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S. Schael,
R. Barate,
R. Brunelière,
I. De Bonis,
D. Decamp,
C. Goy,
S. Jézéquel,
J.-P. Lees,
F. Martin,
E. Merle, [......],
G.W. Wilson,
J.A. Wilson,
T.R. Wyatt,
S. Yamashita,
D. Zer-Zion,
L. Zivkovic,
S. Heinemeyer,
A. Pilaftsis,
G. Weiglein,
The LEP Working Group for Higgs Boson Searches
[show abstract]
[hide abstract]
ABSTRACT: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by
the Minimal Supersymmetric standard model (MSSM). The data of the four collaborations are statistically combined and examined
for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no
significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper
bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number
of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large
exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses
of neutral Higgs bosons.
European Physical Journal C 04/2012; 47(3):547-587. · 3.63 Impact Factor
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The Collaboration,
P. Achard,
O. Adriani,
M. Aguilar-Benitez,
J. Alcaraz,
G. Alemanni,
J. Allaby,
A. Aloisio,
M. G. Alviggi,
H. Anderhub, [......],
An. Zalite,
Yu. Zalite,
Z. P. Zhang,
J. Zhao,
G. Y. Zhu,
R. Y. Zhu,
H. L. Zhuang,
A. Zichichi, B. Zimmermann,
M. Zöller
[show abstract]
[hide abstract]
ABSTRACT: Bose–Einstein correlations of pairs of identical charged pions produced in hadronic Z decays are analyzed in terms of various
parametrizations. A good description is achieved using a Lévy stable distribution in conjunction with a model where a particle’s
momentum is correlated with its space–time point of production, the τ-model. Using this description and the measured rapidity and transverse momentum distributions, the space–time evolution of
particle emission in two-jet events is reconstructed. However, the elongation of the particle emission region previously observed
is not accommodated in the τ-model, and this is investigated using an adhoc modification.
European Physical Journal C 04/2012; 71(5):1-25. · 3.63 Impact Factor
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R. Rosch,
D. M. Tanenbaum,
M. Jorgensen,
M. Seeland,
M. Barenklau,
M. Hermenau,
E. Voroshazi,
M. T. Lloyd,
Y. Galagan, B. Zimmermann, [......],
G. Teran-Escobar,
M. Lira-Cantu,
A. Rivaton,
G. Y. Uzunoglu,
D. Germack,
B. Andreasen,
M. V. Madsen,
K. Norrman,
H. Hoppe,
F. C. Krebs
[show abstract]
[hide abstract]
ABSTRACT: The investigation of degradation of seven distinct sets (with a number of individual cells of n >= 12) of state of the art organic photovoltaic devices prepared by leading research laboratories with a combination of imaging methods is reported. All devices have been shipped to and degraded at Riso DTU up to 1830 hours in accordance with established ISOS-3 protocols under defined illumination conditions. Imaging of device function at different stages of degradation was performed by laser-beam induced current (LBIC) scanning; luminescence imaging, specifically photoluminescence (PLI) and electroluminescence (ELI); as well as by lock-in thermography (LIT). Each of the imaging techniques exhibits its specific advantages with respect to sensing certain degradation features, which will be compared and discussed here in detail. As a consequence, a combination of several imaging techniques yields very conclusive information about the degradation processes controlling device function. The large variety of device architectures in turn enables valuable progress in the proper interpretation of imaging results-hence revealing the benefits of this large scale cooperation in making a step forward in the understanding of organic solar cell aging and its interpretation by state-of-the-art imaging methods.
Energy & Environmental Science 01/2012; 5(4):6521-6540. · 9.61 Impact Factor
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Y. Galagan, B. Zimmermann,
E. W. C. Coenen,
M. Jørgensen,
D. M. Tanenbaum,
F. C. Krebs,
H. Gorter,
S. Sabik,
L. H. Slooff,
S. C. Veenstra,
J. M. Kroon,
R. Andriessen
[show abstract]
[hide abstract]
ABSTRACT: Indium-tin-oxide (ITO) free polymer solar cells prepared by ink jet printing a
composite front electrode comprising silver grid lines and a semitransparent PEDOT:PSS conductor are demonstrated. The effect of grid line density is explored for a large series of devices and a careful modeling study enabling the identifi cation of the most rational grid structure is presented. Both optical and light beam induced current (LBIC) mapping of the devices are used to support the power loss model and to follow the evolution of the performance over time. Current generation is found to be evenly distributed over the active area initially progressing to a larger graduation in areas with different performance. Over time coating defects also become much more apparent in the LBIC images.
