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The limiting factors of the charge resolving power of energy-loss detectors are determined.

A liquid xenon drift chamber with an electron drift space of 13 mm in length has been constructed and the spatial resolution of the drift chamber was investigated by using alpha particles. In this experiment, the scintillation light directly produced by an alpha particle was used as trigger signal. To detect the drifted electrons, a proportional counter was used with proportional ionization or proportional scintillation mode. The best value of the spatial resolution (r.m.s.), achieved in the drift chamber, was about 20 μm for both modes. From analytical considerations it is concluded that the main part of the resolution comes from the position uncertainty caused by the finite range of alpha particles in liquid xenon and the finite size of the alpha source. This shows that, if such a drift chamber is used for minimum ionizing particles, a spatial resolution of less than ±10 μm can be expected.

A simple method of electroplating very thin ( A ) layers of 241 Am is described. The thickness of the obtained films is checked by a new recoil catcher technique. In this technique one counts the γ-rays emitted by excited 237 Np nuclei which recoil, as a result of the α-decay of 241 Am, through a known distance.

The comparative study of three differnt types of fast neutron dosimeters based on solid state nuclear track detectors is presented; the dosimeters studied were: • microscopic soda glass in contact with 232 Th; • polycarbonate Makrofol E; and • cellulose nitrate Kodak LR 115. All detectors were evaluated by visual counting in a microscope. We have studied such properties as the background, angular as well as energetical dependences of detectors. The results obtained show that all studied detectors are suitable for fast neutron dosimetry; their application depends however on the concrete experimental conditions (neutron spectrum, fluence etc.). We present both advantages and disadvantages of each of them.

UVT-PMMA Cherenkov detectors have been tested in a particle beam at the Frascati electron linear accelerator. The scintillation light is 1 45 of the Cherenkov light. These counters have good uniformity, in spite of the strong angular dependence of the Cherenkov light.

The efficiency calibration of a coaxial Ge(Li) detector was established experimentally and fitted to a semi-empirical function based on Mowatt's formula. The good agreement obtained in the relative efficiency curve (2–3%) within the energy range 50–1300 keV shows that a development of Mowatt's formula is possible for coaxial devices. The same function, with some simplifications, was fitted to the experimental efficiencies measured for a planar Si(Li) detector in the energy range 8–60 keV. For the Ge(Li) detector the IAEA set of calibrated sources was used for absolute efficiency determinations and another set (75Se, 133Ba, 226Ra, 56Co) for the relative efficiency measurements. Both the IAEA set and a new one named “Variable energy X-ray sources” which provides a fixed geometry, were used for the Si(Li) detector measurements. The semi-empirical fit used enables the determination of the physical parameters of each detector which are then compared with the values predicted by Paradellis and Hontzeas.

Precision measurements of high energy transitions in the nuclei 28Al, 92Zr, 114Cd, 165Dy, 168Er, 200Hg and 239U were performed with the beta spectrometer BILL at the High Flux Reactor in Grenoble via internal and external conversion. The energy calibration was carried out with high energy transitions in the decay scheme of 200Hg, whose absolute energies have been related to the energy of the 411.8 keV decay line of 198Au with a precision of 16 ppm. The following absolute values for neutron binding energies have been deduced: 28Al: 7725.35 ± 0.20 keV; 92Zr: 8635.11 ± 0.24 keV; 114Cd: 9043.13 ± 0.20 keV; 165Dy: 5716.60 ± 0.14 keV; 168Er: 7771.33 ± 0.20 keV; 200Hg:8028.79 ± 0.15 keV and239U: 4806.44 ± 0.20 keV. Some transitions below 1600 keV in 114Cd and 200Hg have been measured with a precision of a few eV.

Energy resolution, linearity of the response versus energy of γ-rays, peak-to-total ratio, photoelectron yield, light pulse shape and time resolution for different ranges of energy lost by γ-rays in CsF scintillators were determined for several samples coupled to XP2020 photomultipliers. A time resolution equal to 230 ps for 60 Co was measured. It is therefore comparable to that of plastic scintillators. A light pulse with rise and decay time equal to 0.35 ns respectively was observed for a 6 mm thick clear sample of CsF crystal. The 25% energy resolution for 662 keV γ-rays from a 137 Cs source and a light yield equivalent to about 500 photoelectrons per 1 MeV were determined. The investigations show that CsF crystals seem to be powerful scintillators for several applications.

