The main goals we pursued during the accelerator design and development were to develop a compact self-shielded device for flexible materials irradiation in one pass which might be installed by a Customer into common industrial premises not equipped with any lifting devices. These goals were successfully achieved in the “Electron-10” accelerator design

Ivanov, A.S.

Nikiforov, E.K.

Ovchinnickov, V.P.

Svinin, M.P.

Tolstun, N.G.

Valtman, D.S.

Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

“ELECTRON-10” HIGH VOLTAGE ACCELERATOR FOR DOUBLE-SIDED IRRADIATION OF FLEXIBLE MATERIALSD.S. Valtman, A.S. Ivanov, E.K. Nikiforov, V.P. Ovchinnikov, M.P. Svinin, N.G. TolstunEfremov Research Institute of Electrophysical apparatus, St. Petersburg, RussiaThe  main  goals  we  pursued  during  the accelerator design and development were to develop a compact  self-shielded  device  for  flexible  materials irradiation in  one pass which might be installed by a Customer  into  common  industrial  premises  not equipped with any lifting devices.These goals were successfully achieved in the “Electron-10” accelerator design.Technical parameters of the accelerator are given in the Table 1.Table 1№ Parameter Value1 Accelerating voltage 500-750 kV2 Accelerating voltage non-stability during one hour of operation (not counting ripples with frequency 50 Hz and more), not higher±5%3 Beam current range (in the two-window operation mode) 0-70 mA4 Irradiation zone size in each outlet window 1500×80 mm5 Non-uniformity of linear beam current in the irradiation zone region on the 50 mm distance from the outlet window foil, not higher±5%6 Non-uniformity of linear beam current density during one hour of operation (from 10% to max value of the beam current), not higher±5%7 Scan frequency along the outlet windows, not less 300 Hz8 Window to window beam transfer frequency range (regulated) 20-50 Hz9 Average operation time between prophylactics, not less 200 h10 Technical  use  coefficient  determined  as  Ctu=operation  time/(operation  time  + prophylactics), not less0,8511 Ionizing irradiation dose power on the outer surface of the radiation shielding А/kg (mR/h), не более1,003×10-10  (1,4)The  accelerator  consists  of  a  high  voltage generator,  an  accelerating  structure,  and  systems providing  beam  irradiation  field  forming,  power supplying and control. Auxiliary equipment and set of spare parts for at  least one year of operation are also included  into  accelerator  specification.  “Electron-10” accelerator  during  its  training  at  the  institute  testing facility is shown in Fig. 1.Fig. 1High  voltage  generator  of  the  accelerator  is built on the base of a single-phase transformer-rectifier, (Fig. 2, plane view) similar to the accelerators described in  [1,  2],  one  of  its  distinctions  is  a  horizontal orientation  of  the  HV  generator  and  accelerating structure. Conical primary winding of the HV generator made  from  the  water-cooled  copper  pipe  is  fastened inside  an  insulating  frame  that  allowed  to  minimize distance  between  primary  and  secondary  windings  of the transformer-rectifier and thus improve the magnetic coupling between them.Fig 21 - Primary Winding           7 - Vacuum Pump2 - Secondary Winding       8 - Vacuum Chamber3 – High - Pressure Tank    9 - Outlet Window4 – Electron Source            10 - Turning Magnet5 –Accelerating Tube         11 - Local Radiation Shielding6 – Scanning DeviceThe secondary winding is combined from the 27  rectifying  voltage-doubling  modules;  the  module average DC voltage is 27,5 kV. The modules are placed on  the  insulating  supporting  bar  made  from  organic glass.  Position  and  form of  each  coil  of  the  primary winding has been optimized by numerical simulation of magnetic and electric field that allowed, firstly, to get rather homogenous magnetic flux distribution along the rectifying  column  and,  secondly,  to  smooth  electric gradient in the surface of coils of the primary winding.ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.Серия: Ядерно-физические исследования (34), с. 16-18.160 10 20 30 40 50 60 70 80Z, сm020406080100120150 мА83 мАAxial magnetic flux distributionIload=0Umod/UaverageFig. 3As a result there are not any gradient screens presented at  the  primary  winding that  simplifies  the  accelerator design and improves cooling condition of insulating gas. DC voltage distribution measured along the rectifying column  under  total  75  DC  voltage  and  various  load currents is shown in Fig. 3. As it may be seen from the dependencies, non-homogeneity of the distribution does not exceed  ±10% in a load current range from 0 to 15 mA  that  corresponds  to  0-150  mA  under  operating accelerating voltage of 750 kV.0.2 0.6 1.0 1.40.0 0.4 0.8 1.2 1.6Window Length, m0.00.20.40.60.81.0Linear Beam Current Density123Fig. 41 – in accelerator with traditional triangular shaped vacuum chamber2, 3 – in the windows of the accelerator with beam forming system with turning magnetsAn  accelerating  tube  made  by  the  diffusion  welding method  and  combined  from  the  four  200  mm  long sections  is  placed  as  a  cantilever  inside  the  HV generator and on the same axis with it. Resistive voltage divider for smooth potential distribution along the tube and electromagnetic screening rings decreasing the field value on tens are fastened on the outer side of the tube electrodes.  