Advanced Energy Materials. 01/2012; 2:103-110.
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M. Aguilar,
J. Alcaraz,
J. Allaby,
B. Alpat,
G. Ambrosi,
H. Anderhub,
L. Ao,
A. Arefiev,
L. Arruda,
P. Azzarello, [......],
Z. P. Zhang,
D. X. Zhao,
F. Zhou,
Y. Zhou,
G. Y. Zhu,
W. Z. Zhu,
H. L. Zhuang,
A. Zichichi, B. Zimmermann,
and P. Zuccon
[show abstract]
[hide abstract]
ABSTRACT: 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.
The Astrophysical Journal 07/2011; 736(2):105. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We report on the fabrication of inverted ITO-free P3HT:PCBM solar cell modules on glass and PET foil as substrate where the organic functional layers are deposited with slot die coating, a reel to reel compatible coating technique. The active layers have been processed in ambient atmosphere, which will be of advantage in a future production and is especially remarkable as the metallic cathode is already deposited on the substrate at this stage of fabrication. The modules comprise two busses of 11 cell elements connected in series each. The series connection leads to an open circuit voltage of up to 6.88 V on glass substrate, which translates to 625 mV per cell element, a very competitive value for P3HT:PCBM based solar cells on glass. Although the designated area is as large as 41 cm2 and the active area 26.4 cm2, we obtain fill factors of up to 65% for these modules, which again is a typical value for small area laboratory cells. Remarkably the values for PET foil as substrate with an open circuit voltage of 6.5 V and a fill factor of 64% are very close to the results on glass and to our knowledge the highest fill factors for flexible organic solar cells, even if compared to small area devices. The short circuit current densities and therefore efficiencies are also comparable to small area devices, if only the photoactive area is accounted for. Therefore we have demonstrated that the scale up of organic solar cells can be achieved with a suited circuitry scheme.
Solar Energy Materials and Solar Cells 01/2011; 95(7):1587 - 1589. · 4.54 Impact Factor
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M. Aguilar,
J. Alcaraz,
J. Allaby,
B. Alpat,
G. Ambrosi,
H. Anderhub,
L. Ao,
A. Arefiev,
L. Arruda,
P. Azzarello, [......],
Z. P. Zhang,
D. X. Zhao,
F. Zhou,
Y. Zhou,
G. Y. Zhu,
W. Z. Zhu,
H. L. Zhuang,
A. Zichichi, B. Zimmermann,
and P. Zuccon
[show abstract]
[hide abstract]
ABSTRACT: 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 Astrophysical Journal 11/2010; 724(1):329. · 6.02 Impact Factor
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International Symposium on Circuits and Systems (ISCAS 2010), May 30 - June 2, 2010, Paris, France; 01/2010
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[show abstract]
[hide abstract]
ABSTRACT: Ultra thin heteroepitaxial PrO2 films on Si(111) were annealed under UHV conditions and investigated by x-ray diffraction (XRD), x-ray reflectometry (XRR) and spot profile analysis low energy electron diffraction (SPALEED) with regard to structural stability and phase transitions due to the high oxygen mobility of the oxide. This gives information about the manageability of the material and its application as a model catalyst system in surface science. While the samples are stable in UHV at room temperature, annealing at 300 °C exhibits a terminated phase transition from PrO2 and PrO2−Δ to cub-Pr2O3 with an increase in the silicate at the interface and a decrease in the crystalline praseodymia layer mainly due to atomic diffusion of silicon into the oxide film. Strain effects during the phase transition also cause mosaic formation at the surface. Further annealing up to 600 °C shows only little change in the film structure. This will finally lead to a model of the film structure during the annealing process.
