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The design, construction, and performance of a segmented-target, cathode-strip, tracking-detector is discussed. The chamber was made of low- Z materials in order to allow photons to leave the target region. It was used to determine the reaction vertex of stopping kaons, and was successfully operated in a high-intensity kaon beamline at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. The vertical and horizontal resolutions of the stopping kaon reaction positions were σ X ∼0.454 mm and σ Y ∼1.180 mm , respectively. The uncertainty in the longitudinal ( Z ) direction is given by one-half the thickness of a target segment.

A particle-tracking program has been written for simulating the acceleration cycle of a rapid-cycling proton synchrotron. A lattice can consist of up to 100 cells and rf cavities. Transport of the beam in six dimensions includes all second-order optical terms. The rf field and proton velocity are treated exactly. Longitudinal space charge is handled in a self-consistent manner. The fluctuations due to the finite number of particles are handled by a Gaussian smoothing algorithm. The program runs on a VAX 11/780 and can track 100 particles without space charge through the full acceleration cycle from 0.8 to 32 GeV in 49 minutes. A thousand particles with space charge takes about ten hours of computer time.

Protons are accumulated into the low-energy booster of the SSC (Superconducting Super Collider) by utilizing H/sup -/ to H/sup +/ conversion in a 225- mu g/cm/sup 2/ carbon stripping foil. Synchronous injection is performed for 26 turns into stationary RF buckets, thereby allowing operation with variable bunch spacing. By injecting the beam offset in x and y, the required RMS normalized transverse emittance area of 0.75 pi mm-mr is obtained. Similarly, the required RMS longitudinal emittance area of 1.75 mu *10/sup -3/ eVs is obtained by injecting single linac micropulses, centered at phi =0 and dp/p=+0.12%, into each 49.9-MHz RF bucket formed with an RF voltage of 350 kV. The transverse space-charge tune shift is -0.17 for 10/sup 10/ protons/bunch accumulated at 600 MeV. >

Proposed designs for kaon factory accelerators require that the RF cavities support beam currents of the order of several amperes. The beam current has Fourier components at all multiples of the RF frequency. Empty RF buckets produce additional components at all multiples of the revolution frequency. If a Fourier component of the beam coincides with the resonant frequency of a higher-order mode of the cavity, which is inevitable if the cavity has a large frequency swing, significant excitation of this mode can occur. The induced voltage may then excite coupled bunch mode instabilities. Effective means are required to damp higher modes without significantly affecting the fundamental mode. A mode damping scheme based on coupled transmission lines has been investigated and is reported. Theoretical analysis and measurement indicate that this scheme is effective for damping higher-order TEM (transverse electromagnetic) modes without significantly affecting the fundamental mode. >

A method for measuring the response of a beam current monitor is described, and response and impedance measurement results for a Proton Storage Ring (PSR) wall current monitor are reported. The through-short-delay calibration method (TSD) is extended to measure the response of a current monitor embedded within hardware that interfaces to a network analyzer. Error correction parameters generated with the TSD-calibration are used to calculate the actual current present at the current monitor. The results show a marked increase in impedance due to the cables and combiners. >

The beam diagnostics for the Los Alamos Proton Storage Ring (PSR) are being upgraded in several areas, including the closed-orbit beam-position system, the high-frequency longitudinal and transverse beam diagnostics, and the extraction-line beam-position monitoring system. The closed-orbit beam-position measuring system is based on detecting the 201 MHz modulation on the injected beam, which disappears in about 10 mu s, due primarily to the beam's momentum spread (about +or-0.1%), and the consequent spread in the revolution frequencies. Thus, although the first few turns of the injected beam are monitored with the system, the main body of the stored beam, which has lost its 201 MHz component, is not. In order to monitor the position of the stored beam, the ring beam-position system is being redesigned to operate at the revolution frequency, 2.8 MHz. >

A prototype RF cavity and RF drive system for a hadron facility main ring has been designed and is tested in the Proton Storage Ring (PSR) at Los Alamos National Laboratory (LANL) as part of a collaborative effort between LANL and TRIUMF. The cavity uses an orthogonally biased ferrite tuner. The design provides for accelerating gap voltages up to 200 kV for the 49.3-50.8-MHz range. Progress on the cavity construction and testing is described. >

