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The Inductive Coupling of the Magnets in MICE and its Effect onQuench Protection

Description: The inductive coupling between various MICE magnet circuits is described. The consequences of this coupling on magnet charging and quenching are discussed. Magnet quench protection is achieved through the use of quench-back. Calculations of the quenching of a magnet due to quench-back resulting from circulating currents induced in the magnet mandrel due to quenching of an adjacent magnet are discussed. This report describes how the MICE magnet channel will react when magnets in that channel are quenched.
Date: September 8, 2005
Creator: Green, Michael A. & Witte, Holger
Partner: UNT Libraries Government Documents Department

Jet and Leading Hadron Production in High-energy Heavy-ionCollisions

Description: Jet tomography has become a powerful tool for the study ofproperties of dense matter in high-energy heavy-ion collisions. I willdiscuss recent progresses in the phenomenological study of jet quenching,including momentum, colliding energy and nuclear size dependence ofsingle hadron suppression, modification of dihadron correlations and thesoft hadron distribution associatedwith a quenched jet.
Date: November 1, 2005
Creator: Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Quench Protection and Magnet Supply Requirements for the MICEFocusingand Coupling Magnets

Description: This report discusses the quench protection and power supply requirements of the MICE superconducting magnets. A section of the report discusses the quench process and how to calculate the peak voltages and hotspot temperature that result from a magnet quench. A section of the report discusses conventional quench protection methods. Thermal quench back from the magnet mandrel is also discussed. Selected quench protection methods that result in safe quenching of the MICE focusing and coupling magnets are discussed. The coupling of the MICE magnets with the other magnets in the MICE is described. The consequences of this coupling on magnet charging and quenching are discussed. Calculations of the quenching of a magnet due quench back from circulating currents induced in the magnet mandrel due to quenching of an adjacent magnet are discussed. The conclusion of this report describes how the MICE magnet channel will react when one or magnets in that channel are quenched.
Date: June 8, 2005
Creator: Green, Michael A. & Witte, Holger
Partner: UNT Libraries Government Documents Department

Singlet Quenching of Tetraphenylporphyrin and its Metal Derivatives by Iron(III) Coordination Compounds

Description: This article reports on the singlet quenching of 5, 10, 15, 20-tetraphenylporphyrin (Hâ‚‚TPP) and its magnesium(II) and zinc(II) derivatives (MgTPP and ZnTPP) by a series of iron(III) coordination compounds bearing different ligand systems.
Date: January 6, 1990
Creator: D'Souza, Francis & Krishnan, V.
Partner: UNT College of Arts and Sciences

Multidimensional Analysis of Quenching: Comparison of Inverse Techniques

Description: Understanding the surface heat transfer during quenching can be beneficial. Analysis to estimate the surface heat transfer from internal temperature measurements is referred to as the inverse heat conduction problem (IHCP). Function specification and gradient adjoint methods, which use a gradient search method coupled with an adjoint operator, are widely u led methods to solve the IHCP. In this paper the two methods are presented for the multidimensional case. The focus is not a rigorous comparison of numerical results. Instead after formulating the multidimensional solutions, issues associated with the numerical implementation and practical application of the methods are discussed. In addition, an experiment that measured the surface heat flux and temperatures for a transient experimental case is analyzed. Transient temperatures are used to estimate the surface heat flux, which is compared to the measured values. The estimated surface fluxes are comparable for the two methods.
Date: November 18, 1998
Creator: Dowding, K.J.
Partner: UNT Libraries Government Documents Department

Systemsize dependence of associated yields in hadron-triggered jets

Description: We present results on the system size dependence of high transverse momentum di-hadron correlations at {radical}s{sub NN} = 200 GeV as measured by STAR at RHIC. Measurements in d+Au, Cu+Cu and Au+Au collisions reveal similar jet-like correlation yields at small angular separation ({Delta}{phi} {approx} 0, {Delta}{eta} {approx} 0) for all systems and centralities. Previous measurements have shown that the away-side yield is suppressed in heavy-ion collisions. We present measurements of the away-side suppression as a function of transverse momentum and centrality in Cu+Cu and Au+Au collisions. The suppression is found to be similar in Cu+Cu and Au+Au collisions at a similar number of participants. The results are compared to theoretical calculations based on the parton quenching model and the modified fragmentation model. The observed differences between data and theory indicate that the correlated yields presented here will provide important constraints on medium density profile and energy loss model parameters.
Date: July 5, 2010
Creator: Collaboration, STAR & Abelev, Betty
Partner: UNT Libraries Government Documents Department

