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A rapid transfersystem for the study of cyclotron-activated shortlived isotopes
NUCLEAR
INSTRUMENTS
AND METHODS
0969) 5~-55; ©
72
NORTH-HOLLAND
PUBLISHING
CO.
A RAPID T R A N S F E R S Y S T E M F O R T H E S T U D Y OF C Y C L O T R O N - A C T I V A T E D S H O R T L I V E D I S O T O P E S H. W. J O N G S M A
a n d H. V E R H E U L
Natuurkundig Laboratorium, Vrije Universiteit, Amsterdam, The Netherlands R e c e i v e d 20 J a n u a r y 1969 W i t h a n a u t o m a t i c a l l y driven p n e u m a t i c transfersystem ( " r a b b i t s y s t e m " ) i r r a d i a t e d t a rge t s c a n be t ra ns fe rre d f r o m the i r r a d i a t i o n p o s i t i o n in the e x t e r n a l b e a m of our A V F c y c l o t r o n over a distance of 75 m to t he s e p a r a t i o n or r a d i a t i o n de t e c t i ng e q u i p m e n t w i t hi n 6 sec.
1. Introduction
external beam of our AVF cyclotron 1' 2). The target is mounted on a so-called rabbit, which is transferred to the spectroscopy laboratory by compressed air. A schematic drawing of the system is given in fig. 1. It consists of three parts A, B and C. The starting and receiver station (A and C) are installed in the spectroscopy laboratory, which is at a distance of ~ 50 m
To investigate shortlived isotopes with half-lives clown to about 1 sec, targets are irradiated in the A
$2
-EX l EX2
(~) L--~ J
~-LOR ",.pp
IN2 ~ - ] ,
CC
®
ZnS
L
"~pp
F V9
IN 3
~.V7
N
(Z) L" ~LDR ~-pp
c
__---Z I~--
/f Fig. 1. S c h e m a t i c d r a w i n g of t he t ra ns fe r system.
A B C D E F
-
S t a r t i n g statio n Irradiation station Receiver s t a t i o n Diafragm Compressor F a r a d a y cup
L LDR PP IN EX S
-
Neon lamp L i g h t detecting resistor P n e u m a t i c pen A i r inlet Air exhaust A i r valve
V M
- V a c u u m va l ve - Vacuum measuring device RP - Rotation pump D P - Diffusion p u m p
51
CC - Cyclotron ZnS - ZnS screen Sc ~ hor. a n d vert. b e a m scanners Bs - B e a m s t o p
52
H.W. JONGSMA AND H, VERHEUL
Fig. 2. The irradiation station installed in the cyclotron hall.
from the cyclotron building. The irradiation station (B) has schematically the form of a cross (fig. 2); the way of the rabbit is vertical and the direction of the particle beam is horizontal. Two parallel transfer tubes, about 75 m each, with one way traffic connect the starting and receiver station with the irradiation station. The system is driven automatically.
2. The transfer system 2.1. THE RABBIT The rabbit (figs. 3, 4) consists of an aluminium body with two teflon rings for isolation in the irradiation station and for conductance in the transfer tubes. A copper rod with a selfsupporting target or a targetholder is mounted on this body.
A RAPID TRANSFERSYSTEM
45mm
60.Smm
Cu- rod
At Teflon
53
target
adjustabte air exhaust
)~-detect0r
Fig. 3. The rabbit in the receiver station. In the irradiation position only the target is irradiated, no serious activation of the copper rod or the aluminium body occurs. The copper rod conducts the heat, developed during the irradiation, from the target to the body, which serves as a heat reservoir. 2.2. THE PNEUMATIC TRANSFER The transfer tube consists of coupled pieces of PVC
tube with a length of 6 m each. The internal diameter is 21 mm. To irradiate a target, the rabbit has to be inserted in the starting station (A). When a pressure of 3 atm is used the rabbit reaches in ~ 5 sec the irradiation station (B). After passing an air exhaust (for instance EX I in fig. 1) the rabbit decelerates by compressing the air in the remaining part of the transfer tube. Through the irradiation station the rabbit
Fig. 4. Photograph of the receiver station.
