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The EB10 10 MeV, 30 kW electron irradiation facility
Radiat. Phys. Chem. Vol. 35, Nos 4 ~ , pp. 670q572, 1990 lnt. J. Radiat. Appl. lnstrum., Part C Printed in Great Britain
THE EBIO I0 MeV,
0146-5724/90 $3.00 + 0.00 Pergamon Press plc
30 kW E L E C T R O N I R R A D I A T I O N F A C I L I T Y
Mikael K a r l s s o n
Husbyborg,
S c a n d i t r o n i x AB S-752 29 Uppsala,
Sweden
ABSTRACT An i r r a d i a t i o n plant including a i0 MeV, 30 kW e l e c t r o n a c c e l e r a t o r is described. The a c c e l e r a t o r is a four stage linac of standing wave type. Using a 90 degrees bending magnet for energy d e f i n i t i o n it irradiates boxes on a conveyor from below. The system design emphasizes the n e c e s s i t y for d o c u m e n t a t i o n of a b s o r b e d dose for each i r r a d i a t e d box by continuous m o n i t o r i n g and r e c o r d i n g of the beam process parameters. This makes the system well suitable for i r r a d i a t i e n sterilization. A magnet at the exit w i n d o w corrects for the divergent field i n t r o d u c e d by the scanning magnet, giving vertical electrons over the full scanning width. This feature provides more u n i f o r m i r r a d i a t i o n and it also increases the e f f i c i e n c y of the unit by almost 20 %.
KEYWORDS I r r a d i a t i o n plant, documentation.
electron beam,
electron accelerator,
high power,
process
INTRODUCTION A service center for r a d i a t i o n p r o c e s s i n g will be started up in JOnkOping, Sweden, in late 1989 by Beta Tech AB. T h e i0 MeV/30 kW a c c e l e r a t o r is built and d e l i v e r e d by S c a n d i t r o n i x AB. The system is made to meet all the variety of r e q u i r e m e n t s that a service center can expect from different customers and to provide customers with good d o c u m e n t a t i o n of the dose given to each batch with the p o s s i b i l i t y to trace individual articles. H i g h p e r f o r m a n c e is needed for the a c c e l e r a t o r power and s t a b i l i t y as well as for the d o c u m e n t a t i o n and product h a n d l i n g system, in order to achieve a good and well d o c u m e n t e d throughput. ACCELERATOR The a c c e l e r a t o r is to a large extent built around standard components used in other S c a n d i t r o n i x a c c e l e r a t o r s in order to m a i n t a i n an efficient p r o d u c t i o n and to be able to offer to the customer a good supply of spare parts. Also the use of well known components should give EBI0 a good reliability. The a c c e l e r a t o r structure consists of four, 40 cm, S-band standing wave linac sections. This gives a total a c c e l e r a t i n g length of only 1.6 meters. The linacs, which are well known from use in S c a n d i t r o n i x a c c e l e r a t o r s for radiotherapy, have a good ability to handle the power dissipated, and there is no tendency of beam break up at specified pulse currents. The temperature of each section is i n d i v i d u a l l y c o n t r o l l e d by water cooling in order to have a stable beam i m m e d i a t e l y after the operator has switched the beam on and to 670
7th International Meeting on Radiation Processing
Fig. I. EBIO accelerator showing four stage accelerating section, 90 degrees magnet and scan horn
671
672
MIKAEL KARLSSON
enable a d j u s t i n g for different beam loads and different resonant frequencies between the sections. General p a r a m e t e r s Pulse length Rep rate Pulse current Energy
for the a c c e l e r a t e d beam are: 15 us I000 Hz 200 mA I0 MeV (+- 4 % spread)
The i n j e c t i o n part consists of a I00 kV gun and an i n j e c t i o n line with a prebuncher in order to obtain a low energy spread of the a c c e l e r a t e d beam. Two f o c u s i n g q u a d r u p o l e d o u b l e t s are used in the beam transport system, one before, and one after the 90 degrees bending magnet. The last q u a d r u p o l e is used to set the spot size at the 0.3 mm thick a l u m i n u m exit window. The use of q u a d r u p o l e s gives a large and well defined beam spot with a good overlapping and a good dose d i s t r i b u t i o n as a result. A c o r r e c t i o n magnet at the exit w i n d o w gives a v e r t i c a l beam spot over the total (80 cm) scan width. This provides more u n i f o r m i r r a d i a t i o n as well as a better u t i l i z a t i o n of the beam power available. The control system consists of a PLC system for general control and for m o n i t o r i n g the a c c e l e r a t o r and a d i s t r i b u t e d i n t e l l i g e n c e system for m o n i t o r ing and fast r e c o r d i n g of the beam p a r a m e t e r s n e c e s s a r y for the i r r a d i a t i o n process control. M a x i m u m and m i n i m u m p o i n t e r s for parameters as beam energy, beam current, conveor speed etc. w h i c h are all n e c e s s a r y for the d o c u m e n t ation are r e c o r d e d and forwarded to the d o c u m e n t a t i o n system for each parcel irradiated.