The dihadron fragmentation function and its evolution

Description: Dihadron fragmentation functions and their evolution arestudied in the process of e+e- annihilation. Under the collinearfactorization approximation and facilitated by the cut-vertex technique,the two hadron inclusive cross section at leading order (LO) is shown tofactorize into a short distance parton cross section and a long distancedihadron fragmentation function. We provide the definition of such adihadron fragmentation function in terms of parton matrix elements andderive its DGLAP evolution equation at leading log. The evolutionequation for the non-singlet quark fragmentation function is solvednumerically with a simple ansatz for the initial condition and resultsare presented for cases of physical interest.
Date: February 24, 2004
Creator: Majumder, Abhijit & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Dihadron Tomography of High-Energy Nuclear Collisions inNext-to-Leading Order Perturbative QCD

Description: Back-to-back dihadron spectra in high-energy heavy-ioncollisions are studied within the next-to-leading order (NLO)perturbative QCD parton model with jet quenching incorporated viamodified jet fragmentation functions due to radiative parton energy lossin dense medium. The experimentally observed appearance of back-to-backdihadron sat high p_T is found to originate mainly from jet pairsproduced close and tangential to the surface of the dense matter.However, a substantial fraction of observed high p_T dihadrons also comesfrom jets produced at the center of the medium after losing finite amountof energy. Consequently, the suppression factor of such high-p_T hadronpairs is foundto be more sensitive to the initial gluon density than thesingle hadron spectra that are dominated by surface emission. Asimultaneous chi2-fit to both the single and dihadron spectra can beachieved within an arrow range of the energy loss parametersepsilon_0=1.6-2.1 GeV/fm. Because of the flattening of the initial jetproduction spectra, high p_T dihadrons at the LHC energy are found to bemore robust as probes of the dense medium.
Date: January 17, 2007
Creator: Zhang, Hanzhong; Owens, Joseph F.; Wang, Enke & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Energy dependence of pi, p and pbar transverse momentum spectra for Au+Au collisions at sqrt sNN = 62.4 and 200 GeV

Description: We study the energy dependence of the transverse momentum (pT) spectra for charged pions, protons and anti-protons for Au+Au collisions at sqrt sNN = 62.4 and 200 GeV. Data are presented at mid-rapidity (lbar y rbar< 0.5) for 0.2< pT< 12 GeV/c. In the intermediate pT region (2< pT< 6 GeV/c), the nuclear modification factor is higher at 62.4 GeV than at 200 GeV, while at higher pT (pT> 7 GeV/c) the modification is similar for both energies. The p/pi+ and pbar/pi- ratios for central collisions at sqrt sNN = 62.4 GeV peak at pT _~;; 2 GeV/c. In the pT range where recombination is expected to dominate, the p/pi+ ratios at 62.4 GeV are larger than at 200 GeV, while the pbar/pi- ratios are smaller. For pT> 2 GeV/c, the pbar/pi- ratios at the two beam energies are independent of pT and centrality indicating that the dependence of the pbar/pi- ratio on pT does not change between 62.4 and 200 GeV. These findings challenge various models incorporating jet quenching and/or constituent quark coalescence.
Date: March 26, 2007
Creator: Ritter, H
Partner: UNT Libraries Government Documents Department

Energy dependence of jet transport parameter and parton saturationin quark-gluon plasma

Description: We study the evolution and saturation of the gluondistribution function in the quark-gluon plasma as probed by apropagating parton and its effect on the computation of jet quenching ortransport parameter $\hat q $. For thermal partons, the saturation scale$Q2_s$ is found to be proportional to the Debye screening mass $\mu_D2$.For hard probes, evolution at small $x=Q2_s/6ET$ leads to jet energydependence of hat q. We study this dependence for both a conformal gaugetheory in weak and strong coupling limit and for (pure gluon) QCD. Theenergy dependence can be used to extract the shear viscosity $\eta$ ofthe medium since $\eta$ can be related to the transport parameter forthermal partons in a transport description. We also derive upper boundson the transport parameter for both energetic and thermal partons. Thelater leads to a lower bound on shear viscosity-to-entropy density ratiowhich is consistent with the conjectured lower bound $\eta/s\geq 1/4\pi$.Implications on the study of jet quenching at RHIC and LHC and the bulkproperties of the dense matter are discussed.
Date: June 24, 2007
Creator: Casalderrey-Solana, Jorge & Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Selective Fluorescence Quenching to Discriminate Between Alternant and Non-alternant Polycyclic Aromatic Hydrocarbons: Acephenanthrylene Derivatives as Exceptions to the Nitromethane Quenching Rule

