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Electron linacs of the Efremov Institute for industrial applications
Radiation Physics and Chemistry 58 (2000) 197±201
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Technical note
Electron linacs of the Efremov Institute for industrial applications M.I. Demski*, V.V. Rumjantsev, Yu.A. Svistunov, M.F. Vorogushin Sci. Res. Efremov Institute of Electrophysical Apparatus, St. Petersburg, Metallostroj, 189631, Russia Received 8 February 1999; accepted 23 October 1999
Abstract Ten types of new generation linear electron accelerators are produced. Their energy range is 3±30 MeV, beam power range is 2±30 kW. Disc-loaded waveguide, resonators and combined structure are used as accelerating systems. Both klystron and magnetrons are used as RF power sources. Both accelerators and ancillary systems have automatic control systems. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Linacs; Nondestructive testing; Radioisotopes; Radiation technologies; Researchers
1. Introduction D.V. Efremov Institute (NIIEFA) is a main enterprise of Russia that is designing dierent types of accelerators for fundamental physical research and applied purposes. Independent division of NIIEFA Ð the Scienti®c Production Complex of Linacs and Cyclotrons (NPK LUTS) is engaged in design, fabrication, mounting and maintenance of the linear electron accelerators (Linacs). The ®rst industrial and medical linacs were designed and manufactured at the same time as linacs were used for scienti®c research. At that time industrial technology of accelerator fabrication had been worked out. Since the 1960s the Efremov Institute have designed and manufactured more then 80 linacs of energy range from 5 to 20 MeV. These accelerators have been installed at more than thirty Russian and foreign cities.
* Corresponding author. Tel.: +7-812-464-4466; fax: +7812-464-4460. E-mail address: [email protected] (M.I. Demski).
Now a large number of technological processes are used in national economy thanks to accelerated electron beam and bremsstrahlung. Maximal economical gain is obtained by use of linac in welding fault detection, secondary radiations analysis, sterilization, radiation chemistry. On the other hand a maximal number of linacs are used in medicine (electron beam and photon (x-ray) radiotherapy) (Vakhrushin et al., 1992). Latterly demands on stability and reliability of linac has raised and there is a tendency to buy accelerators together with technological equipment (Vakhrushin et al., 1995a). NPK LUTS understand these demands. Now NPK LUTS is ready to design and manufacture such equipment or to make it with help of subcontractors. For example our complex for sterilization of medical products consists of linac UELV-8-15S2 and product handling system. Complex of industrial inspection system was designed on the basis of electron linac, but it includes arrangement for placing of controlled products. NPK LUTS had designed and manufactured x-ray inspection system for trucks and sea containers. A review of the Efremov Institute's production of RF electron linacs for last 30 years is given below,
0969-806X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 6 X ( 9 9 ) 0 0 4 6 4 - 8
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M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
Table 1 NPK LUTS parameters of accelerators for nondestructive testing Accelerator type Parameters
UELV-6-1D-15
UELV-10-2D-40
UELV-15-2D-80
Controlled thickness of steel (mm) Electron energy (MeV) Maximal bremsstrahlung dose rate (on 1 m) (Gy/min) Beam diameter on the target (mm)
40±400 6 15 <2
50±500 8±10 40 R2
75±600 12±15 80 <3
including industrial installation of dierent applications, complexes on the linac basis, and long-term research. 2. Linacs for nondestructive testing Contemporary nuclear industry and ship-building need nondestructive testing of welded joints, moldings, forgings to determine their quality. Since 1970 more then 25 linacs have been manufactured for this purpose. These accelerators have output energies from 5 to 15 MeV. Linacs are working at Izhora plant (StPetersburg), at Atommash plant (Volgodonsk), in Komsomolsk-on-Amur, Severodvinsk, Sumy and other cities. For example, Izhora plant which delivered energy equipment for nuclear power stations to East European countries, new independent countries on the USSR territory, Finland and Cuba had tested all of nuclear reactors with the help of the Efremov Institute linacs. Radiographic testing of steel components Ð having thickness from 40 to 600 mm, was done with contrast sensitivity better then 1%. More contemporary control methods are introscopy and tomography. Industrial introscopy that have been developed in NPK LUTS consist of accelerator UELV-10-2D-40 as irradiator, crystal detector line (crystals sizes are 3 3 mm2) and computer for data processing. It is possible to obtain ¯aw detectability of defects less than 1 mm and densitive sensitivity 1. These results were obtained when steel which had thickness up to 200 mm was X-rayed. Maximal photon energy of bremsstrahlung was 8 MeV. Accelerator radiography system is used for x-ray inspection for trucks and sea containers. NPK LUTS has a demonstration installation with linac UELV-10-2D-40 as irradiator to examine large containers and trucks. Container with cross section 2.5 2.5 m2 and length 6 or 12 m is scanned with bremsstrahlung beam. Its velocity is 0.3±0.4 m/s. It is possible to examine twenty containers of 12 m length in 1 h. Inspection time for one container is 40 s. Space sensitivity is better then 3 mm and for high-contrasting
