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Microwave stability limits for the main ring and growth across transition

Description: The purpose of this paper is to estimate the phase space blowup across transition and give critical absolute value of Z/n limits at each stage of performance. It turns out that the most stringent limit is absolute value of Z/n approx.1.3 ..cap omega.. which occurs during the RF manipulation of the proton bunches at 120 GeV in preparation of anti p production.
Date: January 1, 1986
Creator: Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Mechanical properties testing of several 800 MeV proton irradiated BCC metals and alloys. [Candidate window materials for SIN beam stop]

Description: A spallation neutron source for the 600-MeV proton accelerator facility at the Swiss Institute for Nuclear Research (SIN) consists of a vertical cylinder filled with molten Pb-Bi. The proton beam enters the cylinder, passing upward through a window in contact with the Pb-Bi eutectic liquid. Investigations are underway at the 800-MeV proton accelerator at LAMPF to test the performance of candidate SIN window materials. Based on considerations of chemical compatibility with molten Pb-Bi, as well as radiation damage mechanisms, Fe, Ta, Fe-2.25Cr-1Mo, and Fe-12Cr-1Mo (Ht-9) were chosen as candidate materials. Sheet tensile samples were sealed inside capsules containing Pb-Bi and were proton-irradiated at LAMPF to two fluences, 4.8 and 54 x 10/sup 23/ p/m/sup 2/. The beam current was approximately equal to the 1 mA anticipated for the upgraded SIN accelerator. Yield and ultimate strengths increased upon irradiation in all materials, while the ductility decreased. The pure metals, Ta and Fe, exhibited the greatest radiation hardening and embrittlement. The HT-9 alloy showed the smallest changes in strength and ductility.
Date: January 1, 1986
Creator: Brown, R.D.; Wechsler, M.S. & Tschalaer, C.
Partner: UNT Libraries Government Documents Department

Influence of radiation-induced segregation on ductility of a nickel-silicon alloy

Description: Flat tensile specimens 60 ..mu..m thick of Ni-8 at. % Si were irradiated to bulk damage levels of 0.1 to 0.3 dpa with either 7 MeV protons or 28 MeV alpha particles at 750 K. The alpha bombarded specimens incurred 750 at. ppM He per 0.1 dpa in the course of their damage-generating irradiation. Radiation-induced silicon segregation gave rise to Ni/sub 3/Si layers at internal and external surfaces. Postirradiation tensile tests conducted either at 300 K or 720 K revealed fully ductile (chisel-edged) transgranular fracture profiles. There were no significant differences between the proton-bombarded specimens and the unbombarded controls, both exhibiting >25% total elongations, while the alpha-bombarded specimens showed ductile fractures with somewhat lower (17 to 18%) elongation values probably due to hardening caused by small helium bubbles. Certain specimens that were preimplanted with 250 to 1000 at. ppM He at 970 K to encourage intergranular failure and expose grain boundaries did fail intergranularly. It is concluded that radiation-induced silicon segregation does not cause intrinsic embrittlement.
Date: January 1, 1986
Creator: Packan, N.H.; Schroeder, H. & Kesternich, W.
Partner: UNT Libraries Government Documents Department

Field ion microscopy study of depleted zones in tungsten after proton irradiation

Description: Depleted zones in tungsten, that resulted from medium-energy proton irradiations, were studied using the Field Ion Microscope (FIM). The shapes and sizes of depleted zones is an important aspect of basic radiation damage. These data can be compared to models that have been suggested as well as aid development of new models. These depleted volumes are of interest not only for an understanding of basic radiation effects, but also because they affect material properties and can act as nucleation sites for voids or gas bubbles. Depleted zones were produced in annealed tungsten wires by irradiation with 600 to 800 MeV protons at the Los Alamos Meson Physics Facility. The defects observed in the irradiated samples included vacancies, depleted zones, grain boundaries, and dislocations. Single vacancies were the most commonly observed defect. Of the samples ''imaged,'' over 50 depleted zones were found within the area of high resolution in the area between the prominent (112) poles in a (110) oriented sample. The number of layers photographed in each sample was dependent upon the initial shape of the tip and ranged from 60 to 200 (110) sequential layers.
Date: January 1, 1986
Creator: Farnum, D.J.; Sommer, W.F.; Inal, O.T. & Yu, J.
Partner: UNT Libraries Government Documents Department