A new detector for measurements on flux and energy of fast neutrons is described. The spectrometer contains liquid 3 He, which acts both as target material for the 3 He(n, p) 3 H reaction and as scintillator for the detection of the charged reaction products. A detailed description of the construction is given, and the properties of the detector are reported.

The performance of a three-Ge(Li) Compton polarimeter with kinematic selection has been investigated. It has been shown that elimination of unwanted events by kinematic selection makes it possible to construct a polarimeter which has high polarization sensitivity, large solid angle and good signal-to-noise ratio. The usefulness of the polarimeter has been demonstrated in an example of the spin-parity assignment of the 2432 keV state in 49Cr.

Visible and ultraviolet radiation observed during keV ion bombardment of solids has been interpreted as deexcitation radiation from molecules built up by atoms from the incoming beam (Ar), from the target material (Be, Nb, Mo), and from impurities (H, O). Molecular argon (Ar 2 ) is suggested to be formed from argon atoms implanted into a carbon target.

The efficiency of a Si(Li) X-ray detector has been determined in the 1.5–60 keV energy region using five different methods. The data given by the different methods have been compared and a fitting procedure has been worked out, by means of which the low energy (1.5–5 keV) efficiency data can be well described analytically. From the fitting the values of some of the detector-parameters can be determined of the accuracy of their values can be checked.

A review of techniques used in the production and operation of NaI(Tl) detectors is provided. The scintillation mechanism itself is summarized, and examples of the use of NaI(Tl) detectors is several areas of science and technology are given.

For yield determinations of short-lived fission products, an automatic pneumatic rabbit system has been developed to measure without chemical separations the formed radioactive products, the γ-counting starting within one second. Irradiations are performed in a pneumatic tube system installed in an out-of-pile horizontal beam hole for thermal neutrons or near the deuterium target of a 3 MeV neutron generator. The capsule is positioned with good accuracy in front of the Ge/Li detector. The whole sequence of irradiation, transportation, and counting is controlled by automatic timers. Details of the mechanical system are given.

The electron spectrometer consists of two Si(Li) detectors, two superconducting magnet transporters and auxiliary equipment. The electron transmission reaches 76% (from 4π for two detectors) and is independent of electron energy up to about 1600 keV at the maximum 3.2 T magnetic field of the solenoids. For the sake of background reduction in some on-line experiments baffles were used in front of the detectors. In this case the transmission is 25%–30% in the 150–650 keV electron energy interval. The obtained resolution is 2.5-3 keV (fwhm at 300 keV electron energy).

A sampling total absorption detector was calibrated at Fermilab for energies in the range 5–250 GeV. The calorimeter consisted of a sandwich of scintillator slabs and 4'' thick steel plates. Energy resolutions (rms) of ±33%, ±16%, and ±9% were achieved for the energies 10, 50, and 150 GeV, respectively.

A modified version of a time-of-flight spectrometer developed previously for neutrons from 1 to 500 MeV achieves a substantial reduction in backgrounds and permits extension of the upper energy limit to 1 GeV or perhaps higher. Basically, the spectrometer measures the time-of-flight of a neutron scattered elastically between two scintillation counters. The addition of a counter telescope to detect the recoil-proton from a neutron-proton elastic scattering event in the first detector results in a substantial reduction in backgrounds from competing inelastic neutron-carbon and neutron-proton reactions and from chance coincidences; however, since the recoil protons must escape the first detector, the spectrometer becomes increasingly inefficient below about 175 MeV. We have used the modified spectrometer to measure the neutron spectrum at 0° from beryllium bombarded by the circulating beam of 724 MeV protons in the 184″ cyclotron at the Lawrence Berkeley Laboratory. This measurement demonstrates the ability of the spectrometer to measure neutrons to about 724 MeV and confirms the calculated energy resolution of the spectrometer.

Evaporated copper specimens were bombarded with 40 keV Cu+ ions in an electromagnetic isotope separator. The specimens were investigated for texture by X-ray diffraction techniques before and after irradiation. It was found that before irradiation, a preponderance of {111} crystallographic planes parallel to the surface plane of the film exists. During irradiation, however, a pronounced preponderance of {110} planes parallel to the surface plane of the specimens develops. The magnitude of this reorientation effect is shown to be dependent on the crystallographic properties of the specimens before irradiation. The importance of the effect for the interpretation of results of ion bombardment experiments, such as sputtering and ion ranges, is discussed. A tentative explanation for the occurrence of the effect is presented.

