479 research outputs found
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Spin matching conditions in large electron storage rings with purely horizontal beam polarization
In a storage ring with a purely horizontal spin and a Siberian Snake, the spin matching conditions are similar to the spin matching conditions for vertical polarization; a combination of beam bumps has to be found which compensate the depolarizing effects. These bumps compensate the random emission of synchrotron emission on the spin. The aim of this paper is to define spin matching conditions that compensate this effect
The influence of a superconducting split-pair solenoid as an insertion device on the performance of a storage ring for synchrotron radiation
EINFLUSS EINES ALS INSERTION DEVICE VERWENDETEN SUPRALEITENDEN SPLIT-PAIR SOLENOIDEN AUF DAS VERHALTEN EINES SPEICHERRINGES FĂśR SYNCHROTRONSTRAHLUNG
Zur Erhöhung der Photonenenergie von Synchrotronstrahlungsquellen wird die Verwendung von starken nichtlinearen Magneten in Betracht gezogen. Solche Magnete können einen starken Einfluß auf die Funktion von Speicherringen ausüben, da sie die Emittanz vergrößern und die dynamische Apertur verringern können. In der vorliegenden Arbeit wird eine Methode vorgestellt, mit deren Hilfe der Einfluß der nichtlinearen Felder auf die dynamische Apertur berechnet werden kann. Mit dieser Methode wird die mögliche Auswirkung eines als Wellenlängenschieber eingesetzten kommerziellen 12 T Split-pair Solenoiden auf die dynamische Apertur der zukünftigen Synchrotronstrahlungsquelle ANKA untersucht
Localization of Human RNase Z Isoforms: Dual Nuclear/Mitochondrial Targeting of the ELAC2 Gene Product by Alternative Translation Initiation
RNase Z is an endonuclease responsible for the removal of 3′ extensions from tRNA precursors, an essential step in tRNA biogenesis. Human cells contain a long form (RNase ZL) encoded by ELAC2, and a short form (RNase ZS; ELAC1). We studied their subcellular localization by expression of proteins fused to green fluorescent protein. RNase ZS was found in the cytosol, whereas RNase ZL localized to the nucleus and mitochondria. We show that alternative translation initiation is responsible for the dual targeting of RNase ZL. Due to the unfavorable context of the first AUG of ELAC2, translation apparently also starts from the second AUG, whereby the mitochondrial targeting sequence is lost and the protein is instead routed to the nucleus. Our data suggest that RNase ZL is the enzyme involved in both, nuclear and mitochondrial tRNA 3′ end maturation
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A fast optics and orbit correction program
CEBAF is a large recirculating linear accelerator with approximately 1600 magnet power supplies in the beam transport system. The average beam power can be as great as 800 kW, concentrated into a spot of area less than 0.01 mm{sup 2}. Control of the transport is therefore quite critical, to avoid missteering the beam. To prevent dangerous beam losses and to prepare optics changes, the control programs must read the magnet power supplies and calculate the optics in a virtually real-time manner. A program named OLE (On-Line Envelope) has been developed at CEBAF to give a graphical display of the calculated machine {beta} function or, equivalently, the beam envelope. The time interval necessary to execute the program is somewhat less than one second, short enough that the operator can use it for setting up his lattice. Emphasis in the design was placed on speed of program execution at the expense of generality of application. As a result, the accelerator operator will be able to alter the magnetic field in any element in the machine, calculate the {beta} functions in both planes at the entrance and exit of each magnet, and display graphs of the functions, all within one second. The time that is required is short enough that the process approximates fairly well real-time operation
Generation of x-ray radiation in a storage ring by a superconductive cold-bore invacuum undulator
The first beam measurements with a cold-bore superconducting in-vacuum undulator in a storage ring are reported. Undulators are x-ray generators in light sources. The physical limitations of these devices limit the intensity and the brilliance of the x-ray beam. At present the undulators are made from permanent magnets. It was shown in earlier papers that at low electron beam intensities superconductive wires in the vacuum beam pipe can overcome the limitations inherent to permanent magnet undulators. It was argued that the use of these novel devices in light sources with high beam currents may be limited by the extreme anomalous skin effect regime in Cu at 4.2 K, which has so far undergone very little investigation, and the power deposited by the infrared part of the synchrotron radiation. The purpose of this paper is to present measurements of these effects at the synchrotron light source ANKA with stored currents up to 200 mA
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