1 Industrial Electron Accelerators type ILU for Industrial Technologies

1 Industrial Electron Accelerators type ILU for Industrial Technologies The present work describes industrial electron accelerators of the ILU family. Their main parameters, design, principle of action, electron beam extraction systems, wide set of auxiliary equipment for various technological processes and ways of their development are given.

1.1 Main parameters

Since 1970 in The Institute of Nuclear Physics the pulse linear accelerators type ILU are developed and supplied to the industry. The ILU machines are purposed for wide application in various technological processes and designed for continuous and round-theclock work in industrial conditions. The pulse nature of the generated electron beam (their main dierence from the widely used high voltage accelerators generating continuous electron beam) permits to adapt ILU machines easily to technological processes requiring formation of an irradiation zone with a complex con guration. The most bright example of such process is the irradiation of polymer insulation of cables and thermoshrinkable tubes. In this case the usage of 4-sided irradiation permits sharply to raise the productive rate of process, to improve quality of production and to expand the nomenclature of treated products without increase of electron energy. The ILU machines designed and produced in the Institute cover the energy range from 0.7 MeV to 4.0 MeV, and the maximum beam power is 50 kW. Main parameters of the machines are given below. Parameter ILU-8 ILU-6 ILU-6M ILU-10 ILU-10M Electron energy range, MeV 0.61.0 1.22.5 1.02.0 2.54.0 2.54.0 Electron beam power (max), kW 20 20 40 50 30 Average beam current (max), mA 25 17 20 20 12 Productivity (10 Mrad), kg/h 400 400 800 1000 600 Consumption (3380V), kW 80 100 120 150 120 Weigt, t Accelerator 0.6 2.2 2.2 2.9 2.5 Local shielding 76 -

21 INDUSTRIAL ELECTRON ACCELERATORS TYPE ILU FOR INDUSTRIAL TECHNOLOGIES

1.2 Design and Main Features

Each of the ILU accelerators consists of: 1. Accelerating system with beam extraction device, vacuum system and HF generator; 2. Pulse power supply; 3. Control rack. The accelerating system is placed inside biological protection, all other equipment - in not protected premises. The dimensions of main units of the various ILU machines are shown on Fig. 1 6.

Figure 1: Accelerator ILU-6

Figure 2: ILU-8 accelerator in local radiation shielding

1.2 Design and Main Features

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Figure 3: Accelerator ILU-10

Figure 4: Accelerator ILU-10M

The base model of the family is ILU-6. At modest dimensions this machine has rather high parameters and can be applied to wide spectrum of technological processes. The protected hall with inner dimensions 3 4 5 m is enough for its placement. The necessary volume of concrete for construction of such hall is about 180 m3 at wall thickness of about 1,5 m. The model ILU-6 is widely used as in our country and abroad. The model ILU-8 is the result of further development. It is designed mainly for processing of cables and tubes. This accelerator does not require construction of a special protected hall and can be placed in usual industrial shop. This accelerator can be placed inside the local biological shielding. The local shielding of the accelerator is a kind of a box made from steel plates. Inside the box is divided into two parts. In top part are placed accelerating system with HF resonator with magnetodischarge vacuum pumps and forevacuum system. In bottom part the beam extraction device, air pipes of ventillation system and technological equipment are placed. The back wall of the shielding has the channels (labyrinths) for input of cables, air and water pipes. The removable front wall serves a door of a protective box. The thickness of radiation protection in bottom part is 330 mm and in top is 240 mm. Gross weight of protection is 76 tons. The reduction factor for (brake radiation) Bremsstrahlung at electron energy 1.0 MeV is not less than 5 107 .


Figure 5: Control rack

Figure 6: Pulse power supply source

1.3 Accelerating system

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The model ILU-10 is a new development and is intended mainly for processes

