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PSR beam-pulse formation and control

Description: The Proton Storage Ring (PSR) is a major addition to the Weapons Neutron Research Facility (WNR) at LAMPF. It will act as a bunch compressor for the relatively long linac macropulses from LAMPF, tailoring them into short, intense pulses ideally suited for neutron-scattering research. This paper concentrates on the methods used to form these pulses before injection into the linac, to multiplex the PSR beam with other LAMPF users, and to synchronize the storage ring with pulse arrival time at injection and with the WNR mechanical neutron chopper at extraction.
Date: January 1, 1983
Creator: Hardekopf, R.A.
Partner: UNT Libraries Government Documents Department

PROGRESS IN DESIGN OF THE SNS LINAC

Description: The Spallation Neutron Source (SNS) is a six-laboratory collaboration to build an intense pulsed neutron facility at Oak Ridge, TN. The linac design has evolved from the conceptual design presented in 1997 to achieve higher initial performance and to incorporate desirable upgrade features. The linac will initially produce 2-MW beam power using a combination of radio-frequency quadruple (RFQ) linac, drift-tube linac (DTL), coupled-cavity linac (CCL), and superconducting-cavity linac (SCL). Designs of each of these elements support the high peak intensity and high quality beam required for injection into the SNS accumulator ring. This paper will trace the evolution of the linac design, the cost and performance factors that drove architecture decisions, and the progress made in the R&D program.
Date: November 1, 2000
Creator: HARDEKOPF, R.
Partner: UNT Libraries Government Documents Department

Pulsed beam chopper for the PSR at LAMPF

Description: A traveling-wave beam chopper has been designed to provide properly structured negative-ion beam to the Proton Storage Ring (PSR) and other LAMPF users. The chopper must provide a 20-mrad kick with pulse rise time <5 ns for the 750-keV H/sup -/ ions in the injector transpoft line. Variable pulse lengths from 15 ns to 750 ..mu..s at repetition rates up to 16.7 MHz must be generated in synchronization with the PSR circulation frequency. Parameter studies led to an optimized design combining good deflection efficiency and bandwidth with minimum deleterious effects from plate-to-plate coupling. Both positive and negative 600-V pulses, with lengths up to 1 ms and maximum 10% duty factor, can be generated to drive the deflectors.
Date: January 1, 1983
Creator: Lunsford, J.S. & Hardekopf, R.A.
Partner: UNT Libraries Government Documents Department

Ferrite kicker magnet for the LAMPF switchyard upgrade

Description: The new LAMPF switchyard requires a kicker magnet as the first element in the transport line leading to the Proton Storage Ring (PSR). The magnet must produce 1-ms-long pulses with 40-..mu..s rise time and <0.3% flat-top regulation to deflect the 800-MeV H/sup -/ beam by 1.2/sup 0/. We have constructed two 1-m-long, single-turn ferrite magnets, each powered by a modulator supplying up to 2400 A at a maximum rate of 24 Hz. The modulators use a transistor amplifier/regulator, a dual pulse-forming-network (PFN), and a compensating circuit driven by a function generator to achieve a total 0.1% current variation in the pulse. The system also produces an alternate kicking mode consisting of 150-..mu..s-long pulses at a maximum rate of 120 Hz; the two modes can be multiplexed within the charging power-supply limitations. 3 refs., 6 figs.
Date: January 1, 1985
Creator: Hardekopf, R.A.; Higgins, E.F. & Lunsford, J.S.
Partner: UNT Libraries Government Documents Department

Experience with a double-compensating beam calorimeter

Description: In an experiment to measure the D(t,..cap alpha..)n cross section at beam energies of 10 to 120 keV, we have developed a double-compensating beam calorimeter, based on a Swiss design to measure the partical beam intensity. A Faraday cup is not useful because of considerable charge exchange in the target gas at such low beam energies. We calibrated the calorimeter both with 10- and 3-MeV protons (comparing with a Faraday-cup measurement of the beam flux) and with the heat generated in a precision resistor. Both methods agree and give a calibration accurate to +- 0.08% over a range of 10 to 800 mW beam power. Beam powers as low as 5 mW may be used, but with less accuracy. The beam energy must be known in order to calculate the particle intensity. Some difficulties with and peculiarities of the device are discussed.
Date: January 1, 1982
Creator: Jarmie, N.; Brown, R.E.; Hardekopf, R.A. & Martinez, R.
Partner: UNT Libraries Government Documents Department

