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Experiments on few-electron very high-Z ions

Description: The measurement of the Lamb shift in heliumlike uranium and outlines future experimental tests of QED using few-electron very high atomic number (Z) ions are presented. A discussion of the possibility of using ultrarelativistic atomic collisions to produce very heavy leptons is also presented. 38 refs., 4 figs., 1 tab.
Date: July 1, 1986
Creator: Gould, H. & Munger, C.
Partner: UNT Libraries Government Documents Department

Experiments and prospects for induction linac drivers

Description: In the last three years, the US program in Heavy Ion Fusion has concentrated on understanding the induction linac approach to a power-plant driver. In this method it is important that the beam current be maximized throughout the accelerator. Consequently, it is crucial to understand the space-charge limit in the AG transport system in the linac and, also, to achieve current amplification during acceleration to keep pace with the kinematical increase of this limit with energy. Experimental results on both these matters and also on the use of multiple beams (inside the same accelerating structure) will be described. A new examination of the most attractive properties of the induction linac for a fusion driver has clearly pointed to the advantage of using heavy ions with a charge-state greater than unity - perhaps q = 3 may be an optimum. This development places even greater importance on understanding space-charge limits and mechanisms for emittance growth; also, it will require a new emphasis on the development of a suitable ion source.
Date: May 1, 1986
Creator: D., Keefe
Partner: UNT Libraries Government Documents Department

Highlights of the heavy ion fusion symposium

Description: The current status and prospects for inertial confinement fusion based on the use of intense beams of heavy ions will be described in the light of results presented at the International Symposium on Heavy Ion Fusion, (Washington, DC, May 27-29, 1986).
Date: July 1, 1986
Creator: Keefe, D.
Partner: UNT Libraries Government Documents Department

Further measurements of electron transmission and avalanche gain in narrow lead glass tubing

Description: Measurements of electron transmission and multiplication in lead glass tube arrays, in which a resistive field shaping electrode is provided by reduction of a surface layer of lead oxide, have been continued. The transmission losses have been successfully modeled allowing the true avalanche gains to be extracted. Gains of up to 100 have been observed. Applications as a photon shield in Cherenkov imaging detectors are discussed. 8 refs., 7 figs.
Date: October 1, 1985
Creator: Fujieda, I.; Mulera, T.A.; Perez-Mendez, V. & del Guerra, A.
Partner: UNT Libraries Government Documents Department

MLE (Maximum Likelihood Estimator) reconstruction of a brain phantom using a Monte Carlo transition matrix and a statistical stopping rule

Description: In order to study properties of the Maximum Likelihood Estimator (MLE) algorithm for image reconstruction in Positron Emission Tomographyy (PET), the algorithm is applied to data obtained by the ECAT-III tomograph from a brain phantom. The procedure for subtracting accidental coincidences from the data stream generated by this physical phantom is such that he resultant data are not Poisson distributed. This makes the present investigation different from other investigations based on computer-simulated phantoms. It is shown that the MLE algorithm is robust enough to yield comparatively good images, especially when the phantom is in the periphery of the field of view, even though the underlying assumption of the algorithm is violated. Two transition matrices are utilized. The first uses geometric considerations only. The second is derived by a Monte Carlo simulation which takes into account Compton scattering in the detectors, positron range, etc. in the detectors. It is demonstrated that the images obtained from the Monte Carlo matrix are superior in some specific ways. A stopping rule derived earlier and allowing the user to stop the iterative process before the images begin to deteriorate is tested. Since the rule is based on the Poisson assumption, it does not work well with the presently available data, although it is successful wit computer-simulated Poisson data.
Date: October 1, 1987
Creator: Veklerov, E.; Llacer, J. & Hoffman, E.J.
Partner: UNT Libraries Government Documents Department

Nuclear breakup and particle densities in 200 A GeV - /sup 16/O interactions with emulsion nuclei

Description: Experiment EMU-01 makes use of emulsion chambers and conventional stacks to study the interactions in matter of 200 A GeV /sup 16/O nuclei accelerated at the CERN SPS. Projectile fragmentation is compatible with such interactions of /sup 16/O nuclei at 2 A GeV, indications of limiting fragmentation. Particle production is examined via high precision pseudo-rapidity distributions. Energy densities up to about 3 GeVfm/sup 3/ are observed in central /sup 16/O + Ag(Br) interactions. Pseudo-rapidity density distributions and fluctuations are well reproduced by the MC model Pritiof, although the existence of new and unknown sources of density fluctuations are not excluded by the data. 7 refs., 7 figs.
Date: September 1, 1987
Creator: Adamovich, M.I.; Alexandrov, Y.A.; Asimov, S.A.; Badyal, S.K.; Basova, E. & Bhalla, K.B.
Partner: UNT Libraries Government Documents Department

