Upgraded gamma-ray generator based on ironless pulsed betatron

The paper concerns an upgraded gamma-ray generator which is a cyclic electron accelerator based on the ironless pulsed betatron with a dump of the accelerated electrons onto the tantalum gamma-ray converter target. The generator is designed for the radiography of dynamic objects with the large optical thickness and allows generation of up to three gamma-ray pulses per acceleration cycle. The description of the accelerator and results of its test runs in 2021-2022 are provided. The estimated cutoff energy of the electron beam is equal to 70 MeV. The beam quality allows the beam to be focused on a thin tantalum converter target to an elliptic spot with the dimensions of $2\times4$ mm. Bremsstrahlung scattering in the target produces a forward gamma-ray pulse with an exposure dose of 30 R determined in air 1 m downstream. The thickness of the lead test object transilluminated by gamma-rays is 160 mm at the distance of 4 m from the converter target. The full-width at half maximum of the gamma-ray output pulse in a single-pulse mode is equal to 100 ns, the full-width at half maximum in a three-pulse mode is equal to 200 ns, 150 ns and 120 ns for sequential pulses. The application of such generators within radiographic complexes will improve the hydrodynamic investigations efficiency by increasing the complex output parameters and optimizing the experiments geometry.