| 1. |
- Adcox, K, et al.
(författare)
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PHENIX detector overview
- 2003
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 499:2-3, s. 469-479
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX detector is designed to perform a broad study of A-A, p-A, and p-p collisions to investigate nuclear matter under extreme conditions. A wide variety of probes, sensitive to all timescales, are used to study systematic variations with species and energy as well as to measure the spin structure of the nucleon. Designing for the needs of the heavy-ion and polarized-proton programs has produced a detector with unparalleled capabilities. PHENIX measures electron and muon pairs, photons, and hadrons with excellent energy and momentum resolution. The detector consists of a large number of subsystems that are discussed in other papers in this volume. The overall design parameters of the detector are presented. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 2. |
- Adler, SS, et al.
(författare)
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Bose-Einstein correlations of charged pion pairs in Au+Au collisions at root(NN)-N-s = 200 GeV
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:15
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Tidskriftsartikel (refereegranskat)abstract
- Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au+Au collisions at roots(NN)=200 GeV. The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision. Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R-out/R-side is within 0.8-1.1 for 0.25<<1.2 GeV/c. The centrality dependence of all radii is well described by a linear scaling in N-part(1/3), and R-out/R-side for similar to0.45 GeV/c is approximately constant at unity as a function of centrality.
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| 3. |
- Adler, SS, et al.
(författare)
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Elliptic flow of identified hadrons in Au+Au collisions at root s(NN)=200 GeV
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:18: 182301
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Tidskriftsartikel (refereegranskat)abstract
- The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at roots(NN)=200 GeV for identified and inclusive charged particle production at central rapidities (eta<0.35) with respect to the reaction plane defined at high rapidities (eta=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.
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| 4. |
- Adler, SS, et al.
(författare)
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J/psi production from proton-proton collisions at root s=200 GeV
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 92:5
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Tidskriftsartikel (refereegranskat)abstract
- J/psi production has been measured in proton-proton collisions at roots=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mub. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.
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| 5. |
- Adler, SS, et al.
(författare)
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J/psi production in Au-Au collisions at root s(NN)=200 GeV
- 2004
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 69:1
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Tidskriftsartikel (refereegranskat)abstract
- First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/psi's measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au-Au reactions at roots(NN) = 200 GeV is analyzed as a function of collision centrality. For this analysis we have studied 49.3x10(6) minimum bias Au-Au reactions. We present the J/psi invariant yield dN/dy for peripheral and midcentral reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits. We compare these results with our J/psi measurement from proton-proton reactions at the same energy. We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.
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| 6. |
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| 7. |
- Adler, SS, et al.
(författare)
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Scaling properties of proton and antiproton production in root s(NN)=200 GeV Au+Au collisions
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:17: 172301
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Tidskriftsartikel (refereegranskat)abstract
- We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at rootS(NN)=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5
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| 8. |
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| 9. |
- Adcox, K, et al.
(författare)
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PHENIX central arm tracking detectors
- 2003
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 499:2-3, s. 489-507
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX tracking system consists of Drift Chambers (DC), Pad Chambers (PC) and the Time Expansion Chamber (TEC). PC1/DC and PC2/TEC/PC3 form the inner and outer tracking units, respectively. These units link the track segments that transverse the RICH and extend to the EMCal. The DC measures charged particle trajectories in the r-phi direction to determine P-T of the particles and the invariant mass of particle pairs. The PCs perform 3D spatial point measurements for pattern recognition and longitudinal momentum reconstruction and provide spatial resolution of a few mm in both r-phi and z. The TEC tracks particles passing through the region between the RICH and the EMCal. The design and operational parameters of the detectors are presented and running experience during the first year of data taking with PHENIX is discussed. The observed spatial and momentum resolution is given which imposes a limitation on the identification and characterization of charged particles in various momentum ranges. (C) 2002 Published by Elsevier Science B.V.
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| 10. |
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| 11. |
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| 12. |
- Du, Chun-Xia, et al.
(författare)
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Efficient 1.54 µm light emission from Si/SiGe/Si : Er
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 81:1-3, s. 105-108
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Tidskriftsartikel (refereegranskat)abstract
- Si/SiGe/Si:Er:O-heterojunction bipolar transistor (HBT)-type light emitting devices with Er3+ ions incorporated in the collector region have been fabricated using layered structures prepared by differential molecular beam epitaxy (MBE). Intense light emission at 1.54 µm has been observed at room temperature by hot electron impact excitation at rather low injection current and applied voltage. Separate controls of the injection current and bias voltage make it possible to perform detailed electroluminescence (EL) studies that can not be done with conventional Si:Er light emitting diodes (LEDs). Saturation of the EL intensity occurs at very low current densities indicating a 100-fold increase of the effective excitation cross-section for Si/SiGe/Si:Er:O-HBTs compared with Si:Er-LEDs. © 2001 Elsevier Science B.V.
