A CAMAC (1M) single-channel time-to-digital converter has been designed for measuring time intervals with a time resolution of 2 ns in the range from 0 to ~131 μs. This range can be extended by connecting an additional external counter. This converter is of the counting-pulse type with a calibrated conversion scale. A recirculation generator based on a K500LM101 chip is used as a source of counting pulses. One time interval can be measured at once. Several time-to-digital converters can be combined into a multistop measuring system to increase the number of time intervals recorded by a single Start signal. The differential nonlinearity is 1%, and the integral nonlinearity in the above range is 0.001%. The relative instability of the conversion coefficient caused by supply-voltage variations within the range of–6 V ± 2.5% is 0.24%. The temperature drift of the conversion coefficient in the temperature range of 22.6–65.7°C is 0.07%/°C.

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.

The PEN Collaboration is conducting a new measurement of the π+ → e + vL branching ratio at the Paul Scherrer Institute, with the goal uncertainty of δB/B πe2 = 5 × 10−4 or lower. At present, the combined accuracy of all published πe2 decay measurements lags behind the theoretical calculation by a factor of 40. In this contribution we report on the PEN detector configuration and its performance during two development runs done in 2007 and 2008.

An AA-32 32-channel CAMAC module is intended for reading information from the anode wires of multiwire proportional chambers. The amplifying part, signal delay module, and digital part for writing information into the computer are all placed on the same two-layer CAMAC board. ANODE-2-50M 8-channel microcircuits are used for amplifying signals. A two-port memory is used to delay (for up to hundreds of microseconds and more) the signals. The digital part of the system, including a two-port memory, is designed on Altera programmable gate arrays.

The construction and characteristics of the PIBETA spectrometer are described. This spectrometer is designed to implement a program of precise measurement of pion β decay π+ → π0 + e + + νe at the Paul Scherrer Institute (Switzerland). A spherical calorimeter, consisting of 240 crystals of pure CsI scintillator and embracing a solid angle of ∼3π, is the main detector of the setup. In addition, the spectrometer is composed of an active collimator (which also acts as a beam degrader), a segmented active plastic target, two multiwire cylindrical proportional chambers, a 20-element cylindrical plastic hodoscope, and veto counters of cosmic muons.

We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, π+→π0e+νe, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering ∼3πsr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure, which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two 3-month beam periods in 1999/2000 with π+ stopping rates between 1.3·103π+/s and 1.3·106π+/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5–150MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds.

E. Frlež, ∗ D. Počanić, V. A. Baranov, W. Bertl, M. Bychkov, N. V. Khomutov, A. S. Korenchenko, S. M. Korenchenko, T. Kozlowski, N. P. Kravchuk, N. A. Kuchinsky, W. Li, R. C. Minehart, D. Mzhavia, B. G. Ritchie, S. Ritt, A. M. Rozhdestvensky, V. V. Sidorkin, L. C. Smith, I. Supek, Z. Tsamalaidze, B. A. VanDevender, E. P. Velicheva, Y. Wang, H.-P. Wirtz, † and K. O. H. Ziock Department of Physics, University of Virginia, Charlottesville, VA 22904-4714, USA Paul Scherrer Institut, Villigen PSI, CH-5232, Switzerland Joint Institute for Nuclear Research, RU-141980 Dubna, Russia Institute for Nuclear Studies, PL-05-400 Swierk, Poland Institute for High Energy Physics, Tbilisi State University, GUS-380086 Tbilisi, Georgia Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287, USA Rudjer Bošković Institute, HR-10000 Zagreb, Croatia (Dated: 9 December 2003)

A special feature of the system is the integration of the amplifying section, signal delay unit, and digital section for the data outputting to computer into a common АДД-32 module (CAMAC). The 1-M-size АДД-32 module contains the electronics for 32 wires, which makes it possible to place up to 672 data channels in the CAMAC crate with a standard bus. To amplify signals, Ampl 8.3 eight-channel microcircuits are used. The output logic signals are delayed by 9-channel IDT72421 FIFO microcircuits enabling us to obtain a total signal delay of up to hundreds of microseconds and longer. The digital section of the system is based on ALTERA programmable logic arrays. At present, this system with a total of 576-channels is used in the PIBETA experiment to study rare pion decays on the PSI accelerator (Switzerland).

About three thousand events of the decay K- --> mu(-)nu pi(0) from the ISTRA-M setup (U-70, Protvino) are analyzed. In the V-A theory and the Linear approximation in the form factors, this analysis yields lambda(+) = 0.029+/- 0.024 and lambda(0) = 0.062+/-0.024. The results are compared with some theoretical predictions.

The decays K- --> mu(3)(-)V pi(o)(K-mu 3) and K- --> e-v pi(o)(K-e3) observed with the ISTRA-M detector operating at the 70-GeV Protvino accelerator are analyzed. Under the assumption of mu-e universality, a simultaneous fit to K-mu 3 and K-e3 data yields the values of lambda(+)= 0.017 +/- 0.006 and lambda(o) = 0.057 +/- 0.017 for the form-factor parameters.

A method for calculation of the momentum of a charged particle in magnetic spectrometers in high energy experiments with fixed targets is proposed. It is compared with the widely used method of Lechanoine, Martin and Wind [Nucl. Instr. and Meth. 69 (1969) 122]. The method gives an improvement in the number of coefficients by more than one order and in the number of computer instructions by approximately two orders and is much simpler. The method is tested on the magnetic spectrometers of experimental setups ISTRA-M and HYPERON at IHEP (Serpukhov, USSR).

In this article a simple method for making multiwire chambers is described. The chamber design does not involve any frame structure, which permits the

The possibility of registration of ionization clusters by a drift chamber with luminous data acquisition is investigated. Light is collected by a reemitter-containing light guide, which views two photomultipliers connected in coincidence. For registration of clusters, a mixture if Ar + 15% CH/sub 4/ is blown through the chamber, which operates in the proportional mode. The duration of a signal from a single electron is 5-7 nsec. The average density of clusters registered from beta particles is 12 or 9.5 cm/sup -1/ for a drift field of 40 or 100 V/cm in transverse-drift geometry for a digitizations time of 2 nsec.

B. A. VanDevender, ∗ M. Bychkov, E. Frlež, D. Počanić, V. A. Baranov, W. Bertl, Ch. Brönnimann, M. Daum, J. F. Crawford, R. Horisberger, N. V. Khomutov, A. S. Korenchenko, S. M. Korenchenko, T. Kozlowski, N. P. Kravchuk, N. A. Kuchinsky, W. Li, R. C. Minehart, D. Mzhavia, D. Renker, B. G. Ritchie, S. Ritt, A. M. Rozhdestvensky, R. Schnyder, V. V. Sidorkin, L. C. Smith, W. A. Stephens, I. Supek, Z. Tsamalaidze, E. P. Velicheva, K. O. H. Ziock, Y. Wang, and H. P. Wirtz 8

V. A. Baranov, W. Bertl, M. Bychkov, M. V. Chizhov, E. Frlež, N. V. Khomutov, A. S. Korenchenko, S. M. Korenchenko, M. Korolija, T. Kozlowski, N. P. Kravchuk, N. A. Kuchinsky, W. Li, R. C. Minehart, D. Mzhavia, D. Počanić, B. G. Ritchie, P. Robmann, A. M. Rozhdestvensky, T. Sakhelashvili, V. V. Sidorkin, L. C. Smith, U. Straumann, I. Supek, P. Truöl, Z. Tsamalaidze, A. van der Schaaf, B. A. VanDevender, E. P. Velicheva, and Y. Wang