Nuclear reactions among the hydrogen isotopes at low energies

Description: The low-energy fusion cross-section (LEFCS) apparatus installed at the Los Alamos Van de Graaff facility has been used to measure the cross sections for the important fusion-energy reaction D(t,..cap alpha..)n over the triton bombarding energy range of 12.5 to 117 keV. This corresponds to an equivalent deuteron bombarding energy range of 8.3 to 78.1 keV and to a D + T plasma temperature (kT) range of 0.7 to 18.8 keV. Over most of the energy range the cross sections are accurate to 1.4%, with the error rising to 4.8% at the lowest energy. A data base was constructed for deuteron bombarding energies up to about 250 keV that included our data and four other data sets. This data base can be fitted quite well with a single-level (3/2/sup +/) resonance formula in the R-matrix formalism. Work is currently in progress on the D(d,p)T and D(d,/sup 3/He)n reactions, with studies of D(t,..gamma..) and T(t,..cap alpha..)nn planned for the future.
Date: January 1, 1982
Creator: Brown, R.E.; Jarmie, N. & Hardekopf, R.A.
Partner: UNT Libraries Government Documents Department

Analyzing-power formalism for three-body final states

Description: Various relations important for extraction of analyzing powers from data on reactions involving three particles in the final state were derived. Several of the results pertinent for spin-1/2 and spin-1 polarized beams are presented here. These may be used in analysis of the /sup 1/H(d-vector,pp)n reaction. 3 figures. (RWR)
Date: January 1, 1980
Creator: Ohlsen, G.G.; Brown, R.E.; Correll, F.D. & Hardekopf, R.A.
Partner: UNT Libraries Government Documents Department

Analyzing powers for the three-nucleon breakup reaction /sup 1/H(d vector,p)pn at 16 MeV

Description: Analyzing powers for the /sup 1/H(d,p)pn reaction were measured at 16.0 MeV and beam polarization of approximately 0.82. Similar data for the elastic scattering /sup 1/H(d,p)/sup 2/H were also taken. The breakup analyzing power A/sub xz/, which attains the largest magnitude, is shown as a function of excitation energy. Angular distributions of elastic and breakup analyzing powers are compared; large differences are noted for A/sub xx/ and A/sub xz/. It is found that 1-MeV energy bins are too large to use in the study of singlet-state effects. 2 figures. (RWR)
Date: January 1, 1980
Creator: Brown, R.E.; Ohlsen, G.G.; Correll, F.D.; Hardekopf, R.A. & Jarmie, N.
Partner: UNT Libraries Government Documents Department

The (t,d) reaction on the Ni isotopes with polarized tritons

Description: The (t vector,d) reaction has been measured on targets of /sup 58/ /sup 60/ /sup 62/ /sup 64/Ni with 17 MeV polarized tritons. Spectroscopic factors, angular momentum and total spin transfer were obtained from the differential cross section and A/sub y/ values of levels up to 3.5 MeV in excitation energy. The present (t,d) measurement enables a better description of the 9/2/sup +/ and 5/2/sup +/ states which show significant shell crossing effects as a function of increasing neutron number.
Date: January 1, 1980
Creator: Flynn, E.R.; Cizewski, J.A.; Brown, R.E.; Hardekopf, R.A. & Sunier, J.W.
Partner: UNT Libraries Government Documents Department

Cross sections for neutron-producing reactions induced by 6- and 10-MeV neutrons incident on /sup 10/B and /sup 11/B

Description: Using the time-of-flight technique, the /sup 10/B and /sup 11/B neutron emission spectra at incident neutron energies of 6.00 and 10.00 MeV for angles between 20/sup 0/ and 145/sup 0/ have been measured. Double differential cross sections and their integrated values have been extracted and are presented in tables and graphs. The integrated values (corrected for charged particle cross sections, if necessary) are in excellent agreement with measured total cross sections. 15 refs., 39 figs., 14 tabs.
Date: May 1, 1986
Creator: Drosg, M.; Lisowski, P.W.; Drake, D.M.; Hardekopf, R.A. & Muellner, S.M.
Partner: UNT Libraries Government Documents Department

Los Alamos high-current proton storage ring: a status report

Description: The Proton Storage Ring (PSR), whose installation was recently completed at Los Alamos, is a fast-cycling high-current accumulator designed to produce intense 800 MeV proton pulses for driving a spallation neutron source. The ring converts long beam pulses from the LAMPF linear accelerator into short bunches well matched to requirements of a high-resolution neutron-scattering materials science program. The initial performance goal for this program is to provide 100-..mu..A average current at the neutron production target within a 12-Hz pulse rate. Project construction began in May 1982, and was completed in mid-April 1985. First beam was circulated in the ring on April 26. Operation at 20 ..mu..A is scheduled for September 1985, with full intensity within the next year. The storage ring was originally designed to function in a second mode in which six 1-ns bunches are accumulated and separately extracted every LAMPF macropulse. Implementation of this mode, which would serve a fast-neutron nuclear-physics program, has been deferred in favor of initial concentration on the neutron-scattering program. This paper summarizes the PSR design and status. Unique machine features include high peak current, two-step charge-stripping injection, a low-impedance buncher amplifier to counter beam-loading, and a high-repetition-rate strip-line extraction kicker. 19 refs., 31 figs., 3 tabs.
Date: January 1, 1985
Creator: Lawrence, G.P.; Hardekopf, R.A.; Jason, A.J.; Clout, P.N. & Sawyer, G.A.
Partner: UNT Libraries Government Documents Department

