18 Matching Results

Search Results

Advanced search parameters have been applied.

CRAB Cavity in CERN SPS

Description: Beam collisions with a crossing angle at the interaction point are often necessary in colliders to reduce the effects of parasitic collisions which induce emittance growth and decrease beam lifetime. The crossing angle reduces the geometrical overlap of the beams and hence the luminosity. Crab cavity offer a promising way to compensate the crossing angle and to realize effective head-on collisions. Moreover, the crab crossing mitigates the synchro-betatron resonances due to the crossing angle. A crab cavity experiment in SPS is proposed as a proof of principle before deciding on a full crab-cavity implementation in the LHC. In this paper, we investigate the effects of a single crab cavity on beam dynamics in the SPS and life time.
Date: May 1, 2010
Creator: Kim, H.J.; Sen, T. & /Fermilab
Partner: UNT Libraries Government Documents Department

Reactions between medium-mass nuclei at subbarrier energies

Description: A number of diverse theories can account, to a similar extent, for experimentally observed large enhancements in subbarrier fusion cross sections. For example, coupled-channels, neck-formation, distributed-barrier, and direct absorption theories have been used with comparable degrees of success to analyze the enhancement in {sup 58}Ni + {sup 58}Ni fusion cross sections at subbarrier energies. This example illustrates that, although necessary, fusion cross sections alone are not sufficient to assess what really is the underlying enhancement mechanism. Although their details vary, these theories share a reliance on interactions between the incident and one or more outgoing reaction channels to produce the enhancement. Being microscopic, the coupled-channels approach requires interactions with specific individual exit channels, such as inelastic and nucleon transfer. On the other hand, being macroscopic in nature, the neck-formation and distributed-barrier theories treat the interactions in a more global way. Thus, in addition to fusion, detailed studies of exit channels in general at subbarrier energies are very much needed in order to develop a good theoretical understanding of how the enhancement really comes about. We present results from our study of transfer reactions between {sup 50}Ti and {sup 93}Nb that pertain to the subbarrier neck. Since the experimental arrangement used is the same as that of our previous study, only a brief description is given. Target and target-like ejectiles emitted forward from the bombardment of thin {sup 50}Ti targets by {sup 93}Nb beams were first magnetically analyzed and then detected by a hybrid position-sensitive gas detector system, which was placed at the nominal focal plane of the magent; ejectiles emitted at 10{degree} {le} {theta} {le} 20{degree} angular range were investigated at bombarding energies of 283.1, 291.2, 273.2, 302.0, and 306.9 MeV.
Date: November 1, 1990
Creator: Kim, H.J.
Partner: UNT Libraries Government Documents Department

Nuclear structure effects on alpha reduced widths

Description: A review of ..cap alpha.. widths for s-wave transitions is presented together with a discussion of the following topics: (1) a new determination of the /sup 218/Ra half-life and its relation to reflection asymmetry in nuclei near N = 130, (2) a measurement of the /sup 194/Pb ..cap alpha..-decay rate and the influence of the Z = 82 gap on neutron-deficient Pb nuclei, and (3) an up-date of ..cap alpha..-decay-rate systematics for isotopes in the rare earth and medium-weight mass regions. 16 refs., 6 figs.
Date: January 1, 1987
Creator: Toth, K.S.; Ellis-Akovali, Y.A.; Kim, H.J. & McConnell, J.W.
Partner: UNT Libraries Government Documents Department

Assessment of RELAP5/MOD3.1 with the LSTF SB-SG-06 experiment simulating a steam generator tube rupture transient

