[en] Charged particles with an energy between 2 GeV and 25 GeV can be identified in the DELPHI barrel RICH detector by using the technique of Cerenkov ring image detection. The method of identification is based on a determination of the Cerenkov angle by measuring the positions of the emitted Cerenkov photons to high precision in a photon detector. The resolution in the photon that can be obtained depends mainly on the chromatic dispersion in the radiators and on the resolution in the photon detector is used in the barrel RICH in combination with two radiators. The photon detector consists of 48 drift tubes, constructed from quarz plates, each equipped with a wire chamber at the end. The drift gas with which the tubes are filled contains a small admixture of TMAE vapour from which the Cerenkov photons can liberate photoelectrons. It is shown in this thesis that an efficient photon detection and an accurate localization of the photon conversion points is possible. The spatial resolution of the photon detector is determind by the resolution of the wire chambe, the accuracy of the drift measurement, the distortions in the paths of the drifting electrons. The resolution of the wire chamber has been measured to be 0.8 mm in the x- and 1.7 mm in the y-coordinate. The error in the z-coordinate introduced by the drift time measurement is 0.2 mm. The distortions in the paths of the drifting electrons have been measured both in the x and y-direction. The longitudinal and transverse diffusion coefficients have been measured as a function of the field strength for two different drift gas mixtures. (author). 96 refs.; 61 figs.; 11 tabs

[en] For the measurements of exotic X-rays we designed two GSPC's and a background suppression system. The suppression is based on the recognition of a typical pulseform from X-rays absorbed in the right detector region and reduces the background by a factor of ∝ 300. This pulseform is obtained by operating the GSPC's in a prescintillation mode where scintillation occurs also in the absorption region. (orig.)

[en] The DELPHI Barrel RICH (ring-imaging Cherenkov) detector is based on the principle of the drift of single electrons over distances up to 1.5 m in TPC-like drift tubes made of quartz. The drift is performed in a longitudinal electric field of 0.53 kV/cm and in a gas mixture of 80% CH₄, 20% C₂H₆ and ≅ 1000 ppm of TMAE as photosensitive additive. The electron loss during the drift has been measured for different TMAE concentrations and different TMAE qualities. It will be shown that an absorption length λ>10 m can be obtained even for high TMAE concentrations. This could only be achieved by taking extreme care in the purity of the TMAE and the drift gas. We will also report on the systematic errors in the reconstruction of the photon conversion point due to distortions in the electron drift. Small focusing effects have been observed close to the walls. (orig.)

[en] The gating system of the MWPCs of the DELPHI Barrel RICH is essentially a means to prevent positive ions originating from avalanches in the chambers to escape into the Barrel RICH drift tubes. These ions would otherwise seriously affect the imaging quality of the Barrel RICH. We describe the gating grid, the gating pulser and results of tests at pressures of 1 and 1.3 bar in a magnetic field of 1.2 T and without. In the ungated ('closed') mode, transfer of electrons and ions are 8% and 0% respectively; a further reduction of electron transfer is limited by power dissipation of the pulsing circuit. The occupation time of the readout electronics after the gating pulse is less than 1 μs. The test results are compared with those of electrostatic simulations. A triggering scheme is proposed. (orig.)

[en] We discuss the performance of multiwire proportional chambers to be used as photoelectron detectors on the Barrel Ring Imaging Cherenkov counter of the LEP DELPHI spectrometer. The chamber is used for the 3-dimensional localization of Cherenkov photons and can be gated by means of a pulsed grid. It has been operated in a 10 GeV/c π^- test beam setup allowing the production and the detection of Cherenkov light. With an isobutane gas radiator, we have measured a 93% relative cathode efficiency, a quality factor N₀=89 cm^-1 and a Cherenkov angle resolution of 3.9 mrad, in good agreement with Monte Carlo simulation. (orig.)

[en] The yields of K and L series X-rays from anti pp atoms and of the L series X-rays from anti pd atoms have been measured at gas densities of 0.25, 0.92, 2.0 and 10.0 ρ_STP. For anti pp atoms the strong interaction shift and width for the 1s state and the width of the 2p state have been measured. The results are in good agreement with the predictions of potential models. (orig.)

[en] Energies and yields of K-series X-rays from anti pp atoms have been measured with two gas scintillation proportional detectors at target gas densities of 0.25 and 0.92 ρ_STP. Values for the strong interaction shift and width of the 1s state obtained from the X-ray spectra are compared with the predictions of a variety of theoretical models. Upper limits for the yield of K-series X-rays from anti pd atoms have also been obtained. (orig.)

[en] A short explanation is given of the Barrel Ring Imaging CHerenkov (BRICH) detector and its performance. We discuss in brief some of the requirements to run this detector. Special attention is paid to the functioning of the Cherenkov photon detector - a photosensitive gas-filled drift chamber where the photoelectrons drift to a MWPC of special construction. We illustrate the BRICH performance with some preliminary results. (orig.)