Journal of Physics Condensed Matter 03/2009; 21(17):175408. · 2.55 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: In expectation of high potentials for cost reduction, many new approaches for thin film solar cell concepts achieved increased attention in the last time. With improving efficiencies, the accurate determination of the solar cell parameters has received growing attention. Calibration laboratories, such as the calibration laboratory of Fraunhofer ISE (ISE CalLab PV Cells), need to develop procedures to determine reliable solar cell parameters of such technologies, in accordance with standard testing conditions (STC, IEC 60904-3). A central requirement is the control of the junction temperature. Many thin film technologies, such as organic solar cells, need to be encapsulated in order to protect the material from environmental influences. This means that the junction temperature cannot be determined by direct probing, and other methods are required. If the solar cell is additionally affected by light soaking, the VOC-method also cannot be performed to determine the junction temperature. Model calculations were performed to predict the spatial and temporal distributions of changes in the temperature of an encapsulated thin film layer. These are confirmed by experiments with specially prepared organic solar cells that also contained a temperature sensor and by infrared recordings. Further experiments to understand the nature of light soaking and investigate the use of the VOC-method were performed.
Proceedings of the 24th European Photovoltaic Solar Energy ConferenceProceedings of the 24th European Photovoltaic Solar Energy Conference, Hamburg, Germany; 01/2009
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P. Achard,
O Adriani,
M. Aguilar-Benitez,
M. van den Akker,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
H Anderhub, [......],
J Zhao,
S J Zhou,
G Y Zhu,
R Y Zhu,
Q. Q. Zhu,
H L Zhuang,
A. Zichichi, B. Zimmermann,
M. Zoeller,
A. N. M. Zwart
[show abstract]
[hide abstract]
ABSTRACT: Context. Primary cosmic rays experience multiple deflections in the non-uniform galactic and heliospheric magnetic fields which may generate anisotropies. Aims. A study of anisotropies in the energy range between 100 and 500 GeV is performed. This energy range is not yet well explored. Methods. The L3 detector at the CERN electron-positron collider, LEP, is used for a study of the angular distribution of atmospheric muons with energies above 20 GeV. This distribution is used to investigate the isotropy of the time-dependent intensity of the primary cosmic-ray flux with a Fourier analysis. Results. A small deviation from isotropy at energies around 200 GeV is observed for the second harmonics at the solar frequency. No sidereal anisotropy is found at a level above 10(-4). The measurements were performed in the years 1999 and 2000.
Astronomy and Astrophysics 03/2008; 488:1093-1100. · 4.59 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We report on the development of two types of organic solar cell modules one for energy autonomous systems and one for large area energy harvesting. The first requires a specific tailoring of the solar cell geometry and cell interconnection in order to power an energy autonomous system under its specific operating conditions. We present an organic solar cell module with 22 interconnected solar cells. A power conversion efficiency of 2% under solar illumination has been reached on the active area of 46.2 cm(2). A voltage of 4 V at the maximum power point has been obtained under indoor illumination conditions. Micro contact printing of a self assembling monolayer was employed for the patterning of the polymer anode.
Large area photovoltaic modules have to meet the requirements on efficiency, lifetime and costs simultaneously. To minimize the production costs, a suitable concept for efficient reel-to-reel production of large area modules is needed. A major contribution to reduce the costs is the substitution of the commonly used indium tin oxide electrode by a cheap material. We present the state of the art of the anode wrap through concept as a reel-to-reel suited module concept and show comparative calculations of the module interconnection of the wrap through concept and the standard ITO-based cell architecture. As a result, the calculated overall module efficiency of the anode wrap through module exceeds the overall efficiency of modules based on ITO on glass (sheet resistance 15 Omega/square) and on foils (sheet resistance 60 Omega/square). (c) 2007 Elsevier B.V. All rights reserved.
