A prototype of a 2D detector based on specially designed straw tubes with cathode data readout has been developed and tested. This detector exhibits comparable accuracies in measuring radial and longitudinal coordinates. Its rate capability is similar to the capabilities of traditional detectors whose tubes are smaller by half in diameter.

Precise measurement of straw axial coordinate (along the anode wire) with accuracy compatible with straw radial coordinate determination by drift time measurement and increase of straw detector rate capability by using straw cathode readout instead of anode readout are presented.

Detector rate capability is one of the main parameters for designing a new detector for high energy physics due to the permanent rise of the beam luminosity of modern accelerators. One of the widely used detectors for particle track reconstruction is a straw-detector based on drift tubes. The rate capability of such detectors is limited by the parameters of readout electronics. The traditional method of increasing detector rate capability consists in increasing their granularity (the number of “elementary” detectors = readout channels) by reducing the straw diameter and/or by dividing the straw anode wire into two parts (for decreasing the rate per readout channel). A new method of designing straw detectors with a high rate capability is presented and tested. The method is based on dividing the straw cathode into parts and the independent readout of each part.

The coordinate detectors based on straw tubes provide a high accuracy of the radial coordinate measurement using the drift time and a small amount of matter in the way of the measured particles. However, the measurement of the coordinate along the wire constitutes a problem. This paper proposes a method for measuring the hit coordinate along the wire with an accuracy better than 1 mm in a straw tube detector using the signals from the cathodes of the detector.

The PEN collaboration carries out a precision measurement of the π+ → e +ν decay branching ratio at the Paul Scherrer Institute (PSI, Switzerland). A special mini time-projection chamber (mTPC) has been developed for registration of particles in the pion beam. The chamber contains 14 × 10−3 g/cm2 of matter on the particle path. The chamber was successfully used during one-year-long run. Design and characteristics of the mTPC are described.

A detector with a profile-based cathode and a two-coordinate cathode readout system has been experimentally investigated. Cathode pads located in each profile along the anode wire are diagonally interconnected, thus forming strips that cross the detector at some angle with respect to the anode wire. Owing to the availability of the two cathode coordinates and the coordinate associated with the anode wire, it is possible to solve the problem of identifying high-multiplicity events in a single detector.

The high-voltage divider consists of a high-resistance linear resistive divider setting the potential distribution between photomultiplier electrodes and a circuit of emitter-follower amplifiers maintaining this distribution. The divider is characterized by a small current consumption (similar to 300 mu A). In this case, the photomultiplier characteristic remains linear up to a similar to 1.5-mA average current.

A magnetic spectrometer intended for a wide range of investigations of rare particle and nuclear processes is described. The spectrometer consists of cylindrical proportional chambers (∼ 15000 signal wires) with gas supply and gas leakage systems, cylindrical scintillation hodoscopes, a magnet, electronics with power supplies, and a data acquisition system. Basic characteristics of the spectrometer are discussed and results of first physics experiments are presented.

Eight events of the radiative pion decay pi+ --> e+ nu(e)e+ e- were found with the ARES spectrometer. The branching ratio for the decay due to the presence of the structure is GAMMA(pi --> evee(SD))/GAMMA(pi --> munu) = (4.6 +/- 1.6 +/- 0.7) . 10(-10).

A search with the large solid angle spectrometer (ARES) for the lepton-number-nonconserving decay mu+ --> e+e+e- has been carried out. Cylindrical multiwire proportional chambers and cylindrical scintillation hodoscopes were used. The upper limit for the branching ratio GAMMA (mu+ --> e+e+e-) / GAMMA(mu+ --> e+nu-e-nu-mu) less-than-or-equal-to 3.6 x 10(-11) (90% C.L.) has been derived. The investigation has been performed in the Laboratory of Nuclear Problems, JINR.

A search is made for the decay mu+ --> e+e+e- violating lepton-number conservation using a wide solid-angle magnetic spectrometer (ARES). The spectrometer utilizes cylindrical proportional chambers and cylindrical scintillation hodoscopes. We find that the upper limit on the branching ratio for the decay mu+ --> e+e+e- is GAMMA(mu+ --> e+e+e-)/GAMMA(mu+ --> e+nu-e nu-muBAR) less-than-or-equal-to 3.6.10(-11) at the 90% confidence level.

A method is described for fabricating 600 x 87 x 5 mm plastic scintillation counters which are constituent elements of a 673 mm in diameter cylindrical hodoscope. Results of investigations into the amplitude and temporal characteristics of a separate scintillation are presented. Light losses in the transitional and main lightguides were determined primarily by the absorption length of the organic glass. The time resolution of the counter with the beta source placed at the center of the scintillator equaled 1 nsec; the velocity of propagation of light in the scintillator equals 12.1 cm/nsec. The ARES spectrometer detects electrons and gamma rays under conditions of high meson-stopping intensity and will be used for pion and muon rare decay studies.