Pion Spectrometer Research Articles

Low energy analyzing powers in pion–proton elastic scattering

Analyzing powers of pion–proton elastic scattering have been measured at PSI with the Low Energy Pion Spectrometer LEPS and a novel polarized scintillator target. Angular distributions between 40 and 120 deg (c.m.) were taken at 45.2, 51.2, 57.2, 68.5, 77.2, and 87.2 MeV incoming pion kinetic energy for π+p scattering, and at 67.3 and 87.2 MeV for π−p scattering. These new measurements constitute a substantial extension of the polarization data base at low energies. Predictions from phase shift analyses are compared with the experimental results, and deviations are observed at low energies.

Preliminary results with the CLAMSUD pion spectrometer at the Moscow Meson Factory

A magnetic spectrometer has been recently installed at the new proton beam facility of the Moscow Meson Factory, to study charged pion production from proton-nucleus interactions at 200–400 MeV bombarding energy. Preliminary reults obtained during the first runs are reported. The planned physics program is also discussed.

A method for monitoring the stability of photomultipliers

A method for monitoring hundreds of photomultipliers has been developed in conjunction with the first level trigger of the pion spectrometer CHAOS being constructed at TRIUMF. The system for monitoring the photomultiplier gain stability simply consists of a xenon lamp which operates in the nanosecond time region, a light guide which diffuses the light, and bundles of optical fibers which transport the light to photocathodes. The photomultiplier gain stability can be probed up to few percent (FWHM).

Left-right resolution in high magnetic fields for the CHAOS inner drift chamber

Design considerations for a pion spectrometer being built at TRIUMF led to the development of a thin, low mass, single plane cylindrical drift chamber with a simple cell structure consisting of alternating anode and cathode wires. To date no solution to the left-right ambiguity in chambers of this type has been found which works in high magnetic field environments and for arbitrary incident track angles. We hypothesized that the left-right ambiguity could be resolved in a chamber of this type by comparing the induced charge on cathode strips which are parallel to the sense wire and located in diagonally opposed corners of the cell. Measurements with prototype chambers in magnetic fields up to 1.6 T show that the left-right ambiguity is indeed resolved well for tracks with incident angles between −45° to +45°. The measured intrinsic chamber resolution for tracks at normal incidence at B = 1 T is 150 μm ( σ).

Normalisation of scattering cross sections for low-energy pions

Reliable cross section normalisation of the low-energy scattering of pions has been the source of one of the great weaknesses in that experimental field. Here we describe techniques used at the Low-Energy Pion Spectrometer (LEPS) at PSI/SIN to provide normalisations with a precision of the order of several percent.

Isospin mixing of the 1 + doublet in 12C determined by low-energy pion scattering

With the Low Energy Pion Spectrometer (LEPS) at PSI the inelastic scattering of 50 MeV positive and negative pions to the 1 + excitations at 12.71 MeV ( T = 0) and 15.11 MeV ( T = 1) in 12C has been measured in the angular range 35°−105°. The angular distributions are in good agreement with impulse approximation calcculations. From the double ratio of the 1 + cross sections for π + and π − scattering an isospin mixing matrix element of H 01 = 157 ± 35 keV is derived. In contrast to a previous study of this reaction these results do not question the validity of the impulse approximation at low energies.

Cryogenic liquid neon targets

A cryogenic target has been constructed and used with both liquid 20Ne and 22Ne as well as liquid deuterium in the temperature range of 18–26 K. The target was designed for use with the Triumf low-energy QQD pion spectrometer, and it presented to an incident pion beam a bubble-free slab of liquid isotopically enriched neon which was 3 mm thick and 75 mm in diameter.

Low energy charged pion production from the deuteron

Electroproduction of positive pions from the deuteron near the threshold has been used to isolate the 1S 0 state of the residual nn-system. This unbound state has an energy width of about 1 MeV. Cross sections were measured at incident electron energies of 170 MeV and 183 MeV for a pion kinetic energy of 23 MeV using a flat liquid deuterium target and a magnetic pion spectrometer. The charged pion production at low energies can be well described by the Born amplitudes constructed from an effective hamiltonian with pseudovector πNN coupling. We find a good agreement between theory and experiment in contrast to previous results.