objects it is better then 1 mm. X-ray imaging system enable to obtain positive or negative imprint, pseudocolour picture or picture with underlined contours. It is possible to change scale or to pick out interested fragment to make easier identi®cation of suspicious object. If two accelerators irradiate with X-rays container from side and from above then much more information may be obtained, but special arrangement permit to obtain stereo-image with only one accelerator. Accelerated electron beam is split by pulse magnet to two beams and both are directed to the target by achromatic magnetic systems. Transversal sizes of the beam is retained unchanged. Their central trajectories are directed under 38 angle to primary beam and are coming together in detector lines plane. Dividing magnets ®eld change its sign according to frequency of current pulses 50, 100, 150 Hz. Sizes of special arrangement are 700 450 210 mm3. Installation with pulsed 350 kV X-ray generator as irradiator is used for control of small containers, for example aviation ones. Installation has line detector system. Considered above systems may be supplemented by installation for customs examination of baggage. It is an X-ray tube with extensive target which is scanned by electron beam. Velocity and step of scanning are determined by computer. Parameters of three models of accelerators for nondestructive testing which are manufactured by NPK LUTS are given in Table 1. 3. Linacs for activation analysis and production of shortlived radioisotopes NIIEFA electron linacs and suitable targets are powerfull sources of bremsstrahlung or neutron beams. The Efremov Institute has signi®cant experience to use electron linacs for activation analysis with photonuclear reactions. Since 1979 LUE-8-5A (8 MeV) and LUE-15A (15 MeV) are exploited successfully at Muruntau mines (Uzbekistan). They are used for activation analysis of ore probes, which are analysed to seek gold and accompanying elements. Under interaction photons of bremsstrahlung and gold nucleus golds isomer
M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
199
Table 2 NPK LUTS linacs for radioisotope production Accelerator type Parameters
UELV-8-12A
UELV-15-8A
UELV-30-15R2
UELV-30-3R
Electron energy (MeV) Average beam power (kW) Photon output along beam axis, Gy/min (on 1 m)
8 12 up to 300
15 8 up to 500
30 15 up to 1400
30 3 up to 300
197m
Au with half-life 7.2 s are generated. Isomer emits photons of 279 keV energy and they are detected. For the ®rst time this method was developed in Russia and now is used in industry. Method combines promptness and sensitivity. Its throughput (1200 analysis for 24 h, sensitivity 0.4 g/ton, accuracy 210) are better than characteristics of other methods (Glukhikh et al., 1979). Mining-metallurgical Navois plant has 20 year experience of using NIIEFA accelerators and now plans to create installation for ore assortment immediately after unloading of tip-up lorry. Project supposes using of 8 MeV linac of 12 kW beam power (UELV-812A type). Beam of Navois accelerator is two times as much as beam of Muruntau accelerator. This will permit to increase installations throughput and will provide better veri®cation of analysis. Accelerator UELV8-12A has beam de¯ecting system on three of directions and circular, elliptic or stripe scanning of the beam before braked targets. De¯ecting technological system are controlled by main computer which controls the whole technological complex of ores sorting. Successful exploitation of NIIEFA accelerators at Uzbekistan stimulated of creation such installations at Yakutia and Magadan (Glukhikh et al., 1985). Low threshold energy of braked photons was proved optimal one for golds isomer exciting. Higher photon energies are required for analysis such elements as lead in metallic ores, oxygen in vanadium, niobium or tantalum, carbon and nitrogen in biological samples, pure metals or semiconductors. For these aims accelerator types UELV-30-3R and UELV-30-15-R2 with output energy 30 MeV have been designed. Possibilities of activation analysis may be enlarged under use of neutrons side by side photons. The electron of 30 MeV energy and 500 mA current intensity will produce 51013 neutrons per second on uranium target. Electron energy will be decreased when beryllium targets are used. The same accelerators are used eectively for short-lived isotopes production. Photo-nuclear reactions produce more pure radionuclides then reactions with heavy particles (Levin et al., 1981). It is very important because today accelerators are used primarily as sources of short-lived isotopes, mainly for medical applications. Here radionuclide output is smaller as compared with cyclotron production, but contempor-
ary linacs provide power which is enough for practical purposes under using of enriched targets. For example, accelerator UELV-30-15R2 with energy 25 MeV can produce iodine-123 for neediness of big region under using of 99% xenon-124 target and molybdenum-99 as generator of technetium-99 isomer. This linac can provide production of dysprosium-159, terbium-155, thulium-167, etc. Now four linacs types had been developed by NPK LUTS for activation analysis. Their RF system use klystrons KIU-111 and KIU-147. Main accelerator parameters are given in Table 2.