White neutron source from 1 to 400 MeV

Description: A new high intensity white neutron source has recently been constructed at Los Alamos. Beams of nuetrons with a continuous energy distribution up to several hundred MeV are produced by the spallation reaction using the 800 MeV pulsed proton beam from the Los Alamos Meson Physics Facility (LAMPF) linear accelerator. The neutron facility has been designed to make very efficient use of the LAMPF beam with several experiments being able to operate simultaneously. Typical running conditions involve approximately 50,000 bursts/sec and proton beam currents of 2.5 microamperes. Experiments planned for this fall include gamma-ray production, neutron induced fission, and medium energy (n,p) and (p,n) studies. 1 ref., 7 figs., 1 tab.
Date: January 1, 1986
Creator: Wender, S. A. & Lisowski, P. W.
Partner: UNT Libraries Government Documents Department

Polarized proton acceleration at the Brookhaven AGS

Description: At the conclusion of polarized proton commissioning in February 1986, protons with an average polarization of 45%, momentum of 21.7 GeV/c, and intensity of 2 x 10/sup 10/ protons per pulse, were extracted to an external polarimeter at the Brookhaven AGS. In order to maintain this polarization, five intrinsic and nearly forty imperfection depolarizing resonances had to be corrected. An apparent interaction between imperfection and intrinsic resonances occurring at very nearly the same energy was observed and the correction of imperfection resonances using ''beat'' magnetic harmonics discovered in the previous AGS commissioning run was further confirmed.
Date: January 1, 1986
Creator: Ahrens, L.A.
Partner: UNT Libraries Government Documents Department

Experimental results on spin physics at the AGS

Description: The AGS ran with polarized protons towards the end of 1985 and through the first two months of 1986. This comprised commissioning periods interleaved with two runs for physics at 13.5 GeV/c with beam polarization of 50 to 60%, and 18.5 GeV/c with an average beam polarization of 40%. Later, the AGS polarized beam reached peak energy of 22 GeV/c and polarization of 46%. This article describes the various spin related experimental efforts since the VI Symposium at Marseille. These will be grouped into those using unpolarized beams and the rest are the polarized proton beam users. Afterwards the future of the program is described as extensions of current experiments in addition to other measurements that are yet to be proposed.
Date: January 1, 1986
Creator: Makdisi, Y.I.
Partner: UNT Libraries Government Documents Department

Acceleration of electrons by the wake field of proton bunches

Description: This paper discusses a novel idea to accelerate low-intensity bunches of electrons (or positrons) by the wake field of intense proton bunches travelling along the axis of a cylindrical rf structure. Accelerating gradients in excess of 100 MeV/m and large ''transformer ratios'', which allow for acceleration of electrons to energies in the TeV range, are calculated. A possible application of the method is an electron-positron linear collider with luminosity of 10/sup 33/ cm/sup -2/ s/sup -1/. The relatively low cost and power consumption of the method is emphasized.
Date: January 1, 1986
Creator: Ruggiero, A.G.
Partner: UNT Libraries Government Documents Department

Los Alamos experiments on the few nucleon systems

Description: A summary of recently studied proton-, pion-, and neutron-induced reactions on nuclei up to /sup 4/He at LAMPF is given. Upgrades to the LAMPF experimental facilities for these studies are described. Some new proton-proton total cross sections in pure helicity states (..delta..sigma/sub L/(pp)) from the ZGS near 3 GeV/c are also presented. 46 refs., 4 figs.
Date: January 1, 1986
Creator: Spinka, H.
Partner: UNT Libraries Government Documents Department