Description: The objective of the present work is to identify the predictability of RELAP5/MOD3.1 regarding thermal-hydraulic behavior during a steam generator tube rupture (SGTR). To evaluate the computed results, LSTF SB-SG-06 test data simulating the SGTR that occurred at the Mihama Unit 2 in 1991 are used. Also, some sensitivity studies of the code change in RELAP5, the break simulation model, and the break valve discharge coefficient are performed. The calculation results indicate that the RELAP5/MOD3.1 code predicted well the sequence of events and the major phenomena during the transient, such as the asymmetric loop behavior, reactor coolant system (RCS) cooldown and heat transfer by natural circulation, the primary and secondary system depressurization by the pressurizer auxiliary spray and the steam dump using the intact loop steam generator (SG) relief valve, and so on. However, there are some differences from the experimental data in the number of the relief valve cycling in the affected SG, and the flow regime of the hot leg with the pressurizer, and the break flow rates. Finally, the calculation also indicates that the coolant in the core could remain in a subcooled state as a result of the heat transfer caused by the natural circulation flow even if the reactor coolant pumps (RCPs) turned off and that the affected SG could be properly isolated to minimize the radiological release after the SGTR.
Date: September 1, 1996
Creator: Seul, K. W.; Bang, Y. S.; Lee, S. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Electromagnetic method for analyzing the property of steel casing

Description: It has been shown that electromagnetic (EM) imaging, in particular in borehole applications, can be effective in characterizing and monitoring subsurface processes involved in improved oil recovery operations and production management. In this report the authors present an innovative EM method for extracting information about a steel casing in terms of its electrical conductivity, magnetic permeability, and the casing thickness. The method is based on accurate evaluation of magnetic fields near the transmitting loop in a steel-cased borehole, and the least squares inversion of thus measured data. The need to make measurements close to the source stems from the two related considerations. One reason is that by making measurements close to the transmitter one can keep the formation response from entering the measurement to a minimum. The other reason concerns with the practical consideration involved in fabricating a borehole tool. The measurement accuracy in terms of PPM to the primary field can best be achieved when the transmitter and receiver are close to each other. To facilitate this requirement one can consider a single loop acting as the source and the receiver operating in time domain, or a closely coupled frequency-domain system with the source-receiver separation of just a few inches apart. Results are discussed.
Date: February 1, 1998
Creator: Lee, K.H.; Kim, H.J. & Song, Y.
Partner: UNT Libraries Government Documents Department

Three-dimensional transient electromagnetic modeling in the Laplace Domain

Description: In modeling electromagnetic responses, Maxwell's equations in the frequency domain are popular and have been widely used (Nabighian, 1994; Newman and Alumbaugh, 1995; Smith, 1996, to list a few). Recently, electromagnetic modeling in the time domain using the finite difference (FDTD) method (Wang and Hohmann, 1993) has also been used to study transient electromagnetic interactions in the conductive medium. This paper presents a new technique to compute the electromagnetic response of three-dimensional (3-D) structures. The proposed new method is based on transforming Maxwell's equations to the Laplace domain. For each discrete Laplace variable, Maxwell's equations are discretized in 3-D using the staggered grid and the finite difference method (FDM). The resulting system of equations is then solved for the fields using the incomplete Cholesky conjugate gradient (ICCG) method. The new method is particularly effective in saving computer memory since all the operations are carried out in real numbers. For the same reason, the computing speed is faster than frequency domain modeling. The proposed approach can be an extremely useful tool in developing an inversion algorithm using the time domain data.
Date: September 1, 1998
Creator: Mizunaga, H.; Lee, Ki Ha & Kim, H.J.
Partner: UNT Libraries Government Documents Department

Assessment of RELAP5/MOD3.1 for gravity-driven injection experiment in the core makeup tank of the CARR Passive Reactor (CP-1300)