Product h a n d l i n g In the i r r a d i a t i o n area the conveyor belts are s p e c i a l l y d e s i g n e d to resist the hard e n v i r o n m e n t due to the i r r a d i a t i o n and the ozone g e n e r a t e d by the radiation. The conveyor speed is a d j u s t e d with beam current to keep the dose rate constant. All product h a n d l i n g is based on bar coding d e t e c t o r s c o n n e c t e d to a d o c u m e n t a t i o n system. The d o c u m e n t a t i o n of articles submitted to i r r a d i a t i o n is c o n t r o l l e d by a U N I X based m i n i c o m p u t e r . The d o c u m e n t a t i o n system handles the r e g i s t r a t i o n of articles, i d e n t i f i c a t i o n of a r r i v i n g articles, bar code tagging, a c c e p t a n c e of i r r a d i a t e d goods, p r o d u c t i o n of billing forms etc. RESULTS Factory tests at S c a n d i t r o n i x at a beam power of 15 kW show a good general b e h a v i o u r of the accelerator. All beam pulse p a r a m e t e r s fulfill the specifications i n d i c a t i n g that the tests for system i n t e g r a t i o n at the site of Beta Tech in JOnkOping, in September 1989, will be successful and that the a c c e l e r a t o r will be able to deliver at least 30 kW m a x i m u m beam power. ACKNOWLEDGEMENT The authour e x p r e s s e s his g r a t i t u d e to the S c a n d i t r o n i x staff w h i c h in less than two years time has s u c c e s s f u l l y c o m p l e t e d the first EBIO a c c e l e r a t o r and also to E.B. S v e n d s e n at Beta Tech AB who, with his long e x p e r i e n c e in r a d i a t i o n processing, has set the framework for the overall design of the EBIO system.
REFERENCES EUCOMED (1988). R e c o m m e n d a t i o n s for the S t e r i l i z a t i o n of Medical Devices and Surgical Products, Rev. Ed. E u r o p e a n C o n f e d e r a t i o n of Medical Suppliers Association, London Miller A. (1988). A p p r o v a l and Control of R a d i a t i o n Processes, EB and Gamma. Radiat. Phys. Chem. 31 t 385-393
THE EBIO I0 MeV,
0146-5724/90 $3.00 + 0.00 Pergamon Press plc
30 kW E L E C T R O N I R R A D I A T I O N F A C I L I T Y
Mikael K a r l s s o n
Husbyborg,
S c a n d i t r o n i x AB S-752 29 Uppsala,
Sweden
ABSTRACT An i r r a d i a t i o n plant including a i0 MeV, 30 kW e l e c t r o n a c c e l e r a t o r is described. The a c c e l e r a t o r is a four stage linac of standing wave type. Using a 90 degrees bending magnet for energy d e f i n i t i o n it irradiates boxes on a conveyor from below. The system design emphasizes the n e c e s s i t y for d o c u m e n t a t i o n of a b s o r b e d dose for each i r r a d i a t e d box by continuous m o n i t o r i n g and r e c o r d i n g of the beam process parameters. This makes the system well suitable for i r r a d i a t i e n sterilization. A magnet at the exit w i n d o w corrects for the divergent field i n t r o d u c e d by the scanning magnet, giving vertical electrons over the full scanning width. This feature provides more u n i f o r m i r r a d i a t i o n and it also increases the e f f i c i e n c y of the unit by almost 20 %.
KEYWORDS I r r a d i a t i o n plant, documentation.