Thin Solid Films 01/2008; 516(20):7181-7187. · 1.89 Impact Factor
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P. Achard,
O. Adriani,
M. Aguilar-Benitez,
J. Alcaraz,
G. Alemanni,
J. Allaby,
A. Aloisio,
M.G. Alviggi,
H. Anderhub,
V.P. Andreev, [......],
Y. Zalite,
Z.P. Zhang,
J. Zhao,
G.Y. Zhu,
R.Y. Zhu,
H.L. Zhuang,
A. Zichichi, B. Zimmermann,
M. Zöller,
The Collaboration
[show abstract]
[hide abstract]
ABSTRACT: Measurements of inclusive production of the Λ, Ξ- and Ξ*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections
for Λ and Ξ- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, η. The mean number of Λ, Ξ- and Ξ*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4GeV<pt<2.5GeV, |η|<1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive
production of the pentaquark θ+(1540) in two-photon collisions through the decay θ+→pK0
S is also presented. No evidence for production of this state is found.
European Physical Journal C 12/2006; 49(2):395-410. · 3.63 Impact Factor
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P. Achard,
O Adriani,
M Aguilar-Benítez,
M. van den Akker,
J Alcaraz,
G. Alemanni,
James V Allaby,
A Aloisio,
M G Alviggi,
H Anderhub, [......],
J Zhao,
S J Zhou,
G Y Zhu,
R Y Zhu,
Q. Q. Zhu,
H L Zhuang,
A. Zichichi, B. Zimmermann,
M Zöller,
A. N. M. Zwart
[show abstract]
[hide abstract]
ABSTRACT: Several experiments have reported observations on possible correlations between the flux of high energy muons and intense solar flares. If confirmed, these observations would have significant implications for acceleration processes in the heliosphere able to accelerate protons and other ions to energies of at least tens of GeV. The solar flare of the 14 July 2000 offers a unique opportunity for the L3+C experiment to search for a correlated enhancement in the flux of muons using the L3 precision muon spectrometer. Its capabilities for observing a directional excess in the flux of muons above 15 GeV (corresponding to primary proton energies above 40 GeV) are presented along with observations made on the 14th of July 2000. We report an excess which appeared at a time coincident with the peak increase of solar protons observed at lower energies. The probability that the excess is a background fluctuation is estimated to be 1%. No similar excess of the muon flux was observed up to 1.5 hours after the solar flare time.
Astronomy and Astrophysics 11/2006; 456:351-357. · 4.59 Impact Factor
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P. Achard,
O Adriani,
M. Aguilar-Benitez,
M. van den Akker,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
H Anderhub, [......],
J Zhao,
S J Zhou,
G Y Zhu,
R Y Zhu,
Q. Q. Zhu,
H L Zhuang,
A. Zichichi, B. Zimmermann,
M Zöller,
A. N. M. Zwart
[show abstract]
[hide abstract]
ABSTRACT: Aims.Several experiments have reported observations on possible correlations between the flux of high energy muons and intense solar flares. If confirmed, these observations would have significant implications for acceleration processes in the heliosphere able to accelerate protons and other ions to energies of at least tens of GeV. Methods: .The solar flare of the 14 of July 2000 offered a unique opportunity for the L3+C experiment to search for a correlated enhancement in the flux of muons using the L3 precision muon spectrometer. Its capabilities for observing a directional excess in the flux of muons above 15 GeV (corresponding to primary proton energies above 40 GeV) are presented along with observations made on the 14th of July 2000. Results: .We report an excess which appeared at a time coincident with the peak increase of solar protons observed at lower energies. The probability that the excess is a background fluctuation is estimated to be 1%. No similar excess of the muon flux was observed up to 1.5 h after the solar flare time.
Astronomy and Astrophysics 05/2006; 456:351-357. · 4.59 Impact Factor
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P. Achard,
O Adriani,
M. Aguilar-Benitez,
M. van den Akker,
J Alcaraz,
G. Alemanni,
J. Allaby,
A Aloisio,
M G Alviggi,
H Anderhub, [......],
J Zhao,
S J Zhou,
G Y Zhu,
R Y Zhu,
Q. Q. Zhu,
H L Zhuang,
A. Zichichi, B. Zimmermann,
M. Zoller,
A. N. M. Zwart
[show abstract]
[hide abstract]
ABSTRACT: The L3+C muon detector at the CERN electron-positron collider, LEP, is used for the detection of very-high-energy cosmic gamma-ray sources through the observation of muons of energies above 20, 30, 50 and 100 GeV. Daily or monthly excesses in the rate of single-muon events pointing to some particular direction in the sky are searched for. The periods from mid July to November 1999, and April to November 2000 are considered. Special attention is also given to a selection of known gamma-ray sources. No statistically significant excess is observed for any direction or any particular source. (c) 2006 Elsevier B.V. All rights reserved.