requiring increased electron energy. The dimensions of this machine are not suciently greater than the dimensions of ILU-6. For needs of processes requiring increased beam power the accelerator can be supplied by two HF generators. A principle of high-voltage acceleration is used in majority of modern accelerators, i.e. the energy of electrons corresponds to a voltage generated by the recti er. The industrial accelerators type ILU are the exception of this rule. A principle of acceleration of electrons in the gap of HF resonator is used in the ILU machines. Such accelerator does not contain details, potentials of which in respect to the ground is comparable to accelerating voltage. So the complex high-voltage units (accelerating tubes, sections of recti ers and etc.) which are damaged by the discahges are not used in ILU machines. And so there is also no necessity to use insulating gas and high-pressure vessels. Use of a principle of high-frequency acceleration has allowed to create rather simple in its design accelerator with modest dimensions and weight. As a result the machine can be placed inside the hall of the smaller sizes, than halls for high-voltage accelerators with same parameters. The pulse nature of electron beam generated by ILU machines permits to direct the beam into various channels of the beam extraction device without beam losses. Hence, there is the opportunity to create the extraction devices forming an irradiation zone according to the form of a treated product, that permits to increase eciency of beam usage.

1.3 Accelerating system Fig. 7 represents the accelerating system of the accelerator ILU-6 for explanation of a principle of action of the ILU accelerators. The accelerating system consists of copper toroidal resonator 1 placed inside the vacuum tank 2. The resonator consists of top and bottom halves, on the internal protrusions of which the electrodes forming an accelerating gap are installed. The top electrode has a built-in control grid. The cathode unit is mounted on this electrode on the insulator, and together with the grid it forms an electron injector (gun). The bottom electrode and the injector together form the accelerating system. The current of a beam of accelerated electrons is controlled by varying the value of positive bias on cathode concerning the grid. To suppress the high-frequency resonance discharge in resonator the bottom half of it is installed on insulators and the bias vaoltage is passed on it through inductance 3. An axially symmetric magnetic lens 13 is installed inside the protrusion of the bottom half of the resonator to forming an electron beam in the channel of the accelerator and extraction device 6. The extraction device is connected to the ange of the magnet lens through the vacuum valve and sylphone unit. The design of the beam extraction device varies and dependends on the technological process. The single-valve HF generatorinstalled directly on the vacuum tank of the resonator (models ILU-6, ILU-10) or close to it (model ILU-8) and is connected to the resonator by means of coupling loop. The generator is designed using the circuit with a common grid. It works in the self-excitation mode with frequency close to the speci c frequency of the resonator. In accelerator ILU-8 the output HF power of the generator is passed to the coupling loop through coaxial feeder, and the feedback signal is passed to the generator from resonator through feedback loop and cable.

61 INDUSTRIAL ELECTRON ACCELERATORS TYPE ILU FOR INDUSTRIAL TECHNOLOGIES The pumping out of the vacuum tank during the operation of accelerator is done by high-vacuum spallation pumps 4, placed directly on the tank. The preliminary pumping out of air after opening of tank is done by the vorevacuum pump, installed near to the accelerating system.

Figure 7: General view of ILU-6 accelerator. 1-vacuum tank, 2-resonator, 3-coil of bias for the bottom half of the resonator, 4-magnetodischarge pumps, 5-electron injector, 6extraction device, 7-measuring loop, 8-valve of the generator, 9-support of the coupling loop, 10-vacuum capacitor of coupling loop, 11-movable plate of the feedback capacitor, 12-cathode stub

1.4 Pulse Power Supply

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1.4 Pulse Power Supply The pulse power supply source is uni ed for all models of the ILU machines. This source feeds the anode of the valve of the HF generator by pulsed voltage. It works directly from three-phase mains (voltage 380/220) without using of the intermediate transformer (see Fig. 8).

Figure 8: Simpli ed circuit of pulse power supply source.G1-recti er, L1-storage inductance, G2-recharge circuit, C1, C2-recharge capacitors, N1 - N7-thyristor switches, C13 C28, L2, L3-forming line, T2-pulse transformer, G3-source of pre-excitation voltage The storage inductance L1 is connected to the output of the thyristor recti er G1, and when the thyristor switches N1 and N2 are opened, the current in L1 is increasing. When the switches N3 and N4 open the switches N1 and N2 are switched o, the accumulation of a current stops and all energy stored in the inductance L1 is passed in the capacitors of a forming line (C13... C28, L2, L3), charging them up to the voltage, determined by the amount of the stored energy. After termination of a charging of a forming line the switches N5 and N6 open and connect the lines to a primary winding of the pulse transformer T2. The voltage pulse with the amplitude up to 30 kV, duration 0.4 - 0.7 ms at load current up to 150 A is formed on the secondary winding of T2. This voltage pulse feeds the anode of a valve of the HFgenerator. The trailing edge of a pulse is formed by a switch N7 shortening a primary winding of the pulse transformer. The pulse repetition frequency can vary from 2 up to 50 Hz (up to 100 Hz if the pulse amplitude is not close to maximum). The constant voltage is passed on the anode of HF generator's valve from the source G3 through secondary winding of the pulse transformer T2 to organize the pre-excitation of the generator. It is also used for demagnetization of the core of this transformer after high-voltage pulse. The usage of the inductive storage has allowed not to use the high voltage recti er, considerably reduce the dimensions of a source and to increase its eciency.


