In an attempt to increase the efficiency, a proton recoil neutron spectrometer was built in which the proton detection crystal is in the shape of the surface formed by the rotation of the cos/sup 3/ THETA curve about the THETA = 0 axis where THETA is the angle between the direction of travel of the incident neutron and the direction of travel of the recoil proton. Such a construction makes the detector crystal conform to the range envelope of the protons recoiling from a neutron beam of sufficiently high energy into a gas in which the proton range is proportional to the 3/2 power of the proton energy. Sixteen pieces of thallium-activated cesium iodide were assembled as a mosaic arranged in the cos/sup 3/ THETA shape so that the maximum THETA was 30 deg . Calculations show that 25% of the protons recoil within 30 deg . The Po-Be snd Po-B spectra were measured with the instrument using xenon in the chamber. The resolution of the spectra obtained was low due to nonuniform pulse height response of the CsI crystal sections and excessive gamma-ray response even though sn anthracene proton radiator was used in a coincidence scheme designed to minimize …

Introduction: Recently a new type of charged particle detector, the so-called spark chamber, has been developed. The detector has certain advantages in high energy physics over bubble chambers aside from its much lower cost.

The Livermore 90 deg inch variable-energy cyclotron was used to measure the 90 deg excitation function for the Al/sup 27/(p, gamma )Si/sup 28/ reaction. Proton energies between 5 and 13 Mev were used which gave excitation energies in Si/sup 28/ corresponding to the region of the photonuclear giant resonance. Two gamma rays were observed: gamma /sub O/, the groundstate gamma ray and gamma / sub 1/ resulting from deexcitation through the first excited state of Si/sup 28/ at 1.78 Mev. They were detected by a 5-in.-diam by 6-in.-long NaI(Tl) crystal. A Pb collimator was used to improve the resolution of the detector. The results indicated that both gamma /sub O/ and gamma /sub 1/ display the giant resonance behavior; the gamma /sub O/ carve reached a peak value of approximately -8 mu barns/sr at E/sub p/ = 8.75 Mev, while the gamma /sub 1/ peak was approximately -14 mu barns/sr at E/sub p/ = 10 Mev. Both curves displayed the fine structure previously reported by Gove et al. A detailed balance calculation was made, using the gamma /sub O/ data. A comparison with the measurements of Johansson on the total yield of protons from the Si/sup 28/( gamma ,p)Al reaction …

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