Nuclear matter equation of state from relativistic heavy ions to supernovae

Description: In this presentation the relationship between relativistic nucleus-nucleus collisions and the nuclear equation of state is discussed. The connection between observables measured in the experiments and thermodynamic variables used to describe the system is made. Through this connection a semi-empirical nuclear equation of state is extracted from the data. The resulting equation of state is discussed in terms of nuclear matter calculations, neutron star stability and supernova collapse. 22 refs., 7 figs.
Date: June 1, 1986
Creator: Harris, J.W.
Partner: UNT Libraries Government Documents Department

Faults and gravity anomalies over the East Mesa hydrothermal-geothermal system

Description: Detailed interpretations of gravity anomalies over geothermal systems may be extremely useful for mapping the fracture or fault systems that control the circulation of the thermal waters. This approach seems to be particularly applicable in areas like the Salton Trough where reactions between the thermal waters and the porous sediments produce authigenic-hydrothermal minerals in sufficient quantity to cause distinct gravity anomalies at the surface. A 3-D inversion of the residual Bouguer gravity anomaly over the East Mesa geothermal field was made to examine the densified volume of rock. We show that the data not only resolve a north-south and an intersecting northwest structure, but that it may be possible to distinguish between the active present-day hydrothermal system and an older and cooler part of the system. The densified region is compared spatially to self-potential, thermal and seismic results and we find a good concordance between the different geophysical data sets. Our results agree with previous studies that have indicated that the main feeder fault recharging the East Mesa reservoir dips steeply to the west.
Date: May 1, 1986
Creator: Goldstein, N.E. & Carle, S.
Partner: UNT Libraries Government Documents Department

From pion production to the nuclear matter equation of state

Description: Equilibrium rate calculations are used to show that thermal and chemical equilibrium are approached during the high density stage in central nucleus-nucleus collisions. The total pion multiplicity is established as a probe of the high density stage. The observed pion multiplicities are compared to predictions of a hadrochemical model with Rankine-Hugoniot compression. Assuming a partition of the internal energy per nucleon into thermal and compressional energy fractions, a nuclear matter equation of state is found which is very similar to that derived using an independent intranuclear cascade approach. 20 references.
Date: January 1, 1984
Creator: Harris, J.W. & Stock, R.
Partner: UNT Libraries Government Documents Department

An instrument control and data analysis program for NMR imaging and spectroscopy

Description: We describe a software environment created to support real-time instrument control and signal acquisition as well as array-processor based signal and image processing in up to five dimensions. The environment is configured for NMR imaging and in vivo spectroscopy. It is designed to provide flexible tools for implementing novel NMR experiments in the research laboratory. Data acquisition and processing operations are programmed in macros which are loaded in assembled from to minimize instruction overhead. Data arrays are dynamically allocated for efficient use of memory and can be mapped directly into disk files. The command set includes primitives for real-time control of data acquisition, scalar arithmetic, string manipulation, branching, a file system and vector operations carried out by an array processor. 6 figs.
Date: January 1, 1988
Creator: Roos, M.S.; Mushlin, R.A.; Veklerov, E.; Port, J.D.; Ladd, C. & Harrison, C.G.
Partner: UNT Libraries Government Documents Department

Baryon production at PEP

Description: Measurements of inclusive ..lambda.. + anti ..lambda.. production for 1.0 less than or equal to p less than or equal to 10.0 GeV/c and p + anti p production for 0.4 less than or equal to p less than or equal to 2.0 GeV/c show significant baryon production in e/sup +/e/sup -/ annihilation at E/sub cm/ = 29 GeV. ..lambda.. + anti ..lambda.. production represents 0.2 ..lambda..'s or anti ..lambda..'s per PEP event while the observed p + anti p production implies all baryon-antibaryon pair production is occurring at least as often as 0.6 per event, depending on the yet to be measured p + anti p production at high momentum. Comparisons are made with the first theoretical attempts to account for baryon production at these energies.
Date: September 1, 1981
Creator: Goldhaber, G. & Weiss, J.M.
Partner: UNT Libraries Government Documents Department

Collision of fast highly charged ions in gas targets: ionization, recoil-ion production, and charge transfer

Description: Electron-capture, ionization, and recoil-ion-production cross sections are measured and calculated for fast highly charged projectiles in hydrogen and rare-gas targets. Recoil-ion-production cross sections are found to be large; the low energy and high charge states of the recoil ions make them useful for subsequent collision studies.
Date: July 1, 1982
Creator: Schalchter, A.S.; Berkner, K.H. & Beyer, H.F.
Partner: UNT Libraries Government Documents Department