Description: Article on selective fluorescence quenching to discriminate between alternant and non-alternant polycyclic aromatic hydrocarbons and acephenanthrylene derivatives as exceptions to the nitromethane quenching rule.
Date: September 1994
Creator: Tucker, Sheryl A. (Sheryl Ann); Griffin, Jason M.; Acree, William E. (William Eugene); Mulder, Patrick P. J.; Lugtenburg, Johan & Cornelisse, Jan
Partner: UNT College of Arts and Sciences

Low temperature quench performance of Fermilab Low-{Beta} insertion quadrupoles

Description: The recently revived superconducting magnet program at Fermilab is currently focused on the development of high gradient quadrupoles for possible use in the Large Hadron Collider (LHC) interaction regions at CERN. In order to provide input for the new quadrupole design which will operate in superfluid helium, we have tested a Fermilab Tevatron low-{beta} quadrupole cold mass and compared its low temperature performance to a newly assembled heavily instrumented version which was mechanically modified to take advantage of the gain in critical current.
Date: April 1, 1997
Creator: Bossert, R.; Lietzke, A.; McInturff, A.D.; Scanlan, R. & Collaboration, LHC
Partner: UNT Libraries Government Documents Department

Development of a high gradient quadrupole for the LHC Interaction Regions

Description: A collaboration of Fermilab, Lawrence Berkeley National Laboratory and Brookhaven National Laboratory is engaged in the design of a high gradient quadrupole suitable for use in the LHC interaction regions. The cold iron design incorporates a two-layer, cos(2{theta}) coil geometry with a 70 mm aperture operating in superfluid helium. This paper summarizes the progress on a magnetic, mechanical and thermal design that meets the requirements of maximum gradient above 250 T/m, high field quality and provision for adequate cooling in a high radiation environment.
Date: April 1, 1997
Creator: Bossert, R.; Feher, S. & Gourlay, S.A.
Partner: UNT Libraries Government Documents Department

The Role of Quench-back in the Passive Quench Protection of Uncoupled Solenoids in Series with and without Coil Sub-division

Description: This paper is the final paper in a series of papers that discusses passive quench protection for high inductance solenoid magnets. This report describes how passive quench protection system may be applied to superconducting magnets that are connected in series but not inductively coupled. Previous papers have discussed the role of magnet sub-division and quench back from a conductive mandrel in reducing the hot-spot temperature and the peak coil voltages to ground. When magnets are connected in series, quench-back from a conductive mandrel can cause other magnets in a string to quench even without inductive coupling between magnets. The magnet mandrels must be well coupled to the magnet circuit that is being quenched. When magnet circuit sub-division is employed to reduce the voltages-to-ground within magnets, the resistance across the subdivision becomes the most important factor in the successful quenching of the magnet string.
Date: October 15, 2010
Creator: Guo, Xing Long; Green, Michael A; Wang, Li; Wu, Hong & Pan, Heng
Partner: UNT Libraries Government Documents Department

A Quenchofluorometric Study of Polycyclic Aromatic Hydrocarbons in Molecularly Organized Media

Description: Detection, identification and separation of polycyclic aromatic compounds in environmental samples are of extreme importance since many of these compounds are well known for their potential carcinogenic and/or mutagenic activities. Selective quenching of molecular fluorescence can be utilized effectively to analyze mixtures containing different polycyclic aromatic hydrocarbons. Molecularly organized assemblies are used widely in detection and separation of these compounds mainly because of less toxicity and enhanced solubilization capabilities associated with these media. Feasibility of using nitromethane and the alkylpyridinium cation as selective fluorescence quenching agents for discriminating between alternant versus nonalternant polycyclic aromatic hydrocarbons (PAHs) is critically examined in several molecularly organized micellar solvent media. Fluorescence quenching is used to probe the structural features in mixed micelles containing the various combinations of anionic, cationic, nonionic and zwitterionic surfactants. Experimental results provide valuable information regarding molecular interactions between the dissimilar surfactants.
Date: May 1998
Creator: Pandey, Siddharth
Partner: UNT Libraries

Selective Fluorescence Quenching to Discriminate Between Alternant and Non-alternant Polycyclic Aromatic Hydrocarbons: Acephenanthrylene Derivatives as Exceptions to the Nitromethane Quenching Rule

