146 Matching Results

Search Results

Advanced search parameters have been applied.


Description: Mechanical vibrations of the RHIC interaction region triplets has been identified as the dominant source of orbit jitter for frequencies up to 20 Hz. We report the results of detailed measurements that were performed to characterize these effects. We discuss the impact on beam dynamics and possible cures.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor

Description: The synthesis, aqueous stability and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7 (1)]. A very poor metal centered quantum yield with Eu(III) was observed ({Phi}{sub tot} = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) {sup 5}D{sub 0} emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the Near Infra-Red (NIR).
Date: June 2, 2008
Creator: Jocher, C.J.; Moore, E.G.; Pierce, J.D. & Raymond, K.N.
Partner: UNT Libraries Government Documents Department

C0 low-{beta} optics

Description: A low-{beta} insertion has been designed for the BTeV experiment at C0. With {+-} 12 m for detector space, a {beta}* of 0.5 m can be achieved using 170 T/m magnets in the final focus triplets. A total half-crossing angle of 240 {micro}r is necessary to keep the beams separated by 5{sigma} at the 2nd parasitic crossing. There are 2 possible Tevatron collision scenarios: B0 and D0, but not C0, and; C0, but not B0 or D0.
Date: February 2, 2001
Creator: Johnstone, J.A.
Partner: UNT Libraries Government Documents Department

Muon Acceleration with RLA and Non-scaling FFAG Arcs

Description: Recirculating Linear Accelerators (RLA) are the most likely means to achieve the rapid acceleration of shortlived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. In this paper, we present a novel return-arc optics design based on a Non Scaling Fixed Field Alternating Gradient (NS-FFAG) lattice that allows 5 and 9 GeV/c muons of both charges to be transported in the same string of magnets. The return arcs are made up of super cells with each super cell consisting of three triplets. By employing combined function magnets with dipole, quadrupole, sextupole and octupole magnetic field components, each super cell is designed to be achromatic and to have zero initial and final periodic orbit offsets for both 5 and 9 GeV/c muon momenta. This solution would reduce the number of arcs by a factor of 2, simplifying the overall design.
Date: May 1, 2010
Creator: Vasiliy Morozov,Alex Bogacz,Dejan Trbojevic
Partner: UNT Libraries Government Documents Department

Direct observation of photoinduced bent nitrosyl excited-state complexes

Description: Ground state structures with side-on nitrosyl ({eta}{sup 2}-NO) and isonitrosyl (ON) ligands have been observed in a variety of transition-metal complexes. In contrast, excited state structures with bent-NO ligands have been proposed for years but never directly observed. Here we use picosecond time-resolved infrared spectroscopy and density functional theory (DFT) modeling to study the photochemistry of Co(CO){sub 3}(NO), a model transition-metal-NO compound. Surprisingly, we have observed no evidence for ON and {eta}{sup 2}-NO structural isomers, but have observed two bent-NO complexes. DFT modeling of the ground and excited state potentials indicates that the bent-NO complexes correspond to triplet excited states. Photolysis of Co(CO){sub 3}(NO) with a 400-nm pump pulse leads to population of a manifold of excited states which decay to form an excited state triplet bent-NO complex within 1 ps. This structure relaxes to the ground triplet state in ca. 350 ps to form a second bent-NO structure.
Date: June 28, 2008
Creator: Sawyer, Karma R.; Steele, Ryan P.; Glascoe, Elizabeth A.; Cahoon, James F.; Schlegel, Jacob P.; Head-Gordon, Martin et al.
Partner: UNT Libraries Government Documents Department

Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene

Description: Heats of formation of the lowest triplet state of ethylene and the ground triplet state of ethylidene have been predicted by high level electronic structure calculations. Total atomization energies obtained from coupled-cluster CCSD(T) energies extrapolated to the complete basis set limit using correlation consistent basis sets (CBS), plus additional corrections predict the following heats of formation in kcal/mol: Delta H0f(C2H4,3A1) = 80.1 at 0 K and 78.5 at 298 K, and Delta H0f(CH3CH,3A") = 86.8 at 0 K and 85.1 at 298 K, with an error of less than +-1.0 kcal/mol. The vertical and adiabatic singlet-triplet separation energies of ethylene were calculated as Delta ES-T,vert = 104.1 and Delta ES-T,adia = 65.8 kcal/mol. These results are in excellent agreement with recent quantum Monte Carlo (DMC) values of 103.5 +- 0.3 and 66.4 +- 0.3 kcal/mol. Both sets of computational values differ from the experimental estimate of 58 +- 3 kcal/mol for the adiabatic splitting. The computed singlet-triplet gap at 0 K for acetylene is Delta ES-T,adia(C2H2) = 90.5 kcal/mol, which is in notable disagreement with the experimental value of 82.6 kcal/mol. The heat of formation of the triplet is Delta H0f(C2H2,3B2) = 145.3 kcal/mol. There is a systematic underestimation of the singlet-triplet gaps in recent photodecomposition experiments by ~;;7 to 8 kcal/mol. For vinylidene, we predict Delta H0f(H2CC,1A1) = 98.8 kcal/mol at 298 K (exptl. 100.3 +- 4.0), Delta H0f(H2CC,3B2) = 146.2 at 298 K, and an energy gap Delta ES-T-adia(H2CC) = 47.7 kcal/mol.
Date: June 28, 2007
Creator: Nguyen, M.T.; Matus, M.H.; Lester Jr, W.A. & Dixon, David A.
Partner: UNT Libraries Government Documents Department

Interpretation of High Energy p-p Scattering.

Description: High energy p-p scattering has been interpreted by several authors in terms of highly singular noncentral interactions. The triplet state calculations were carried out in the Born approximation and, together with the singlet, yielded an almost isotropic (c.m. system) differential cross section. Agreement with experiment was good at large angles but the theoretical peak in the forward direction, due mostly to singlet d scattering, was too large. It is not clear however that the Born approximation should be valid for singular potentials.
Date: September 19, 1952
Creator: Swanson, Don R.
Partner: UNT Libraries Government Documents Department

Half-Life for Double Beta-Decay

Description: Fireman(1) has reported the results of a rather difficult beta-particle coincidence counting experiment in which the decay of Sn{sup 124} by the simultaneous emission of two negative beta-particles, with a half-life between 0.4 x 10{sup 16} years and 0.9 x 10{sup 16} years, seems to have been observed. This note reports the results obtained from a different and somewhat simpler method of looking for the phenomenon of simultaneous emission of two beta-particles. These results are negative so far and show that this process is considerably less probable in the case chosen by us than in that reported by Fireman. The method consists of looking in uranium samples for 90-year Pu{sup 238} which would come from U{sup 238} by the double beta-particle mechanism since Np{sup 238} is heavier than U{sup 238}, which in turn is substantially heavier than Pu{sup 238}, in the isobaric triplet {sub 92}U{sup 238}-{sub 93}Np{sup 238}-{sub 94}Pu{sup 238}. This chemical method of investigation is particularly applicable to this isobaric triplet because there appears to be no other mechanisms to account for the Pu{sup 238} should it be found. The energetics of the situation are summarized in the following diagram, where the disintegration energies are derived from sources which may be traced through a recent compilation.
Date: October 21, 1949
Creator: Levine, C.A.; Ghiorso, A. & Seaborg, G.T.
Partner: UNT Libraries Government Documents Department

Detonation of Meta-stable Clusters

Description: We consider the energy accumulation in meta-stable clusters. This energy can be much larger than the typical chemical bond energy (~;;1 ev/atom). For example, polymeric nitrogen can accumulate 4 ev/atom in the N8 (fcc) structure, while helium can accumulate 9 ev/atom in the excited triplet state He2* . They release their energy by cluster fission: N8 -> 4N2 and He2* -> 2He. We study the locus of states in thermodynamic state space for the detonation of such meta-stable clusters. In particular, the equilibrium isentrope, starting at the Chapman-Jouguet state, and expanding down to 1 atmosphere was calculated with the Cheetah code. Large detonation pressures (3 and 16 Mbar), temperatures (12 and 34 kilo-K) and velocities (20 and 43 km/s) are a consequence of the large heats of detonation (6.6 and 50 kilo-cal/g) for nitrogen and helium clusters respectively. If such meta-stable clusters could be synthesized, they offer the potential for large increases in the energy density of materials.
Date: May 31, 2008
Creator: Kuhl, Allen; Kuhl, Allen L.; Fried, Laurence E.; Howard, W. Michael; Seizew, Michael R.; Bell, John B. et al.
Partner: UNT Libraries Government Documents Department

