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Residual gas pressure profile in the recycler ring

Description: We simulate the pressure profile of residual gases from basic principles using detailed beam pipe geometry and the relevant physical parameters. These profiles are compared with the actual ion gauge measurements and is being used to predict the vacuum contribution to the Recycler Ring beam lifetime.
Date: May 27, 2003
Creator: Gounder, Krish; Marriner, John & Mishra, Shekhar
Partner: UNT Libraries Government Documents Department

B physics at the Tevatron Collider

Description: Precision B-physics results from the CDF and DO Collaborations based on data collected during the Tevatron 1992-96 run are presented. In particular we discuss the measurement of B hadron lifetimes, and B{sup 0} - {anti B}{sup 0} mixing results obtained using time- evolution analyses. Perspectives for the next Tevatron run, starting in 1999, are also reported.
Date: May 1, 1997
Creator: De Troconiz, J. F.
Partner: UNT Libraries Government Documents Department

Review of Charm and Beauty Lifetimes

Description: A review of the latest experimental results on charm and beauty particle lifetimes is presented together with a brief summary of measurement methods used for beauty particle lifetime measurements. There have been significant updates to the D{sub s}{sup +}/D{sup 0}, B{sup +}/B{sub d}{sup 0} and {Lambda}{sub b}{sup 0}/B{sub d}{sup 0} lifetime ratios which have some theoretical implications. However more precise measurements are still needed before one can make conclusive statements about the theory used to calculate the particle lifetimes.
Date: February 5, 1999
Creator: Cheung, Harry W. K.
Partner: UNT Libraries Government Documents Department

COMPARISON BETWEEN THE PREDICTIONS AND MEASUREMENTS FOR THE BEAM GAS INTERACTIONS DURING THE LAST GOLD AND PROTON RUNS IN RHIC.

Description: The last gold-gold and polarized proton-proton collision runs were performed at energies of 100 GeV/nucleon. The beam gas interactions in RHIC are very important for the beam lifetime in RHIC. In this report the lifetime predicted by pressure data differences between the beams ON and beams OFF, at the energies of 100 GeV/nucleon. are compared to the predictions for the beam gas interaction and beam lifetimes.
Date: June 2, 2002
Creator: TRBOJEVIC,D.; HSEUH,H.C.; FISCHER,W.; ZHANG,S.Y. & MACKAY,W.W.
Partner: UNT Libraries Government Documents Department

Growth of laser damage in fused silica: diameter to depth ratio

Description: Growth of laser initiated damage plays a major role in determining optics lifetime in high power laser systems. Previous measurements have established that the lateral diameter grows exponentially. Knowledge of the growth of the site in the propagation direction is also important, especially so when considering techniques designed to mitigate damage growth, where it is required to reach all the subsurface damage. In this work, we present data on both the diameter and the depth of a growing exit surface damage sites in fused silica. Measured growth rates with both 351 nm illumination and with combined 351 nm and 1054 nm illumination are discussed.
Date: October 29, 2007
Creator: Norton, M A; Adams, J J; Carr, C W; Donohue, E E; Feit, M D; Hackel, R P et al.
Partner: UNT Libraries Government Documents Department

Isoelectronic trends of line strength data in the Li and Be isoelectronic sequences

Description: The decays of the 2p J = 1/2 and J = 3/2 levels of Li-like ions and of the 2s2p {sup 1,3}P{sub 1}{sup 0} levels of Be-like ions can be used as simple-atom test beds for experimental lifetime measurements and for the development of accurate calculations of the transition rates. They have summarized and filtered the experimental data in order to obtain consistent data sets and isoelectronic trends that can be compared to theoretical predictions. The graphical presentation of line strength data enables direct comparison and evaluation of the merit of data along extended isoelectronic sequences. From this, the precision that is necessary in future meaningful experiments can be deduced.
Date: March 1, 2006
Creator: Trabert, E & Curtis, L J
Partner: UNT Libraries Government Documents Department

