. B. Palmer [1]. The results of the wakefield estimations are used to calculate possible quality factor reduction of the TESLA cavities during FEL operation. Results are presented.
High perveance negative ion beams with low emittance are essential for several next generation particle accelerators (i. g. spallation sources like ESS [1] and SNS [2]). The extraction and transport of these beams have intrinsic difficulties different from positive ion beams. Limitation of beam current and emittance growth have to be avoided. To fulfill the requirements of those projects a detailed knowledge of the physics of beam formation the interaction of the H- with the residual gas and transport is substantial. A compact cesium free H- volume source delivering a low energy high perveance beam (6.5 keV, 2.3 mA, perveance K= 0.0034) has been built to study the fundamental physics of beam transport and will be integrated into the existing LEBT section in the near future. First measurements of the interaction between the ion beam and the residual gas will be presented together with the experimental set up and preliminary results.
High perveance negative ion beams with low emittance are essential for several next generation particle accelerators (i. g. spallation sources like ESS [1] and SNS [2]). The extraction and transport of these beams have intrinsic difficulties different from positive ion beams. Limitation of beam current and emittance growth have to be avoided. To fulfill the requirements of those projects a detailed knowledge of the physics of beam formation the interaction of the H- with the residual gas and transport is substantial. A compact cesium free H- volume source delivering a low energy high perveance beam (6.5 keV, 2.3 mA, perveance K= 0.0034) has been built to study the fundamental physics of beam transport and will be integrated into the existing LEBT section in the near future. First measurements of the interaction between the ion beam and the residual gas will be presented together with the experimental set up and preliminary results.