4. Linacs for radiation technologies There are many technological processes where application of RF linacs as radiation source is pro®table. Range of used energies is from 5 to 15 MeV. These processes are: . rubber and polymer modi®cation; . crosslinking for plastics tubes and cable production; . sterilization of medical and surgical products, laundry, drugs and so on; . food pasteurization and sterilization to increase storage time or for AIDS patients; . decontamination of wood; . sterilization of hospital waste products; . decontamination of organic fertilizers and industrial waste water; . smoke scrubbing (SO2 and NO); etc. If accelerator beam power is more then 100 kW process will have economical pro®t under irradiation doses 100±200 kGy. But usually irradiation doses 15± 25 kGy are quite enough and beam power may be limited to 10±30 kW. Such accelerators have been developed and are produced at the Efremov Institute. First accelerators with 5±8 MeV energy were installed in 1963±75 at Research Institute of Plastics, at Research Institute of Tire Production, at Research Institute of Radiation Technology, Institute of Bio-Physics etc. These accelerators were used for research of dierent technological processes. In 1972±76 two of 8 MeV accelerators with beam power 5±7 kW were installed at Kurgan city (plant ``Synthesis''). They are working
200
M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
Table 3 NPK LUTS processing linacs Accelerator type Parameters
UELV-5-15T
UELV-8-15-S1
UELV-8-15-S2
UELV-10-30
UELV-8-2 S
Electron energy (MeV) Range of energy regulation (MeV) Pulse beam power (max) (kW) Size of irradiation ®eld (cm cm) Position of irradiator
5 4±8 15 3 100 Vertical & horizontal
8 4±12 15 2.5 50 Vertical & horizontal
8 6±10 15 2.5 50 Vertical
10 6±18 30 3 100 Horizontal
8 6±10 2 2.5 50 Vertical
until now as part of conveyor to produce medical devices. 15 MeV linac of 10 kW beam power had been installed at Warsaw Radiation Center (Poland) in 1971. This linac is working until now too. It is used as commercial accelerator to irradiate dierent devices for Polish and European countries. Main direction of works Ð electron and X-ray sterilization. 8 MeV accelerator (5 kW beam power) was delivered to Budapest plant of plastics and insulators in 1977 and it is used until now to treat cables. LUE-8-5B is used as commercial linac at radiation center in Bio-Physical Institute (Moscow), Sci. Res. Institute of Plastics (Moscow) and Sci. Production Enterprise ``Corad'' (St. Petersburg) to irradiate dierent products. At many radiation centers NIIEFA accelerators are exploited 24-h, they had worked longer than their guaranteed lifetime and need modernization or substitution. Linac types parameters which NPK LUTS of NIIEFA produces for radiation processing of products, materials and devices are given in Table 3. These accelerators have common circuit technology and their RF feeding sources are low-voltage klystrons KIU-147 (5 MW, 25 kW) and -111 (5 MW, 5 kW). 5. Long-term research We mean in future to use magnetron type generators, not klystron only, for example, MI-262. MI-262 were used by our in the past and this device was working reliable. It is possible to use the new devices MI451 (pulse power Ð 2.3 MW, average power Ð 3 kW) and MI-456 (2.5 MW, 3.5 kW). Magnetron MI-451 is analog of M-5125 magnetron type, which is used in dierent countries in accelerators for medicine, nondestructive inspection and so on. Working frequency of magnetron is 2998 MHz. As base of RF system MI-451 is suggested to use in accelerators for medical devices sterilization in hospitals such as gloves, laundry, bandage material and so on. Accelerator has radiation self-shielding and may be installed instead of noneconomical and noneective gas sterilizators. One may use two accelerators to
irradiate simultaneously two sides of sterilized devices. Only one RF generator can feed both accelerating sections. Electron energy of accelerator is 3 MeV, average current 200±300 mA. Standing wave accelerating structure is developed with output energy 9 MeV. The 2.5 MW magnetron is used as the RF source. Another direction of research is creation of improved accelerating structures. For example Ð combined accelerating structure with optimal multicavities buncher (Vakhrushin et al., 1993). It is impossible to obtain electron bunches of high quality in short buncher of waveguides accelerator because features of construction and ®eld distribution. First part of combined structure is working in standing wave regime and second one has travelling wave regime. Input cells are shorted out to RF oscillations, output cells are loaded on the