High precision floating wire measurements of large dipole magnets at LAMPF

The current-carrying, floating wire technique was used to measure the particle momentum versus magnetic field calibration of the EPICS pion spectrometer at LAMPF. Wire orbits were measured through a pair of dipoles bending through 120° in the vertical plane. Measurements were made in situ and corrected for gravitational and frictional effects. The specific manner of correcting for gravitational effects is given. Magnetic field versus particle momentum calibrations were derived with an accuracy of 2 parts in 10 4.

The triumf low energy pion spectrometer and channel

A low energy pion spectrometer has been developed for use with the TRIUMF M13 pion channel. The combined channel and spectrometer resolution is presently 1.1. MeV at T = 50 MeV. This is limited by the amount of gas and detector material in the spectrometer in addition to the inherent resolution of the channel. Improvements to both the spectrometer and channel are discussed.

Superconducting pion facility for medical application

June, 1980, the superconducting pion spectrometer of the radiotherapy facility was successfully put into operation. Motivation, general design features, construction, operational characteristics and first application experience are reported.

Large angle pion-carbon scattering near the πN(3, 3) resonance

Pion-carbon 12 elastic and inelastic scattering was measured for both π + and π − at 162 MeV between 135° and 180°. For this purpose, the angular range of the SIN pion spectrometer was increased to 180° by placing a magnet at the target position. In addition, an amplitude analysis taking Coulomb effects into account was performed.

The SIN high resolution pion channel and spectrometer

The optical properties of the SIN high resolution pion channel and spectrometer are briefly reviewed. The operation of the whole system, including detectors and data acquisition is then described. Finally the tune-up method and the actual performances are given.

A 180° scattering facility for the SIN pion spectrometer

A system was built that increases the angular range of the SIN pion spectrometer from 135° to 180° which can be fairly easily inserted whenever large angle data is desired. This is obtained by placing a modified SIN standard magnet at the target position.

Radiative corrections to pion nucleus scattering

The radiative corrections to elastic pion-nucleus scattering are evaluated for kinematical conditions pertaining to the pion spectrometer facilities at the newer meson factories, and are found to be experimentally relevant. A reasonably simple, experimentally useful approximation to the exact expression for the radiative correction is given.

π+ and π− scattering from 12C at 150 MeV

High-resolution elastic and inelastic data were obtained for π + and π − scattering 12C. Spectra were taken with the SIN pion spectrometer at 148 MeV over a wide angular range.

Basic considerations in simulated treatment planning for the Stanford Medical Pion Generator (SMPG)

Recent interest in charged heavy particle irradiation is based upon expected improved local tumor control rates because of the greater precision in dose localization and the increased biological effectiveness of the high linear energy transfer ionization of particle beams in their stopping regions (Bragg peaks). A novel 60 beam cylindrical geometry pion spectrometer designed for a hospital-based pion therapy facility has been constructed at Stanford. In conjunction with the development and testing of the SMPG a program of simulated treatment planning is being conducted. This paper presents basic considerations in treatment planning for pions and other charged heavy particles. It also presents the status of simulated treatment planning calculations for the SMPG including a discussion of the principle of irradiation of hypothetical tumor volumes illustrated by examples of simplified treatment plans incorporating tissue density inhomogeneity corrections. Also presented are considerations for realistic simulated treatment planning calculations using computerized tomographic scan cross sections of actual patients and a conceptual plan for an integrated treatment planning and patient treatment system for the SMPG.

Comparison of Conventional L and S-Band Electron Linacs as Pion Sources Suitable for Radiotherapy

A discussion on target configuration and negative pion yield, supported by high power electron beam experimental data, establishes 250-330 kW at 500 MeV to be desirable beam parameters for an electron linac which, in combination with a Stanford carrousel type pion spectrometer, would provide a practical source of π- mesons suitable for radiotherapy applications. A preliminary analysis confirms that peak current limitations imposed by cumulative beam breakup may be avoided by adopting specific microwave design procedures, which minimize higher order mode transverse shunt impedances in potentially troublesome zones of individual waveguides, and which introduce higher order mode stop bands at specific locations along the beam centerline, similar to the techniques used for the MIT and IKO high duty factor linacs.