V. V. Kim

Electromagnetic showers induced by high energy electrons in aligned tungsten crystals

Abstract The experimental results of the development of electromagnetic showers induced by 28 GeV electrons in aligned tungsten crystals with thicknesses 0.07,0.3,1.0mm are presented. At this energy of electrons the “constant strong field” effect starts to show and the development of showers in aligned crystals is distinguished from the one in an amorphous substance.

Spectrometers for Recording Electromagnetic Showers Emerging from Oriented Crystals

The design and main characteristics of combined shower spectrometers (CSSs) are presented: combined Cherenkov and lead-scintillation spectrometers that are intended for investigating shower processes in oriented crystals and that consist of ten independent lightproof counters with thicknesses of 1X0 and 1.18X0, respectively. At an electron energy Ee = 26 GeV, the energy resolutions of both CSSs together with a Cherenkov spectrometer with a thickness of 15X0, which was placed behind them, were 2.4 and 4.3% for the combined Cherenkov and lead-scintillation shower spectrometers, respectively.

Orientation dependences of the response of an electromagnetic spectrometer with oriented crystal converter

The experimental results of the study of orientation dependences of the response of a composite Cherenkov shower spectrometer with a converter made of a 1-mm tungsten crystal oriented along the 〈111〉 axis at an electron energy of 28 GeV and two converter temperatures, 293 and 77 K, are presented. The parameters of the cascade curve of the shower development are varied depending on the orientation angle and crystal temperature. It is found that there is a point S in the cascade curve of the shower development in the spectrometer, at which all cascade curves intersect at any converter orientation. The position of this point in the spectrometer depth depends on the converter temperature.

Multiplicity of charged particles in electron-induced showers developing in oriented silicon and tungsten crystals

A more than twofold increase in the average multiplicity of charged particles in electromagnetic showers initiated by electrons with an energy of 26 GeV in tungsten crystals 2.7, 5.8, and 8.4 mm thick, oriented along the 〈111〉 axis, in comparison with misoriented crystals is shown. For a silicon crystal 20 mm thick, oriented along the 〈110〉 axis, at an electron energy of 28 GeV, the average multiplicity of charged particles increases by a factor of ∼1.6. The widths of the orientation dependences of the average multiplicity of charged particles in electron-induced showers in silicon and tungsten crystals are proportional to the crystal thickness and depend on the electron energy as E−1/2.

Effect of oriented crystalline converter temperature on spectrometer response

Cooling of a 1-mm crystalline tungsten converter oriented along the 〈111〉 axis situated in front of an electromagnetic spectrometer of thickness 25X0, recording showers of 28-GeV electrons, to a temperature of 77 K results in a decrease of the crystal radiation length by ∼30%, shifts the cascade curve of the shower development in the spectrometer by ∼7%, and improves the spectrometer energy resolution by ∼5% in comparison with similar parameters of the spectrometer at a crystal temperature of 293 K.

Charged particle multiplicity in showers formed by gamma-rays in oriented tungsten crystal

It is shown that the average charged particle multiplicity in electromagnetic showers induced by γ-rays with energies of 9–26 GeV in the tungsten crystal 1 mm thick (T = 77 K) oriented along the 〈111〉 axis approximately twofold increases in comparison with a misoriented crystal.

Transformation of the amplitude spectrum and direction rejection of particles transmitted through a crystal

When high-energy photons, electrons, or positrons pass through a crystal, anomalous electromagnetic showers are formed, which differ from ordinary showers in an amorphous substance. Introducing the transformation coefficient β of the amplitude spectrum and the rejection coefficient R allows one to precisely determine the degree of difference of anomalous showers from ordinary ones upon changes in the particle energy, angle of crystal orientation, etc., and distinguish the specified direction of moving particles and the probability of falling of particles from other directions within this direction of particles.

Electromagnetic showers in oriented garnet crystals

The orientation dependences of the energy release in showers formed in transparent garnet crystals with thicknesses of 23 and 50 mm are measured, and the influence of the orientation of the crystals on the absorption of a shower in an amorphous radiator is determined.