Comparison of the dynamic apertures in the RHIC 100 GeV and 250 GeV polarized proton runs

Description: In this note we carry out dynamic aperture calcuations to understand the lifetime difference between the 2009 RHIC 100 GeV and 250 GeV polarized proton (p-p) runs. In these two runs the {beta}*s at the interatcion points (IPs) IP6 and IP8 are 0.7 m. We also compare the impacts of interaction region (IR) multipole errors with 2000 A and 5000 A triplet currents on the dynamic aperture. We calculated the dynamic apertures for RHIC 100 GeV and 250 GeV run lattices with same {beta}* = 0.7 m. We found that the dynamic apertures in units of mm are 12.5% and 4.3% smaller at 250 GeV than those at 100 GeV for particles with ({Delta}p/p0) = 3 x 0.0002828 and 3 x 0.0001414 respectively. However, in units of {sigma}, the dynamic apertures at 250 GeV are 36.4% and 51.7% bigger than those at 100 GeV. For particles with the same 3 x ({Delta}p/p0){sub rms}, the dynamic aperture at 250 GeV is almost twice of that at 100 GeV. We conclude that the lifetime difference for the 100 GeV and 250 GeV p-p runs with same {beta}* = 0.7 m lattices is mainly due to the fact that the relative rms momentum spread and rms transverse beam size are smaller than those at 100 GeV. If we install IR multipole errors of 5000 A triplet current to 100 GeV run, the dynamic apertures are reduced by 12.5% and 7% for particles with ({Delta}p/p0) = 3 x 0.0002828 and 3 x 0.0001414 particles, compared to that with IR multipole errors of 2000 A.
Date: January 1, 2011
Creator: Luo, Y.; Gu, X.; Fischer, W. & Trbojevic, D.
Partner: UNT Libraries Government Documents Department


Description: About 730 BPMs are mounted on the RHIC CQS and Triplet super-conducting magnets. Semi-rigid coaxial cables are used to bring the electrical signal from the BPM feedthroughs to the outside flanges. at the ambient temperature. Every year around 10 cables will lose their signals during the operation. The connection usually failed at the warm end of the cable. The problems were either the solder joint failed or the center conductor retracted out of the SMA connector. Finite element analyses were performed to understand the failure mechanism of the solder joint. The results showed that (1) The SMA center conductor can separate from the mating connector due to the thermal retraction. (2) The maximum thermal stress at the warm end solder joint can exceed the material strength of the Pb37/Sn63 solder material and (3) The magnet ramping frequency (-10 Hz), during the machine startup, can possibly resonant the coaxial cable and damage the solder joints, especially when a fracture is initiated. Test results confirmed that by using the silver bearing solder material (a higher strength material) and by crimping the cable at the locations close to the SMA connector (to prevent the center conductor from retracting) can effectively resolve the connector failure problem.
Date: June 25, 2007
Partner: UNT Libraries Government Documents Department

Simple Beam-Optic Simulations and Proposed Mechanical Mitigation for the Triplet Oscillation Problem