A set of 1 cm gap wire spark chambers with a sensitive surface of 300 × 100 cm 2 was constructed for an experiment at the CERN proton synchrotron. The Coulomb scattering was limited by using aluminium wires and by adopting a crossed-wire configuration, which allowed us to minimize the number of chambers for a given number of pairs of coordinates. The wire planes were pulsed by feeding the high voltage from strip-lines along the whole boundary of the chambers.

A set of proportional chambers has been constructed for a multiparticle spectrometer at the CERN Intersecting Storage Rings (ISR). The detector consists of 73 000 wires and covers an effective area of 300 m 2 . In this paper we will describe the design and performance of this detector.

Thin-film plastic scintillators have been developed for use as fission detectors in direct-reaction-induced fission experiments. The method of detector fabrication is described. Typical response to fission fragments produced both by a 252 Cf source and by charged-particle-induced fission of natural uranium is shown and discussed.

For muon-nucleon scattering experiments 24 large drift chamber planes are being built at the University of Freiburg. As the intense muon beam has to pass through the chambers, insensitive regions are constructed in the beam area by increasing the diameter of the anode wires from 20 μm to 100 μm by electroplating. Test results in a high intensity beam are presented, showing the effectiveness of the desensitising technique.

Impurities dissolved in liquid ionization chamber media are monitored by infrared absorption spectroscopy. Detection of low levels (ppm-ppb) of impurities is demonstrated.

A Hall plate system with a CAMAC interfaced mini-computer for measuring the magnetic field harmonics of quadrupole magnets is presented. Errors and their minimization are discussed in detail.

Measurement has been made of the distribution of secondary particles in a steel side shield near a tungsten alloy target illuminated by high-energy protons. Secondaries were detected using 11 C activation, and the effect of unspecified targets was cancelled by subtracting “target-out”.data. The resulting distribution does not support a uniform attenuation length. These results provide design criteria for steel side shields, particularly close-coupled shields.

The development of a large aperture (30 cm × 30 cm) positron camera is described. It is based on the particular hybrid MWPC structure developed at the Rutherford Laboratory ∗ which consists of multiple MWPC detectors with laminated metal cathode foils which function simultaneously as converters for the 511 keV positron annihilation gamma rays and inductive readout strips. The solutions found for the many structural and electronic problems encountered in the design are described. Results are presented showing good imaging ability (spatial resolution of 6 mm fwhm) with high sensitivity (1000–2000 counts/μCi · min) with positron emitting test phantoms ( 22 Na and 68 Ga).

This report presents conclusive evidence that the variation of the prompt resolution curves with the size of a fast liquid scintillator results in a high degree from the self-absorption effect on the fluorescence characteristics of the scintillator. This was demonstrated by measurements of the equivalent illumination function (i.e. radioluminescence decay curve); the analysis of the experimental results shows an important increase of the fwhm of the scintillation pulse shape with the dimensions of the scintillator. The experimental data are discussed in terms of optical reflections on the surface of the scintillator and of fluorescence self-absorption: a prevailing influence of the latter must be postulated. A time resolution of 176 ps for 22 Na has been obtained with a fast liquid scintillator of cylindrical shape with 2 cm diameter and 1 cm height.

A large magnetic spectrometer for cosmic-ray studies has been built at Cosmic Ray Laboratory, University of Tokyo, which consists of two 400 t solid iron magnets, multiwire proportional chambers (MWPC), wire spark chambers and a calorimeter. In this paper the trigger system will be described whose geometrical acceptance is about 1300 cm 2 sr including the magnets. The trigger system consists of twenty large area MWPCs. The trigger selection is made up of the momentum selection, which excludes low momentum muons, and the particle-number selection limiting the number of particles hitting the trigger detectors simultaneously. This combination for trigger reduces the background level and improves the ratio of muons to background. The trigger rate is about 1.0 per minute in the usual operation.

Accurate analytical descriptions of peaks in Ge(Li) and Si(Li) detectors are important in various areas of current interest. A variety of functional forms is tested using a coaxial Ge(Li) detector and a guard-ring Si(Li) detector to provide experimental data. A two-component description of the tailing is necessary for the Ge(Li) detector, while a one-component description suffices for the Si(Li).

