Status of AMS-TRD-Straw modules Kirn, Th; Chung, C.H.; Dömmecke, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2004, Letnik:
522, Številka:
1
Journal Article
Recenzirano
The AMS02 experiment will be installed on the International Space Station for a data taking period of 3 years. The TRD consists of 20 layers of straw modules and fleece radiator with a total of 328 ...modules (16 straws each). The housing consists of a conically shaped octagon structure made out of CFC-Al-honeycomb material and is closed by a lower and upper honeycomb plate. The gas is a 80:20 Xe/CO
2 mixture. The straw modules will be operated in proportional mode at a gasgain of 3000. The signals are readout by VA chips. The detector is under construction at RWTH Aachen, the gas system will be built at MIT, slow-control at INFN Rome and DAQ at TH Karlsruhe. In the presentation special emphasis will be dedicated to the space qualification aspects and the status of the straw module production.
The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight STS-91 (June 1998) in a 51.7° orbit at altitudes between 320 and.A search for antihelium nuclei in the ...rigidity range 1–was performed. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of <1.1×10−6 was obtained.The high energy proton, electron, positron, helium, antiproton and deuterium spectra were accurately measured.For each particle and nuclei two distinct spectra were observed: a higher energy spectrum and a substantial second spectrum. Positrons in the second spectrum were found to be much more abundant than electrons. Tracing particles from the second spectra shows that most of them travel for an extended period of time in the geomagnetic field, and that the positive particles (p and e+) and negative ones (e−) originate from two complementary geographic regions. The second helium spectrum flux over the energy range 0.1–was measured to be . Over 90 percent of the helium flux was determined to be at the 90% confidence level. (Elsevier)
Measurement of the chemical and isotopic composition of cosmic rays is essential for the precise understanding of their propagation in the galaxy. While the model parameters are mainly determined ...using the B/C ratio, the study of extended sets of ratios can provide stronger constraints on the propagation models. In this paper, the relative abundances of light-nuclei lithium, beryllium, boron, and carbon are presented. The secondary-to-primary ratios Li/C, Be/C, and B/C have been measured in the kinetic energy range 0.35-45 GeV nucleon--1. The isotopic ratio 7Li/6Li is also determined in the magnetic rigidity interval 2.5-6.3 GV. The secondary-to-secondary ratios Li/Be, Li/B, and Be/B are also reported. These measurements are based on the data collected by the Alpha Magnetic Spectrometer AMS-01 during the STS-91 space shuttle flight in 1998 June. Our experimental results are in substantial agreement with other measurements, where they exist. We describe our light-nuclei data with a diffusive-reacceleration model. A 10%-15% overproduction of Be is found in the model predictions and can be attributed to uncertainties in the production cross-section data.
The variety of isotopes in cosmic rays allows us to study different aspects of the processes that cosmic rays undergo between the time they are produced and the time of their arrival in the ...heliosphere. In this paper, we present measurements of the isotopic ratios 2H/4He, 3He/4He, 6Li/7Li, 7Be/(9Be+10Be), and 10B/11B in the range 0.2-1.4 GeV of kinetic energy per nucleon. The measurements are based on the data collected by the Alpha Magnetic Spectrometer, AMS-01, during the STS-91 flight in 1998 June.
Gallioaluminosilicate hydrogels with composition 0.1 Ga2O3:0.9 Al2O3:10 SiO2:4.0 Na2O:150 H2O were prepared using sodium aluminate, colloidal silica, and a soluble galliosilicate with composition ...Ga2O3:15 SiO2:10 Na2O:400 H2O as a source of gallia. The hydrothermal transformation of these gels at 95°C yields crystals with the faujasite structure when the crystallization reaction is performed in the absence of stirring and with the gmelinite structure (with minor amount of Pt) when crystallization is completed with stirring of the hydrogel. The crystallization time for Na(Ga,Al)Y can be decreased to 15 h from 48 h by raising the crystallization temperature to 110°C from 95°C. The calcined Na(Ga,Al)Y crystals have surface area in the 600 to 660 m2/g range and, unless La-stabilized, suffer partial lattice degradation when, following an exchange with an NH4NO3 solution, the NH4(Ga,Al)Y crystals are calcined at 500°C in air. This finding is clearly indicated by 27Al, 71Ga, and 29Si MAS NMR spectroscopic results. The 29Si NMR spectra of samples exchanged and calcined in the absence of La are poorly resolved and their quantitative analysis indicates substantial loss of Al and Ga from the faujasite framework. Consistent with this interpretation, 27Al MAS NMR spectra reveal large amounts of octahedrally coordinated species in H(Ga,Al)Y. Moreover, the 71Ga spectra show no evidence of tetrahedrally coordinated framework Ga. In contrast, the multinuclear NMR data of the H(Ga,Al,La)Y crystals indicate only minor Al and Ga losses from the framework, thus revealing the stabilizing influence of La. Thermodesorption of pyridine and microcalorimetry results with NH3 have indicated that the La-stabilized H(Ga,Al,La)Y crystals have a more moderate acidity than the reference HY sample. Model fluid cracking catalyst (FCC)-containing H(Ga,Al,La)Y crystals are more active when cracking gas oil under microactivity testing conditions than similarly prepared FCC-containing HY-type zeolites and a reference equilibrium catalyst containing a rare-earth-stabilized HY, indicating that these crystals should be considered as acidic components in commercial FCC preparations.
