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Electron Accelerators at SINP, Moscow

Built in collaboration with World Physics Technologies Inc, Blacksburg, VA, USA.

Fig.1a: 70-MeV pulsed race-track microtron

Many applications require compact, inexpensive and efficient source of electron beam in energy range 10-100 MeV. Such application can be:

  • mobile source of bremsstrahlung radiation for search of buried explosive materials and drugs
  • production of isotopes for positron emission tomography
  • cancer radiation therapy
  • substance elemental analysis
  • injector to synchrotrons and storage rings
  • free electron laser driver
  • nuclear physics research

Our 70 MeV race-track microtron (RTM), seen in Fig. 1(a) and schematically in Fig. 1(b) with parameters given in the list below (without modulator), consists of injector, accelerating, bending, focusing, extraction, RF, cooling, vacuum, and control systems. Low energy electrons from the gun (1) are longitudinally compressed by a pre-buncher (2) and then injected into the accelerating section (7) using an α-magnet (3) and focusing lenses (4). The accelerated electrons emerges from the section, are bent through 180 by the 1st end magnet (5) and, after traversing a drift space and electron beam phase shifter (8), are bent again by the 2nd end magnet (6) which returns them again to the section entrance on axis for next cycle of acceleration. Beam is focused by accelerating structure, which acts as RF quadrupole singlet, quadrupole triplets (12) installed at the even orbits return path and by electromagnet quadrupole singlet (9) installed at common axis. The beam can be extracted from any orbit after the second by exciting the extraction magnet (14).

Fig.1b: 70-MeV RTM Schematic

Our RTM includes several innovations such as large ~1 T rare-earth permanent end magnets, a narrow rectangular bi-periodic accelerating structure with RF quadrupole focusing, a pre-bunched electron gun beam injected through a compact fixed gradient rare-earth permanent α-magnet, and a rare-earth permanent magnet based electron beam phase shifter, rare-earth permanent magnet compact quadrupole triplets. Our 1st orbit beam clears the accelerating structure without additional contrivances and so the accelerator tuning and operation is simplified while the additional RF focusing helps to realize the desired dynamics with simpler beam optics. In our RTM the accelerating structure and multi-beam klystron operate in the auto-oscillation mode without a precision RF generator, complex and expensive wave-guide system, and additional frequency and phase stabilization system.

The parameters of a pulsed racetrack microtron

  • Injection energy: 48 keV
  • Energy gain: 4.8 MeV / orbit
  • Orbits: 14
  • Output energy: 14.8 - 68.3 MeV
  • Output current at 68.3 MeV: 10 mA
  • Orbit circumference increase: 1l/orbit
  • Operating frequency: 2,856 MHz
  • Klystron power pulsed: 6 MW
  • End magnet field induction: 0.963 T
  • RTM dimensions: 2.2x1.8x0.9 m3