[en] The authors show the layout of the experiment HISS 320. This experiment is designed to capture and analyze all charged projectile fragments produced in the interaction of 2 GeV/nucleon 12C with C, CH, Cu or U targets. Analysis consists of identifying charge, mass and vector momentum for each fragment. This is accomplished through use of a drift chamber system to give trajectories through the magnetic field of the HISS dipole, combined with velocity measurement provided by a time-of-flight scintillator array called the TOF wall. This report describes the present status of the TOF wall system

[en] The properties of ion-implanted layers in undoped semi-insulating GaAs substrates have been studied and found to be correlated to the initial bulk resistivity of the wafers, which in turn is determined by the content of residual shallow acceptors. With decreasing resistivity from > approx 10⁸ Ωcm to < approx 10⁷ Ωcm the implanted layer sheet resistance decreases, the pinch-off voltage increases and the carrier profiles become broader. High purity material with very low background acceptor concentration shows highest carrier activation and superior reproducibility and appears to be favourable for ion-implantation applications. (author)

[en] Numerical models in atmospheric sciences do not only need to approximate the flow equations on a suitable computational grid, they also need to include subgrid effects of many non-resolved physical processes. Among others, the formation and evolution of cloud particles is an example of such subgrid processes. Moreover, to date there is no universal mathematical description of a cloud, hence many cloud schemes were proposed and these schemes typically contain several uncertain parameters. In this study, we propose the use of algorithmic differentiation (AD) as a method to identify parameters within the cloud scheme, to which the output of the cloud scheme is most sensitive. We illustrate the methodology by analyzing a scheme for liquid clouds, incorporated into a parcel model framework. Since the occurrence of uncertain parameters is not limited to cloud schemes, the AD methodology may help to identify the most sensitive uncertain parameters in any subgrid scheme and therefore help limiting the application of Uncertainty Quantification to the most crucial parameters.

[en] The authors have constructed and tested a small prototype drift chamber designed for high energy heavy ions. When a drift chamber is used as a tracking detector for heavy projectile fragments from high energy nucleus-nucleus reactions, the major problem comes from the many spurious hits due to delta-rays. Three methods have been developed to solve this problem. The first one is to use a constant fraction discriminator to pick up the timing signal from the core ionization under the large background of delta-rays. The second one is to use pulse height information from the drift chamber to find the cell hit by the heavy ion. The last one is the idea of distributed planes. Modular planes (12 in this case) are distributed 10 cm apart on a rigid base plate to provide accurate relative positioning of the wires. The performance of the prototype chamber has been measured as a function of the high voltage bias and of the charge of the heavy ion from protons up to uranium at around 1 GeV/nucleon

[en] The authors have developed a highly sensitive velocity measuring detector using total internal reflection Cerenkov counters of a type described by Jelley in 1958. The detector uses the Cerenkov light which is produced at an angle theta/sub c/ = cos(1/βn), when a charged particle with velocity β passes through a medium with an index of refraction n. If the Cerenkov angle is bigger than the angle of total reflection, and the radiator is shaped so that all surfaces are either perpendicular or parallel to the direction of the particle, the produced Cerenkov light is trapped in the radiator. By placing a photomultiplier in optical contact with the radiator some distance away from the particle track only the trapped Cerenkov light is detected. Since real materials are dispersive, n = n(lambda), the Cerenkov light is produced over a range of angles and the intensity for the trapped light is not a step function but has some width in velocity

No abstract available

[en] The authors have begun a program to measure charge changing cross sections of projectile fragments using a quite different technique that is capable of much higher data acquisition rates. The primary beam impinges on a stack of 50 Lucite strips having an average thickness of 3.17 mm, emitting Cerenkov light as its passes through them. Since at a given velocity the intensity of light is proportional to Z², where Z is the charge of the particle, a fragmentation reaction in a particular strip will be registered as a drop in the light output from that and subsequent strips. The authors use total internal reflection to transport the light to photomultiplier tubes so that there is no wrapping between the strips. Since the energy threshold of the device is approx.1.1 GeV/nucleon, low energy target fragments will not contribute to the signal, a distinct advantage over similar schemes using energy loss to measure the fragment charge. The resolution of the individual strips is typically 0.58 charge units, full width at half maximum, allowing reactions to be well localized even for single unit charge changes. In addition to the C detectors, scintillators and Si(Li) detectors were used to measure precisely the position and charge of the incoming beam particle. The authors have taken data using two beams, ⁵⁶Fe and ⁴⁰Ar, at 1.88 and 1.82 GeV/nucleon respectively, and two trigger modes, a free trigger to measure the reaction rate of the incoming beam and an inelastic trigger in which a reaction was required to occur in one of the first 14 C detectors. A total of 909,000 ⁵⁶Fe interactions and 460,000 ⁴⁰Ar interactions have been analyzed so far

[en] We have developed a highly sensitive velocity measuring detector using total-internal-reflection Cerenkov counters of a type mentioned by Jelly in 1958. If the velocity of the particle is above the threshold for total-internal-reflection these counters have a charge resolution of sigma = 0.18e for a 3mm thick glass radiator. For the velocity measurement we use a fused silica radiator so that the velocity of the particles are near the threshold for total-internal reflection. For momentum-analyzed projectile fragments of 1.6 GeV/nucleon ⁴⁰Ar, we have measured a mass resolution of sigma = 0.1u for isotope identification

No abstract available

[en] We have investigated the excitation spectrum of ⁴He around Esub(x) = 20 MeV by inelastic scattering of 64 MeV α-particles from ⁴He. From an R-matrix representation of our data we have extracted level parameters for the αsup(*), the first excited state of ⁴He: Esub(lambda) = 20.29(2) MeV, GAMMA₀ = 89(4) MeV and (THETAsub(N))₀ = 0.4(1). We are able to predict reliable low-energy p + ³H and n + ³He s-wave phase shifts. Our results help to resolve a long standing ambiguity in the neutron scattering lengths of ³He, for which we obtain αsub(s) = 7.0(4) + i4.4448(9) fm and a₁ = 3.4(2) fm. We find the αsup(*) to be an instructive example for the influence of thresholds on level parameters and line shapes. (orig.)