Description: The purpose of these simulations is to gain a better understanding of the relative contributions to the beam perturbation from the main horizontal oscillation modes (yawing and rolling) of Q1, Q2, and Q3. For this purpose, a simple beam transport program was implemented with an EXCEL spreadsheet to calculate the horizontal beam envelop through the Q1, Q2, Q3 triplet up to the IP, with the possibility of specifying horizontal displacements of the singlets. For now, the weak focusing properties of D0 and DX have been ignored, but could easily be included in the future if necessary. In a first simulation, quadrupole strengths have been adopted that correspond to {beta}* = 2m at the IP. The parameters used listed in Table 1 were obtained from references [1] and [2].
Date: May 1, 2008
Creator: Thieberger,P.; Montag, C.; Snydstrup, L.; Trbojevic, D. & Tuozzolo, J.
Partner: UNT Libraries Government Documents Department

Field Quality Measurements and Analysis of the LARP Technology Quadrupole Models

Description: One of the US-LHC accelerator research program goals is to develop and prove the design and technology of Nb{sub 3}Sn quadrupoles for an upgrade of the LHC Interaction Region (IR) inner triplets. Four 1-m long technology quadrupole models with a 90 mm bore and field gradient of 200 T/m based on similar coils and different mechanical structures have been developed. In this paper, we present the field quality measurements of the first several models performed at room temperature as well as at superfluid helium temperature in a wide field range. The measured field harmonics are compared to the calculated ones. The field quality of Nb{sub 3}Sn quadrupole models is compared with the NbTi quadrupoles recently produced at Fermilab for the first generation LHC IRs.
Date: June 1, 2008
Creator: Chlachidze, G.; DiMarco, J.; Kashikhin, V.V.; Lamm, M.; Schlabach, P.; Tartaglia, M. et al.
Partner: UNT Libraries Government Documents Department

The application of Tiny Triplet Finder (TTF) in BTeV pixel trigger

Description: We describe a track segment recognition scheme called the Tiny Triplet Finder (TTF) that involves grouping of three hits satisfying a constraint such as forming of a straight line. The TTF performs this O(n{sup 3}) function in O(n) time, where n is number of hits in each detector plane. The word ''tiny'' reflects the fact that the FPGA resource usage is small. The number of logic elements needed for the TTF is O(Nlog(N)), where N is the number of bins in the coordinate considered, which for large N, is significantly smaller than O(N{sup 2}) needed for typical implementations of similar functions. The TTF is also suitable for software implementations as well as many other pattern recognition problems.
Date: March 1, 2006
Creator: Wu, Jin-Yuan; Wang, M.; Gottschalk, E.; Shi, Z. & /Fermilab
Partner: UNT Libraries Government Documents Department

Performance of a High Resolution Cavity Beam Position Monitor System

Description: It has been estimated that an RF cavity Beam Position Monitor (BPM) could provide a position measurement resolution of less than one nanometer. We have developed a high resolution cavity BPM and associated electronics. A triplet comprised of these BPMs was installed in the extraction line of the Accelerator Test Facility (ATF) at the High Energy Accelerator Research Organization (KEK) for testing with its ultra-low emittance beam. The three BPMs were each rigidly mounted inside an alignment frame on six variable-length struts which could be used to move the BPMs in position and angle. We have developed novel methods for extracting the position and tilt information from the BPM signals including a robust calibration algorithm which is immune to beam jitter. To date, we have demonstrated a position resolution of 15.6 nm and a tilt resolution of 2.1 {micro}rad over a dynamic range of approximately {+-} 20 {micro}m.
Date: December 18, 2006
Creator: Walston, S; Boogert, S; Chung, C; Fitsos, P; Frisch, J; Gronberg, J et al.
Partner: UNT Libraries Government Documents Department

Energy deposited in the high luminosity inner triplets of the LHC by collision debris

Description: The 14 TeV center of mass proton-proton collisions in the LHC produce not only debris interesting for physics but also showers of particles ending up in the accelerator equipment, in particular in the superconducting magnet coils. Evaluations of this contribution to the heat, that has to be transported by the cryogenic system, have been made to guarantee that the energy deposition in the superconducting magnets does not exceed limits for magnet quenching and the capacity of the cryogenic system. The models of the LHC base-line are detailed and include description of, for energy deposition, essential elements like beam-pipes and corrector magnets. The evaluations made using the Monte-Carlo code FLUKA are compared to previous studies using MARS. For the consolidation of the calculations, a dedicated comparative study of these two codes was performed for a reduced setup.
Date: June 1, 2008
Creator: Wildner, E.; /CERN; Broggi, F.; /INFN, Milan; Cerutti, F.; Ferrari, A. et al.
Partner: UNT Libraries Government Documents Department