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| 13. |
- Du, Chun-Xia, et al.
(författare)
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Electroluminescence studies of Er and SiO co-doped Si layers prepared by molecular beam epitaxy
- 2000
-
Ingår i: Optical materials (Amsterdam). - 0925-3467 .- 1873-1252. ; 14:3, s. 259-265
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Tidskriftsartikel (refereegranskat)abstract
- Er/O co-doped Si light emitting diodes (LEDs) have been fabricated using layer structures prepared by molecular beam epitaxy (MBE). The Er/O doping was realized by sublimation of elemental Er and silicon monoxide simultaneously with Si during MBE growth. Intense Er-related electroluminescence (EL) at 1.54 mu m was observed at room temperature from p(+)-SiGe/i-SiGe-Si/Si:Er/n(+)-Si LEDs by electron impact excitation under reverse bias. It has been found that the EL intensity was increased with increasing growth temperature of the Si:Er/O layer in the range of 430-575 degrees C. The electrical pumping power dependence of EL intensity has been studied. An excitation cross section value of similar to 1 x 10(-16) cm(2) was estimated based on the experimental data and model fitting. The EL decay behavior under various injection and bias conditions has been studied by time-resolved EL measurements. The overall luminescence decay time is found to strongly depend on the injection parameters. Two types of de-excitation mechanisms due to Auger energy transfer to free carriers introduced by either dopant ionization or carrier injection have been discussed. Both Auger processes play an important role in reduction of the EL intensity when there is a high density of carriers with excited Er ions. (C) 2000 Elsevier Science B.V. All rights reserved.
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| 14. |
- Du, Chun-Xia, et al.
(författare)
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Si/SiGe/Si : Er
- 2001
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:12, s. 1697-1699
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Tidskriftsartikel (refereegranskat)abstract
- Si/SiGe/Si:Er:O heterojunction bipolar transistor (HBT) type light-emitting devices with Er3+ ions incorporated in the collector region have been fabricated using a layered structure grown by differential molecular-beam epitaxy. Electroluminescence measurements on processed light-emitting HBTs can be performed in either constant driving current mode or constant applied bias mode, which is an important advantage over conventional Si:Er light-emitting diodes. Intense room-temperature light emission at the Er3+ characteristic wavelength of 1.54 µm has been observed at low driving current density, e.g., 0.1 A cm-2, and low applied bias, e.g., 3 V, across the collector and emitter. © 2001 American Institute of Physics.
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| 15. |
- du Rietz, Rickard, et al.
(författare)
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Effective Charges in the fp Shell
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:22
-
Tidskriftsartikel (refereegranskat)abstract
- Following the heavy-ion fusion-evaporation reaction S-32+Mg-24 at 95 MeV beam energy the lifetimes of analogue states in the T-z=+/-1/2 A=51 mirror nuclei Fe-51 and Mn-51 have been measured using the Cologne plunger device coupled to the GASP gamma-ray spectrometer. The deduced B(E2;27/2(-)-->23/2(-)) values afford a unique opportunity to probe isoscalar and isovector polarization charges and to derive effective proton and neutron charges, epsilon(p) and epsilon(n), in the fp shell. A comparison between the experimental results and several different large-scale shell-model calculations yields epsilon(p)similar to1.15e and epsilon(n)similar to0.80e.
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| 16. |
- Duteil, F., et al.
(författare)
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Er/O doped Si1-xGex alloy layers grown by MBE
- 2001
-
Ingår i: Optical materials (Amsterdam). - 0925-3467 .- 1873-1252. ; 17:1-2, s. 131-134
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Silicon-based light emitting diodes (LEDs) containing an Er/O-doped Si1-xGex active layer have been studied. The structures were grown by molecular beam epitaxy (MBE), with Er and O concentrations of 5 × 1019 and 1 × 1020 cm-3, respectively, using Er and silicon monoxide sources. The microstructure has been studied by X-ray diffraction (XRD) and cross-sectional transmission electron microscopy, and it is found that Er/O-doped Si0.92Ge0.08 layers of high crystalline quality, can be obtained. Electroluminescence (EL) measurements have been performed on reverse-biased Er/O doped diodes both from the surface and from the edge and the emission at 1.54 µm associated with the Er3+ ions has been studied at 300 K and lower temperatures. To evaluate the possibility to use a Si1-xGex layer for waveguiding in Si-based optoelectronics, studies of the refractive index n of strained Si1-xGex as a function of the Ge concentration have been done by spectroscopic ellipsometry in the range 0.3-1.7 µm. At 1.54 µm the refractive index increases monotonically with the Ge concentration up to n = 3.542 for a Ge concentration of 21.3%. © 2001 Elsevier Science B.V.