54
H. W. J O N G S M A
moves by gravity and from the irradiation station to the receiver station again by compressed air. When a fragile target is used air pressure is reduced; this lengthens of course the transfertime. For instance at 0.2 atm it takes 20 sec for the rabbit to reach the irradiation station.
3. The irradiation station The irradiation station consists of 4 stages, 1-4 (fig. 1). At each stage there are a pneumatic pen (PP) controlled by a microswitch and opposite a neonlamp (L) and a light detecting resistor (LDR). When the body of the rabbit rests on the pen PP, the copper rod interrupts the light beam from the lamp L to the LDR. The resulting signal is used for the automaton. The various vacuum valves V, air inlets I N and air exhausts EX are also pneumatically driven and controlled by microswitches. In the stages 2 and 3 the pressure is measured; when a preset value is reached, signals are taken from the measuring devices and used for the automaton. The preset value for the highvacuum at stage 3 is adjusted to the cyclotron vacuum. The complete working of the system as given in fig. 1 is as follows: a. After passing EX 1 the rabbit decelerates and arrives in stage 1. Air valve $2 and the air exhaust (EX 1) close and in the transfer tube the air pressure is built up again; b. After arriving in the second stage, V 1 closes. Now the rabbit is in an airsluice between V~ and V 2. In about 15 sec the air pressure in this sluice is pumped down by RP to a preset prevacuum value, because the vacuumsluice between V 2 and V7 is on highvacuum before the rabbit arrives; c. After arriving in stage 3, Vz closes, the target is in irradiation position now. When the preset highvacuum value is reached, after 5-15 sec, V 5 and the beamstop BS open for a preset irradiation time. This preset time can be chosen from 1 till 100 sec with steps of I sec. (The irradiation time can also be controlled manually.) Next BS, Vs, V4 and V 9 are closed. Air is led into the c r o s s V 2 V 5 V 7 V 9 by the inlet I N 2 and ~ 0.5 sec after the end of the irradiation V7 opens; d. After arriving in the 4th stage V7 closes, and by pressed air the rabbit is shot to the receiver station. Now the mentioned cross is brought on highvacuum again. 4. Beamhandling and current measurement The focusing of the beam of charged particles can be checked by a ZnS screen and by a horizontal and vertical beamscanner (fig. 1).
A N D H. V E R H E U L 15.000
10000
"~,
5.000
Arriva~
In recewer station
0 Enid of
"~'
"~'~'
-~.~,~.~,~,~.~
I0
40 • TIME (sec)
the irradiation
Fig. 5. Multiscale s p e c t r u m of a n irradiated nickel target.
A graphite diafragm D, with a central hole of 4 mm, is placed in the vacuum tube just in front of the target in the irradiation position. The beamcurrent can be measured on two places: a. The isolated rabbit is electrically connected with the isolated pen PP3 which offers the possibility to measure the current on the target directly; b. The current going through the target can be measured by the Faraday cup F. Focusing of the beam is also controlled by requiring the current on the target or Faraday cup to be maximal, and the current on the diafragm D to be minimal.
5. Applications The result of an experiment performed with this system is given in fig. 5. To measure the half-life of 58Cu a nickel target was irradiated for 5 sec with 18 MeV protons. The decay of the 511 keV annihilation radiation was followed with a 3"× 3" NaI(T1)-crystal and a multiscale unit. The pulses were stored in a 1024 words Nuclear Data 160 memory. The detector was placed at the position as indicated in fig. 3. The counting was started at the end of the irradiation. In fig. 5 one can see that the rabbit arrives within 6 sec at the receiver station3). The resulting half-life of the short-lived component is (3.2 + 0.2) sec and has to be assigned to the t + decay of SSCu 4). In development are still on-line connections of the receiver station to an isotope separator and to a chemical separation equipment. We greatly appreciate stimulating and encouraging discussions with and assistance of many people in our laboratory during the development and test-runs of this system. Especially we wish to express our gratitude to dr. J.
