Test of internal halo targets in the HERA proton ring Hast, C.; Ehret, K.; Hofmann, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/1995, Volume:
354, Issue:
2
Journal Article
Peer reviewed
Open access
Internal wire targets in the halo of stored proton beams provide a line source of proton-nucleus interactions for highest-rate fixed target experiments. We have studied such internal halo targets at ...the 820 GeV proton ring of the HERA ep collider. The tests showed that most of the protons in the beam halo — which would otherwise hit the collimators — can be brought to interaction in a relatively thin target wire at distances of 7 to 8 beam widths from the center of the beam. At less than 10% of the HERA total design current, and less than 20% of the current per bunch, interaction rates up to 8 MHz were observed, corresponding to more than 2 interactions per bunch crossing. The halo targets were used in parallel to the HERA luminosity operation; no significant disturbances of the HERA ep experiments, of the machine stability or beam quality were observed. We present data on the steady-state and transient behaviour of interaction rates and discuss the interpretation in terms of a simple beam dynamics model. Issues of short-, medium- and long-term rate fluctuations and of rate stabilization by feedback are addressed.
An assembly concept of the radiation resistant, direct converting counting X-ray line detector is presented. Special efforts on radiation protection of the sensitive analogue electronics and the ...realization of the arrangement of several sensor modules are discussed.
In this paper an assembly concept of the radiation resistant, direct converting X-ray line detector is presented. In addition to efforts on radiation protection of sensitive electronics, realization ...of arranging several sensor modules is discussed. Furthermore, the electrical behavior of the designed and manufactured GaAs sensors is explained.
Effective from 2005, benefits for long-term unemployed have been reduced in Germany to the level of social assistance. This measure reflects the view that "all who are able to work, should work" - a ...view which makes sense only if the government can distinguish the disabled from the productive. In this paper we augment the standard model of optimal taxation, where the governemnt has no information about individual productivities, by this very assumption: Partial information means that the government can distinguish the disabled from the productive, but cannot distinguish among the different productive types. An interesting proposition about the shape of optimal tax-transfer schemes under partial information is derived. Moreover, it is shown that unemployment on the side of the productive poor may still by optimal.
Online monitoring of dispersion functions and transfer matrices at the SLC
Nuclear instruments and methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment/Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/1990
Journal Article
The inner 10 pc of our Galaxy contains many counterpart candidates of the very high energy (VHE; > 100 GeV) g-ray point source HESS J1745-290. Within the point spread function of the H.E.S.S. ...measurement, at least three objects are capable of accelerating particles to VHE and beyond and of providing the observed g-ray flux. Previous attempts to address this source confusion were hampered by the fact that the projected distances between these objects were of the order of the error circle radius of the emission centroid (34 arcsec, dominated by the pointing uncertainty of the H.E.S.S. instrument). Here we present H.E.S.S. data of the Galactic Centre region, recorded with an improved control of the instrument pointing compared to H.E.S.S. standard pointing procedures. Stars observed during g-ray observations by optical guiding cameras mounted on each H.E.S.S. telescope are used for off-line pointing calibration, thereby decreasing the systematic pointing uncertainties from 20 to 6 arcsec per axis. The position of HESS J1745-290 is obtained by fitting a multi-Gaussian profile to the background-subtracted g-ray count map. A spatial comparison of the best-fitting position of HESS J1745-290 with the position and morphology of candidate counterparts is performed. The position is, within a total error circle radius of 13 arcsec, coincident with the position of the supermassive black hole Sgr A* and the recently discovered pulsar wind nebula candidate G359.95-0.04. It is significantly displaced from the centroid of the supernova remnant Sgr A East, excluding this object with high probability as the dominant source of the VHE g-ray emission.
The inner 10 pc of our Galaxy contains many counterpart candidates of the very high energy (VHE; >100 GeV) γ-ray point source HESS J1745-290. Within the point spread function of the H.E.S.S. ...measurement, at least three objects are capable of accelerating particles to VHE and beyond and of providing the observed γ-ray flux. Previous attempts to address this source confusion were hampered by the fact that the projected distances between these objects were of the order of the error circle radius of the emission centroid (34 arcsec, dominated by the pointing uncertainty of the H.E.S.S. instrument). Here we present H.E.S.S. data of the Galactic Centre region, recorded with an improved control of the instrument pointing compared to H.E.S.S. standard pointing procedures. Stars observed during γ-ray observations by optical guiding cameras mounted on each H.E.S.S. telescope are used for off-line pointing calibration, thereby decreasing the systematic pointing uncertainties from 20 to 6 arcsec per axis. The position of HESS J1745-290 is obtained by fitting a multi-Gaussian profile to the background-subtracted γ-ray count map. A spatial comparison of the best-fitting position of HESS J1745-290 with the position and morphology of candidate counterparts is performed. The position is, within a total error circle radius of 13 arcsec, coincident with the position of the supermassive black hole Sgr A* and the recently discovered pulsar wind nebula candidate G359.95-0.04. It is significantly displaced from the centroid of the supernova remnant Sgr A East, excluding this object with high probability as the dominant source of the VHE γ-ray emission. PUBLICATION ABSTRACT
Recent theoretical predictions of the lowest very high energy (VHE) luminosity of SN 1006 are only a factor 5 below the previously published H.E.S.S. upper limit, thus motivating further in-depth ...observations of this source. Deep observations at VHE energies (above 100 GeV) were carried out with the High Energy Stereoscopic System (H.E.S.S.) of Cherenkov Telescopes from 2003 to 2008. More than 100 hours of data have been collected and subjected to an improved analysis procedure. Observations resulted in the detection of VHE gamma-rays from SN 1006. The measured gamma-ray spectrum is compatible with a power-law, the flux is of the order of 1% of that detected from the Crab Nebula, and is thus consistent with the previously established H.E.S.S. upper limit. The source exhibits a bipolar morphology, which is strongly correlated with non-thermal X-rays. Because the thickness of the VHE-shell is compatible with emission from a thin rim, particle acceleration in shock waves is likely to be the origin of the gamma-ray signal. The measured flux level can be accounted for by inverse Compton emission, but a mixed scenario that includes leptonic and hadronic components and takes into account the ambient matter density inferred from observations also leads to a satisfactory description of the multi-wavelength spectrum.
Were most commoners in ancient Mesoamerica poor? In a material sense, yes, probably so. Were they poor in their beliefs and culture? Certainly not, as Commoner Ritual and Ideology in Ancient ...Mesoamerica demonstrates. This volume explores the ritual life of Mesoamerica's common citizens, inside and outside of the domestic sphere, from Formative through Postclassic periods. Building from the premise that ritual and ideological expression inhered at all levels of society in Mesoamerica, the contributors demonstrate that ideology did not emanate solely from exalted individuals and that commoner ritual expression was not limited to household contexts. Taking an empirical approach to this under-studied and under-theorized area, contributors use material evidence to discover how commoner status conditioned the expression of ideas and values. Revealing complex social hierarchies that varied across time and region, this volume offers theoretical approaches to commoner ideology, religious practice, and sociopolitical organization and builds a framework for future study of the correlation of ritual and ideological expression with social position for Mesoamericanists and archaeologists worldwide.
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