The study of a possible chopping system for the Advanced Hadron Facility (AHF) and the Superconducting Super Collider (SSC) is presented. A 200 MHz RFQ (radio-frequency quadrupole accelerator) may be preferable to lower-frequency structures for the injection linacs of the AHF and SSC. To achieve a pulse frequency of 50 MHz, a chopper must be developed to eliminate three out of four bunches at the tenth of a percent level. Conventional choppers suffer from risetime limitations due to the finite separation of the deflecting plates. One alternative is a spectrometer chopper which modulates the energy of each bunch and then separates the bunches with a spectrometer transport. Initial design studies are presented for this concept. >

The Superconducting RF Cavity Development Program at Los Alamos has designed, fabricated, and tested single-cell niobium cavities at 3 GHz and 805 MHz. This work is being done in preparation for procuring and testing a multicell niobium cavity. The multicell cavity is designed to accelerate protons at /spl beta/=0.9; initial tests will be without beam. Programmatic changes have required us to modify our plans to install a 6800 litre helium cryostat and a 12.8 g/s helium pump. We will use an installed cryostat to test the multicell cavity. Also, the cavity will be modified from a seven-cell to a four-cell structure to match the dimensions of the installed cryostat. Previous reports concentrated on 3 GHz results. In this paper, some of the latest results of the 805 MHz cavity tests are presented. Modifications to allow high pulsed power testing on 805 MHz single- and four-cell cavities are proceeding. Glow discharge cleaning of an 805 MHz niobium cavity resulted in a decrease in cavity performance. The cavity was restored to previous performance levels with buffered chemical polishing. Initial results with high-pressure water cleaning show the process is useful in restoring cavity performance. >

In recent operation of the Los Alamos Proton Storage Ring (PSR), the vertical and horizontal tunes have been moved closer to the integers ( nu /sub y/=2.12, nu /sub x/=3.17) to enlarge the low-loss working region. In this region, the beam can be significantly affected by space charge. The first observed effects are a nondestructive distortion of the beam profile and vertical growth of beam size sufficient to keep the shifted tunes from crossing the integer, but without large beam loss. At higher intensities, or with tunes closer to the integer, beam blow-up, accompanied by beam losses, can occur. A report is presented on recent observations of this intensity-dependent effect and implications for future PSR operation are discussed. >

A pion linear accelerator (PILAC) is being designed as a new experimental facility for the Los Alamos Meson Physics Facility (LAMPF). The design goal is a flux of 10/sup 9/ pions per second at an energy of 920 MeV into a spectrometer having a resolution of 200 keV. To meet this design goal, the system will have to accept a large phase space of particles which, in turn, implies that higher-order aberrations will be significant and have to be corrected. The computer program MOTER is being used to investigate the size of the aberrations and their effect on the resolution of the system. To meet this challenge a number of improvements were made to MOTER. This work describes those improvements, shows how MOTER can be used to design the high-resolution channel, and indicates the direction that future developments of this program will take. >

The peak intensity of the PSR is limited by a fast transverse instability. In 1996 we started a project to upgrade the PSR to 200 /spl mu/A at 30 Hz, which requires operation above the instability threshold achieved with our present RF system. We have, therefore, resumed our experimental program to understand and control the instability. In this paper we will present our latest data.

The ability to model and simulate beam behavior in the Proton Storage Ring (PSR) of the Los Alamos Neutron Science Center (LANSCE) is an important diagnostic and predictive tool. This paper gives the results of an effort to model the ring apertures and lattice and use beam simulation programs to track the beam. The results are then compared to measured activation levels from beam loss in the ring. The success of the method determines its usefulness in evaluating the effects of planned upgrades to the Proton Storage Ring.

An upgrade is in progress to the Los Alamos Proton Storage Ring (PSR) to allow direct injection of the H/sup -/ beam into the ring and provide a beam bump system to move the circulating beam off the stripper foil. The primary benefits of this upgrade are matching the transverse phase space of the injected beam to the PSR acceptance and reduction of foil hits by the circulating beam by a factor of ten. Foil thickness is optimized to minimize the combination of circulating-beam losses plus losses due to excited H/sup 0/ states produced at injection. An overall factor of five reduction in losses is expected. The project comprises extensive modifications of the injection line, the injection section of the ring, and the waste-beam transport line. We will discuss the goals of the project, present an overview of the technical design, and describe the status of the implementation plan.

