E. V. Demidova

Acoustic field generated by a beam of protons stopping in a water medium

In an experiment with a beam of protons accelerated up to an energy of 200 MeV, the space-time structure of the hydroacoustic field generated by protons stopping in the water medium was observed. The contributions of three components were separated: a cylindrical wave diverging from the middle part of the acoustic antenna and the signals from the ends of the antenna, namely, from the region of the maximal energy density release by protons (the Bragg peak) and from the other end corresponding to the beam entrance into water.

Measurements of the Parameters of the Acoustic Radiation Accompanying the Moderation of an Intense Proton Beam in Water

Using the external proton beam of the accelerator at the Institute of Theoretical and Experimental Physics (ITEP), an experiment was performed on recording the acoustic signals accompanying the moderation (up to termination) of an intense proton beam with an energy of up to 200 MeV in water. The signals are damped quasi-periodic oscillations, whose initial period reflects the features of the radiating system. Parameters of the acoustic signal are measured in a wide range of energy release (from 1016to 1.2 × 1019eV) for three values of the beam diameter.

Measuring the Ultrasonic Field Generated in Water upon the Deceleration of a Proton Beam

The scanning-detector technique was used for the first time to observe the spatial–temporal structure of an ultrasonic field generated upon the deceleration and stopping in a water medium of a proton beam from the ITEP accelerator having an energy of 200 MeV and intensity of 4 × 1010. Measurements were performed in the near-field zone at 120 points that were located in the plane running through the beam axis. The latter coincided with the axis of the acoustic antenna that appeared. Contributions from three antenna segments were discriminated: from the extended middle part, the region of the maximum energy-release density at the end of the proton range (the Bragg peak), and from the plug near entrance of the beam into the water.

Angular distribution of acoustic radiation created in water by a beam of accelerated protons

We present the results of experimental investigations into the hydroacoustic field of a source created by a beam of protons accelerated to an energy of 200 MeV. We obtain the angular distribution of the signal amplitude arising in the most intensively radiating area of the source, localized at the end of an ionized path of protons. We simulate the physical processes accompanying the passage of electrons in a water medium. The results of simulation calculations agree with the experimental data.

ITEP INVESTIGATION OF ACOUSTIC PHENOMENA FROM HIGH ENERGY PARTICLES

The mechanisms of sound wave generation from high energy protons and features of detector response are investigated in ITEP. The attention is attracted to the different possible mechanisms than the dominant thermoradiation excitation of sound. The search of sonic signals from cosmic particles, acoustic accelerator experiments and specific hardware - are the three vectors of ITEP acoustic activity.

Investigation of semicoherent interactions of 1-GeV protons with silicon

An experiment on studying the 28Si(p, p′ γ0X)24Mg semicoherent reaction is carried out at the MAG setup on the 1-GeV proton beam of the U-10 ITEP accelerator. Two particles, proton and γ-ray photon, which accompanies the transition of the 24Mg* nucleus from the first excited state to the ground state, are detected. When the events with the proton emission angle from 3° to 6.5° are selected, the following four processes are observed: the direct knockout of a nuclear α cluster by a proton, the formation of a ΔSi isobaric nucleus, the formation of a Δ1232 isobar, and the production of a π0 meson at rest in the nuclear coordinate system. The cross sections for the indicated processes are obtained.

Study of the acoustic field produced by a 50-MeV electron beam in water

For the first time, a detailed space-time dependence of acoustic pressure produced by a 50-MeV electron beam in water are obtained at the electron accelerator of Moscow State University. Measurements are performed at 100 points taken along one line parallel to the beam axis and spaced 6.5 cm apart from this axis. The 2D (time-distance) patterns display two paths corresponding to signals from two sound sources: a cylindrical acoustic antenna produced by the electron beam and the entrance cap separating the water and air media.

Formation of 24Mg* in the spallation of 28Si nuclei by 1-GeV protons

The 28Si(p, p′γ0 X)24Mg reaction has been studied at the ITEP accelerator by the hadron-gamma coincidence method for a proton energy of 1 GeV. Two reaction products are detected: a 1368.6-keV γ-ray photon accompanying the transition of the 24Mg* nucleus from the first excited state to the ground state and a proton p′ whose momentum is measured in a magnetic spectrometer. The measured distribution in the energy lost by the proton in interaction is attributed to five processes: the direct knockout of a nuclear α cluster, the knockout of four nucleons with a total charge number of 2, the formation of the ΔSi isobaric nucleus, the formation of the Δ isobar in the interaction of the incident proton with a nuclear nucleon, and the production of a π meson, which is at rest in the nuclear reference frame. The last process likely corresponds to the reaction of the formation of a deeply bound pion state in the 28P nucleus. Such states were previously observed only on heavy nuclei. The cross sections for the listed processes have been estimated.

Measurement of cross sections for gamma transitions induced in excited nuclei by the interaction of 1.1-GeV protons with silicon nuclei

The cross sections for the production of excited nuclei were measured in the reaction 28Si(p, xpyn)A* followed by a gamma transition to a state of lower excitation energy or to the ground state. The experiment was performed in an extracted proton beam from the accelerator of the Institute of Theoretical and Experimental Physics (ITEP, Moscow). The reaction in question was identified by a Ge(Li)-NaI(Tl) anticoincidence spectrometer that recorded prompt gamma radiation emitted by the excited final nucleus. The sensitivity of the experiment was 1.5 mb. The cross-section values were obtained for 24 gamma transitions in 17 nuclear products. The cross sections for spallation reactions were estimated. A comparison was performed with known experimental data and with the results of calculations by a semiempirical formula, as well as with the results obtained by simulating hadron interactions on the basis of the GEANT and INUCL codes.

An Acoustic Converter Used to Measure Ionizing Radiation Energy Loss

A monitor is proposed based on ultrasonic production when ionizing radiation passes through a medium. The recording element is a 0.2 mm aluminum plate mounted in a ceramic acoustic converter AC in the form of a wedge of thickness 2 mm. The low plate thickness minimizes the beam parameter distortion, while special technology used in the AC provides high sensitivity. The device has been calibrated in the proton beam from the ITEP accelerator at 200 MeV with 2·109–6·1010 particles in a pulse and a pulse length of 70 nsec.