The relation between resolution and dead-time losses in nuclear radiation spectrometers is discussed both for non-adaptive and adaptive filters.

The lateral distribution of the energy of hadron showers initiated by 10 GeV/c pi /sup -/ and protons has been measured at various depths in Fe and Al absorbers. It is found to scale with the density of the absorber. The energy flow is characterized by a cone of +or-65 mrad opening angle. The direction of the energy flow can be determined by two points, the vertex of the primary interaction and the centre of gravity of the energy deposited by the shower. The fluctuation of the centre of gravity has been measured using a fine-grained calorimeter and is found to give the shower direction with an r.m.s. spread of 60 mrad. (9 refs).

In order to study multiple scattering effects both in the gas and particularly in the solid materials of high-pressure gas scintillators, two asymmetry experiments have been performed by scattering of 15.6 MeV polarized neutrons from helium contained in stainless steel vessels of different wall thicknesses. A Monte Carlo computer code taking into account the polarization dependence of the differential scattering cross sections has been written to simulate the experiments and to calculate corrections for multiple scattering on helium, xenon and the gas containment materials. Besides the asymmetries for the various scattering processes involved, the code yields time-of-flight spectra of the scattered neutrons and pulse height spectra of the helium recoil nuclei in the gas scintillator. The agreement between experimental results and Monte Carlo calculations is satisfactory.

The properties of a drift chamber, filled with pure xenon at pressures from 5 to 20 atm are investigated. The electron drift in gas in a uniform electric field is studied. A photomultiplier detects the photons emitted by the electrons in an intense field close to the thin anode wire. The best spatial resolution of 16 μ m on the drift way of 20 mm was obtained at a xenon pressure of 20 atm; diffusion of electrons contribution amounts to 12 μ m. Possible applications are discussed.

We describe a set of large multiwire proportional chambers used in an experiment at the CERN Super Proton Synchrotron. The sensitive area is 2320 × 2320 mm 2 , and four detecting planes, each with different orientation, are grouped together within the same mechanical frame. The number of wires for each module is 5000. Very uniform efficiency over the whole area is achieved by means of a simple mechanical construction. The chambers were operated for a long time without any damage under high particle flux.

Thermal neutron measurements by thermoluminescence dosimeters have been studied in paired 6LiF and 7LiF or UD-136N and UD-137N. The results have a similar meaning to that of Au foils. The detectable minimum thermal neutrons fluence by the present method is about 104 n/cm2, which corresponds to a thermal neutron flux of several n/cm2 s with one hour exposure.

A low momentum positive muon beam has been developed at LAMPF, utilizing muons which originate from pion decays at rest near the surface of the pion production target and are transported by the LAMPF stopped muon channel. The muon beam has a total flux of 2.5 × 104μ+ per s per μA of a proton beam (8 × 106μ+ s−1 for the present operating current at LAMPF of 300 μA), an extremely narrow range spread of 50 mg/cm2 in CH2, and a positron contamination (e+/gm+) of 60%.

An improved large-area gas scintillation proportional counter has been built, suitable for use in X-ray astronomy. This counter employs electron focusing in a drift region to achieve uniform response. It is shown that a window area of 60 sq cm and a spectral resolution of 10% fwhm or better at 5.9 keV can be obtained.

It is shown that axial current lenses made of iron can be used efficiently for focusing and transporting high energy muon beams. A model lens was constructed and its focal properties as obtained by measuring the deflection of high energy muons, are presented.

Trajectory calculations have been carried out for secondary electrons emitted on the electrodes and in the interelectrode gaps of inclined-field acceleration tubes. It was shown that a number of trajectories originating in the neighbourhood of the prismatic field sections will be inflected in the paraxial region. Consequently, the corresponding electrons will be accelerated to considerable energies before being stopped by other electrodes. The presence of high-energy electrons in inclined-field tubes was experimentally proved by X-ray measurements around the 5 MV Van de Graaff generator in this Institute. Similar measurements performed with a homogeneous field tube enable us to compare the behaviour of tubes of different types.

A 52 cm × 52 cm drift chamber telescope has been exposed to electron and tagged gamma-ray beams at DESY in order to assess its performance as a detector for gamma-ray astronomy.