Limitations of the Arrhenius Methododolgy

Description: The Arrhenius methodology has been utilized for many years to NOV 171998 predict polymer lifetimes in various applications. Unfortunately, there are numerous potential limitations associated with this methodology, o ST I many of which can lead to non-Arrhenius behavior. This paper will review several of these limitations, including a brief mention of diffusion-limited oxidation (DLO) effects and a more extensive discussion of the implication of changes in the effective Arrhenius activation energy E. or in the dominant reactions as the temperature changes. Changes in Ea or in the dominant reactions with temperature can happen for any material, making extrapolations beyond the experimental temperature range problematic. Unfortunately, when mechanistic changes occur, they invariably result in a reduction in effective Arrhenius activation energy, leading to lower than expected material lifetimes. Thus it is critically important to derive methods for testing the Arrhenius extrapolation assumption. One approach that we have developed involves ultrasensitive oxygen consumption measurements. Results from the application of this approach will be reviewed.
Date: October 27, 1998
Creator: Celina, M.; Clough, R.L. & Gillen, K.T.
Partner: UNT Libraries Government Documents Department

A SUMMARY OF TEST OBSERVATIONS WHEN IBUTTONS ARE SUBJECTED TO RF ENERGY

Description: The iButton is a 'one-wire', temperature sensor and data logger in a short metal cylinder package 17 mm in diameter and 6 mm tall. The device is designed to be attached to a surface and acquire temperature samples over time periods as short as 1 second to as long as 300 minutes. Both 8-bit and 16-bit samples are available with 8kB of memory available. Lifetime is limited to an internal battery that cannot be replaced or recharged. The RF test interest originated with the concern that the data logger could inadvertently record electrical emanations from other nearby equipment. The normal operation of the data logger does not support high speed sampling but the control interface will operate at either 15.4 kbps or 125 kbps. There were no observable effects in the operation of the module or in the data that could be attributed to the use of RF energy. They made the assumption that these devices would potentially show RF sensitivity in any of the registers and in the data memory equally, therefore gross changes in the data might show RF susceptibility. No such sensitivity was observed. Because significant power levels were used for these tests they can extrapolate downward in power to state that no RF susceptibility would occur at lower power levels given the same configurations.
Date: October 26, 2011
Creator: Kane, R J & Baluyot, E V
Partner: UNT Libraries Government Documents Department

RF Driven Multicusp H- Ion Source

Description: An rf driven multicusp source capable of generating 1-ms H{sup -} beam pulses with a repetition rate as high as 150 Hz has been developed. This source can be operated with a filament or other types of starter. There is almost no lifetime limitation and a clean plasma can be maintained for a long period of operation. It is demonstrated that rf power as high as 25 kW could be coupled inductively to the plasma via a glass-coated copper-coil antenna. The extracted H{sup -} current density achieved is about 200 mA/cm{sup 2}.
Date: June 1, 1990
Creator: Leung, K.N.; DeVries, G.J.; DiVergilio, W.F.; Hamm, R.W.; Hauck, C.A.; Kunkel, W.B. et al.
Partner: UNT Libraries Government Documents Department

Quantifying the Thermal Fatigue of CPV Modules

Description: A method is presented to quantify thermal fatigue in the CPV die-attach from meteorological data. A comparative; study between cities demonstrates a significant difference in the accumulated damage. These differences are most; sensitive to the number of larger (&#916;T) thermal cycles experienced for a location. High frequency data (<1/min) may; be required to most accurately employ this method.
Date: February 1, 2011
Creator: Bosco, N. & Kurtz, S.
Partner: UNT Libraries Government Documents Department

Some results of the advanced photon source beam lifetime studies

Description: Total beam lifetime consists of two components: the residual-gas-scattering lifetime and Touschek lifetime. The residual-gas lifetime is comprised of the elastic and inelastic scattering on electrons and elastic and inelastic scattering on nuclei. Touschek scattering involves scattering of particles within the bunch. One usually calculates only the elastic scattering on nuclei (single Coulomb scattering) and inelastic scattering on nuclei (bremsstrahlung) of the residual-gas-scattering lifetime component. Experience gained from computing the beam lifetime in the Advanced Photon Source (APS) storage ring shows that the electron scattering should not be neglected, particularly the inelastic contribution. Given the measured quantities from the APS storage ring, one can compare theoretical predictions with experimental results. Uncertainties in calculating the various contributions to lifetime will be discussed.
Date: June 1, 1997
Creator: Bizek, H.M.
Partner: UNT Libraries Government Documents Department

Consequences of return to power after a beam interruption in the blanket of an accelerator driven system.

