Nuclear Instruments and Methods最新文献

A new instrument which combines the good energy resolution of the gas scintillation proportional counter with the high position resolution of the microchannel plate is proposed. A study of the factors which determine the combined energy and position resolution of the new instrument is discussed. Submillimeter position resolution along with good energy resolution (8% fwhm at 6 keV) should be achievable.

To measure charge exchange and charged-prong annihilation cross sections in the low momentum $\text{pp}$ reaction, we used a cylindrically shaped scintillation counter surrounding the liquid hydrogen target. It was contained in a target vacuum chamber and was optically coupled to a photomultiplier tube outside the vacuum chamber by a lucite light guide. Optical coupling between the scintillator and the lucite light guide was attained by a half-cylinder lucite piece. An analysis of this optical coupling method is also described.

The convoluting effects of detector response on a continous photon spectrum was studied in a 30% Ge detector and three NaI(Tl) spectrometers using detailed Monte Carlo calculations. The diameters and length of the cylindrical scintillation crystals were:5.08 × 5.08 cm², 7.62 cm², and 12.7 × 12.7 cm². The internal bremsstrahlung spectrum of ⁹⁰Y was calculated using the theory of Ford and Martin which include nuclear diagrams. It is clearly shown that recent experimental results, which deviate seriously from theory, are not explained by detector response. A direct comparison to the method of Lidén and Starfelt is made in a typical case. The calculations suggest aan experimental geometry which minimizes the distortion due to photons scattering out of the detector.

We describe the gas and erogel threshold Cherenkov counters built for the TASSO experiment at the DESY e⁺e⁻ storage ring PETRA. The counters are arranged in two diametrically opposed groups as part of the two hadron arms. The gas counters contain Freon 114 and CO₂ respectively; 128 ellipsoidal mirrors focus the Cherenkov light through funnels onto Philips 5″ photomultipliers coated with wavelength shifter. β = 1 charged particles are detected with at least 99.9% efficiency. The aerogel counters are of the diffusing wall type. They have a sensitive area of 12 m², divided into 32 cells and use a total of 192 RCA Quantacon 5″ photomultipliers. The average aerogel refractive index is around 1.025. The efficiency for β = 1 charged particles is 98%. Design considerations, prototype evaluation, construction details, and performance of the final counter system are described.

The neutron detection efficiency of an NE104 plastic scintillator (10 cm diameter × 10 cm thick) has been measured in the energy range E_n = 0.3–7 MeV. The T(p, n), D(d, n) and T(d, n) reactions were employed as neutron sources. Experimental results have been compared with the calculleted efficiency obtained from three different Monte Carlo codes.

MINIMAFOOS is an ECRIS type source delivering multiply charged ion beam like MICROMAFIOS [1,2,7] but where the first and second stages are compound in a unique microwave cavity. There the microwaves create the cold plasma and heat the electrons, the plasma being confined by the min. B magnetic well in which the cavity is imemersed.

The room temperature thermoluminescence (RTL) decay from γ-irradiated LiF single crystal (Harshaw), NaF and KF powders (40–60 mesh) were studied as a function of the gamma radiation dose. The total luminescence reaches a maximum for a particular dose depending on the nature of the crystal. The emission spectra for LiF, NaF and KF showed one, two and three emission bands, respectively, in the range 375 to 700 nm. The RTL disappears at higher doses for these fluorides. The results are explained on the basis of postulated metastable energy level.

The properties of a microchannel plate exposed to a high energy hadron beam have been studied. When the beam was passed through the plate transverse to the microchannel axes, about 2 microchannels per millimeter were excited and an rms error of less than 10μm was obtained. Prospects for improvement are discussed.

The humidity was measured with an accuracy of ±5% using a double ionization chamber with α-ray sources in order to remove the effects of the temperature and the atmospheric pressure.

The function S(E) of luminescence intensity of NE-102A scintillator irradiated by ionizing particles, in the energy range from 0.2 to 20 MeV, is studied by means of numerical integration of an expression already developed for specific luminescence, dS/dx.

Good agreement is observed between calculated curves and experimental results obtained by us and by other authors, with α-particles (1.75–5.28 MeV) and protons (0.5–10.0 MeV).

An identification method for ionizing particles for charge +1 at low energies (below 1.5 MeV), based only on measurements of energy and total and delayed luminescence, is suggested.