Überlegungen zum Managementkonzept der Lernenden Organisation nehmen seit Jahren einen breiten Raum in Wissenschaft und Praxis ein. Dabei avancierte das Konzept zum Hoffnungsträger für die Steigerung ...der Innovations- und Wettbewerbsfähigkeit von Unternehmen. Mittlerweile weist eine Reihe von Befunden daraufhin, dass es bei der Umsetzung der theoretischen Überlegungen in die Praxis zu großen Schwierigkeiten kommt. Während von wissenschaftlicher Seite häufig die Praktiker für Umsetzungsprobleme verantwortlich gemacht werden, deutet einiges auf fundamentalere Mängel im Konzept der Lernenden Organisation hin. In dem angefügten Beitrag werden zwei zentrale Missverständnisse herausgearbeitet.
Purpose - To highlight an unconventional way out of the "innovation dilemma," relevant to many business organizations, innovative management and risk friendliness are necessary, but the way in which ...failure is handled and the resulting fear of making mistakes block the (innovative) efforts of specialists and managers.Design methodology approach - The paper draws on theoretical as well as empirical work: first, the seemingly crystal-clear concept of "error" is elaborated and the rare category of "creative errors" is introduced. Second, illustrative findings from a case study in the automotive sector are reported.Findings - Suggests that a culturally exacerbated antipathy towards errors leads ultimately to a situation of pronounced innovational incompetence in which creative behavior is avoided. Points out, that not an "absolution of mistakes" is required, but a tolerance for legitimate errors which should only occur under exceptional circumstances. Underlines, that fairness in dealing with errors is considerably more important than a misguided attempt to create or maintain harmony. In addition to the philosophy and potential of this unusual incentive system, possible practical implementation problems are considered.Research limitations implications - Generalization is limited because the findings are based on only one case study. However, because of the vital importance of the so-called "innovation dilemma,," the exploratory findings of the study may trigger further empirical research on "creative errors."Practical implications - An initiative like the "Creative Error of the Month" may help to bring about cultural change towards a climate of trust and confidence in which innovative commitment is treated fairly even if it does not in fact succeed.Originality value - Common approaches to enhance organizational innovativeness reward "success stories" or praise "zero-based cultures." This case study suggests that a sophisticated initiative revolving around the "hidden" innovative potential of "creative errors" and "tragic failures" might prove to be a successful off-beat attempt at stimulating creativity and innovative behavior in enterprises.
The hydrothermal transformation at 95°C of galliosilicate hydrogels with molar oxide composition Ga
2O
3 : 10SiO
2 : 4.5 Na
2O : 150 H
2O, prepared from colloidal silica and sodium gallate mixtures, ...yields crystals with the faujasite or natrolite structure if the crystallization reaction is performed in the absence or presence of stirring. Raising the crystallization temperature to 150°C causes the formation of analcime crystals. Moreover, when 10% of the hydrogel Ga
2O
3 content is added in the form of a seeding solution with composition Ga
2O
3 : 15SiO
2 : 10 Na
2O : 400 H
2O, the crystallization time for GaY formation decreases by about 50% and Ga incorporation in the crystals increases. In either case, the crystallization reaction is not stoichiometric and the crystals' silica to gallia molar ratio (SGR) is always less then that in the parent hydrogel. The calcined GaY crystals have surface areas in the 500–550
m
2
g
−1 range and, for a given hydrogel composition, the SGR decreases to 3.7 from 4.4 when a seeding solution is used. The thermal stability of GaY can be drastically increased by the introduction of rare earth ions such as La. In fact,
71Ga MAS NMR spectra have shown that in both GaY and H(Ga,La)Y, no extraframework Ga(VI) species are present. In addition,
29Si NMR spectra yield an SGR molar ratio in agreement with chemical analysis. FTIR results from pyridine thermodesorption, together with microcalorimetry experiments with NH
3, indicate that the isomorphous substitution of Al with Ga in the faujasite framework reduces acid site strength, density and distribution.
The primary proton spectrum in the kinetic energy range 0.2 to 200 GeV was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS–91 at an altitude of 380 km. The complete ...data set combining three shuttle attitudes and including all known systematic effects is presented.
Leptons in near earth orbit Ambrosi, G.; Ao, L.; Arefiev, A. ...
Physics letters. B,
06/2000, Letnik:
484, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The lepton spectra in the kinetic energy ranges 0.2 to 40 GeV for e
− and 0.2 to 3 GeV for e
+ were measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS–91 at altitudes ...near 380
km. From the origin of the leptons two distinct spectra were observed: a higher energy spectrum and a substantial second spectrum with positrons much more abundant than electrons. Tracing leptons from the second spectra shows that most of these leptons travel for an extended period of time in the geomagnetic field and that the e
+ and e
− originate from two complementary geographic regions.
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