Description: Article on selective fluorescence quenching to discriminate between alternant and non-alternant polycyclic aromatic hydrocarbons and acephenanthrylene derivatives as exceptions to the nitromethane quenching rule.
Date: September 1, 1994
Creator: Tucker, Sheryl A. (Sheryl Ann); Griffin, Jason M.; Acree, William E. (William Eugene); Mulder, Patrick P. J.; Lugtenburg, Johan & Cornelisse, Jan
Partner: UNT College of Arts and Sciences

SEMI-ANNUAL PROGRESS REPORT FOR THE PERIOD JANUARY 1960 THROUGH JUNE 1960

Description: Modifications were made in the Carlson and Banks procedure for the spectrophotometric determination of silicon in beryllium metal and oxide. The refractory oxide is dissolved directly in hydrofluoric acid. The identical procedure is used for metal after ignition to the oxide. Concentrations of beryllium over certain limits have a quenching effect on the fluorescence of the aluminum-Portachrome Blue Black R complex. The determination of trace amounts of aluminum in beryilium can be carried out despite this quenching effect by the method of standard addition. Samples of plutonium sulfate tetrahydrate prepared 9 to 12 months earlier were under investigation to determine the suitability of this compound as a primary analytical standard of plutonium. The compound was determined experimentally to contain four molecules of water of crystallization. Plutonium sulfate tetrahydrate was found to lose a major portion of its water of crystallization when heated at 115 ts C. Indications, but no conclusive evidence, of the existence of another intermediate hydrate of plutonium(IV) sulfate, were found. Microscopic examination of 1-year-old crystals of Pu(S0/sub 4/)/sub 2/.4H/sub 2/0 shows no evidence of the effect of any alpha radiolysis on the water of crystallization. Continued exposure to a fluctuating atmosphere caused no apparent changes in crystal structure or weight. Heating Pu(SO/sub 4/)/sub 2/.4H/sub 2/0 to 325 ts C produced a dehydrated salt of weight equivalent to the formula, Pu(S0/sub 4/)/sub 2/. This material, although slightly hygroscopic, can be readily dried at 120 ts C and appears to be satisfactory for further investigation of its suitability as an alternate primary stand ard of plutonium. A method is presented for the rapid determination of milligram quantities of sulfateiIn pure plutonium sulfates. Plutonium is adsorbed on a cation resin and an acidimetric titration is made of the displaced hydrogen ion which is equivalent to the sulfate content of the ...
Date: January 1, 1961
Creator: Rodden, C.J.
Partner: UNT Libraries Government Documents Department

Simple model relating recombination rates and non-proportional light yield in scintillators

Description: We present a phenomenological approach to derive an approximate expression for the local light yield along a track as a function of the rate constants of different kinetic orders of radiative and quenching processes for excitons and electron-hole pairs excited by an incident {gamma}-ray in a scintillating crystal. For excitons, the radiative and quenching processes considered are linear and binary, and for electron-hole pairs a ternary (Auger type) quenching process is also taken into account. The local light yield (Y{sub L}) in photons per MeV is plotted as a function of the deposited energy, -dE/dx (keV/cm) at any point x along the track length. This model formulation achieves a certain simplicity by using two coupled rate equations. We discuss the approximations that are involved. There are a sufficient number of parameters in this model to fit local light yield profiles needed for qualitative comparison with experiment.
Date: September 24, 2008
Creator: Moses, William W.; Bizarri, Gregory; Singh, Jai; Vasil'ev, Andrey N. & Williams, Richard T.
Partner: UNT Libraries Government Documents Department

Hyperfine Quenching of the 2s2p 3P0 State of Berylliumlike Ions

Description: The hyperfine-induced 2s2p {sup 3}P{sub 0}-2s{sup 2} {sup 1}S{sub 0} transition rate for Be-like {sup 47}Ti{sup 18+} was recently measured in a storage-ring experiment by Schippers et al. [Phys. Rev. Lett. 98, 033001 (2007)]. The measured value of 0.56(3) s{sup -1} is almost 60% larger than the theoretical value of 0.356 s{sup -1} from a multiconfiguration Dirac-Fock calculation by Marques et al. [Phys. Rev. A 47, 929 (1993)]. In this work, we use a large-scale relativistic configuration-interaction method to calculate these hyperfine-induced rates for ions with Z = 6-92. Coherent hyperfine-quenching effects between the 2s2p {sup 1,3}P{sub 1} states are included in a perturbative as well as a radiation damping approach. Contrary to the claims of Marques et al., contributions from the {sup 1}P{sub 1} state are substantial and lead to a hyperfine-induced rate of 0.67 s{sup -1}, in better agreement with, though larger than, the measured value.
Date: March 13, 2008
Creator: Cheng, K T; Chen, M H & Johnson, W R
Partner: UNT Libraries Government Documents Department