matched load, RF generator feed structure via intermediate accelerating cell. This cell works as wave type transformer. Standing wave resonance structure with co-axis cells of coupling is excited on p/ 2 mode. It will work as multicavity buncher to form electron short bunches and to obtain relative energy spread 240 keV on the UELV-8-15 output. Such accelerating structure has been created and tested `cool' tests. Now it is tasted with beam. There is designed other combined structure which have high ®eld stability at the structures beginning as disc-loaded waveguide and high shunt-impedance as accelerating negative dispersions structures (Vakhrushin et al., 1995b). Main part of this combined structure is periodical chain of O-shape cells. Cells geometry was optimized to obtain high Ze on the oscillation mode 5p/6. Theoretical meanings Ze=87.1 MOm/m and quality factor Q = 18200 have been obtained for f = 2.45 GHz. A new system of energy regulation has been designed and it is functioning successfully. Simplest way of energy regulation is beam load changing, but it gives a poor energy spectrum. Standing wave accelerators of the Efremov Institute do not have this defect. Phase-shifter cells in the middle of accelerating struc-
M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
ture realize change of synchronous phase with beam current change. Search of new radiative technologies are continued in NPK LUTS too. NPK LUTS and St.Petersburg's Special Designing Institute had been designed out complex installation for puri®cation of hospital sewage. Two linear accelerators with the beams of 6±8 MeV energy produced puri®cation of hospital sewage in radiative-chemical reactors. Simultaneously puri®cation of sewage from farm-preparations and degelatinization are produced. Installations throughput is 50 m3 for 24 h. Radiation dose is up to 10 kGy (Vakhrushin et al., 1995c). There were researches to sterilize revolved logs with bremsstrahlung of energy 6±8 MeV (Vyasmenova et al., 1996). There is a method to augment mechanical and thermal solidity of insulators with 8 MeV electron irradiation, and this method is used now.
6. Conclusion At present NPK LUTS oer 10 types of new generations linacs. Their energy range is 3±30 MeV, beam power range is 2±30 kW. Disc-loaded waveguide, resonators and combined structure are used as accelerating systems. Both klystron and magnetrons are used as RF power sources. If customers need technological complexes they may be manufactured together which electron linacs. Both accelerators and complexes have automatic control systems. NPK LUTS does scienti®c works continuously to improve operational characteristics of its linacs.
201
References Glukhikh, V.A. et al., 1979. Industrial laboratory for g-analysis of gold ore samples. In: 3rd Workshop, Application of accelerators in medicine and industry. Leningrad, Proceedings, vol. 4, p. 3, Theses of reports (in Russian). Glukhikh, V.A., et al., 1985. Laboratorial accelerator complex for multielemental analysis of geological samples. In: 5th Workshop, Application of accelerators in medicine and industry. Moscow, p. 122 Theses of reports (in Russian). Levin, V.M., et al., 1981. Production of radionuclides by photonuclear reactions. Radiochem. Radioanal. Letters 49/2, 111±118. Vakhrushin, YuP, Glukhikh, V.A., Nikolaev, V.M., 1992a. United line of industrial and medical linacs. In: 7th Workshop, Application of accelerators in medicine and industry. St.Petersburg, p. 31 Theses of reports (in Russian). Vakhrushin, YuP, Vyazmenova, G.A., Kuznetsov, V.S., Fidelskaya, R.P. 1992b. Sewage desinfection by the electron beam at infections hospitals. Ibid p. 65 (in Russian). Vakhrushin, YuP, Rjabtsov, A.V., Smirnov, V.L., Terentiev, V.V., 1993. Combined accelerating structure with optimal multicaviting Buncher. In: Proceedings of the 13th Workshop on Accelerators of Charged Particles. Dubna, vol. 1, p. 249, (in Russian). Vakhrushin, YuP, Glukhikh, V.A., Nikolaev, V.M., Rumjantsev, V.V., 1995a. Development of united line for industrial a medical linacs. In: 8th Workshop, Application of accelerators in medicine and industry. St.Petersburg, p. 52 Theses of reports (in Russian). Vakhrushin, YuP, Kalinichenko, M.A., Rjabtsov, A.V., 1995b. High-eective accelerating structure for travellingwave linacs. In: 8th Workshop, Application of accelerators in medicine and industry. St.Petersburg, p. 8 Theses of reports (in Russian). Vyasmenova, G.A. et al., 1996. The Providing of uniformed dose in the time of bremstrahlungs irradiation from accelerators. In: Proceedings of the 15th Workshop on charge particle accelerators. Protvino, vol. 2, p. 342, (in Russian).
