A method of testing of threshold SiO2 aerogel Cherenkov detectors using cosmic radiation is described. The method requires a minimum amount of additional electronics and does not involve massive absorber layers (e.g., lead). The method makes it possible to directly take into account the threshold in determining the efficiency of the detectors under study and to test their operation in different energy ranges for relativistic charged particles. Good agreement between the results of the simulation and measurements was obtained.

For photonuclear research with γ-quanta having energies Eγ ≤ 40 MeV at the source under developing with backward Compton scattering of laser radiation on accelerated electrons, activation experiments are proposed as initial ones. These experiments are important both for developing techniques for tuning and monitoring such γ-beams, and for studying the excitation of pygmy and giant resonances in nuclei at Eγ near the threshold of the (γ, n) reaction, as well as the multiplicity of photoneutrons during deexcitation of giant resonances at Eγ above the threshold of (γ, 2n)-reaction.

To study the E1 giant resonance in atomic nuclei, it is important to study the energy and emission angle distributions of fast neutrons from (γ, n)-reactions. The paper considers some features of such studies on beams of γ-quanta produced by inverse Compton scattering with small spreads of their energy, angles, transverse dimensions, duration, and polarization in these beams. It is proposed to use fast neutron spectrometers using both amplitude and time-of-flight data.

The possibilities of studying the reaction yields of ^13 C (γ,p)^12 B, ^14 N (γ,2p)^12 B, and ^14 N (γ,2n)^12 N through measurements of induced ( ^12 B, ^12 N) activities with thin Δ E detector telescopes in temporal intervals between electron accelerator pulses have been analyzed. Estimates for the production of ( ^12 B, ^12 N) nuclei and registration of their decay are provided, taking into account the parameters of the electron beam, Ta radiator, irradiated targets made of graphite or NH _4 NO _3 , and telescopes of plastic scintillation Δ E detectors.

Based on the analysis of development of photonuclear reaction studding at 𝐸𝛾 ≲ 40 MeV and the unique parameters of the Compton source of 𝛾–quanta under projecting, a program of priority photonuclear research using this source is proposed. The program includes research on: structures of giant E1 resonances and pygmy resonances; cross sections for partial photonucleon reactions; nuclear resonant fluorescence; photofission; problems of astrophysics and nucleosynthesis.

A variant of testing threshold SiO2 aerogel Cherenkov detectors using cosmic radiation is described. The implementation requires a minimum amount of additional electronics and does not involve massive absorber layers (lead, etc.). The method makes it possible to accurately determine efficiency of detectors under study and to study operation of detectors in different energy ranges for relativistic particles.

The possibilities are analyzed for studying the yields of reactions 13C(𝛾, 𝑝) 12B, 14N(𝛾, 2𝑝) 12B, 14N(𝛾, 2𝑛) 12N by measuring the induced (12B, 12N)-activity with telescopes of thin Δ𝐸–detector in time intervals between electron accelerator pulses. For production of (12B, 12N)- nuclei and registration of their decay, estimates are given taking into account the parameters of the electron beam, Ta–radiator and irradiated targets made from graphite or NH4NO3, as well as the parameters of scintillation Δ𝐸 detector telescopes made from thin plastic plates.

A method for testing threshold SiO2-aerogel Cherenkov detectors using cosmic radiation is described. The implementation requires a minimal amount of additional electronics and does not involve massive absorber layers (such as lead, etc.). The method allows for accurate determination of the efficiency of the investigated detectors and for the study of the detectors' operation in different energy intervals for relativistic particles.

Proceeding from the comparison of parameters for the γ -ray source based on backward Compton scattering, which is under development now, and the known methods of monitoring γ -ray beams themselves to monitor the intensity and energy spectrum of γ quanta in the beams from this γ -ray source during photonicuclear research in the energy range from a few megaelectronvolts to ∼ 40 MeV, a system comprising scintillation plastic and inorganic detectors, as well as a magnetic pair spectrometer, has been proposed.

Based on a comparison of the parameters of the projected 𝛾–source from backward Compton scattering and the known ways of monitoring the beams of 𝛾–quanta themselves to monitor the intensity and energy spectrum of 𝛾–quanta in their beams at this 𝛾–source in photonuclear studies in the region from several MeV to ∼40 MeV, a system of scintillation plastic and inorganic detectors, as well as a pair magnetic spectrometer, was proposed.

The authors discuss problems of studying the yields of the reactions 13 C(γ, p ) 12 B, 14 N(γ, 2 p ) 12 B, and 14 N(γ, 2 n ) 12 N with ( 12 B, 12 N) activity measured by the telescopes of Δ E detectors in the intervals between electron accelerator pulses. The fluxes and spectra of irradiating bremsstrahlung γ-quanta are found for chosen radiators and targets. The effect the parameters of targets and telescopes of Δ E detectors have on the production of ( 12 B, 12 N) nuclei and the registration of their decay is estimated.

In this article, we describe an experimental verification of the correctness of registration of delayed neutrons from 238U photofission at a maximum energy of 10 MeV of bremsstrahlung γ quanta on a pulsed linear electron accelerator LUE-8-5 in an interval of (1–5) ms after each beam pulse at times ≳7 min from the onset of irradiation. The measurements have been carried out using the scintillation spectrometer of fast neutrons based on a single stilbene crystal with pulse shape discrimination of γ quanta and fast neutrons. The temporal dependence of the counting rate of delayed neutrons in 238U photofission has been measured at a repetition rate of 300 s–1 in a time interval of (1.25–3.30) ms after the beam pulse.

A study is performed of distortions in the registration of fluxes and energy spectra of delayed neutrons by a stilbene scintillation spectrometer inside Pb shielding. The delayed neutrons are products of 238 U photofission on a pulsed electron linear accelerator. The dependences of these distortions on the neutron energy and wall thickness of the Pb shielding are considered. Contributions from processes in the walls of the irradiation hall are described.

Conditions are considered that allow the separation of a hypothetical short-lived component (T1/2 = 1 ms) in delayed neutrons from 238U photofission on a pulsed linear electron accelerator when neutrons are detected during intervals between beam pulses using a stilbene scintillation spectrometer with pulse shape discrimination of background γ-quanta scintillations.