Description: A sudden drop in power after a beam interruption leads to thermal fatigue effects in structural components in the blanket of an accelerator driven system. These thermal fatigue effects limit component lifetimes. A sudden return to power after a beam interruption can contribute significant additional thermal fatigue and greatly reduce component lifetimes. One obvious solution is a gradual return to power after a beam interruption. There are two potential problems with this solution. One problem involves interruptions that are longer than the thermal time constants of thin structural members but shorter than the time constants of thick structural members. In such a case, a gradual return to power reduces the additional thermal fatigue in the thin structural members but increases the thermal fatigue in thick structural members. Some compromise is necessary. The other problem is that for thick components with long thermal time constants a long, gradual return to power is required to minimize additional thermal fatigue. Such a slow return to power can reduce the utilization or the effective load factor of the system. Specific examples of beam interruptions with various assumptions on return to power are provided for a preliminary design for the blanket of the Accelerator Driven Test Facility. Also, mitigation options to increase component lifetime are discussed. These mitigation options include improving beam reliability and modifying the blanket design to better tolerate beam interruptions.
Date: August 9, 2001
Creator: Dunn, F.
Partner: UNT Libraries Government Documents Department

Tune-Shift Compensation Using the Tevatron Electron Lens

Description: The Tevatron Electron Lens was originally designed to alleviate the tune shift and spread induced in Tevatron antiproton bunches from interactions with the proton bunches. We report recent developments and successful results of such tune-shift compensation. Lifetime measurements are central to our data and the basis of our analysis. Future goals and possible uses for the lens are also discussed.
Date: August 20, 2003
Creator: al., Kip Bishofberger et
Partner: UNT Libraries Government Documents Department

B physics in Run II

Description: Run II at the Tevatron started on March 1, 2001 with a design instantaneous luminosity of 2 x 10{sup 32} cm{sup -2} s{sup -1}. The upgraded D0 detector is expected to collect 2 fb{sup -1} of data at {radical}s = 2.0 TeV in approximately 2 years. The D0 collaboration is planning to make measurements in a number of important areas of B physics, including sin(2{beta}), B{sub s} mixing, the {Lambda}{sub b} lifetime and rare B decays. In this note we describe the upgraded D0 detector and highlights of the B physics program in D0.
Date: October 7, 2002
Creator: Kuznetsov, Valentin E
Partner: UNT Libraries Government Documents Department

Heavy flavor lifetimes and lifetime differences

Description: The authors give an overview of heavy flavour lifetime measurements, focusing on recent results from the Tevatron and the B factories. In the first part of this article we summarize the status and latest measurements of B-hadron lifetimes and lifetime ratios, including some recent result from the Tevatron and the B factories, and compare those results with the predictions from Heavy Quark Expansion (HQE). Future prospects for lifetime measurements at the B factories and the Tevatron are discussed. In the second part, we review the status and prospects of measuring the difference between the lifetimes of the two CP eigenstates in the B{sub s}{sup 0}-{bar B}{sub s}{sup 0} system.
Date: September 17, 2003
Creator: Rademacker, Jonas
Partner: UNT Libraries Government Documents Department

The CDFII Silicon Detector

Description: The CDFII silicon detector consists of 8 layers of double-sided silicon micro-strip sensors totaling 722,432 readout channels, making it one of the largest silicon detectors in present use by an HEP experiment. After two years of data taking, we report on our experience operating the complex device. The performance of the CDFII silicon detector is presented and its impact on physics analyses is discussed. We have already observed measurable effects from radiation damage. These results and their impact on the expected lifetime of the detector are briefly reviewed.
Date: July 23, 2004
Creator: Thom, Julia
Partner: UNT Libraries Government Documents Department