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Technical note
Electron linacs of the Efremov Institute for industrial applications M.I. Demski*, V.V. Rumjantsev, Yu.A. Svistunov, M.F. Vorogushin Sci. Res. Efremov Institute of Electrophysical Apparatus, St. Petersburg, Metallostroj, 189631, Russia Received 8 February 1999; accepted 23 October 1999
Abstract Ten types of new generation linear electron accelerators are produced. Their energy range is 3±30 MeV, beam power range is 2±30 kW. Disc-loaded waveguide, resonators and combined structure are used as accelerating systems. Both klystron and magnetrons are used as RF power sources. Both accelerators and ancillary systems have automatic control systems. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Linacs; Nondestructive testing; Radioisotopes; Radiation technologies; Researchers
1. Introduction D.V. Efremov Institute (NIIEFA) is a main enterprise of Russia that is designing dierent types of accelerators for fundamental physical research and applied purposes. Independent division of NIIEFA Ð the Scienti®c Production Complex of Linacs and Cyclotrons (NPK LUTS) is engaged in design, fabrication, mounting and maintenance of the linear electron accelerators (Linacs). The ®rst industrial and medical linacs were designed and manufactured at the same time as linacs were used for scienti®c research. At that time industrial technology of accelerator fabrication had been worked out. Since the 1960s the Efremov Institute have designed and manufactured more then 80 linacs of energy range from 5 to 20 MeV. These accelerators have been installed at more than thirty Russian and foreign cities.
* Corresponding author. Tel.: +7-812-464-4466; fax: +7812-464-4460. E-mail address: [email protected] (M.I. Demski).
Now a large number of technological processes are used in national economy thanks to accelerated electron beam and bremsstrahlung. Maximal economical gain is obtained by use of linac in welding fault detection, secondary radiations analysis, sterilization, radiation chemistry. On the other hand a maximal number of linacs are used in medicine (electron beam and photon (x-ray) radiotherapy) (Vakhrushin et al., 1992). Latterly demands on stability and reliability of linac has raised and there is a tendency to buy accelerators together with technological equipment (Vakhrushin et al., 1995a). NPK LUTS understand these demands. Now NPK LUTS is ready to design and manufacture such equipment or to make it with help of subcontractors. For example our complex for sterilization of medical products consists of linac UELV-8-15S2 and product handling system. Complex of industrial inspection system was designed on the basis of electron linac, but it includes arrangement for placing of controlled products. NPK LUTS had designed and manufactured x-ray inspection system for trucks and sea containers. A review of the Efremov Institute's production of RF electron linacs for last 30 years is given below,
0969-806X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 9 - 8 0 6 X ( 9 9 ) 0 0 4 6 4 - 8
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M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
Table 1 NPK LUTS parameters of accelerators for nondestructive testing Accelerator type Parameters
UELV-6-1D-15
UELV-10-2D-40
UELV-15-2D-80
Controlled thickness of steel (mm) Electron energy (MeV) Maximal bremsstrahlung dose rate (on 1 m) (Gy/min) Beam diameter on the target (mm)
40±400 6 15 <2
50±500 8±10 40 R2
75±600 12±15 80 <3
including industrial installation of dierent applications, complexes on the linac basis, and long-term research. 2. Linacs for nondestructive testing Contemporary nuclear industry and ship-building need nondestructive testing of welded joints, moldings, forgings to determine their quality. Since 1970 more then 25 linacs have been manufactured for this purpose. These accelerators have output energies from 5 to 15 MeV. Linacs are working at Izhora plant (StPetersburg), at Atommash plant (Volgodonsk), in Komsomolsk-on-Amur, Severodvinsk, Sumy and other cities. For example, Izhora plant which delivered energy equipment for nuclear power stations to East European countries, new independent countries on the USSR territory, Finland and Cuba had tested all of nuclear reactors with the help of the Efremov Institute linacs. Radiographic testing of steel components Ð having thickness from 40 to 600 mm, was done with contrast sensitivity better then 1%. More contemporary control methods are introscopy and tomography. Industrial introscopy that have been developed in NPK LUTS consist of accelerator UELV-10-2D-40 as irradiator, crystal detector line (crystals sizes are 3 3 mm2) and computer for data processing. It is possible to obtain ¯aw detectability of defects less than 1 mm and densitive sensitivity 1. These results were obtained when steel which had thickness up to 200 mm was X-rayed. Maximal photon energy of bremsstrahlung was 8 MeV. Accelerator radiography system is used for x-ray inspection for trucks and sea containers. NPK LUTS has a demonstration installation with linac UELV-10-2D-40 as irradiator to examine large containers and trucks. Container with cross section 2.5 2.5 m2 and length 6 or 12 m is scanned with bremsstrahlung beam. Its velocity is 0.3±0.4 m/s. It is possible to examine twenty containers of 12 m length in 1 h. Inspection time for one container is 40 s. Space sensitivity is better then 3 mm and for high-contrasting