Probe initial parton density and formation time via jet quenching

Description: Medium modification of jet fragmentation function due to multiple scattering and induced gluon radiation leads directly to jet quenching or suppression of leading particle distribution from jet fragmentation. One can extract an effective total parton energy loss which can be related to the total transverse momentum broadening. For an expanding medium, both are shown to be sensitive to the initial parton density and formation time. Therefore, one can extract the initial parton density and formation time from simultaneous measurements of parton energy loss and transverse momentum broadening. Implication of the recent experimental data on effects of detailed balance in parton energy loss is also discussed.
Date: September 20, 2002
Creator: Wang, Xin-Nian
Partner: UNT Libraries Government Documents Department

Detailed modeling and laser-induced fluorescence imaging of nitric oxide in a NH(i)-seeded non-premixed methane/air flame

Description: In this paper we study the formation of NO in laminar, nitrogen diluted methane diffusion flames that are seeded with ammonia in the fuel stream. We have performed numerical simulations with detailed chemistry as well as laser-induced fluorescence imaging measurements for a range of ammonia injection rates. For comparison with the experimental data, synthetic LIF images are calculated based on the numerical data accounting for temperature and fluorescence quenching effects. We demonstrate good agreement between measurements and computations. The LIF corrections inferred from the simulation are then used to calculate absolute NO mole fractions from the measured signal.The NO formation in both doped and undoped flames occurs in the flame sheet. In the undoped flame, four different mechanisms including thermal and prompt NO appear to contribute to NO formation. As the NH3 seeding level increases, fuel-NO becomes the dominant mechanism and N2 shifts from being a net reactant to being a net product. Nitric oxide in the undoped flame as well as in the core region of the doped flames are underpredicted by the model; we attribute this mainly to inaccuracies in the NO recycling chemistry on the fuel-rich side of the flame sheet.
Date: December 14, 2001
Creator: Bell, John B.; Day, Marcus S.; Grcar, Joseph F.; Bessler, Wolfgang G.; Schulz, Christof; Glarborg, Peter et al.
Partner: UNT Libraries Government Documents Department

Preliminary investigation of grain refinement in a U-0.2 wt % V alloy casting by true isothermal transformation at 516{degree}C

Description: Laboratory-scale isothermal transformation from beta phase to alpha phase at 516 C was accomplished using one U-0.2 wt % V alloy composition and with specimens up to 7.6 mm in thickness. Gravity was used to transfer individual specimens from a furnace at 720 C to one at 516 C. The lower-temperature, furnace contained two copper blocks between which the specimens were quenched by contact. The furnace also contained a partial atmosphere of helium. Results duplicate those of Reisse et al. at this temperature. Their work was done on smaller samples. Grain sizes obtained were consistently ASTM 7 to 8 (20 to 30 {mu}m), indicating that the cooling rates at the center of even the thicker samples were adequate to miss the nose of the (upper) TTT curve. The microstructure obtained, including the grain size, appears to be equivalent to that obtained by carefully controlled wrought processing, but we believe these castings lack the strong crystallographic textures that exist in wrought products.
Date: July 1, 1995
Creator: Wood, D.H.; Flores, R. & Kershaw, R.P.
Partner: UNT Libraries Government Documents Department

Detection of the normal zone with cowound sensors in cable-in conduit conductors

Description: Tokamaks in the future will use superconducting cable-in-conduit- conductors (CICC) in all poloidal field (PF) and toroidal field (TF) magnets. Conventional quench detection, the measurement of small resistive normal zone voltages ({lt}1 V) in the magnets will be complicated by the presence of large inductive voltages ({gt}4 kV). In the quench detection design for TPX, we have considered several different locations for internal co-wound voltage sensors in the cable cross-section as the primary mechanism to cancel this inductive noise. The Noise Rejection Experiment (NRE) at LLNL has been designed to evaluate which internal locations will produce the best inductive- noise cancellation, and provide us with experimental data for comparison with previously developed theory. The details of the experiments and resulting data are presented and analyzed.
Date: July 30, 1996
Creator: Martovetsky, N.N. & Chaplin, M.R.
Partner: UNT Libraries Government Documents Department