A RAPID TRANSFERSYSTEM Rethmeier and his cyclotron staff, to messrs. W. Jongsma, W. F. L. R o o d a and their collaborators of the mechanical w o r k s h o p and to messrs. J. K n o l and B. Bakker of the electronical workshop. This w o r k has been supported in part by the F o u n d a tion of F u n d a m e n t a l Research o f Matter (F.O.M.), financially supported by the Netherlands Organization of Pure and Scientific Research (Z.W.O.).
55
References 1) C. C. Jonker, IEE Trans. Nucl. Sci. NS-13 (1966) 446. 3) j. Rethmeier, J. G. Nijenhuis and R. Langkau, Nuel. Instr. and Meth. 68 (1969) 135. a) C. E. Bemis, Jr. and J. W. Irvine, Jr., Nucl. Instr. and Meth. 34 (1965) 57. 4) C. M. Lederer, J. M. Hollander and I. Perlman, Table of Isotopes (Wiley, New York, 1967).
INSTRUMENTS
AND METHODS
0969) 5~-55; ©
72
NORTH-HOLLAND
PUBLISHING
CO.
A RAPID T R A N S F E R S Y S T E M F O R T H E S T U D Y OF C Y C L O T R O N - A C T I V A T E D S H O R T L I V E D I S O T O P E S H. W. J O N G S M A
a n d H. V E R H E U L
Natuurkundig Laboratorium, Vrije Universiteit, Amsterdam, The Netherlands R e c e i v e d 20 J a n u a r y 1969 W i t h a n a u t o m a t i c a l l y driven p n e u m a t i c transfersystem ( " r a b b i t s y s t e m " ) i r r a d i a t e d t a rge t s c a n be t ra ns fe rre d f r o m the i r r a d i a t i o n p o s i t i o n in the e x t e r n a l b e a m of our A V F c y c l o t r o n over a distance of 75 m to t he s e p a r a t i o n or r a d i a t i o n de t e c t i ng e q u i p m e n t w i t hi n 6 sec.
1. Introduction
external beam of our AVF cyclotron 1' 2). The target is mounted on a so-called rabbit, which is transferred to the spectroscopy laboratory by compressed air. A schematic drawing of the system is given in fig. 1. It consists of three parts A, B and C. The starting and receiver station (A and C) are installed in the spectroscopy laboratory, which is at a distance of ~ 50 m
To investigate shortlived isotopes with half-lives clown to about 1 sec, targets are irradiated in the A
$2
-EX l EX2
(~) L--~ J
~-LOR ",.pp
IN2 ~ - ] ,
CC
®
ZnS
L
"~pp
F V9
IN 3
~.V7
N
(Z) L" ~LDR ~-pp
c
__---Z I~--
/f Fig. 1. S c h e m a t i c d r a w i n g of t he t ra ns fe r system.
A B C D E F
-
S t a r t i n g statio n Irradiation station Receiver s t a t i o n Diafragm Compressor F a r a d a y cup
L LDR PP IN EX S
-
Neon lamp L i g h t detecting resistor P n e u m a t i c pen A i r inlet Air exhaust A i r valve
V M
- V a c u u m va l ve - Vacuum measuring device RP - Rotation pump D P - Diffusion p u m p
51
CC - Cyclotron ZnS - ZnS screen Sc ~ hor. a n d vert. b e a m scanners Bs - B e a m s t o p
52
H.W. JONGSMA AND H, VERHEUL
Fig. 2. The irradiation station installed in the cyclotron hall.
from the cyclotron building. The irradiation station (B) has schematically the form of a cross (fig. 2); the way of the rabbit is vertical and the direction of the particle beam is horizontal. Two parallel transfer tubes, about 75 m each, with one way traffic connect the starting and receiver station with the irradiation station. The system is driven automatically.
2. The transfer system 2.1. THE RABBIT The rabbit (figs. 3, 4) consists of an aluminium body with two teflon rings for isolation in the irradiation station and for conductance in the transfer tubes. A copper rod with a selfsupporting target or a targetholder is mounted on this body.