objects it is better then 1 mm. X-ray imaging system enable to obtain positive or negative imprint, pseudocolour picture or picture with underlined contours. It is possible to change scale or to pick out interested fragment to make easier identi®cation of suspicious object. If two accelerators irradiate with X-rays container from side and from above then much more information may be obtained, but special arrangement permit to obtain stereo-image with only one accelerator. Accelerated electron beam is split by pulse magnet to two beams and both are directed to the target by achromatic magnetic systems. Transversal sizes of the beam is retained unchanged. Their central trajectories are directed under 38 angle to primary beam and are coming together in detector lines plane. Dividing magnets ®eld change its sign according to frequency of current pulses 50, 100, 150 Hz. Sizes of special arrangement are 700 450 210 mm3. Installation with pulsed 350 kV X-ray generator as irradiator is used for control of small containers, for example aviation ones. Installation has line detector system. Considered above systems may be supplemented by installation for customs examination of baggage. It is an X-ray tube with extensive target which is scanned by electron beam. Velocity and step of scanning are determined by computer. Parameters of three models of accelerators for nondestructive testing which are manufactured by NPK LUTS are given in Table 1. 3. Linacs for activation analysis and production of shortlived radioisotopes NIIEFA electron linacs and suitable targets are powerfull sources of bremsstrahlung or neutron beams. The Efremov Institute has signi®cant experience to use electron linacs for activation analysis with photonuclear reactions. Since 1979 LUE-8-5A (8 MeV) and LUE-15A (15 MeV) are exploited successfully at Muruntau mines (Uzbekistan). They are used for activation analysis of ore probes, which are analysed to seek gold and accompanying elements. Under interaction photons of bremsstrahlung and gold nucleus golds isomer
M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
199
Table 2 NPK LUTS linacs for radioisotope production Accelerator type Parameters
UELV-8-12A
UELV-15-8A
UELV-30-15R2
UELV-30-3R
Electron energy (MeV) Average beam power (kW) Photon output along beam axis, Gy/min (on 1 m)
8 12 up to 300
15 8 up to 500
30 15 up to 1400
30 3 up to 300
197m
Au with half-life 7.2 s are generated. Isomer emits photons of 279 keV energy and they are detected. For the ®rst time this method was developed in Russia and now is used in industry. Method combines promptness and sensitivity. Its throughput (1200 analysis for 24 h, sensitivity 0.4 g/ton, accuracy 210) are better than characteristics of other methods (Glukhikh et al., 1979). Mining-metallurgical Navois plant has 20 year experience of using NIIEFA accelerators and now plans to create installation for ore assortment immediately after unloading of tip-up lorry. Project supposes using of 8 MeV linac of 12 kW beam power (UELV-812A type). Beam of Navois accelerator is two times as much as beam of Muruntau accelerator. This will permit to increase installations throughput and will provide better veri®cation of analysis. Accelerator UELV8-12A has beam de¯ecting system on three of directions and circular, elliptic or stripe scanning of the beam before braked targets. De¯ecting technological system are controlled by main computer which controls the whole technological complex of ores sorting. Successful exploitation of NIIEFA accelerators at Uzbekistan stimulated of creation such installations at Yakutia and Magadan (Glukhikh et al., 1985). Low threshold energy of braked photons was proved optimal one for golds isomer exciting. Higher photon energies are required for analysis such elements as lead in metallic ores, oxygen in vanadium, niobium or tantalum, carbon and nitrogen in biological samples, pure metals or semiconductors. For these aims accelerator types UELV-30-3R and UELV-30-15-R2 with output energy 30 MeV have been designed. Possibilities of activation analysis may be enlarged under use of neutrons side by side photons. The electron of 30 MeV energy and 500 mA current intensity will produce 51013 neutrons per second on uranium target. Electron energy will be decreased when beryllium targets are used. The same accelerators are used eectively for short-lived isotopes production. Photo-nuclear reactions produce more pure radionuclides then reactions with heavy particles (Levin et al., 1981). It is very important because today accelerators are used primarily as sources of short-lived isotopes, mainly for medical applications. Here radionuclide output is smaller as compared with cyclotron production, but contempor-
ary linacs provide power which is enough for practical purposes under using of enriched targets. For example, accelerator UELV-30-15R2 with energy 25 MeV can produce iodine-123 for neediness of big region under using of 99% xenon-124 target and molybdenum-99 as generator of technetium-99 isomer. This linac can provide production of dysprosium-159, terbium-155, thulium-167, etc. Now four linacs types had been developed by NPK LUTS for activation analysis. Their RF system use klystrons KIU-111 and KIU-147. Main accelerator parameters are given in Table 2.