In Proton Radiography, one of the goals is a motion picture of a rapidly moving object. The Los Alamos Proton Storage Ring (PSR) in its normal operating mode, delivers a single pulse approximately 120 ns wide (fwhm). In development runs at the PSR, we successfully demonstrated operation of a technique to deliver two pulses, each 40 nsec wide, with adjustable spacing.

A design study for a Pion Linac (PILAC) at LAMPF is under way at Los Alamos National Laboratory. The reference design for a system of pion source, linac, and high-resolution beam line and spectrometer that will provide 10/sup 9/ pions/s on target and 200-keV resolution for the ( pi /sup +/, K/sup +/) reaction at 0.92 GeV is presented. A general-purpose beam line that delivers both positive and negative pions in the energy range of 0.4-1.1 GeV is included, thus opening up the possibility of a broad experimental program. A kicker-based beam sharing system allows delivery of beam to both beam lines simultaneously with independent sign and energy control. Because the pion linac acts like an RF particle separator, all beams produced by PILAC will be free of electron (or positron) and proton contamination. >

A Pion Linac (PILAC) is being designed for LAMPF. Together with its high resolution beam line and spectrometer, the system is optimized to provide 109 pions per second on target and 200‐keV resolution for the (π+, K+) reaction at 920 MeV. There will also be an achromatic beam line capable of utilizing the maximum energy available, thus opening up the possibility of a broad experimental program as is being discussed at this workshop.

High-intensity synchrotrons such as the proposed Advanced Hadron Facility (AHF) [1] and the Los Alamos Proton Storage Ring (PSR) [2] must have a low beam-coupling impedance for stability. The conflicting requirement of low eddy-current effects in the rapid cycling AHF makes the AHF beam-pipe design a particularly difficult problem. A ceramic pipe deposited with conducting stripes has been proposed for AHF. It can have adequately small eddy currents, but it may have an unexpectedly large coupling impedance. Therefore, a facility for measuring transmission-line impedances has been established and is described in this paper. Measurements of transverse and longitudinal coupling impedances for ceramic/metal and other beam-pipe segments are reported; a ceramic/metal chamber can have adequately small impedance. Results of impedance measurements for other AHF and PSR devices, such as a PSR beam pickup and bumper magnet, are also reported.

Nuclear physics issues and particle physics issues for a kaon factory are discussed. Kaon factory accelerator proposals are then considered. Secondary beam considerations are covered and hardware development for a kaon factory is discussed. The prospects for construction are presented. 9 refs., 12 figs., 2 tabs. (GHT)

A new type of multiware proportional chamber with a helical cathode for delay line readout has been developed and studied in detail. It gives cathode delay line pulses nearly as large as the anode pulses, and hence is well-suited for minimum ionizing particles. Measurements on such a chamber yielded spatial resolution better than 0.33 mm fwhm for 90Sr β particles, a resolving time less than 30 ns, and maximum counting rate greater than 2 MHz. The most probable pulse height induced on the delay line by minimum ionizing particles in this chamber is approximately 8 mV.

A proportional chamber with a single wire helical cathode has been employed in the focal plane of a magnetic spectrograph for nuclear reaction studies. The spatial resolution attributable to the detector is less than 0.33 mm fwhm over its 25 cm length with particles incident at an angle of 37° to the plane of the detector. The resolution achieved with a collimated 55Fe X-ray source at normal incidence was 0.25 mm. Rates of 105 counts/s are possible before degradation of the peak shapes is observed. The d E d x resolution is 27% for protons, deuterons and tritons in the energy range of 10–16 MeV. The counter has been used with an on-line computer program to measure the 27Al(d,p)28Al and 59Co(t,d)60Co differential cross sections.

A number of multiwire, position-sensitive, gas proportional chambers have been constructed which use fast delay line (2.5 ns/cm) readouts to provide trajectory position and angle information for particles near the focal planes of the Energetic Pion Channel and Spectrometer (EPICS) and High Resolution Spectrometer (HRS) at the Clinton P. Anderson Meson Physics Facility (LAMPF). These chambers are two dimensional with anode wires in one direction and cathode wires in the other direction. When operated as ordinary delay line chambers, position resolution of 0.5 mm (FWHM) can be obtained in the cathode direction for short cathode wire lengths. If the drift information from the anodes is used, resolution of less than 0.35 mm (FWHM) can be obtained in this direction. The chambers can be operated at count rates of 5 × 105 pulses/sec with live times of greater than 90%. Efficiences, measured at lower counting rates, are typically greater than 99%.