Effects of electronically neutral impurities on muonium in germanium

Description: Low-temperature measurements of muonium parameters in various germanium crystals have been performed. We have measured crystals with different levels of neutral impurities, with and without dislocations, and with different annealing histories. The most striking result is the apparent trapping of Mu by silicon impurities in germanium.
Date: April 1, 1983
Creator: Clawson, C.W.; Crowe, K.M.; Haller, E.E.; Rosenblum, S.S. & Brewer, J.H.
Partner: UNT Libraries Government Documents Department

Probing nuclear matter with dileptons

Description: Dileptons are shown to be of interest in helping probe extreme conditions of temperature and density in nuclear matter. The current state of experimental knowledge about dileptons is briefly described, and their use in upcoming experiments with light ions at CERN SPS are reviewed, including possible signatures of quark matter formation. Use of dileptons in an upcoming experiment with a new spectrometer at Berkeley is also discussed. This experiment will probe the nuclear matter equation of state at high temperature and density. 16 refs., 8 figs. (LEW)
Date: June 1, 1986
Creator: Schroeder, L.S.
Partner: UNT Libraries Government Documents Department

A search for new leptons with heavy neutrinos in e/sup +/e/sup -/ annihilation at. sqrt. s = 29 GeV. [None]

Description: This thesis describes the results of a search for new leptons with associated heavy neutrinos. The search uses 68.1 pb/sup /minus/1/ of data taken with the TPC2..gamma.. detector at the PEP storage ring. New lepton pairs with charged lepton masses m/sub L/ < 12 GeV and mass differences in the approximate range 0.4 GeV < m/sub L/ /minus/ m/sub/nu/L/ < 2.5 GeV are excluded at the 99% confidence level. Results are also given of a study of search techniques for the region m/sub L/ < 12 GeV, m/sub L/ /minus/ m/sub ..nu..L/ < 0.4 GeV.
Date: May 5, 1988
Creator: Mathis, L.G.
Partner: UNT Libraries Government Documents Department

Application of a dc SQUID to rf amplification: NQR

Description: Superconducting QUantum Interference Devices (SQUIDs) have been used for more than a decade for the detection of magnetic resonance. Until recently, these devices had mostly been confined to operation in the audiofrequency range, so that experiments have been restricted to measurements of resonance at low frequencies, or of changes in the static susceptibility of a sample induced by rf irradiation at the resonant frequency. However, the recent extension of the operating range of low noise dc SQUIDs to radiofrequencies (rf) allows one to detect magnetic resonance directly at frequencies up to several hundred megahertz. In this paper, we begin by summarizing the properties of dc SQUIDs as tuned rf amplifers. We then describe first, the development of a SQUID system for the detection of pulsed nuclear quadrupole resonance (NQR) at about 30 MHz and second, a novel technique for observing magnetic resonances in the absence of any externally applied rf fields.
Date: May 1, 1985
Creator: Hilbert, C.; Clarke, J.; Sleator, T. & Hahn, E.L.
Partner: UNT Libraries Government Documents Department

Specialty magnets

Description: A number of basic conceptual designs are explained for magnet systems that use permanent magnet materials. Included are iron free multipoles and hybrid magnets. Also appended is a discussion of the manufacturing process and magnetic properties of some permanent magnet materials. (LEW)
Date: July 1, 1986
Creator: Halbach, K.
Partner: UNT Libraries Government Documents Department

Performance of three 4. 5 m dipoles for SSC reference design D

Description: Three 4.5 m long dipoles for Reference Design D of the proposed Superconducting Super Collider have been successfully tested. The magnets are cold-iron (and cold bore) 1-in-1 dipoles, wound with current density-graded high homogeneity NbTi cable in a two-layer cos theta coil of 40 mm inner diameter. The coil is prestressed by 15 mm wide stainless steel collars, and mounted in a circular, split iron yoke of 267 mm outer diameter, supported in a cylindrical yoke containment vessel. At 4.5 K the magnets reached a field of about 6.6T with little training, or the short sample limit of the conductor, and in subcooled (2.6 to 2.4 K) liquid, 8T was achieved. The allowed harmonics were close to the predicted values, and the unallowed harmonics small. The sextupole trim coil operated at eight times the required current without training.
Date: January 1, 1985
Creator: Dahl, P.; Cottingham, J.; Fernow, R.; Garber, M.; Ghosh, A.; Goodzeit, C. et al.
Partner: UNT Libraries Government Documents Department

Premartensitic microstructures as seen in the high-resolution electron microscope: A study of a Ni-Al alloy

