Proton Storage Ring Research Articles

The Manuel Lujan, Jr. Neutron Scattering Center (LANSCE)

Abstract High in the northcentral mountains of Los Alamos, New Mexico, is the Manuel Lujan, Jr. Neutron Scattering Center (LANSCE), a pulsed-spallation neutron source located at the Los Alamos National Laboratory. At LANSCE, neutrons are produced by spallation when a pulsed 800-MeV proton beam impinges on a tungsten target. The proton pulses are provided by the Clinton P. Anderson Meson Physics Facility (LAMPF). An associated Proton Storage Ring (PSR) then alters the intensity, time structure, and repetition rate of the pulses (Figure 1).

Providing common data access for the LAMPF and PSR control systems

The merging of the Los Alamos Meson Physics Facility (LAMPF) and the Los Alamos Proton Storage Ring (PSR) controls and operations groups in early 1988 motivated planning for a common, probably workstation-based, operator interface. Application programs driving this interface must be able to communicate with both LAMPF and PSR devices in a uniform manner. We would like this communication to be implemented with minimal changes to the current LAMPF and PSR control systems. A common device-naming scheme has made it possible for remote systems to acquire both LAMPF and PSR data through the use of server processes residing in the appropriate network nodes. Remote supervisory control of LAMPF devices has been provided in a similar manner. Incompatibilities between information in the LAMPF and PSR database has made remote supervisory control of PSR devices somewhat more difficult. This paper discusses our experience providing this common access and plans for providing future common communications.

Emulating conventional operator interfaces on window-based workstations

This paper explores an approach to support the LAMPF and PSR control systems on VAX/VMS workstations using DECwindows and VI Corporation DataViews as the operator interface. The PSR control system was recently turned over to MP division and the two control-system staffs were merged into one group. One of the goals of this new group is to develop a common workstation-based operator console and interface which can be used in a single control room controlling both the linac and proton storage ring. The new console operator interface will need a high-level graphics toolkit for its implementation. During the conversion to the new consoles it will also probably be necessary to write a package to emulate the current operator interfaces at the software level. This paper describes a project to evaluate the appropriateness of VI Corporation's DataViews graphics package for use in the LAMPF control-system environment by using it to write an emulation of the LAMPF touch-panel interface to a large LAMPF control-system application program. A secondary objective of this project was to explore any productivity increases that might be realized by using an object-oriented graphics package and graphics editor.

Determination of beam position and angle to minimize beam loss in the Los Alamos proton storage ring

A beam of negatively charged hydrogen ions passes through a stripper magnet to produce a neutral hydrogen beam before it is injected into the proton storage ring at the Los Alamos Meson Physics Facility. Inside the ring the injected beam passes through a carbon foil which strips off the remaining electrons to produce a proton beam. It is desirable to position the foil where it will minimize beam losses due to multiple Coulomb scattering in the ring. Beam loss is also decreased if the position and angle of the injected beam are chosen so that the phase ellipse of the injected beam has the best match with the phase ellipse of the ring beam. To achieve these two objectives, the position and angle of the injected beam must be determined at the foil. This is done by describing the beam path in the ring, and interpolating at the foil. A number of beam-position monitors placed at intervals around the ring provide data on the position of the beam at these points. A multiple-regression algorithm uses the data from the beam-position monitors to estimate the position and angle of the injected beam at the foil, along with correlation coefficients and confidence limits.

The Low-Q Diffractometer at the Los Alamos Neutron Scattering Center

Instrument criteria are presented for the Low-Q Diffractometer (LQD) at the Los Alamos Neutron Scattering Center (LANSCE), and a design is shown to meet these criteria. The collimator consists of multiple-aperture pinhole plates, and incorporates ''dynamic gravity focusing'' to center all wavelengths on the detector. Preliminary test results, making use of the Proton Storage Ring, a liquid hydrogen moderator, and two different position-sensitive detectors are shown.

Transmission-line impedance measurements for an advanced hadron facility

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.

Studies and calculations of transverse emittance growth in proton storage rings

When high energy storage rings are used to collide beams of particles and antiparticles for high energy physics experiments, it is important to obtain

Monte Carlo simulations of thin internal targets in intermediate energy proton storage rings

The feasibility of using thin internal targets in a recirculator mode without beam cooling is studied in a Monte Carlo simulation. The limiting factor is the growth of beam emittance and energy spread by small angle Coulomb scattering and energy loss straggling. The corresponding probability density distributions are derived for proton energies ≳ 1 GeV and target thicknesses ≲ 10 −6 radiation length. It is very important to take the low intensity single scattering tails of those distributions into account as the beam distortions result from on the order of 10 6 passes through the target. The beam emittance, energy spread and survival probability are calculated as a function of turn number. Numerical results are obtained for a typical case (1.5 GeV kinetic energy protons incident on a 10 μg/cm 2 thick carbon target) using the design parameters of the cooler synchrotron COSY. The calculations are compared with simple analytical estimates. They demonstrate that thin self-supporting internal targets can be used for experiments in storage rings above 1 GeV.

