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Offset coil designs for superconducting magnets, a logical development

Description: Dipoles and quadrupoles for any new, large proton ring must be stronger, smaller and have better field shape (systematic error) than those used in the Doubler. The present two-shell designs are rigid in that the coils are too thin but cannot be relatively fatter without destroying the field quality. An examination of the coil shapes for dipoles and quadrupoles which produce perfect fields from a uniform current density shows clearly that our persistent use of a circular form for the inner surface of the coils is a poor approximation. When this is corrected by ''offsets'' there is a striking improvement both in the strength of fields and in the field quality. The same analysis makes clear that the efficient use of superconductor and the overall magnet size is determined by the perfect coil shapes. Any reasonable magnet will not differ significantly from the ideal for these parameters. This will be particularly helpful in setting design goals for very large quadrupoles. The offset two-shell dipole design preserves the mechanical features of the highly successful, resilient doubler magnets while greatly extending the performance.
Date: March 1, 1986
Creator: Collins, T.
Partner: UNT Libraries Government Documents Department

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

NCI dichromatic beam tests

Description: The initial tests of the NCI dichromatic train showed that the momentum bite was within 2% of design. Though the data is by no means definitive, the particle fractions measured at 800 GeV are reasonably close to those predicted from 400 GeV data. A first look at the angular divergence of the beam showed it to be within 10% of design in the horizontal plane and about 35% greater than design in the vertical plane. Several problems were discovered which will be corrected before the next run.
Date: March 1, 1986
Creator: Stutte, L.
Partner: UNT Libraries Government Documents Department

Resonance scraping

Description: Protons lost in a ring leave at a few preferred locations, determined by some non-linear property of the dipoles. This paper suggests taking control of lost protons by beating the magnets at their own game - by means of a designed resonance used as a beam scraper. It is a study of suitable resonances, including estimates of the required multipole element strengths. The appropriate resonances are two-dimensional. A large number of figures is included.
Date: June 1, 1986
Creator: Collins, T.
Partner: UNT Libraries Government Documents Department

Measurement of the main ring longitudinal impedance by debunching

Description: An experiment was carried out to observe microwave signals of the bunched beam in the Fermilab Main Ring. The purpose of this paper is to analyze the experiment and attempt a computation of the longitudinal impedance per unit harmonic Z/n of the Main Ring. The result of the analysis indicates Z/n = 8.6 ..cap omega.. if the driving impedance is a broad band at f/sub MW/ = 1.646 GHz. However, if the driving impedance is a high-Q resonance at 1.646 GHz with RMS width less than approx.0.13 GHz (or Q approx. 50), Z/sub sh//Q of the resonance is 5.2 k..cap omega... We demonstrate that the proton bunches are of Gaussian shape. The time at which the microwave amplitude starts to grow is determined. We find that this occurs when two adjacent bunches overlap each other. A stability criterion is derived for the overlapped bunches. Then Z/n and Z/sub sh//Q are computed. The source of the driving impedance is traced.
Date: February 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

''Econodump'' design for the Fermilab Direct Neutral Lepton Facility

Description: An extensive effort has been directed toward a major redesign of the Fermilab Direct Neutral Lepton Facility (DNLF). The goal has been a very significant cost reduction of the facility, with minimal sacrifice of physics potential. Hence the name ''Econodump'' applied to the redesign effort.
Date: August 1, 1986
Creator: Childress, S.; Brown, C.; Koizumi, G.; Malensek, A.; Morfin, J.G.; Murphy, T. et al.
Partner: UNT Libraries Government Documents Department

The ANL experiment for a wake field accelerator using an rf structure

Description: Experiments are planned at ANL to study a new accelerating concept that has been developed during the last few years named the WAKEATRON. This requires a very special, simple configuration of the beams and of the rf structure involved. The basic concepts are explained. Like most proposed experimental work, this too was initiated by a considerable amount of computational work, both analytical and numerical, on which we would like to report. We will then describe details of the planned experiments we will carry out at ANL to check some of our predictions for this concept. These experiments concentrate on beam and cavity geometry applicable to the Wakeatron.
Date: August 27, 1986
Creator: Ruggiero, A. G.; Schoessow, P. & Simpson, 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