Implementation of Double-Waist Chicane Optics in SPEAR3

Description: The SPEAR3 accelerator upgrade opened up two 7.6m racetrack straights in the magnet lattice. In one of these straights, we recently added a magnetic chicane to separate two insertion device (ID) beam lines by 10mrad. A quadrupole triplet in the center creates a ''double focus'' optics with {beta}y = 1.6m at the middle of each ID, hence the term ''double-waist chicane''. The new optics also reduced {beta}y in the four matching straights adjacent to the racetrack straights to 2.5m. In this paper, we outline design features of the optics and physical implementation of the lattice.
Date: August 16, 2006
Creator: Corbett, J.; Cornacchia, M.; Dao, T.; Dell'Orco, D.; Rafael, F.; Harrington, D. et al.
Partner: UNT Libraries Government Documents Department

Aryl Bridged 1-Hydroxypyridin-2-one: Sensitizer Ligands for Eu(III)

Description: The synthesis, crystal structure, solution stability and photophysical properties of an aryl group bridging two 1-hydroxypyridin-2-one units complexed to Eu(III) are reported. The results show that this backbone unit increases the rigidity of the ensuing complex, and also the conjugation of the ligand. As a result of the latter, the singlet absorption energy is decreased, along with the energy of the lowest excited triplet state. The resulting efficiency of sensitization for the Eu(III) ion is influenced by these phenomena, yielding an overall quantum yield of 6.2% in aqueous solution. The kinetic parameters arising from the luminescence data reveal an enhanced non-radiative decay rate for this compound when compared to previously reported aliphatic bridges.
Date: February 22, 2008
Creator: D'Aleo, Anthony; Xu, Jide; Moore, Evan G.; Jocher, Christoph J. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

Predicting Efficient Antenna Ligands for Tb(III) Emission

Description: A series of highly luminescent Tb(III) complexes of para-substituted 2-hydroxyisophthalamide ligands (5LI-IAM-X) has been prepared (X = H, CH{sub 3}, (C=O)NHCH{sub 3}, SO{sub 3}{sup -}, NO{sub 2}, OCH{sub 3}, F, Cl, Br) to probe the effect of substituting the isophthalamide ring on ligand and Tb(III) emission in order to establish a method for predicting the effects of chromophore modification on Tb(III) luminescence. The energies of the ligand singlet and triplet excited states are found to increase linearly with the {pi}-withdrawing ability of the substituent. The experimental results are supported by time-dependent density functional theory (TD-DFT) calculations performed on model systems, which predict ligand singlet and triplet energies within {approx}5% of the experimental values. The quantum yield ({Phi}) values of the Tb(III) complex increases with the triplet energy of the ligand, which is in part due to the decreased non-radiative deactivation caused by thermal repopulation of the triplet. Together, the experimental and theoretical results serve as a predictive tool that can be used to guide the synthesis of ligands used to sensitize lanthanide luminescence.
Date: October 6, 2008
Creator: Samuel, Amanda P.S.; Xu, Jide & Raymond, Kenneth
Partner: UNT Libraries Government Documents Department

Curved track segment finding using Tiny Triplet Finder (TTF)

Description: We describe the applications of a track segment recognition scheme called the Tiny Triplet Finder (TTF) that involves the grouping of three hits satisfying a constraint forming of a track segment. The TTF was originally developed solving straight track segment finding problem, however, it is also suitable in many curved track segment finding problems. The examples discussed in this document are among popular detector layouts in high-energy/nuclear physics experiments. Although it is not practical to find a universal recipe for arbitrary detector layouts, the method of the TTF application is illustrated via the discussion of the examples. Generally speaking, whenever the data item to be found in a pattern recognition problem contains two free parameters, and if the constraint connecting the measurements and the two free parameters has an approximate shift invariant property, the Tiny Triplet Finder can be used.
Date: November 1, 2006
Creator: Wu, Jin-Yuan; Wang, M.; Gottschalk, E.; Shi, Z. & /Fermilab
Partner: UNT Libraries Government Documents Department