Description: The objective of the present work is to improve the analysis capability of RELAP5/MOD3.1 on the direct contact condensation in the core makeup tank (CMT) of passive high-pressure injection system (PHPIS) in the CARR Passive Reactor (CP-1300). The gravity-driven injection experiment is conducted by using a small scale test facility to identify the parameters having significant effects on the gravity-driven injection and the major condensation modes. It turns out that the larger the water subcooling is, the more initiation of injection is delayed, and the sparger and the natural circulation of the hot water from the steam generator accelerate the gravity-driven injection. The condensation modes are divided into three modes: sonic jet, subsonic jet, and steam cavity. RELAP5/MOD3.1 is chosen to evaluate the cod predictability on the direct contact condensation in the CMT. It is found that the predictions of MOD3.1 are in better agreement with the experimental data than those of MOD3.0. From the nodalization study of the test section, the 1-node model shows better agreement with the experimental data than the multi-node models. RELAP5/MOD3.1 identifies the flow regime of the test section as vertical stratification. However, the flow regime observed in the experiment is the subsonic jet with the bubble having the vertical cone shape. To accurately predict the direct contact condensation in the CMT with RELAP5/MOD3.1, it is essential that a new set of the interfacial heat transfer coefficients and a new flow regime map for direct contact condensation in the CMT be developed.
Date: October 1, 1996
Creator: Lee, S. I.; No, H. C.; Bang, Y. S. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Implications of heavy-ion-induced satellite x-ray emission. II. Production of K and L x rays by 0. 9 to 2. 6 MeV/u Ar ions in thick targets of V, Cu, Nb, Ta, and Pt

Description: Cross sections are reported for x-ray production in targets of /sup 23/V, /sup 29/Cu, /sup 41/Nb, /sup 73/Ta, and /sup 78/Pt by /sup 40/Ar ions of 36.0, 56.4, 76.6, and 103 MeV. Because the targets were relatively thick, approx. 1 mg/cm/sup 2/, the data were corrected, using a novel approach, for projectile energy loss and x-ray attenuation in the targets. The cross sections so analyzed are compared with the predictions of the first Born approximation as well as with those of a more extensive treatment which includes energy loss, Coulomb deflection, perturbed stationary-state, and relativistic effects. The significant discrepancies between the data and this latter theory are atrributed primarily to the influence of multiple ionization on the x-ray emission probabilities.
Date: January 1, 1983
Creator: O'Kelley, G.D.; Auble, R.L.; Hulett, L.D.; Kim, H.J.; Milner, W.T.; Raman, S. et al.
Partner: UNT Libraries Government Documents Department

Washing of Cloth Contaminated with Radionuclides Using A Detergent-Free Laundry System

Description: In this study, we describe a new laundry system to wash clothes, including those contaminated with radionuclides, without using detergent. The main part of this system is electrolytic cell that consists of a cathode with a special coating of nickel, an anode of nickel, and a cation exchange membrane between the two electrodes. The electrolyte is supplied to the anode and the tap-water to the cathode. When an electricity of 5 volts and 25 amperes is applied to the electrodes, the processed water is produced from the cathode. This processed water containing no detergent was investigated experimentally with regard to its decontamination efficiency of radionuclides and detergency of soil as compared to the conventional washing using detergent. It was found that the processed water from this system has an ability to simultaneously remove radionuclides and soil from the cloth with good efficiency.
Date: February 25, 2003
Creator: Yim, S. P.; Ahn, B. G.; Lee, H. J.; Shon, J. S.; Chung, H.; Kim, K. J. et al.
Partner: UNT Libraries Government Documents Department

Far-infrared carrier dynamics in superconducting MgB[sub 2]

Description: We have performed optical-pump terahertz-probe measurements in transmission on MgB{sub 2} thin films in the superconducting state. The initial optical perturbation of the superconducting condensate and subsequent pair recovery display a strong fluence dependence. In conclusion, we have performed the first time-resolved far-infrared studies on the new superconductor MgB{sub 2}. We have observed a strongly fluence dependent pair recovery time that, at the lowest fluences used, is approximately 500 ps. In addition, at the lower excitation fluences where superconductivity is not destroyed, a risetime in the dynamics is observed that may be due to photoinduced gap fluctuations.
Date: January 1, 2002
Creator: Averitt, R. D. (Richard D.); Demsar, J. (Jure); Taylor, Antoinette J.,; Kang, W. N. (Won-Nam); Kim, H. J. (Hoen-Jung); Choi, E. M. (Eun-Mi) et al.
Partner: UNT Libraries Government Documents Department

Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are also important consideration for the LHC upgrades. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both RIDC and the LHC. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: November 24, 2008
Creator: Fischer,W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department

Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. Electron lenses were proposed for both RHIC and the LHC to reduce the head-on beam-beam effect. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: January 12, 2009
Creator: Fischer, W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department

Magnetism as a main origin for the diverse magnetotransport.