Spin Effects in High-P(T)^2 p+p --> p+p at 800 to 900 GeV

Description: We propose to study the spin-orbit Analyzing Power, A, in p+p + p+p at large P{sub {perpendicular}}{sup 2}. We propose to run at Fermilab around Fall 1987 and scatter a high intensity unpolarized proton beam of 800 to 900 GeV from a Polarized Proton Target; we would measure the difference between the d{sigma}/dt when the target spin is up and when it is down. Our main goal is to see if the unexpected large values of A recently found at the 28 GeV AGS in proton-proton elastic scattering persist to Fermilab energies. The large A value of 24 {+-} 8% at P{sub {perpendicular}}{sup 2} = 6.5 (GeV/c){sup 2} was not only unexpected but also seems difficult to reconcile with the A = 0 prediction of conventional models of strong interactions, such as perturbative QCD. The validity of perturbative QCD is believed to improve with increasing energy and with increasing P{sub {perpendicular}}{sup 2}, and this proposed Fermilab experiment would increase the incident energy by about a factor of 30. The experiment would be done using a Polarized Proton Target (PPT) employing radiation-doped NH{sup 3} beads and a 'local' cooling power of about 130 mW at 1/2{sup o} K. Such a target could be used with a beam intensity of 3 to 6 10{sup 10} protons per second, which is 1.5 to 3.0 10{sup 12} protons per pulse with Fermilab's 50 sec rep rate. This high beam intensity would allow good measurements out to about P{sub {perpendicular}}{sup 2} = 10 (GeV/c){sup 2} where the p+p {yields} p+p cross section is quite small. We propose to run in an underground target station such as P-West, which is ideally suited for such a high-P{sub {perpendicular}}{sup 2} elastic scattering experiment. We would use a double-arm spectrometer consisting of magnets with considerable bending power and high ...
Date: March 7, 1986
Creator: Court, G. R.; Crabb, D. G.; Krisch, A. D.; Lin, A. M. T.; Raymond, R. S.; Roser, T. et al.
Partner: UNT Libraries Government Documents Department

Stability of Coastin Beams in the Debuncher

Description: The stability of high intensity beams has been a matter of some concern. While anti-proton operation uses beam currents of 10 a or less, it is sometimes useful to have proton beams with currents of the order of 1 ma and narrow (booster sized) momentum spreads. This note describes calculations of what can be expected for coasting beam instabilities and, in particular, the effect of the (high impedance) 53 MHz cavities. This note specifically does not describe transverse instabilities, bunched beam instabilities, or turbulence in the debunching process. The stability limit can be calculated using standard formulae (van der Meer CERN/PS/AA/80-4 and many others). The result of this calculation is the 'stability plot' shown in figure 1a. This calculation assumes a 1 ma beam with a {Delta}p ({sigma}) of 2 MeV/c. The curve (allowed impedance) scales inversely with beam current and {Delta}p{sup 2}. The momentum spread was assumed to be gaussian. Figures 1b and 1c are the same plot but with different scales. The interpretation of this plot is that if the impedance of any device (or devices) is outside this curve, then the assumed beam distribution is unstable. More rigorously one can make a so-called 'Nyquist plot' where one plots Z{sub w}(w)/Z{sub b}(w) where Z{sub w} is some wall impedance and Z{sub b} is the beam response (or beam impedance) shown in figure 1. These Nyquist plots are shown in figures 2abcd for different cavity tunes. Figure 2a shows the Nyquist plot for the 1 ma of beam assumed above assuming only 1 cavity which is tuned to resonance. The cavity has a shunt impedance of 1.8M{Omega} and a Q of 10,000. The assumed beam distribution is unstable if the curve circles the point (1,0) {approx} quite close in figure 2a. Figure 2b is the same except that 6 ...
Date: February 7, 1986
Creator: Marriner, J.
Partner: UNT Libraries Government Documents Department

A Proposal to Study Beauty Production and Other Heavy Quark Physics Associated with Dimuon Production in 800 (925) GeV/C pp Interactions