Beam lifetime and beam brightness in ALS

Description: Beam lifetime in ALS is dominated by the Touschek scattering. Measurements of lifetime in single-bunch mode with estimates of bunch dimensions obtained from undulator radiation data are consistent with expectations (t=1.8 hours at 1.25 mA per bunch). However, the lifetime is significantly longer in multi-bunch mode (t=ll hours at 400 mA per 320 bunches). This discrepancy has been traced to an increase in the momentum spread and bunch length in the beam caused by longitudinal coupled-bunch motions driven by higher-order modes in the rf cavities. The increased momentum spread leads to a significant degradation in the undulator spectral performance. Feedback stabilization of the coupled-bunch motion improves the spectral characteristics of the undulator beam at the expense of beam lifetime. We observe an increase of {approximately}200% in beam lifetime by operating at the betatron coupling resonance.
Date: April 1, 1995
Creator: Kim, C.; Jackson, A. & Warwick, A.
Partner: UNT Libraries Government Documents Department

Lifetime studies at the APS.

Description: The studies presented in this note are focused on the lifetime characterization with positrons for the symmetrical low {beta}{sub y} lattice. Before switching back to electrons, detailed lifetime studies were performed in order to gather data that could be compared to similar ones with electrons, the ultimate goal being to define a model that could be used to predict lifetimes. The report is divided into three parts: simulations to allow decoupling of the different contributions to the lifetime; review of the experimental conditions and related problems; and analysis of the data and discussion of the limitations.
Date: May 7, 1999
Creator: Ropert, A.
Partner: UNT Libraries Government Documents Department

Upgrade opportunities at the Advanced Photon Source made possible by top-up operations.

Description: The default running mode of the storage ring at the Advanced Photon Source is top-up injection with a horizontal emittance of 3.0 nm-rad and a coupling of 2.0%. For a stored current of 100 mA in 23 bunches the lifetime is 7 h. The ability to run in low beam-lifetime conditions gives us the opportunity to make upgrades that would otherwise be futile. Some of the possible upgrade paths are presented here, such as lower emittance and higher-current operation.
Date: June 28, 2002
Creator: Emery, L. & Borland, M.
Partner: UNT Libraries Government Documents Department

APPR-1 BURNOUT CALCULATIONS

Description: A general non-uniform burnup program was developed to determine the lifetime of the APPR-1. The calculation is performed using two one dimensional multi-region burnout calculations. The approach to the problem, the equations, and derivation of burnout equations are presented. The results are plotted and compared with the rod bank position as measured at Fort Belvoir. On the basis of these calculations the expected total energy release of the APR-1 is 13 Mw-yr. (auth)
Date: April 10, 1958
Creator: Williamson, T.G.
Partner: UNT Libraries Government Documents Department

Procedures for addressing uncertainty and variability in exposure to characterize potential health risk from trichloroethylene contaminated ground water at Beale Air Force Base in California

Description: Conservative deterministic, screening-level calculations of exposure and risk commonly are used in quantitative assessments of potential human-health consequences from contaminants in environmental media. However, these calculations generally are based on multiple upper-bound point estimates of input parameters, particularly for exposure attributes, and can therefore produce results for decision makers that actually overstate the need for costly remediation. Alternatively, a more informative and quantitative characterization of health risk can be obtained by quantifying uncertainty and variability in exposure. This process is illustrated in this report for a hypothetical population at a specific site at Beale Air Force Base in California, where there is trichloroethylene (TCE) contaminated ground water and a potential for future residential use. When uncertainty and variability in exposure were addressed jointly for this case, the 95th-percentile upper-bound value of individual excess lifetime cancer risk was a factor approaching 10 lower than the most conservative deterministic estimate. Additionally, the probability of more than zero additional cases of cancer can be estimated, and in this case it is less than 0.5 for a hypothetical future residential population of up to 26,900 individuals present for any 7.6-y interval of a 70-y time period. Clearly, the results from application of this probabilistic approach can provide reasonable and equitable risk-acceptability criteria for a contaminated site.
Date: October 5, 1999
Creator: Daniels, J I; Bogen, K T & Hall, L C
Partner: UNT Libraries Government Documents Department