4. Linacs for radiation technologies There are many technological processes where application of RF linacs as radiation source is pro®table. Range of used energies is from 5 to 15 MeV. These processes are: . rubber and polymer modi®cation; . crosslinking for plastics tubes and cable production; . sterilization of medical and surgical products, laundry, drugs and so on; . food pasteurization and sterilization to increase storage time or for AIDS patients; . decontamination of wood; . sterilization of hospital waste products; . decontamination of organic fertilizers and industrial waste water; . smoke scrubbing (SO2 and NO); etc. If accelerator beam power is more then 100 kW process will have economical pro®t under irradiation doses 100±200 kGy. But usually irradiation doses 15± 25 kGy are quite enough and beam power may be limited to 10±30 kW. Such accelerators have been developed and are produced at the Efremov Institute. First accelerators with 5±8 MeV energy were installed in 1963±75 at Research Institute of Plastics, at Research Institute of Tire Production, at Research Institute of Radiation Technology, Institute of Bio-Physics etc. These accelerators were used for research of dierent technological processes. In 1972±76 two of 8 MeV accelerators with beam power 5±7 kW were installed at Kurgan city (plant ``Synthesis''). They are working
200
M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
Table 3 NPK LUTS processing linacs Accelerator type Parameters
UELV-5-15T
UELV-8-15-S1
UELV-8-15-S2
UELV-10-30
UELV-8-2 S
Electron energy (MeV) Range of energy regulation (MeV) Pulse beam power (max) (kW) Size of irradiation ®eld (cm cm) Position of irradiator
5 4±8 15 3 100 Vertical & horizontal
8 4±12 15 2.5 50 Vertical & horizontal
8 6±10 15 2.5 50 Vertical
10 6±18 30 3 100 Horizontal
8 6±10 2 2.5 50 Vertical
until now as part of conveyor to produce medical devices. 15 MeV linac of 10 kW beam power had been installed at Warsaw Radiation Center (Poland) in 1971. This linac is working until now too. It is used as commercial accelerator to irradiate dierent devices for Polish and European countries. Main direction of works Ð electron and X-ray sterilization. 8 MeV accelerator (5 kW beam power) was delivered to Budapest plant of plastics and insulators in 1977 and it is used until now to treat cables. LUE-8-5B is used as commercial linac at radiation center in Bio-Physical Institute (Moscow), Sci. Res. Institute of Plastics (Moscow) and Sci. Production Enterprise ``Corad'' (St. Petersburg) to irradiate dierent products. At many radiation centers NIIEFA accelerators are exploited 24-h, they had worked longer than their guaranteed lifetime and need modernization or substitution. Linac types parameters which NPK LUTS of NIIEFA produces for radiation processing of products, materials and devices are given in Table 3. These accelerators have common circuit technology and their RF feeding sources are low-voltage klystrons KIU-147 (5 MW, 25 kW) and -111 (5 MW, 5 kW). 5. Long-term research We mean in future to use magnetron type generators, not klystron only, for example, MI-262. MI-262 were used by our in the past and this device was working reliable. It is possible to use the new devices MI451 (pulse power Ð 2.3 MW, average power Ð 3 kW) and MI-456 (2.5 MW, 3.5 kW). Magnetron MI-451 is analog of M-5125 magnetron type, which is used in dierent countries in accelerators for medicine, nondestructive inspection and so on. Working frequency of magnetron is 2998 MHz. As base of RF system MI-451 is suggested to use in accelerators for medical devices sterilization in hospitals such as gloves, laundry, bandage material and so on. Accelerator has radiation self-shielding and may be installed instead of noneconomical and noneective gas sterilizators. One may use two accelerators to
irradiate simultaneously two sides of sterilized devices. Only one RF generator can feed both accelerating sections. Electron energy of accelerator is 3 MeV, average current 200±300 mA. Standing wave accelerating structure is developed with output energy 9 MeV. The 2.5 MW magnetron is used as the RF source. Another direction of research is creation of improved accelerating structures. For example Ð combined accelerating structure with optimal multicavities buncher (Vakhrushin et al., 1993). It is impossible to obtain electron bunches of high quality in short buncher of waveguides accelerator because features of construction and ®eld distribution. First part of combined structure is working in standing wave regime and second one has travelling wave regime. Input cells are shorted out to RF oscillations, output cells are loaded on the matched load, RF generator feed