Description: The presence of dimuons in final states produced in hadronic interactions has proved to be a valuable indicator that interesting hard physics processes have taken place. These muon pairs provide a mechanism for selecting these relatively rare processes from interactions due to the total cross section. In particular, processes involving heavy quarks are flagged by the presence of muon pairs. We are proposing to use the high rate E705 spectrometer and its dimuon trigger processor which have already functioned well in Experiments E-537 and E-705 to detect and measure several heavy quark phenomena which result in a final state containing a pair of muons. This experiment will use the primary proton beam from the Tevatron at the maximum energy available at the time of execution of the experiment. The spectrometer will be augmented by the addition of a silicon tracker similar to those used in other experiments at the Fermilab. The present P-West High Intensity Laboratory secondary beams will need to be upgraded by addition of sufficient bending power to allow the transport of the 800 to 925 GeV/c primary proton beam to the experiment target (see Appendix A).
Date: May 1, 1986
Creator: Arenton, M.; Chen, T.Y.; Lai, K.W.; Yao, N.; U., /Arizona; Anassontzis, S.E. et al.
Partner: UNT Libraries Government Documents Department

Formation of submicron metastable phase structures in alloys with focused electron or proton beams. [Ni-Al]

Description: Recent theoretical and experimental studies of radiation-induced segregation in alloys under irradiation with focused charged-particle beams have shown that point-defect currents generated by axial and radial displacement-rate gradients can cause significant redistribution of the alloying elements within the irradiated zone. In the case of irradiation of thin films with highly-focused electron beams, two important features have been established experimentally: (1) the diameter of the local region in which the alloy composition and phase are modified is practically equal to the beam diameter, and (2) the time required to produce a given change in the alloy composition in the center of the irradiated zone decreases rapidly with beam diameter. Our theoretical modeling indicates that these features will also be observed in semi-infinite alloys bombarded with focused proton beams. However, in this case, the spatially-nonuniform defect production in both the axial and radial directions renders the compositional redistribution more complex. The present work shows that the ability to locally modify the alloy composition by focused electron or proton beams may offer a new method for producing local regions of controlled composition and microstructure on a submicron scale. The results of our model calculations and experimental studies will be presented to demonstrate the feasibility of this novel technique.
Date: November 1, 1986
Creator: Lam, N.Q.; Okamoto, P.R. & Leaf, G.K.
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

A Solid state accelerator

Description: We present a solid state accelerator concept utilizing particle acceleration along crystal channels by longitudinal electron plasma waves in a metal. Acceleration gradients of order 100 GV/cm are theoretically possible, but channeling radiation limits the maximum attainable energy to 10/sup 5/ TeV for protons. Beam dechanneling due to multiple scattering is substantially reduced by the high acceleration gradient. Plasma wave dissipation and generation in metals are also discussed.
Date: November 6, 1986
Creator: Chen, P. & Noble, R. J.
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

Search for stable quarks produced by the Tevatron

Description: An experiment has been run at the Tevatron to search for stable fractionally charged particles (i.e., quarks) produced by the 800 GeV/c proton beam. The experiment was performed in two phases. In the first run, 1.0 x 10/sup 15/ protons passed through a series of four mercury targets which were distributed among several lead degraders. The lead degraders were arranged so that fractionally charged particles over a wide range of production angles, masses, and energies would stop in the mercury targets. A small amount of this mercury has been analyzed for fractional charge in an automated Millikan apparatus. A second run, which had an integrated proton intensity of 4.1 x 10/sup 13/, used liquid nitrogen tanks to stop any fractionally charged particles produced when the proton beam interacted in an upstream lead target. In the four tanks, electrically charged gold-plated glass fibers attracted and then trapped any fractional charges which were stopped in the liquid nitrogen. After the exposure, the wires were moved through small beads of mercury in which the gold was dissolved. One of these small beads of mercury also has been analyzed in the same Millikan apparatus. The results from the first run show that the upper limit for quark production is less than 1 x 10/sup -6/ quarks per proton interaction at 90% confidence limit, the results from the second run show that the upper limit is 9.3 x 10/sup -10/. The analysis of the mercury is continuing.
Date: June 1, 1986
Creator: Matis, H.S.; Bland, R.W.; Hahn, A.A.; Hodges, C.L.; Lindgren, M.A.; Pugh, H.G. et al.
Partner: UNT Libraries Government Documents Department