1.5 Control rack The accelerator is controlled by help of the computer. The control rack contains electronic units controlling the blocks and systems of the accelerator, and control unit connecting these units to the computer. The operator inputs main parameters of technological process in computer and switches on the power and auxiliary systems of the accelerator. Further control of the accelerator's functioning - beginning and end of irradiation process, maintenance of parameters within inputted limits, the informing of the operator on current conditions of process and switching the accelerator o in emergencies - is done by the computer. All parameters of process can be displayed on the computer's screen in digital form, main parameters in form of the diagrams of current time with change of time scale (8, 80 minutes and 8 hours). Beside it all the parameters of the regime are registered on the hard disk of the computer and then can be stored in the archive (can be on the diskettes) as long as it is necessary. The main parameters of the accelerator and technological process are maintained with accuracy up to 1 % thus permitting to realize the high quality treatment of products. The software of the computer permits to adapt installation easily for wide spectrum of technological processes and to set the program of variation of the parameters in time if necessary. If the computer is damaged the control of technological process and accelerator's operation can done manually after simple switching of the control rack into manual operation mode. In this mode the working parameters of the accelerator and the technological equipments are displayed on the digital indicator and oscilloscope. Dimensions of the controle rack of management are 1 1 2 m. To rack is supplied with the support for placement of the computer and oscilloscope.

1.6 Beam extraction devices The usage of pulse electron accelerators in radiation technologies permits to design the beam extraction devices forming the irradiation zones for multilateral irradiation of objects having the various forms. It enables one to increase beam usage eciency and in some of cases to reduce the electron energy required for irradiation, or to expand the nomenclature of treated products. This is, for example, situation in processing of cables. The irradiation of wires, cables and tubes ought to be made at least from two sides. Bilaterial irradiation is acceptable miniature or at multi-strand wires, bands, etc.. But in case of bilaterial irradiation of thick cables and pipes the inhomogeneity of a doze all over the perimeter of a product occurs to be too high. Moreover, the usage of usual irradiators with linear scanning of a beam and underbeam transportation device ensuring bilaterial irradiation of cable on one level does not give good results due to twist of a product around its longitudinal axis during rewinding. The irradiation scheme is convenient for radiation processing of cables and tubes if it is free from changing of the direction of bending of the treated product during rewinding, i.e., in such scheme the product is irradiated on two levels and at least from two sides. Such irradiation scheme is realized with help of the beam extraction device, shown on Fig. 4. The beam is de ected on 45 o consistently at dierent levels providing 4-sided irradiation of the product rewinded under the extraction windows. Such beam extraction system is rather universal and permits to realize two- or 4-sided irradiation or linear

1.6 Beam extraction devices

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scanning of a beam by simple switching of operation mode of scanning magnets. The three-channel system of beam extraction with linear scanning of it in each channel (Fig. 10) was developed for special purposes. With help of this system the products were treated simultaneously on three separate lines with various irradiation regimes. Any of the ILU machines can be equipped by any of the extraction devices described above. If necessary other types of extraction devices adapted to technology of the customer can be developped.

Figure 9: Beam extraction device for 4-sided irradiation. 1-scanning system, 2-core of scanning magnet, 3-vacuum chamber, 4-focusing lens, 5-extraction windows, 6-treated product

Figure 10: Three-channel beam extraction device. 1-scanning system, 2-longitudinal beam position probes, 3-vacuum chamber, 4-beam position probes across the scanning, 5-extraction windows, 6-irradiated object


1.7 Technological processes The ILU machines have found wide application in industrial technological processes. Main area of their application - irradiation of cables, wires and tubes. They are especially eective in this area because they can realize the process of 4-sided irradiation. The principle of realization of 4-sided irradiation is shown on Fig. 11.

