Contemporary projects such as AUGER in Argentina or HESS in Namibia are rather expensive experiments. We have constructed a simple detector arrangernent based on the water Cherenkov technique to be used for the detection of high-energy particles in cosmic ray experiments either as stand-alone experiment or as addition to other set-ups. A first prototype has been taken into successful operation. The construction of this detector is the starting point for extended studies in future cosmic ray experiments. The detector can be expanded by adding more and more modules at a very low price.

The performance of a new Photonis XP1472 nine-channel photomultiplier (PMT) was studied with the main emphasis to the photoelectron numbers and photoelectron collection efficiency, as measured with a 10 mm in diameter NaI(Tl) crystal coupled to the separate channels. Simultaneously, energy resolution and crosstalk were measured for all channels with a Cs-137 source. Time jitter and time resolution for an LSO crystal coupled to the different channels were measured for 511 keV annihilation quanta and compared to those measured earlier with XP2020Q PMTs. The studies confirmed high photoelectron collection efficiency in the PMT due to a new design of the input focalisation system.

Performances of new fast XP20Y0/DA and XP20Y0Q/DA 8 stage photomultipliers (PMTs) equipped with a screening grid at the anode were studied. The time jitter of the new PMTs was measured using a fast light pulser based on an XP22 light emitting diode. The timing properties in coincidence experiments were measured with BaF/sub 2/, LSO, and LaCl/sub 3/:Ce crystals for /sup 60/Co and /sup 22/Na gamma rays and discussed in terms of the measured photoelectron numbers. Particularly, the normalized time resolutions to the number of photoelectrons measured with BaF/sub 2/ crystals were comparable to that measured in the past with the XP2020Q in a superior dynode-timing mode. A significant improvement of timing up to a factor of 1.2 due to the grid at the anode was shown also in the measurements with LSO and LaCl/sub 3/:Ce crystals.

The absolute light outputs of EGO, CsI(Tl) and some new Ce-doped crystals have been measured to an accuracy of about +/-5 % using calibrated XP2020Q photomultipliers and standard S3590-03 and S2740-03 photodiodes. The use of small crystals, 9 mm in diameter and 1 mm thick, reduces the corrections for imperfections in the light collection process and in the photoelectron collection by the photomultipliers. The measured Light output of 8500+/-350 ph/MeV (photons/MeV) for the EGO crystals agrees well with the earlier measurement done by Hell et al. The carried out study highlighted the importance of die spread in the published emission spectra of the crystals which seems to limit measurement accuracy. Finally, a simple comparative method of measuring light output to an accuracy of +/-10 %, is proposed using an uncalibrated XP2020 photomultiplier and a 1 mm thick EGO crystal as a standard.

A large area electro-optical pre-amplifier photomultiplier combination for the DUMAND array is proposed with excellent single and multi-electron resolution compared with conventional photomultipliers. Photo-electrons from a hemispherical photocathode are accelerated to and collected on a fast phosphor screen, behind which a conventional photomultiplier is placed. The combination works as a photomultiplier with a very high gain (~ 50) first dynode. The design will be described and data will be given on collection efficiency, gain, single electron resolution, background, transit time and afterpulses. These properties will be discussed in view of the requirements for the DUMAND array and other applications.