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| 17. |
- Duteil, F., et al.
(författare)
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Luminescence and microstructure of Er/O co-doped Si structures grown by MBE using Er and SiO evaporation
- 2000
-
Ingår i: Materials Science in Semiconductor Processing. - 1369-8001 .- 1873-4081. ; 3:5-6, s. 523-528
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Tidskriftsartikel (refereegranskat)abstract
- Er and O co-doped Si structures have been prepared using molecular-beam epitaxy (MBE) with fluxes of Er and O obtained from Er and silicon monoxide (SiO) evaporation in high-temperature cells. The incorporation of Er and O has been studied for concentrations of up to 2×1020 and 1×1021 cm-3, respectively. Surface segregation of Er can take place, but with O co-doping the segregation is suppressed and Er-doped layers without any indication of surface segregation can be prepared. Si1-xGex and Si1-yCy layers doped with Er/O during growth at different substrate temperatures show more defects than corresponding Si layers. Strong emission at 1.54µm associated with the intra-4f transition of Er3+ ions is observed in electroluminescence (EL) at room temperature in reverse-biased p-i-n-junctions. To optimize the EL intensity we have varied the Er/O ratio and the temperature during growth of the Er/O-doped layer. Using an Er-concentration of around 1×1020 cm-3 we find that Er/O ratios of 1:2 or 1:4 give higher intensity than 1:1 while the stability with respect to breakdown is reduced for the highest used O concentrations. For increasing growth temperatures in the range 400-575 °C there is an increase in the EL intensity. A positive effect of post-annealing on the photoluminescence intensity has also been observed.
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| 18. |
- Hansson, Göran, et al.
(författare)
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Origin of abnormal temperature dependence of electroluminescence from Er/O-doped Si diodes
- 2001
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 78:15, s. 2104-2106
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Tidskriftsartikel (refereegranskat)abstract
- The temperature dependencies of the current-voltage characteristics and the electroluminescence (EL) intensity of molecular beam epitaxy grown Er/O-doped Si light emitting diodes at reverse bias have been studied. To minimize the scattering of electrons injected from the p-doped Si1-xGex electron emitters, an intrinsic Si layer was used in the depletion region. For many diodes, there is a temperature range where the EL intensity increases with temperature. Data are reported for a structure that shows increasing intensity up to 100°C. This is attributed to an increasing fraction of the pumping current being due to phonon-assisted tunneling, which gives a higher saturation intensity, compared to ionization-dominated breakdown at lower temperatures. © 2001 American Institute of Physics.
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| 19. |
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| 20. |
- Ni, Wei-Xin, et al.
(författare)
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1.54 µm light emitting devices based on Er/O-doped Si layered structures grown by molecular beam epitaxy
- 2001
-
Ingår i: Optical materials (Amsterdam). - 0925-3467 .- 1873-1252. ; 17:1-2, s. 65-69
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Two types of Si:Er light emitting devices have been processed and characterized with an aim to efficiently use hot electrons for impact excitation. One is a p+-SiGe/i-Si/n-Si:Er:O/n+-Si tunneling diode with a design favoring electron tunneling from the SiGe valence band to the Si conduction band and subsequent acceleration. Another type of Si:Er light emitters is based on a heterojunction bipolar transistor (HBT) structure containing an Er-doped active layer in the collector. In these devices, one can introduce hot electrons from the HBT emitter in a controlled way with a collector bias voltage prior to the avalanche breakdown to improve the impact excitation efficiency. Intense electroluminescence was observed at 300 K at low current (0.1 A cm-2) and low bias (3 V). An impact cross-section value of 1 × 10-14 cm2 has been estimated, which is a 100-fold increase compared with the values reported from any other type of Er-doped LEDs. © 2001 Elsevier Science B.V.
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| 21. |
- Ni, Wei-Xin, et al.