The yield of transition radiation is expected to be higher for a low- Z material because of low absorption. Yields of transition radiation from lithium foils have been measured using multiwire proportional chambers and using a thin NaI counter in a beam of electrons and pions from 0.5 to 3.5 GeV/ c . The transition radiator consisted of 1000 foils of 2 mil lithium spaced at 20 mils. Results from a lithium radiator are compared with those of Mylar-foil radiators, and the advantages of lithium radiators in applications are discussed.

The design of a high-intensity muon channel with an acceptance of more than 2 sr is considered. The channel consists of two superconducting magnets; a toroid and a solenoid. Monte Carlo calculations are performed to optimize the channel's design parameters for maximum muon beam intensity. The channel can provide 1.4 × 10 9 muons/s when used in conjuction with a 1 mA, 400 MeV electron linac.

An apparatus was built for an experiment with the CERN polarized deuteron target measuring the polarization in K + n ↑ → K ° p . The detectors and the available acquisition capacity were simultaneously used to take data on several other reactions.

The performance of an electromagnetic shower detector comprised only of active elements was evaluated using a tagged electron beam at various momenta from 30–100 GeV/ c . Cerenkov light from three sections of lead glass blocks provides measurements of total shower energy with a resolution of σ = (0.114±0.008) E GeV /c 2 . A plastic scintillator hodoscope situated behind the first two lead glass layers samples the transverse development of the shower, allowing position determination of the incident electron with σ = 1.4 mm resolution.

We present results on the behavior in a magnetic field parallel to the sense wires and the spatial resolution of a drift chamber with relatively short drift length (7.5 mm) but without electric field shaping. This chamber operates quite well for a field as high as 15 kG, and the spatial resolution is better than ± 100 μm over the major part of the chamber for normally incident tracks. At 4 kG we give results on the spatial resolution as a function of the incident angle.

A measurement of the spatial resolution of a liquid-argon filled chamber was performed with minimum ionizing particles. Two multi-strip chambers with 20-{micro}m strip spacing operating in the ionization mode were used in the experiment. They perform in accordance with a simple model based on electron diffusion. An estimate of the amount of electron diffusion in liquid argon is given and the time jitter distribution has a FWHM of 200 ns. Under best conditions, the spatial resolution is better than 20 {micro}m rms with an efficiency of nearly 100%.

A method is described for calculating, as a function of time, the lateral distribution of the charge induced on the cathode of a multiwire proportional chamber. For this analysis the cathode of interest is assumed to be in the form of a plane of uniformly spaced wires whose direction is parallel to the anode wires. Example calculations using this method are shown.

Pure poly- and single crystalline copper was sputtered by low energy argon, oxygen and nitrogen ions. The use of both reactive and noble sputter ions resulted in a strong roughening increasing with depth of the polycrystalline surface due to lattice orientation dependent sputtering. Single crystals exhibit much less roughening. SIMS depth profiles were measured in a copper single crystal with imbedded thin Ni layers. The Ni layers were resolved by substantially broadened signal peaks. This broadening was larger for argon than for oxygen and nitrogen sputter ions. In all cases the broadening was independent of depth. During sputter erosion of a single crystal the smoothing of the surface was observed and interpreted as prevailing influence of irradiation enhanced surface diffusion.

A fully portable, phoswich-detector-based, radiation survey instrument has been developed. The design takes advantage of the low photon background characteristics of a phoswich scintillator system to detect small amounts of low energy photon emitters such as plutonium and americium. For the portable and unshielded instrument a background reduction of ∼3 compared to an equivalent thin NaI detector is achieved with little loss of sensitivity. With shielding, the background reduction is ∼6 compared to an equivalent thin NaI detector.

An extremely low background betagammagamma coincidence spectrometer has been constructed for the measurement of cosmic ray produced radionuclides carried by extraterrestrial matter accreted on the Earth. The detectors used in this work are a large volume Ge(Li) detector, a pair of GM counters of thin layer type for beta counting, a large volume NaI(Tl) well scintillator and liquid scintillator for guard counter. Six counting modes are applicable; gamma only, gammagamma coincidence, Compton suppression, betagamma, (beta+gamma)gamma and betagammagamma counting modes. The absolute counting efficiency of the betagammagamma mode is slightly lower than that of the betagamma mode, however the figure of merit in the betagammagamma mode becomes better than that in the betagamma mode at higher energies.