This article presents the design and characteristics of a multi-leaf collimator developed for the experimental clinical ion beam therapy system for the U‑70 accelerator of the Institute for High-Energy Physics, Kurchatov Institute National Research Center.

A PF-LDS CAMAC 8-channel programmable pulse shaper module has been developed for reception and preprocessing of information from low-channel detecting systems. The module can operate with input signals of both polarities. Output signals of the module are NIM-level signals. The module supports up to three output channels per input, and the output signals can be direct or inverse. The shaper module is designed in the CAMAC standard, has eight channels for pulse shaping, and takes two slots in a CAMAC crate. The average quantization-step duration of an output pulse is 6.52 ± 0.04 ns. The maximum pulse length of output signals is 404 ± 2 ns. The shaper delays signals by 18.85 ± 0.57 ns on average for all channels. The mean length of the leading edge of shaper output signals is 1.23 ± 0.20 ns. The relative change in the output-pulse duration under a full load of the module channels is at most 3%. The shaper threshold voltage is set in the range from –540 to +540 mV.

The active target with C, Si and Pb plates was irradiated in 70-GeV proton beam at U-70 accelerator. The signal (270 events) from $$\Sigma^{0}\to\Lambda^{0}+\gamma$$ decays was selected in 10695 events with $$\Lambda^{0}$$ and $$\gamma$$ using gamma-detector data. The following values of the $$\Sigma^{0}/\Lambda^{0}$$ ratio were obtained: $$0.34\pm 0.08$$ (C), $$0.32\pm 0.06$$ (Si) and $$0.10\pm 0.09$$ (Pb). The comparison of the results with other experiments is presented.

(SVD-2 Collaboration) A. G. Afonin, E. N. Ardashev, V. F. Golovkin, S. N. Golovnya, S. A. Gorokhov, A. A. Kiryakov, A. G. Kholodenko, V. V. Konstantinov, L. L. Kurchaninov, I. S. Lobanov, E. V. Lobanova, G. A. Mitrofanov, V. S. Petrov, A. V. Pleskach, M. K. Polkovnikov, V. N. Riadovikov*, V. N. Ronzhin, V. A. Senko,N. A. Shalanda, M. M. Soldatov, Yu. P. Tsyupa, A. P. Vorobiev, V. I. Yakimchuk, and V. N. Zapolskii∗ IHEP, Protvino, Moscow region, Russia.

The general architecture and characteristics of the readout electronic system for the vertex detector of the SVD-2 setup at the U-70 accelerator (Kurchatov Institute NRC−IHEP, Protvino) are presented. The SVD-2 setup is intended to study near-threshold charmed-particle production at energies of 50–70 GeV, as well as many-particle processes and collective behavior of particles. The key characteristics of the electronic modules developed for the SVD setup by the Kurchatov Institute NRC−IHEP are briefly described.

A detector consisting of four p-i-n silicon pad structures of size 6 × 6 mm2 and thickness 300 μm was developed for the rapid monitoring of carbon ion beam quality at the Temporary Radiobiology Facility at the Institute for High Energy Physics (TRBF IHEP) by measuring event-by-event energy release on passage of charged particles (ions) through it. This articles describes the detector design and the method used for identifying contaminants in the beam of carbon nuclei. The charge composition of the ion beam of the TRBF IHEP calculated using the amplitude spectra of signals from the p-i-n structures is presented.

A precision vertex microstrip detector has been developed for the spectrometer with a vertex detector (SVD) setup on which the properties of hadrons and short-lived unstable particles are investigated on the accelerator of the Institute for High Energy Physics. The structure and the design of the main detector components—microstrip sensors and an active target—are presented, as well as techniques for manufacturing them. The readout electronics, the data acquisition system, and its software are also described. The accuracy in determining the vertex position is 70–250 µm along the beam axis and 8–15 µm in a transverse direction at a throughput of 500–1000 events/s.

Data from the SVD-2 experiment that were obtained at the IHEP accelerator in 70-GeV/c proton-nucleus interactions are analyzed with the aim of searches for an exotic Θ+ baryon that decays through the pK S 0 channel. The reaction pN → pK S 0 + X characterized by a bounded multiplicity of charged secondaries is used for this analysis. A resonance of mass M = 1526 ± 3(stat.) ± 3(syst.) MeV/c2 and width Γ < 24 MeV/c2 is observed in the invariant-mass spectrum of the pK S 0 system at a statistical significance of 5.6σ. The mass and the width of this resonance correspond to the recently found positive-strangeness Θ+ baryon, which was predicted to be an exotic baryon consisting of five quarks (pentaquark), \(uudd\bar s\). The total cross section for the production of a Θ+ baryon in pA interactions is estimated at a value within the range 30–120 μb for xF ≥ 0. An analysis of the A dependence of the cross section for Θ+-baryon production does not reveal a significant deviation from the A dependence for inelastic events (∼A0.7).

The methods for reconstructing the coordinates of charged-particle tracks in silicon microstrip detectors are analyzed thoroughly. It is shown that the accuracy depends on the reconstruction procedure. The methods are applied to model calculations with the GEANT program of the SVD vertex detector in the experiment E-184.

The Tomsk synchrotron has been used to measure the emission spectrum and orientation dependences of the yield of photons with energies much smaller than the emission energy of channeled electrons. The measurements have been performed with a crystal-diffraction spectrometer. For electrons incident along the (110) axis, the radiation intensity in the energy range 30 ≤ ω ≤ 360 keV exceeds the bremsstrahlung one by almost an order of magnitude. The shape of the emission spectrum does not coincide with that of the bremsstrahlung spectrum. The radiation intensity increases smoothly with the photon energy. The bremsstrahlung spectrum from a disoriented crystalline target is satisfactorily described by the existing theory with phenomenological consideration of the polarization of the medium.

The yield of parametric x-ray radiation from a tungsten single crystal irradiated with a E=500 MeV electron beam from the Tomsk Sirius synchrotron was studied experimentally in Bragg geometry. The tungsten sample was 1.7 mm thick and had a surface mosaicity less than 1.5′; it was oriented in such a way that the (111) face was at the Bragg angle of θB=45° with respect to the electron-beam direction. The x-ray photons were detected at the angle of 2θB=90° with respect to the electron beam. The angular distributions of parametric x rays are compared with those calculatedwith allowance for actual experimental conditions.

The influence of anomalous dispersion on the intensity of parametric x rays (PXR) is experimentally investigated in the present work. An experiment conducted with an inner electron beam generated by the Tomsk synchrotron with energy E 0 = 900 MeV is discussed. A Ge monocrystal 0.17 mm thick oriented so that Bragg's angle Θ B between the electron momentum direction and the (111) plane is 9°30′ is used as a target. The experimental data are compared with the results of calculations in the context of the kinematic PXR theory.