Figure 11: View of a technological line for 4-sided irradiation of cable under four extraction windows A series of underbeam transportation devices for cables, wires and tubes with various parameters - from most thin and up to products with minimum bending radius of 0.75 m and diameter up to 50 mm is developed for industrial realization of this process (Fig. 12, Fig. 13). The radiation installations are supplier to the customers in the nal form according to the nomenclature of their products.

Figure 12: Installation for irradiation of cables and tubes having small and average diameters

1.8 New technologies

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Figure 13: Installation for irradiation of thick cables and pipes The installation on the basis of ILU-8 machine with electron energy up to 1 MeV can treat the cables and wires with insulation thickness of up to 2 mm and tubes with wall thickness of up to 2.5 mm. The bilaterial irradiation of these products requires electron energy of up to 2 MeV. Productivity of such installation for majority of products is restricted by the possibilities of the existing rewinding of devices. So, for example, on the installation used in Korea for irradiation of thermoshrinkable tubes, most of the products are irradiated in two parallel lines with speed of up to 200 m/min. The transportation devices for irradiation of lm products are designed and produced. The installation on the basis of ILU-6 machine with energy of up to 2,5 MeV is capable to treat the cables with insulation of up to 5 mm and polyethylene pipes for hot water supply laminated by aluminium. In China such installation is used for irradiation of cable for working voltage 10 kV and has the productivity up to 100 m/min.

The next area of perspective application of ILU machines is the sterilization of medical products. In Izhevsk (Russia) and Kiev (Ukrain) the installations on the basis of ILU-6 machines are sterilizing the disposal syringes. Productivity of such installation is up to 100,000 syringes per hour. Model ILU-10 with electron energy of up to 4 MeV permits considerably expand the nomenclature of sterilized products.

1.8 New technologies A set of perspective technological processes which can nd wide application is developed in Institute of Nuclear Physics in collaboration with other organizations .

High temperature processes.

The electron beam extracted into the air through foil is capable to provide the power density of up to 400 W/cm2. It enables one to heat a treated material up to 2000 C. And the material is heated up in whole volume of electron penetration, so the thermal inertia inevitable in other ways of heating is practically excluded. The simplicity of control of the beam parameters permits to realize any heating regime with guaranteed high accuracy and reproducibility of process.

121 INDUSTRIAL ELECTRON ACCELERATORS TYPE ILU FOR INDUSTRIAL TECHNOLOGIES The eect of beam ionization adds to the eects of thermal activation of reaction and so increases the reaction speed and permits to reduce the temperature of process. Thus the beam acts as non-traditional source of heating on the one hand and as the radiation activator of reaction on the other. This technology is applied in particularly in manufacturing of the catalyst for synthesis of ammonia on basis of iron oxide, high-temperature glasses and ceramics, high quality ferrite materials, in the processes of surface hardening of metals and powder coverings of steel and ferrite materials. The electron beam processing of passive components in manufacturing of the hybrid integrated circuits is of a large interest. Is thus is reached: improvement of quality of components; increase of density of thick- lm elements; reduction of percentage of defective plates; usage of pastes based on widely widespread metals instead of pastes based on the rare and precious metals; usage of metal plates instead of ceramic ones with improvement of insulation qualities; Complete automation of production process.

Technology of radiation immobilization of biologically active substances.

The advantages of radiation technology in comparison with usual calssical chemical immobilization methods are: essential cost reduction of production process; high speed of technological process (irradiation in ow); reduction of thermal and chemical pollution; reduction of number of chemical ingredients necessary for immobilization of ferments; more eective utilization of the electric power; an opportunity to retune the accelerator for solution of accompanying problems: sterilization of continuous ows of solutions, mixtures, - production of gels; long lifetime of the equipment. These radiation-technological processes are practically wastes-free kinds of manufacturing. The technology of production of medical and veterinary preparations based on immobilized ferments is elaborated on the accelerator ILU-6 as well as the components, used for treatment of wastes of meat, milk and cellulose industry. The preparations are produced in small lots. Researches of new components for radiation immobilization (whey, extracts of medicinal plants) are done with the purpose of creation the biologically of active substances with prolonged action stable to the in uence of an environment.