Simulations of dark current emission for C-band linear accelerating structure were performed taking into account the electric field distributions inside the cavities and the field enhancement factor. Matching calculated dark current energy spectra with the experimentally measured ones made it possible to understand the nature of the dark current and to reveal the areas of the accelerating structure requiring improved surface treatment. Microscopic investigation of the copper accelerating cell surface treated using different techniques showed that gas cluster ion beam irradiation results in the best surface smoothness. Furthermore, it removes the surface insulating layers and prevents from subsequent oxidizing. Both effects can significantly reduce the dark current emission.

The report presents the results of development of applied linear electron accelerators with an energy of up to 10 MeV, performed by the Laboratory of Electron Accelerators MSU. We describe linear accelerators for mobile, stationary and train cargo inspection systems with interlaced energies and pulse repetition rate up to 2 kHz, accelerators for radiography, a sterilization accelerator with beam parameters that are adjustable over a wide range, and an accelerator for a radiotherapy complex. INTRODUCTION Laboratory of Electron Accelerators MSU Ltd. (LEA MSU) was established on the base of Skobeltsyn Institute of Nuclear Physics Lomonosov Moscow State University (SINP MSU) in 2013. Within five years we have designed six different types of linear accelerators for security, industry and medicine and supplied customers with more than 20 units. The customer of accelerators for security systems is the co-founder of the LEA MSU Scantronic Systems LLC, which developed a number of cargo inspection systems, including stationary, train and mobile [1]. LEA MSU closely cooperates with the JSC “SPE” Toriy” [2] enterprise that produces the powerful vacuum RF devices. We use in our accelerators the multi-beam klystrons, accelerating structures and electron guns manufactured by “Toriy” and carry out joint deliveries of accelerators. Our accelerators operate in S-band (2856 MHz) and C-band (5712 MHz). Examples of klystrons and sealed accelerating systems are shown in Figs. 1-2. The accelerators designed by LEA MSU are equipped with a control system based on specialized controllers each controller is responsible for a separate accelerator system [3]. The control system allows remote monitoring of the accelerator operation while saving the accelerator regime and beam parameters on the server. The control system allows changing the parameters of the accelerated beam within wide limits in accordance with the requirements of the technological process. An important part of the RF system of our accelerators is a fast digital AFC system, permitting to reach stable beam energy and dose rate for a time of less than 1 s after start. Figure 1: S-band (left) KIU-168 and C-band KIU-271 klystrons [2]. Figure 2: S-band (upper) and C-band accelerating systems. Preliminary information about LEA MSU accelerators was given in [4-5].

A pulsed 55-MeV race-track microtron that was developed and constructed jointly at the Skobeltsyn Institute of Nuclear Physics, Moscow State University and the Lebedev Physical Institute with the participation of Moscow Engineering Physics Institute is described. The results of calculations of the beam dynamics and the main elements of the accelerator are presented, their design is described, and the results of their measurements and adjustment are presented. The technique and results of the accelerator commissioning are described.

We present the results of the commissioning of the pulsed linear electron accelerator with beam energy of 10 MeV, developed with the participation of scientists and engineers of the SINP MSU, LEA MSU Ltd. and JSC "RPE "Toriy". The source of RF power for accelerator is a multibeam klystron KIU-147A operating at 2856 MHz with pulse output power 6 MW and an average power of 25 kW. As a result of commissioning we received at the output of accelerator scanning system an electron beam with an energy of 10 MeV and an average power of more than 15 kW. Capture ratio and electronic efficiency of 1.24 m long accelerating structure are greater than 60% and 75%, respectively.

The article describes the radiation field forming system for industrial electron accelerators, which would have uniform distribution of linear charge density at the surface of an item being irradiated perpendicular to the direction of its motion. Its main element is nonlinear quadrupole lens made with the use of rare-earth magnetic materials. The proposed system has a number of advantages over traditional beam scanning systems that use electromagnets, including easier product irradiation planning, lower instantaneous local dose rate, smaller size, lower cost. Provided are the calculation results for a 10 MeV industrial electron accelerator, as well as measurement results for current distribution in the prototype build based on calculations.

The experimental setup that is used at the Skobeltsyn Institute of Nuclear Physics of the Moscow State University to study photonuclear reactions using the activation technique is described. The system is based on two modern compact race track microtrons with maximum energy of electrons of up to 55 and 67.7 MeV. A low-background HPGe detector is used to measure the induced gamma activity. The data acquisition and analysis system, used to process the measured spectra, is described. The described system is used to study multiparticle photonuclear reactions and production of nuclei far from the beta stability region.

Doses of ionizing radiation generated by a luggage simulator are measured. The luggage simulator is irradiated under conditions that occur when luggage is inspected by photonuclear detectors for explosive materials. It is shown that the ionizing radiation caused by induced radiation is not dangerous either to passengers or to airport stuff.

Были измерены дозы ионизирующего излучения от имитаторов багажа авиапассажиров после их облучения в условиях, соответствующих облучению при прохождении досмотра в фотоядерном детекторе взрывчатых веществ. Показано, что ионизирующее излучение, обусловленное наведенной активностью, не представляет опасности ни для населения, ни для персонала аэропорта.

A race-track microtron is used to measure the yield of 18 F in the reaction 19 F(γ, n) at an energy of the electron beam of 55 MeV. 18 F is widely used in positron emission tomography for high-sensitivity diagnostics. The currently available data are not sufficient to make accurate estimates of the yield of 18 F in isotope production experiments using the reaction (γ, n). The value of σ −1 estimated in this work is (1.7 ± 0.1) mb.

It was shown that irradiation of the crystals with high-energy (up to 55 MeV) γ-rays leads to the prolonged self-organization of atomic displacements. A tiny portion (at about 10 −9 of the sample volume) of the initially excited atoms organize the entire crystal volume with respect to the time and the space.