Double differential neutron emission cross sections of /sup 10/B and /sup 11/B at 6, 10 and 14 MeV and of /sup 6/Li, /sup 7/Li and /sup 12/C at 14 MeV

Description: Neutron emission spectra of /sup 10/B and /sup 11/B were measured at 6, 10, and 14.1 MeV and those of /sup 6/Li, /sup 7/Li and carbon at 14.1 MeV using time-of-flight technique. Absolute double differential cross sections were obtained by using scattering from hydrogen as a cross section reference. Integration over energy ranges and solid angle yielded integrated elastic and total neutron emission cross sections. At 6 and 10 MeV excellent agreement with total cross section data is found, at 14.1 MeV the new data tend to be higher than expected. The biggest error source in the continuous spectra stems from uncertainties in the input library (ENDF/B-IV) of the Monte Carlo correction for multiple scattering. In particular, the library for /sup 11/B appears to be very unrealistic, with a total elastic cross section at 14.1 MeV which should be higher by 50%.
Date: January 1, 1985
Creator: Drosg, M.; Lisowski, P.W.; Hardekopf, R.A.; Drake, D.M. & Treitl, K.
Partner: UNT Libraries Government Documents Department

Differential cross sections of the reaction /sup 4/He(t,n)/sup 6/Li between 8. 5 and 16. 5 MeV and the n-/sup 6/Li cross-section standard

Description: Differential cross sections of the reaction /sup 4/He(t,n)/sup 6/Li, including some data of the first and second excited states of /sup 6/Li, were measured and compared with an R-matrix analysis of previous data in the /sup 7/Li system. Excellent agreement is observed for the angular distribution at the 0.24-MeV resonance of n-/sup 6/Li, and the shape of the angular distribution for /sup 4/He(t,n/sub 1/)/sup 6/Li at 12.9 MeV is predicted qualitatively by the R-matrix analysis. However, for neutron energies greater than 0.5 MeV for /sup 6/Li(n,t)/sup 4/He the zero-degree excitation function is consistently lower (about 30%) in the R-matrix analysis.
Date: January 1, 1982
Creator: Drosg, M.; Drake, D.M.; Hardekopf, R.A. & Hale, G.M.
Partner: UNT Libraries Government Documents Department

Data discrepancies in and new experiments for D+D, D+T, and T+T fusion reactions

Description: The purpose of this work is to investigate the accuracy of the basic fusion reaction data for the reactions T(d,n)/sup 4/He, T(t,2n)/sup 4/He, D(d,n)/sup 3/He, and D(d,p)T, and to describe an elaborate experiment in progress at the Los Alamos Scientific Laboratory to remeasure the cross sections with improved accuracy.
Date: January 1, 1979
Creator: Jarmie, N.; Hardekopf, R.A.; Brown, R.E.; Correll, F.D. & Ohlsen, G.G.
Partner: UNT Libraries Government Documents Department

Polarized triton scattering from /sup 26/Mg, /sup 27/Al and /sup 28/Si at 17 MeV

Description: Differential-cross-section and analyzing-power angular distributions were measured for 17 MeV tritons elastically scattered from targets of /sup 26/Mg, /sup 27/Al, and /sup 28/Si in the angular range 20 to 160/sup 0/. The experiment was performed at the Los Alamos Scientific Laboratory Van de Graaff facility using the Lamb-shift polarized triton source and the supercube scattering chamber. A pair of detector telescopes with angular resolutions of +-0.4/sup 0/ detected the reaction products, with mass identification and storage performed by an on-line computer. The triton beam intensity available at the target was about 70 nA with a polarization of 0.77. The target thicknesses were about 3 mg/cm/sup 2/, although thinner targets were used for the /sup 27/Al forward-angle data.
Date: January 1, 1980
Creator: Hardekopf, R.A.; Brown, R.E.; Correll, F.D. & Ohlsen, G.G.
Partner: UNT Libraries Government Documents Department