Superconducting correction magnets for the HERA proton storage ring

The Hadron Electron Ring Accelerator proton ring is equipped with superconducting dipole and quadrupole magnets. The adjustment of the working point and the chromaticity correction are provided by quadrupole and sextupole correction coils mounted on the cold beam pipe inside the main dipole magnets by epoxy and a strong-glass-fiber wrapping. The orbit correction in the proton ring is made by superferric correction dipoles mounted in common cryostats with the main quadrupole and beam-position monitors. The layout of both types of correction magnets is described and experimental results on quenching behavior and field quality are presented. >

Charge-exchange studies at the Los Alamos Meson Physics Facility – Weapon Neutron Research Facility

The Los Alamos Meson Physics Facility – Weapon Neutron Research Facility has been used for (p,n) charge-exchange studies leading to a paper on the energy dependence of the nucleon–nucleon spin–isospin interaction at up to 800 MeV. Because of program changes connected with the use of the proton storage ring and the need for a "white" neutron source, a new facility for neutron time-of-flight studies of the (p,n) reaction up to 800 MeV has been designed. In addition, a proposed facility using the white source for (n,p) studies up to 200 MeV is being built. A brief discussion of the results achieved thus far from the (p,n) work is given. Specific plans for the (p,n) facility with a flight path of 250 m, as well as the design for the proposed (n,p) white source, are discussed. Initial results with the (p,n) line at 256, 600, and 880 MeV show that the time spread due to proton-drift distance results in roughly constant neutron resolution.

Cold yoke dipole magnets for HERA

The proton storage ring of HERA will be equipped with a novel type of superconducting dipole magnet, combining an aluminum-collared coil with a cold iron yoke. The magnet features good field homogeneity, high quench currents, a low heat load on the cryogenic system and the possibility of a passive quench protection system. The magnet is described and test results are presented.

Proton storage ring — the man/machine interface

The human interface of the Proton Storage Ring Control System at Los Alamos is described in some detail, together with the software environment in which operator interaction programs are written. Some examples of operator interaction programs are given.

The PSR control system

We have essentially completed the control system for the Proton Storage Ring at Los Alamos and, at present, are applying modifications required in the light of machine physics and operating experience. We describe here in some detail the present design of the system and indicate future planned modifications.

The lepton‒hadron interaction

The scattering of leptons (e, μ, ν) by hadrons at high momentum transfer has been the incisive probe of the internal dynamics of the proton. Point-like ‘partons’ are found inside the protons. These have the electromagnetic and weak properties expected of quarks, and are in dynamical equilibrium with a sea of virtual quark─antiquark pairs and gluons, the quanta of the strong force. Neutrino scattering has probed the weak coupling of the quarks, and their parity-violating handedness. Weak neutral currents (coupling with the Z 0 boson) were discovered in neutrino scattering, and parity-violating γ ─ Z 0 interference was observed in electron─deuteron scattering. The higher momentum transfers that will be available at the HERA electron─proton storage ring, now under construction, will greatly expand the kinematic region available to search for new phenomena at and beyond the W, Z energy scale.

The WNR/PSR facility - neutron physics capabilities from sub-thermal to 800 mev

The Weapons Neutron Research facility (WNR) is a versatile pulsed neutron source used in a variety of research programs ranging from fundamental neutron properties with ultra cold neutrons to medium energy charge exchange reaction studies. Here we describe the WNR facility and the improvements presently in progress as the Proton Storage Ring (PSR) becomes operational. 14 refs., 11 figs.

New 750 KeV H- Beam Transport Line for LAMPF

The injector complex at LAMPF consists of three injectors with associated transport lines to deliver H+, H-, and P- beams to the linac. Early in 1984 the original H- injector (circa 1973) was replaced with one capable of producing a peak current of 20-mA, a 100X improvement. The motivation for this upgrade was the addition of a proton Storage Ring (PSR) for pulsed neutron research. To support the new operating modes associated with the PSR, the H- transport line was replaced by one having a different design that required changes to portions of the H+ and P- lines, also. This paper describes the new transport system and reports on the initial performance of the H- line.

Los Alamos High-Current Proton Siorage Ring; A Status Report

The Proton Storage Ring (PSR),1 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.2 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-?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 ?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 beamloading, and a high-repetion-rate strip-line extraction kicker. LINE-A

Ferrite Kicker Magnet for the LAMPF Switchyard Upgrade

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-ps rise time and <0.3% flat-top regulation to deflect the 800-MeV H- beam by 1.2°. 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-μs-long pulses at a maximum rate of 120 Hz; the two modes can be multiplexed within the charging power-supply limitations.

H-Beam Operation of TrdE IUCF Stripper Loop

The design and development using a 0.62 MeV molecular hydrogen beam for injection of a low energy proton storage ring to enhance the brightness and vary the rf microstructure of the beams from the IUCF cyclotrons were previously reported.1,2 The performance of the device, called a loop, is limited by the stripping properties of the H2+ ion and by the resulting low energy (0.31 MeV) of the circulating proton beam. However, peak bean intensity gains of nearly 6 were obtained. Larger beam intensity gains are predicted when the stripper loop is injected with 0.62 MeV H- ions. In recent development studies using an H- beam for injection, brightness gains of nearly 11 were obtained for proton beam energies of 180 and 200 MeV with pulse periods of about 2 ?S. The modifications required to inject H- ions into the stripper loop and the results of the beam development studies are presented and compared with theoretical predictions.

Los Alamos Neutron Source Meets First Test

26 April was a day for celebrating at the Los Alamos National Laboratory as jubilant researchers stored a beam in the Proton Storage Ring (PSR) on the very first attempt. The PSR is a $22-million addition to the Weapons Neutron Research (WNR) facility whose effect will be to convert the WNR into a world-class pulsed source for neutron scattering on a par with the British Spallation Neutron Source that recently entered the commissioning phase at the Rutherford Appleton Laboratory (l). The combined WNR/PSR facility will be dedicated this August as the Los Alamos Neutron Scattering Center (LANSCE). However, two important provisos to be satisfied before researchers can tap the intense neutron beam the WNR/PSR will provide are the construction of an experimental hall sufficiently large to house research instrumentation and the development of the instrumentation itself. Now set at $17.5 million, funding for this purpose has never made it into the presidential budget.