F. H. Cverna

A position-sensitive, high energy gamma-ray detector

Abstract A position-sensitive detector for gamma rays in the energy range of 50–500 MeV was designed, built and tested. For 100 MeV gammas, it has energy resolution of 26.3% (fwhm), position resolution of 3.1 mm (fwhm) and calculated detection efficiency of 30%. The detectors performance is in good agreement with Monte Carlo calculations of electromagnetic shower development.

Investigation of some properties of multiware proportional chambers with planar cathodes

Abstract This article reports a systematic study of the pulse heights, efficiency, and plateau width of a multiwire proportional chamber with planar cathodes. It is shown that the chamber performs identically to a chamber with wire cathodes when the same electric field exists in the neighborhood of the anode signal wires. A chamber with planar cathodes may thus be operated at higher field strengths and consequently higher pulse-height amplification than a chamber with wire cathodes, which have a tendency to draw current due to field emission of electrons. Data are presented on the time jitter of a chamber with planar cathodes as a function of voltage. The observed performance of such chambers in experimental conditions, with high radiation fields, is described.

A High Resolution Π o Spectrometer for Nuclear Structure Studies

The capability of detecting neutral pions in the medium energy range (T o< 600 MeV) with an energy resolution of 1.5 to 5 MeVΠ (FWHM) and angular resolution of ΔθΠ o = 1.5 to 4° presents numerous new possibilities for studies in nuclear and particle physics involving Π^o production, decay, pion charge exchange, and kaon strangeness exchange reactions. A spectrometer of this design is being constructed and tested at LAMPF for use in experiments scheduled for early 1978.

/sup 3/He(. pi. /sup -/,. pi. /sup 0/) reaction at T/sub. pi. / = 200 MeV

Energy and angle differential cross sections for the /sup 3/He(..pi../sup -/,..pi../sup 0/) reaction at T/sub ..pi../ = 200 MeV have been measured. Angular distributions for the isobaric analog state and the energy integrated continuum have been obtained from 0 to 90/sup 0/. The excitation of the analog state seems to be best represented by Glauber model calculations with nuclear wave functions suitable to explain electron scattering, but all model calculations underestimate the forward angles by 1.5 standard errors. The continuum angular distribution has the same shape as the free p(..pi../sup -/,..pi../sup 0/)n reaction except at forward angles, where the cross section is suppressed by Pauli blocking of the final state. The total isobaric analog state cross section is 6.29 +- 0.94 mb and the total charge exchange cross section from 0 to 90/sup 0/ is 28.4 +- 3.8 mb. The latter is one-half the plane wave impulse approximation value.