Polarized triton elastic scattering data. [17 MeV, differential cross sections, analyzing power angular distribution, tables]

Description: Different-cross-section and analyzing-power angular distrbutions were measured for 17-MeV polarized triton elastic scattering. The 13 target nuclei spanned the range 40 less than or equal to A less than or equal to 208, and the angular range was 20/sup 0/ less than or equal to THETA less than or equal to 160/sup 0/. The data are presented in tables and graphs. 8 references.
Date: July 1, 1979
Creator: Hardekopf, R.A.; Haglund, R.F. Jr.; Ohlsen, G.G. & Veeser, L.R.
Partner: UNT Libraries Government Documents Department

Wide dynamic range beam profile monitor

Description: An economical harp multiplexer system has been developed to achieve a wide dynamic range. The harp system incorporates a pneumatically actuated harp detector with ceramic boards and carbon wires; a high-sensitivity multiplexer packaged in a double-wide NIM module; and flat, shielded ribbon cable consisting of individual twisted pairs. The system multiplexes 30 wires in each of the x and y planes simultaneously and operates with or without computer control. The system has operated in beams of 100 nA to 1 mA, 1- to 120-Hz repetition rate, with a signal-to-noise ratio of greater than 10/1.
Date: January 1, 1985
Creator: Lee, D.M.; Brown, D.; Hardekopf, R.; Bilskie, J.R. & van Dyck, O.B.V.
Partner: UNT Libraries Government Documents Department

Event-analysis language for high-speed data acquisition

Description: A multiparameter data-acquisition program is described that is highly flexible and yet provides optimum machine code for each individual set of sorting conditions. An Event Analysis Language (EVAL) compiler allows the user full control over the handling of events and produces code which runs 4 to 6 times faster than a generalized program. This technique has been integrated into the Los Alamos Physics Division data acquisition system for high-speed sorting of a wide variety of input data from CAMAC or magnetic tape. The EVAL compiler is written in FORTRAN for MODCOMP computers, but can be easily modified for other systems.
Date: January 1, 1981
Creator: Hardekopf, R.A.; Poore, R.V.; Sunier, J.W.; Neiman, M. & Holm, A.
Partner: UNT Libraries Government Documents Department

Kinematically incomplete breakup reaction /sup 1/H(vector d,p)pn at 16 MeV

Description: Angular distributions of the differential cross section sigma(E*,theta/sub 1//sup l/) and of the vector and tensor analyzing powers A/sub y/(E*,theta/sub 1//sup l/), A/sub xz/(E*,theta/sub 1//sup l/), A/sub xx/(E*,theta/sub 1//sup l/), A/sub yy/(E*,theta/sub 1//sup l/) for the 3-nucleon breakup reaction /sup 1/H(vector d,p)pn were measured for a deuteron bombarding energy of 16.0 MeV. The data are reported as functions of the excitation energy E* in the pn system and of the laboratory angle theta/sub 1//sup l/. Laboratory angles between 15 and 42.5/sup 0/ were studied. The excitation energy range varies from 0 to 2.6 MeV at 15/sup 0/ to 0 to 0.2 MeV at 42.5/sup 0/. An excitation energy range (bin) of 0.2 MeV, which corresponds to laboratory energy bins from 0.3 to 0.4 MeV, was used to partition the proton continua. The experimental laboratory energy resolution is about 0.15 MeV. Large effects are seen in the tensor analyzing powers, particularly in A/sub xz/, at the lowest excitation energies. Except for A/sub yy/, there is no similarity of the observed analyzing powers to the corresponding elastic-scattering analyzing powers. Some data for A/sub xz/(E*,theta/sub 1//sup l/) at other energies are also presented. 11 figures, 6 tables.
Date: December 1, 1980
Creator: Ohlsen, G.G.; Correll, F.D.; Brown, R.E.; Jarmie, N. & Hardekopf, R.A.
Partner: UNT Libraries Government Documents Department

Elastic scattering of tritons by helium-4

Description: Angular distributions of the differential cross section and of the analyzing power have been measured for the /sup 4/He(t,t)/sup 4/He reaction at 19 energies from 6 to 17 MeV. The relative errors of the cross section and analyzing power range from 2.0 to 2.5% and 0.005 to 0.01, respectively, and the scale errors are 1% in each case. Complete data tables are presented, and the experimental procedure is described for the present measurements and for earlier cross-section measurements. Graphs of the data are presented, as well as the curves resulting from an energy-independent phase-shift analysis.
Date: November 1, 1980
Creator: Jarmie, N.; Correll, F.D.; Brown, R.E.; Hardekopf, R.A. & Ohlsen, G.G.
Partner: UNT Libraries Government Documents Department