Description: The present study indicates that the B2 ..beta..-phase in quenched Ni/sub 62.5/Al/sub 37.5/ is distorted by displacement waves involving a planar shufflin of atoms resembling the final 7R martensite structure and with wavelenghts of the order of 1.3 nm. The appearance of a <110><110> type modulation with the indicated periodicity corresponds well with recent inelastic neutron scattering results which reveal nonlinear behavior in the TA<110> phonon dispersion curve around the same wavelengths indicating a partial lattice softening for such waves. In bulk material all six equivalent wave-vectors are equally present. These distortional modulations are configured in some form of three-dimensional assembly. Following the interpretation given above, it can be concluded that a one-dimensional domain structure along one of six <110> directions may exist. However, the beating of six displacement waves with apparently uncorrelated phase and wavelengths rules out the existence of a ''conventional'' three-dimensional domain structure. For this reason it is uncertain whether much more information can be gained from such image simulations. There are now numerous indications that the underlying structure to the tweed contrast in this alloy is a precursor effect of the martensitic transformation. However, a detailed description of the effective correlation between the distorted parent phase and the martensitic product phase has yet to be developed. Recent HREM results reveal the existence of a sequence of different structures in the transition region between the modulated ..beta..-phase and the martensitic phase, depending on parameters such as the local composition and stress. Such transition structures include modulated k..beta..-phase in which only one (110) modulation is preferred or in which the periodicity differs from the above described 1.3 nm and the FCT L1/sub o/ martensite with single shear defects. 1 fig., 26 refs.
Date: February 12, 1988
Creator: Schryvers, D.; Tanner, L. & Van Tendeloo, G.
Partner: UNT Libraries Government Documents Department

Preliminary results from MBE-4: a four beam induction linac for heavy ion fusion research

Description: Preliminary results are presented from a scaled experimental multiple beam induction linac. This experiment is part of a program of accelerator research for heavy ion fusion. It is shown that multiple beams can be accelerated without significant mutual interaction. Measurements of the longitudinal dynamics of a current-amplifying induction linac are presented and compared to calculations. Coupling of transverse and longitudinal dynamics is discussed.
Date: May 1, 1986
Creator: Fessenden, T.J.; Judd, D.L.; Keefe, D.; Kim, C.; Laslett, L.J.; Smith, L. et al.
Partner: UNT Libraries Government Documents Department

Preliminary design of a 10 MV ion accelerator

Description: At the low energy end of an induction linac HIF driver the beam current is limited by our ability to control space charge by a focusing system. As a consequence, HIF induction accelerator designs feature simultaneous acceleration of many beams in parallel within a single accelerator structure. As the speed of the beams increase, the focusing system changes from electrostatic to magnetic quadrupoles with a corresponding increase in the maximum allowable current. At that point the beams are merged thereby decreasing the cost of the subsequent accelerator structure. The LBL group is developing an experiment to study the physics of merging and of focusing ion beams. In the design, parallel beams of ions (C/sup +/, Al/sup +/, or Al/sup + +/) are accelerated to several MV and merged transversely. The merged beams are then further accelerated and the growth in transverse and longitudinal emittance is determined for comparison with theory. The apparatus will then be used to study the problems associated with focusing ion beams to a small spot. Details of the accelerator design and considerations of the physics of combining beams are presented.
Date: June 1, 1986
Creator: Fessenden, T.J.; Celata, C.M.; Faltens, A.; Henderson, T.; Judd, D.L.; Keefe, D. et al.
Partner: UNT Libraries Government Documents Department

Recent results from Mark II at SPEAR and PEP

Description: Three results are presented: (1) The semi-leptonic branching ratio of the ..lambda../sub c/ has been measured at SPEAR to be B(..lambda../sub c//sup +/ ..-->.. e/sup +/X) = (4.5 +- 1.7)%. (2) Properties of tau-pair production have been measured at PEP at square root S = 29 GeV: sigma/sup tau tau//sigma/sup QED/ = 0.97 +- 0.05 +- 0.06; the forward-backward asymmetry is A/sub tau tau/ = (-3.5 +- 5.0)%; inclusive branching ratios are B(tau ..-->.. 1 Prong) = (86 +- 4)%, B(tau ..-->.. 3 Prongs) = (14 +- 4)%, B(tau ..-->.. 5 Prongs) < 0.6% (95% C.L.). (3) A search has been performed for the pair production of charged, point-like, spin 0 particles. The existence of such particles can be ruled out at a 90% confidence level for 3 approx. < M approx. < 10 GeV/c/sup 2/ and branching ratio into hadrons approx. < 90%.
Date: April 1, 1982
Creator: Strait, J.
Partner: UNT Libraries Government Documents Department