An electron source with LaB6 emitter  has several thousand hours lifetime.HV  generator  and  accelerating  structure  are placed  in  the  metal  1,8  m3 vessel  filled  with  an insulating gas (SF6 under 0,8 MPa or mixture of 80% of SF6 20% of N2 under 1,2 MPa pressure). Gas handling installation having membrane compressor performs the insulating gas re-pumping, drying and storage. It is the optional equipment to be chosen by a Customer.Electron beam irradiation field forming system consists of magnetic lens, scanning electromagnets and two  elongated  turning  constant  electromagnets.  The turning  magnets  due  to  their  electron  optic characteristics  provide  almost  normal  angles  (90±7°) between  electron  trajectories  and  outlet  window  foil plane.  In  comparison  with  a  typical  scheme of  beam scanning in a triangular vacuum chamber where those angles go up to  30°,  beam loses  here are sufficiently lesser but because of the beam 90° turn its size on the further  side  of  the  outlet  window increases  in  20-25 times and its careful focusing by the magnetic lens in this point is necessary. Linear beam current distribution along the windows is shown in Fig.  4.  As it  may be seen,  the  distribution  differs  very  slightly  from  the traditional one in the triangular vacuum chamber [1]. To achieve a  homogenous heat load on the foil the beam is also scanned in the cross direction. Beam scanning as well as its transfer frequency from window to window is regulated (see Table 1). Foil in the windows is pressed by an atmosphere pressure to the ribs of copper water-cooled  flanges.  Outlet  window  has  about  90% transparency  for  electrons  and  does  not  need  any  air blowing for the foil cooling thus many times decreasing ozone  and  nitrogen  oxides  generation  that  simplifies problems  of  their  neutralization.  Processed  material goes through the systems of stainless steel transporting rolls and is being irradiated consequently from one, and then from another side (see Fig. 5). Water-cooled plates capable to receive full beam power are placed on the inner side of steel-lead local radiation shielding doors, that is being necessary during the accelerator adjustment or in the case of the processed material rupture.VacuumChamberElectronBeamProcessedMaterialFig. 5Mass production thyristor frequency converter having 92-93% efficiency is  used as  a  power  supply. Total  accelerator  electric  efficiency  (without  energy spent on pumping of  the cooling water,  that  is  about 4 m3 per hour) is shown in Fig. 6. Accelerator room has to  be  equipped  with  an  evacuating  ventilation corresponding to the sanitary rules.Control console and two racks are placed in the accelerator control room. We are planning to equip the next similar accelerators with an automated control system on the base of industrial computer that is developed in our institute recently.ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.Серия: Ядерно-физические исследования (34), с. 16-18.160 20 40 60 80Beam Current, mA020406080Efficiency, %Dashed line - 550 keVSolid one- 750 keVFig. 6There  are  3  items  of  the  “Electron-10” accelerator manufactured till now, two of them intended for the soft roofing production lines, and third one – for the foamed polyethylene production.“Electron-10”  installed  in  the  soft  roofing production  line  at  the  Ivanovo  Rubber  Sole  Plant  is displayed in Fig. 7. It  is seen from the photo that the accelerator, due to its compactness, looks quite in place in  the  production line  structure.  During four years  of operation  it  has  been  used  as  for  the  soft  roofing manufacture  as  for  development  of  some  new technologies.  Experience  shows that  the  most  serious problems  are  caused  mainly  by  the  cooling  system. When  the  cooling  water  is  not  clear  enough  or  the pressure  changes  sharply  and  the  season  temperature fluctuations  occurr,  then  the  accelerator  interlock system  sometimes  turns  off  the  accelerator.  These problems have  been  overcome when  the  autonomous water-cooling  was  arranged.  Other  problems  were connected  with  rare  but  serious  malfunctions  of  the thyristors frequency converter. In our new machines we are  planning  to  replace  it  by  the  IGBT based  power supply.Double-windowed  electron  beam  irradiation field  shaping  system  with  two  elongated  turning magnets  has  shown its  serviceability  in  the  industrial conditions and did not bring any unusual difficulties to the line personnel work (foil replacement, re-tuning for the irradiation field width changing).Fig. 7.Experience  gained  during  development  of “Electron-10” accelerators, their testing and running in the  industrial  conditions  gave  necessary  data to  build similar to it compact, self-shielded and easy serviceable accelerators  on  the  energies  up  to  1,5  MeV  and  the beam current up to 100 mA. It should be mentioned that the  accelerator  itself  might  be  used  as  a  good replacement of our “Aurora” type machines, which are being used in the various industrial lines for many years.REFERENCES1. Y.G. Golubenko et al. ELV Electron Accelerators: the State,  Application, Development.  Budker Inst. Preprint 97-7, Novosibirsk, 1997, 30 pp.2. Akulov et al., “Electron-6” High Voltage Accelerator, Abstracts of papers of IV all-union conference on the charged particle accelerators application, Leningrad, 1988, Oct. 11-13. Moscow, 1988, CNIIATOMINFORM, p. 5.ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 1999. №3.Серия: Ядерно-физические исследования. (34), с. 16-18.18

“Electron-10” higt voltage accselerator for double-sided irradiation of flexible materials

http://dspace.nbuv.gov.ua/bitstream/handle/123456789/81138/06-Valtman.pdf?sequence=1

“Electron-10” higt voltage accselerator for double-sided irradiation of flexible materials

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Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)