Description: To compensate modulated beam-beam offsets caused by mechanical vibrations of IR triplet quadrupoles at frequencies around 10 Hz, a fast IR orbit feedback system has been developed. We report design considerations and recent status of the system.
Date: June 26, 2006
Partner: UNT Libraries Government Documents Department


Description: When designing a FFAG accelerator for protons we found convenient to follow this procedure [1]. (1) We assume a Non-Scaling Lattice (NSL) because the aim is toward a compact layout, though we are aware of the issue of multiple resonance crossing. (2) We take a periodic sequence of FDF triplets as these have been proven to exhibit a very small dispersion function. (3) The reference trajectory is taken to be the injection orbit that corresponds to the lowest value of the acceleration momentum range. (4) Finally, the magnets in the triplet have all a linear field profile. We have indeed found recently [2,3] that the Adjusted Field Profile (AFP) to cancel the horizontal chromaticity is exceedingly non-linear and it causes a too large betatron tune variation with the amplitude of motion. A sequence of FDF triplets is shown in Figure 1. They are made of sector magnets having parallel entrance and exit planes facing each other. Only for the injection orbit the trajectory in the magnets is made of arcs of circle. The magnets have sharp edges and there is no entrance or exit angle only for the reference (injection) orbit [4]. This solution minimizes magnet width, has the most stable momentum range, and allows longer drifts between triplets. Figure 2 shows a schematic of a FDF triplet with all the essential parameters. It is defined by 8 variables: the long drift S, the short drift g, the length L{sub F}, the bending field B, on the reference orbit, and the field gradient G{sub F} of the focusing (F) sector magnets, and the same quantities L{sub D}, B{sub D} and G{sub D} of the de-focusing sector magnet (D). To these we need to add the particle magnetic rigidity Bp (or equivalently the momentum p) and the full ring circumference C. ...
Date: December 4, 2005
Creator: RUGGIERO, A.
Partner: UNT Libraries Government Documents Department

Linear optics design of negative momentum compaction lattices for PS2

Description: In view of the CERN Proton Synchrotron proposed replacement with a new ring (PS2), a detailed optics design has been undertaken following the evaluation of several lattice options. The basic arc module consists of cells providing negative momentum compaction. The straight section is formed with a combination of FODO and quadrupole triplet cells, to accommodate the injection and extraction systems, in particular the H{sup -} injection elements. The arc is matched to the straight section with a dispersion suppressor and matching module. Different lattices are compared with respect to their linear optics functions, tuning flexibility and geometrical acceptance properties.
Date: May 4, 2009
Creator: Papaphilippou,Y.; de Maria,R.; Barranco, J.; Bartmann, W.; Benedikt, M.; Carli, C. et al.
Partner: UNT Libraries Government Documents Department

Reduction of beta* and increase of luminosity at RHIC

Description: The reduction of {beta}* beyond the 1m design value at RHIC has been consistently achieved over the last 6 years of RHIC operations, resulting in an increase of luminosity for different running modes and species. During the recent 2007-08 deuteron-gold run the reduction to 0.70 from the design 1m achieved a 30% increase in delivered luminosity. The key ingredients allowing the reduction have been the capability of efficiently developing ramps with tune and coupling feedback, orbit corrections on the ramp, and collimation, to minimize beam losses in the final focus triplets, the main aperture limitations for the collision optics. We will describe the operational strategy used to reduce the {beta}*, at first squeezing the beam at store, to test feasibility, followed by the operationally preferred option of squeezing the beam during acceleration, and the resulting luminosity increase. We will conclude with future plans for the beta squeeze.
Date: May 4, 2009
Creator: Pilat,F.; Bai, M.; Bruno, D.; Cameron, P.; Della Penna, A.; Drees, A. et al.
Partner: UNT Libraries Government Documents Department