structure via intermediate accelerating cell. This cell works as wave type transformer. Standing wave resonance structure with co-axis cells of coupling is excited on p/ 2 mode. It will work as multicavity buncher to form electron short bunches and to obtain relative energy spread 240 keV on the UELV-8-15 output. Such accelerating structure has been created and tested `cool' tests. Now it is tasted with beam. There is designed other combined structure which have high ®eld stability at the structures beginning as disc-loaded waveguide and high shunt-impedance as accelerating negative dispersions structures (Vakhrushin et al., 1995b). Main part of this combined structure is periodical chain of O-shape cells. Cells geometry was optimized to obtain high Ze on the oscillation mode 5p/6. Theoretical meanings Ze=87.1 MOm/m and quality factor Q = 18200 have been obtained for f = 2.45 GHz. A new system of energy regulation has been designed and it is functioning successfully. Simplest way of energy regulation is beam load changing, but it gives a poor energy spectrum. Standing wave accelerators of the Efremov Institute do not have this defect. Phase-shifter cells in the middle of accelerating struc-
M.I. Demski et al. / Radiation Physics and Chemistry 58 (2000) 197±201
ture realize change of synchronous phase with beam current change. Search of new radiative technologies are continued in NPK LUTS too. NPK LUTS and St.Petersburg's Special Designing Institute had been designed out complex installation for puri®cation of hospital sewage. Two linear accelerators with the beams of 6±8 MeV energy produced puri®cation of hospital sewage in radiative-chemical reactors. Simultaneously puri®cation of sewage from farm-preparations and degelatinization are produced. Installations throughput is 50 m3 for 24 h. Radiation dose is up to 10 kGy (Vakhrushin et al., 1995c). There were researches to sterilize revolved logs with bremsstrahlung of energy 6±8 MeV (Vyasmenova et al., 1996). There is a method to augment mechanical and thermal solidity of insulators with 8 MeV electron irradiation, and this method is used now.
6. Conclusion At present NPK LUTS oer 10 types of new generations linacs. Their energy range is 3±30 MeV, beam power range is 2±30 kW. Disc-loaded waveguide, resonators and combined structure are used as accelerating systems. Both klystron and magnetrons are used as RF power sources. If customers need technological complexes they may be manufactured together which electron linacs. Both accelerators and complexes have automatic control systems. NPK LUTS does scienti®c works continuously to improve operational characteristics of its linacs.
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References Glukhikh, V.A. et al., 1979. Industrial laboratory for g-analysis of gold ore samples. In: 3rd Workshop, Application of accelerators in medicine and industry. Leningrad, Proceedings, vol. 4, p. 3, Theses of reports (in Russian). Glukhikh, V.A., et al., 1985. Laboratorial accelerator complex for multielemental analysis of geological samples. In: 5th Workshop, Application of accelerators in medicine and industry. Moscow, p. 122 Theses of reports (in Russian). Levin, V.M., et al., 1981. Production of radionuclides by photonuclear reactions. Radiochem. Radioanal. Letters 49/2, 111±118. Vakhrushin, YuP, Glukhikh, V.A., Nikolaev, V.M., 1992a. United line of industrial and medical linacs. In: 7th Workshop, Application of accelerators in medicine and industry. St.Petersburg, p. 31 Theses of reports (in Russian). Vakhrushin, YuP, Vyazmenova, G.A., Kuznetsov, V.S., Fidelskaya, R.P. 1992b. Sewage desinfection by the electron beam at infections hospitals. Ibid p. 65 (in Russian). Vakhrushin, YuP, Rjabtsov, A.V., Smirnov, V.L., Terentiev, V.V., 1993. Combined accelerating structure with optimal multicaviting Buncher. In: Proceedings of the 13th Workshop on Accelerators of Charged Particles. Dubna, vol. 1, p. 249, (in Russian). Vakhrushin, YuP, Glukhikh, V.A., Nikolaev, V.M., Rumjantsev, V.V., 1995a. Development of united line for industrial a medical linacs. In: 8th Workshop, Application of accelerators in medicine and industry. St.Petersburg, p. 52 Theses of reports (in Russian). Vakhrushin, YuP, Kalinichenko, M.A., Rjabtsov, A.V., 1995b. High-eective accelerating structure for travellingwave linacs. In: 8th Workshop, Application of accelerators in medicine and industry. St.Petersburg, p. 8 Theses of reports (in Russian). Vyasmenova, G.A. et al., 1996. The Providing of uniformed dose in the time of bremstrahlungs irradiation from accelerators. In: Proceedings of the 15th Workshop on charge particle accelerators. Protvino, vol. 2, p. 342, (in Russian).