Rapid cycling proton synchrotrons, such as the proposed LAMPF II accelerator, require approximately 10 MV per turn rf with 17% tuning range near 50 MHz. The traditional approach to ferrite-tuned cavities uses a ferrite which is longitudinally biased (rf magnetic field parallel to bias field). This method leads to unacceptably high losses in the ferrite. At Los Alamos, we are developing a cavity with transverse bias to the bias field) making use of the tensor permeability of the ferrite. Initial tests of a small (10-cm-diam) quarter-wave singly re-entrant cavity tuned by several different ferrites indicate that the losses in the ferrite can be made negligible compared with the losses due to the surface resistivity of the copper cavity. Details of the test results will be presented.

The stability of photomultiplier tube (PMT) gain for signal conditions of high pulsed anode currents requires a PMT base circuit capable of maintaining constant voltage to the last few dynodes for the pulse duration. For the experimental conditions at the Los Alamos Meson Physics Facility (LAMPF) with a macropulse duration of 500 μs at 120 Hz, conventional base circuits do not meet stability requirements. The new base circuit uses high voltage transistors to furnish pulse currents to the last four dynodes of the PMT from a single capacitor source which is recharged during the period between macropulses.

A facility for pion scattering experiments called EPICS is under construction at LAMPF1. The channel part has been installed, and results from the first tests of this channel are reported.

The proton storage ring currently operates at an average current of 30 μA corresponding to 1.25×1013 protons per pulse (ppp) at a repetition rate of 15 Hz. The design operating current for the machine is 100 μA. We are limited to running at the reduced yield because of beam losses during the accumulation period. These losses are understood and arise mainly from emittance growths during the injection and multiple scattering in the stripping foil during the storage. During beam studies we have succeeded in accumulating in excess of 3.7×1013 ppp. We have also observed a coherent transverse instability at high charge levels. The signture for the instability is rapid coherent growth of the transverse beam size followed by a loss of beam in the machine. The threshold for the instability depends most strongly upon rf voltage and beam size.

In the 1987 AHF Workshop, it was pointed out that activation of the accelerator is a serious problem. At this workshop, it was suggested that a new type of slow extraction system is needed to reduce the activation. We report on the response to this need. The Los Alamos plan is reviewed including as elements the long lead‐time R&D in preparation for a 1993 construction start, a menu of accelerator designs, improved losses at injection and extraction time, active participation in the development of PSR, an accelerated hardware R&D program, and close collaboration with TRIUMF. We review progress on magnets and power supplies, on ceramic vacuum chambers, and on ferrite‐tuned rf systems. We report on the plan for a joint TRIUMF‐Los Alamos main‐ring cavity to be tested in PSR in 1989. The problem of beam losses is discussed in detail and a recommendation for a design procedure for the injection system is made. This recommendation includes taking account of single Coulomb scattering, a painting scheme for minimizing foil hits, and a collimator and dump system for containing the expected spills. The slow extraction problem is reviewed and progress on an improved design is discussed. The problem of designing the accelerators for minimum operation and maintenance cost is briefly discussed. The question of the specifications for an advanced hadron facility is raised and it is suggested that the Los Alamos Proposal of a dual energy machine—1.6 GeV and 60 GeV—is a better match to the needs of the science program than the single‐energy proposals made elsewhere. It is suggested that design changes need be made in all of the world’s hadron facility proposals to prepare for high‐intensity operation.

We discuss the possible applications of superconducting rf at LAMPF. These applications include 1) a LAMPF energy upgrade to 1.3 GeV, 2) an afterburner linac for an advanced hadron facility, 3) a pion linac (PILAC), 4) rf separators, 5) 800 MeV proton bunch rotators, 6) pion bunch rotators, and 7) a test cavity for the new high Tc superconducting materials. Cost estimates and performance are discussed.

A technique employing integrating analog-to-digital converters to do pulse shape discrimination between neutron and gamma initiated scintillations in liquid scintillators is described. The technique involves a direct comparison of the fast and slow components of the light output from the scintillator.