electron beam,
electron accelerator,
high power,
process
INTRODUCTION A service center for r a d i a t i o n p r o c e s s i n g will be started up in JOnkOping, Sweden, in late 1989 by Beta Tech AB. T h e i0 MeV/30 kW a c c e l e r a t o r is built and d e l i v e r e d by S c a n d i t r o n i x AB. The system is made to meet all the variety of r e q u i r e m e n t s that a service center can expect from different customers and to provide customers with good d o c u m e n t a t i o n of the dose given to each batch with the p o s s i b i l i t y to trace individual articles. H i g h p e r f o r m a n c e is needed for the a c c e l e r a t o r power and s t a b i l i t y as well as for the d o c u m e n t a t i o n and product h a n d l i n g system, in order to achieve a good and well d o c u m e n t e d throughput. ACCELERATOR The a c c e l e r a t o r is to a large extent built around standard components used in other S c a n d i t r o n i x a c c e l e r a t o r s in order to m a i n t a i n an efficient p r o d u c t i o n and to be able to offer to the customer a good supply of spare parts. Also the use of well known components should give EBI0 a good reliability. The a c c e l e r a t o r structure consists of four, 40 cm, S-band standing wave linac sections. This gives a total a c c e l e r a t i n g length of only 1.6 meters. The linacs, which are well known from use in S c a n d i t r o n i x a c c e l e r a t o r s for radiotherapy, have a good ability to handle the power dissipated, and there is no tendency of beam break up at specified pulse currents. The temperature of each section is i n d i v i d u a l l y c o n t r o l l e d by water cooling in order to have a stable beam i m m e d i a t e l y after the operator has switched the beam on and to 670
7th International Meeting on Radiation Processing
Fig. I. EBIO accelerator showing four stage accelerating section, 90 degrees magnet and scan horn
671
672
MIKAEL KARLSSON
enable a d j u s t i n g for different beam loads and different resonant frequencies between the sections. General p a r a m e t e r s Pulse length Rep rate Pulse current Energy
for the a c c e l e r a t e d beam are: 15 us I000 Hz 200 mA I0 MeV (+- 4 % spread)
The i n j e c t i o n part consists of a I00 kV gun and an i n j e c t i o n line with a prebuncher in order to obtain a low energy spread of the a c c e l e r a t e d beam. Two f o c u s i n g q u a d r u p o l e d o u b l e t s are used in the beam transport system, one before, and one after the 90 degrees bending magnet. The last q u a d r u p o l e is used to set the spot size at the 0.3 mm thick a l u m i n u m exit window. The use of q u a d r u p o l e s gives a large and well defined beam spot with a good overlapping and a good dose d i s t r i b u t i o n as a result. A c o r r e c t i o n magnet at the exit w i n d o w gives a v e r t i c a l beam spot over the total (80 cm) scan width. This provides more u n i f o r m i r r a d i a t i o n as well as a better u t i l i z a t i o n of the beam power available. The control system consists of a PLC system for general control and for m o n i t o r i n g the a c c e l e r a t o r and a d i s t r i b u t e d i n t e l l i g e n c e system for m o n i t o r ing and fast r e c o r d i n g of the beam p a r a m e t e r s n e c e s s a r y for the i r r a d i a t i o n process control. M a x i m u m and m i n i m u m p o i n t e r s for parameters as beam energy, beam current, conveor speed etc. w h i c h are all n e c e s s a r y for the d o c u m e n t ation are r e c o r d e d and forwarded to the d o c u m e n t a t i o n system for each parcel irradiated.
Product h a n d l i n g In the i r r a d i a t i o n area the conveyor belts are s p e c i a l l y d e s i g n e d to resist the hard e n v i r o n m e n t due to the i r r a d i a t i o n and the ozone g e n e r a t e d by the radiation. The conveyor speed is a d j u s t e d with beam current to keep the dose rate constant. All product h a n d l i n g is based on bar coding d e t e c t o r s c o n n e c t e d to a d o c u m e n t a t i o n system. The d o c u m e n t a t i o n of articles submitted to i r r a d i a t i o n is c o n t r o l l e d by a U N I X based m i n i c o m p u t e r . The d o c u m e n t a t i o n system handles the r e g i s t r a t i o n of articles, i d e n t i f i c a t i o n of a r r i v i n g articles, bar code tagging, a c c e p t a n c e of i r r a d i a t e d goods, p r o d u c t i o n of billing forms etc. RESULTS Factory tests at S c a n d i t r o n i x at a beam power of 15 kW show a good general b e h a v i o u r of the accelerator. All beam pulse p a r a m e t e r s fulfill the specifications i n d i c a t i n g that the tests for system i n t e g r a t i o n at the site of Beta Tech in JOnkOping, in September 1989, will be successful and that the a c c e l e r a t o r will be able to deliver at least 30 kW m a x i m u m beam power. ACKNOWLEDGEMENT The authour e x p r e s s e s his g r a t i t u d e to the S c a n d i t r o n i x staff w h i c h in less than two years time has s u c c e s s f u l l y c o m p l e t e d the first EBIO a c c e l e r a t o r and also to E.B. S v e n d s e n at Beta Tech AB who, with his long e x p e r i e n c e in r a d i a t i o n processing, has set the framework for the overall design of the EBIO system.
REFERENCES EUCOMED (1988). R e c o m m e n d a t i o n s for the S t e r i l i z a t i o n of Medical Devices and Surgical Products, Rev. Ed. E u r o p e a n C o n f e d e r a t i o n of Medical Suppliers Association, London Miller A. (1988). A p p r o v a l and Control of R a d i a t i o n Processes, EB and Gamma. Radiat. Phys. Chem. 31 t 385-393