RITM is a source of low-energy high current electron beams of microsecond duration, which generates a quite homogeneous wide-aperture electron beam up to 10 cm in diameter, and is the best-known machine of its class as concerns this parameter. Irradiation by RITM renders mirror-like finish to the surface. The machine can be used for several applications:
- polishing a surface
- stripping a coating
- nanostructuring or homogenising a surface
Moreover, a machine can be ecquipped with one of more magnetron. By depositing thin layers of material and then using the E-Beam treatement it is possible to create surface alloyes, that modify the characteristics of a surface.
In the Machine, an electron gun based on plasma-filled diode with explosive-emission cathode and plasma anode is used. Schematic diagram of electron gun is given below. This scheme allows generating the wide-aperture electron beams with a high current density (up to 103 A/cm2 ) at relatively low accelerating voltages (20-30 kV). The strenght of this tecnology is that it can be used to treat wide areas of a surface, as the E-beam has a diameter of up to 10cm.
Schematic diagram of electron gun: 1 – explosive-emission cathode, 2 – reflected discharge anode,
3 – beam collector, 4 – vacuum chamber, 5 – isolator, 6 – cathode plasma, 7 – anode plasma,
8 – solenoid, 9 and 10 – Rogovsky coils (current transformers).
The picture below shows the diagram of a machine with an E-beam, on the left, and two magnetrons on the right. A sample can be moved under the magnetrons to deposit different materials and then be moved under the E-beam gun, on the right. Different geometries are available.
Each machine is built according to the specifications provided by the customer. It is possible to have different geometries, deposition sistems, and so on. Moreover, the E-Beam gun can be installed in existing systems/facilities as part of a process.
The machine is fully automated and managed by a Windows software that handles all the aspects of the machine, from the vacuum system to the operation of the E-Beam and the magnetrons, if present. The software is very intuitive and shows the whole machine graphically.
|The main screen of the software|
The RTIM machine in Italy
Currently there is one such machine in Europe, installed at the Politecnico di Milano, in Italy. The machine is equipped with an E-Beam and three magnetrons.
|The machine installed in Milan|
|A detailed view of the vacuum chamber, with the E-Beam gun and the magnetrons in the foreground|
Electron beam source
Accelerating voltage in peak, kV adjustable, from 15 to 30 kV Beam current in peak, kA up to 25 Pulse duration, μs non-adjustable, 2-4 Beam energy density*, J/cm2 adjustable, from 3 to10 J/cm2 Pulse repetition rate, pulse per second 0.05, 0.1, 0.2 or single pulse mode Working gas pressure, Pa 0.03−0.2 Residual pressure, Pa below 0.01
*at the beam diameter below 6 cm.
Magnetron deposition system
Power in discharge, kW up to 0.8 Working gas pressure, Pa 0.08-1.5 Cathode diameter, mm 75 Cathode thickness, mm 3-6 Magnetic field induction on the cathode surface, Gs 500 Coolant inlet temperature, less than 30°С Coolant flow, liters per minute 3-4 Deposition rate,μm/hour (at 500 W in discharge) 1-10 Non-uniformity of the thickness of deposited coatings, % ±10 Working gas Ar,N2 , air