Description: Magnetotransport properties of pure Mg metal and MgB{sub 2} samples with varying amounts of unreacted Mg are systematically studied in magnetic fields up to 18 T. With increasing quantity of Mg, the inhomogeneous MgB{sub 2} samples show greatly decreased residual resistivity, enhanced residual resistance ratio (RRR) and enhanced magnetoresistance (MR), gradually approaching the transport behaviors of pure Mg metal. We use the generalized effective medium theory to show that the large RRR and MR of the inhomogeneous MgB{sub 2} samples can be quantitatively explained by a two-phase model in which the two phases are MgB{sub 2} and pure Mg.
Date: January 1, 2001
Creator: Betts, J. B. (Jonathan B.); Jaime, M. (Marcello); Lacerda, A. H. (Alex H.); Boebinger, G. S. (Gregory S.); Jung, C. U. (Chang Uk); Kim, H. J. (Hoen-Jung) et al.
Partner: UNT Libraries Government Documents Department

Long-Range And Head-On Beam-Beam Compensation Studies in RHIC With Lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. Electron lenses were proposed for both RHIC and the LHC to reduce the head-on beam-beam effect. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: November 28, 2011
Creator: Fischer, W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department

Interferometric studies from p-p-fragment coincidences

Description: Exclusive p-p correlations from the {sup 58}Ni + {sup 58}Ni reaction have been measured at an incident energy of 850 MeV. The enhancement in the p-p correlation function for small {Delta}p is satisfactorily explained by p-p final-state interaction effects. the observed enhancement is found to depend on the relative angle between the fragment and p-p c.m. velocities. The observed dependence of the p-p coincidence yield on the orientation of {Delta}p with respect to the plane spanned by the fragment and p-p c.m. velocities is attributed to angular momentum effects. 13 refs., 5 figs.
Date: January 1, 1991
Creator: Korolija, M. (Institut Rudjer Boskovic, Zagreb (Yugoslavia) Joint Inst. for Heavy Ion Research, Oak Ridge, TN (United States)); Shapira, D.; Gomez del Campo, J.; Kim, H.J. (Oak Ridge National Lab., TN (United States)); Cindro, N. (Institut Rudjer Boskovic, Zagreb (Yugoslavia)); Teh, K. (Joint Inst. for Heavy Ion Research, Oak Ridge, TN (United States)) et al.
Partner: UNT Libraries Government Documents Department

Two-proton correlations from the sup 58 Ni + sup 58 Ni reaction at E sub inc approx equal 876. 5 MeV

Description: The enhancement in the p-p correlation function from the {sup 58}Ni + {sup 58}Ni reaction at E{sub inc} = 876.5 MeV is interpreted as a result of the interaction of the emitted protons in the final state. The p-p correlation function has been found to decrease very rapidly with the increase of the relative angle between the fragment and the two-proton c.m. velocities. This causes the extracted p-p correlation function to be dependent on the kinematics of the measurements. The deduced average particle emission times are in the range of 5 {minus} 6 {times} 10{sup {minus}22} s.
Date: January 1, 1990
Creator: Korolija, M. (Institut Rudjer Boskovic, Zagreb (Yugoslavia) Joint Inst. for Heavy Ion Research, Oak Ridge, TN (USA)); Shapira, D.; Del Campo, J.G.; Kim, H.J. (Oak Ridge National Lab., TN (USA)); Teh, K. (Oak Ridge National Lab., TN (USA) Joint Inst. for Heavy Ion Research, Oak Ridge, TN (USA) Vanderbilt Univ., Nashville, TN (USA)) & Shea, J.Y. (Joint Inst. for Heavy Ion Research, Oak Ridge, TN (USA)
Partner: UNT Libraries Government Documents Department