(författare)
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Light emitting SiGe/i-Si/Si : Er
- 2000
-
Ingår i: Thin Solid Films. - 0040-6090 .- 1879-2731. ; 369:1, s. 414-418
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Tidskriftsartikel (refereegranskat)abstract
- p+-SiGe/i-Si/n-Si:Er:O/n+-Si tunneling diodes have been processed using layer structures prepared by molecular beam epitaxy (MBE). Electroluminescence has been observed at room temperature from these devices at reverse bias. The devices have been used for characterizing the optical activation of Er3+ ions in MBE Si:Er:O layers grown at different conditions. In the range of 400-575 °C, a high substrate temperature is favored for formation of Er emission centers, but this is limited by the silicidation process occurring above 600 °C. Several important device parameters such as the impact excitation cross section and various EL decay processes have been carefully studied. A fast decay (approximately 4 µs) due to the Auger carrier transfer process is observed.
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| 22. |
- Nurni, Viswanathan, et al.
(författare)
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Viscosity measurements on some fayalite slags
- 2001
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 41:7, s. 722-727
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, viscosity measurements on Fe-O-Si slags have been carried out using rotating cylinder method. The slag samples for viscosity measurement were prepared by pre-melting appropriate stoichiometric amounts of Fe, Fe2O3 and SiO2 in an iron crucible under argon atmosphere, which ensured that Fe ions in the slag were predominantly in the valence state of +2. The viscosities of the pre-melted slag samples were measured in iron as well as nickel crucibles under argon atmosphere at different temperatures. The measured viscosity values obtained in the two kinds of crucibles were found to be in good agreement, indicating thereby that nickel crucibles can be successfully used for viscosity measurements. In order to investigate the effect of oxidation of Fe2+ to Fe3+, the binary FenO-SiO2 slag was kept in a nickel crucible under oxidising conditions using a CO/CO2 atmosphere and viscosity measurements were carried out dynamically as a function of time at 1 623 and 1 673 K. With time, Fe3+ concentration in the slag increased and hence the viscosity changed progressively. The rate controlling step for the oxidation reaction was considered to be the mass transfer of CO, in the gas stream to the slag-gas interface. A simple kinetic analysis was used to predict the concentration of Fe3+ in the slag with time, The measured viscosity with time indicated that the viscosity remains almost the same during initial period of oxidation. The viscosity raises sharply when the Fe3+ concentration in the slag, calculated as Fe2O3 reached around 7 mass%.
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| 23. |
- Seetharaman, Seshadri, et al.
(författare)
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Estimation of viscosities of ternary silicate melts using the excess Gibbs energy of mixing
- 2000
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Ingår i: Metallurgical and Materials Transactions. A. - : Springer Science and Business Media LLC. - 1073-5623 .- 1543-1940 .- 1073-5615 .- 1543-1916. ; 31:1, s. 105-109
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Tidskriftsartikel (refereegranskat)abstract
- A correlation to predict the viscosities of ternary Silicates using the Gibbs energies of mixing of the silicate melts has been developed. This correlation has been employed to predict the viscosities of liquid slags in the systems FeO-MnO-SiO2, FeO-MgO-SiO2, CaO-FeO-SiO2, CaO-MnO-SiO2, and CaO-MgO-SiO2. The good agreement between the calculated viscosities and the experimental data in the ternary silicate systems has indicated that this approach can be successfully employed to predict the viscosities of ternary silicate melts.
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| 24. |
- Shahbazian, F., et al.
(författare)
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The effect of addition of Al2O3 on the viscosity of CaO-FeO-SiO2-CaF2 slags
- 2002
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Ingår i: ISIJ International. - : Iron and Steel Institute of Japan. - 0915-1559 .- 1347-5460. ; 42:2, s. 155-162
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Tidskriftsartikel (refereegranskat)abstract
- The viscosities of CaO-FeO-SiO2-CaF2 slags with various amounts of alumina addition were measured using a rotating-cylinder method in the temperature range 1714-1757 K. The first part of the experiments was conducted by measuring the viscosities under equilibrium conditions after small additions of Al2O3. Similar experiments were also conducted with one commercial mould flux in order to compare the results. In both cases, the viscosities were found to increase with the addition of Al2O3 at all the experimental temperatures, the increase in viscosity being somewhat linear with Al2O3 addition. In the case of the commercial mould flux, even an addition of 2.6 mass% Al2O3 led to a significant increase in the viscosity. Some isothermal experiments were also conducted with the above set of slags in the dynamic mode, wherein, the changes in the slag viscosities were monitored as a function of time as an Al2O3 disc dissolved continuously into the slag. The experiments were so designed that the dissolution of alumina occurred mainly along the vertical direction. The rate of dissolution of alumina is discussed in the light of the rate of change of viscosity as well as the composition profile in the slag after the experiments. An examination of the Al2O3 disc revealed the counter diffusion of the slag components into the solid alumina and that the dissolution took place by the solid product dissolving in the melt.
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| 25. |
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