Astroparticle Physics 03/2006; 25:298-310. · 3.22 Impact Factor
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P. Achard,
O. Adriani,
M. Aguilar-Benitez,
M. van den Akker,
J. Alcaraz,
G. Alemanni,
J. Allaby,
A. Aloisio,
M.G. Alviggi,
H. Anderhub, [......],
J. Zhao,
S.J. Zhou,
G.Y. Zhu,
R.Y. Zhu,
Q.Q. Zhu,
H.L. Zhuang,
A. Zichichi, B. Zimmermann,
M. Zöller,
A.N.M. Zwart
[show abstract]
[hide abstract]
ABSTRACT: The L3+C muon detector at the CERN electron–positron collider, LEP, is used for the detection of very-high-energy cosmic γ-ray sources through the observation of muons of energies above 20, 30, 50 and 100 GeV. Daily or monthly excesses in the rate of single-muon events pointing to some particular direction in the sky are searched for. The periods from mid July to November 1999, and April to November 2000 are considered. Special attention is also given to a selection of known γ-ray sources. No statistically significant excess is observed for any direction or any particular source.
Astroparticle Physics 03/2006; 25:298-310. · 3.22 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Be-like Ag43+, Sn46+, and Xe50+ ions were produced by beam-foil excitation at the UNILAC accelerator of the GSI. The wavelengths of the 2s2 1S0–2s2p 3P1 intercombination lines were measured using the GSI 5 m grazing incidence spectrometer. The projectile spectra were calibrated in situ with well known ionic lines of a VUV Penning discharge lamp. A precise determination of the Doppler shift was necessary. An experimental precision of 10-4 was realized. Our medium-Z experimental results represent the heaviest Be-like ions studied. They are compared with published MCDF and MBPT calculations along the isoelectronic Be-like series. Excellent agreement exists between our Xe-value and a recent result from an electron beam ion trap.
Physica Scripta 01/2006; 71(1):48. · 1.20 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The production process of organic solar cells (OSCs) is investigated and the effects of parameter variations on experimental results are analysed with the Principal Component Analysis (PCA). This statistical method is applied to an exemplar data set, in which the materials' concentration in the absorber solution and the spincoating speed of the absorber solution were varied intentionally. In addition to the remaining production parameters, the time intervals between the steps were included in the analysis. A large part of the variance in the experimental results can be explained with the evaporation conditions, the spincoating speed and the concentrations in the absorber solution. The PCA also confirms that the OSC is a complex and interdependent system, where one has to analyse the influence of several parameters at the same time in order to understand their effects on the OSC properties. The PCA results will be used to focus further experiments on the identified key parameters.
Photonics for Solar Energy Systems. 01/2006; 6197:H1970-H1970.
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[show abstract]
[hide abstract]
ABSTRACT: We investigated organic bulk-heterojunction solar cells based on an absorber blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) by electrical impedance spectroscopy (EIS). A strong neck in the modulus plot of the EIS-spectra indicates that the absorber is divided into two regions of different conductivities. A similar behaviour was observed for pure P3HT-diodes. Hence, it can be concluded that the PCBM:P3HT absorber is p-doped by impurities of P3HT, so that a Schottky-like contact with aluminium is formed. It is known from literature, that annealing of PCBM:P3HT solar cells leads to drastic improvement of the photovoltaic performance. We compared the current-voltage characteristics and impedance spectra before and after consecutive annealing steps. After the annealing an expansion of the depletion region was observed, indicating that volatile dopants were evaporated out of the absorber. This contributes to an improved photovoltaic performance as the separation of the generated charges in the depletion region is more efficient than in the non-depleted region. Also an improved rectification behaviour might be caused by a lower doping level.
Organic Optoelectronics and Photonics II. 01/2006; 6192:V1921-V1921.