A RAPID TRANSFERSYSTEM
45mm
60.Smm
Cu- rod
At Teflon
53
target
adjustabte air exhaust
)~-detect0r
Fig. 3. The rabbit in the receiver station. In the irradiation position only the target is irradiated, no serious activation of the copper rod or the aluminium body occurs. The copper rod conducts the heat, developed during the irradiation, from the target to the body, which serves as a heat reservoir. 2.2. THE PNEUMATIC TRANSFER The transfer tube consists of coupled pieces of PVC
tube with a length of 6 m each. The internal diameter is 21 mm. To irradiate a target, the rabbit has to be inserted in the starting station (A). When a pressure of 3 atm is used the rabbit reaches in ~ 5 sec the irradiation station (B). After passing an air exhaust (for instance EX I in fig. 1) the rabbit decelerates by compressing the air in the remaining part of the transfer tube. Through the irradiation station the rabbit
Fig. 4. Photograph of the receiver station.
54
H. W. J O N G S M A
moves by gravity and from the irradiation station to the receiver station again by compressed air. When a fragile target is used air pressure is reduced; this lengthens of course the transfertime. For instance at 0.2 atm it takes 20 sec for the rabbit to reach the irradiation station.
3. The irradiation station The irradiation station consists of 4 stages, 1-4 (fig. 1). At each stage there are a pneumatic pen (PP) controlled by a microswitch and opposite a neonlamp (L) and a light detecting resistor (LDR). When the body of the rabbit rests on the pen PP, the copper rod interrupts the light beam from the lamp L to the LDR. The resulting signal is used for the automaton. The various vacuum valves V, air inlets I N and air exhausts EX are also pneumatically driven and controlled by microswitches. In the stages 2 and 3 the pressure is measured; when a preset value is reached, signals are taken from the measuring devices and used for the automaton. The preset value for the highvacuum at stage 3 is adjusted to the cyclotron vacuum. The complete working of the system as given in fig. 1 is as follows: a. After passing EX 1 the rabbit decelerates and arrives in stage 1. Air valve $2 and the air exhaust (EX 1) close and in the transfer tube the air pressure is built up again; b. After arriving in the second stage, V 1 closes. Now the rabbit is in an airsluice between V~ and V 2. In about 15 sec the air pressure in this sluice is pumped down by RP to a preset prevacuum value, because the vacuumsluice between V 2 and V7 is on highvacuum before the rabbit arrives; c. After arriving in stage 3, Vz closes, the target is in irradiation position now. When the preset highvacuum value is reached, after 5-15 sec, V 5 and the beamstop BS open for a preset irradiation time. This preset time can be chosen from 1 till 100 sec with steps of I sec. (The irradiation time can also be controlled manually.) Next BS, Vs, V4 and V 9 are closed. Air is led into the c r o s s V 2 V 5 V 7 V 9 by the inlet I N 2 and ~ 0.5 sec after the end of the irradiation V7 opens; d. After arriving in the 4th stage V7 closes, and by pressed air the rabbit is shot to the receiver station. Now the mentioned cross is brought on highvacuum again. 4. Beamhandling and current measurement The focusing of the beam of charged particles can be checked by a ZnS screen and by a horizontal and vertical beamscanner (fig. 1).
A N D H. V E R H E U L 15.000
10000
"~,
5.000
Arriva~
In recewer station
0 Enid of
"~'
"~'~'
-~.~,~.~,~,~.~
I0
40 • TIME (sec)
the irradiation
Fig. 5. Multiscale s p e c t r u m of a n irradiated nickel target.
A graphite diafragm D, with a central hole of 4 mm, is placed in the vacuum tube just in front of the target in the irradiation position. The beamcurrent can be measured on two places: a. The isolated rabbit is electrically connected with the isolated pen PP3 which offers the possibility to measure the current on the target directly; b. The current going through the target can be measured by the Faraday cup F. Focusing of the beam is also controlled by requiring the current on the target or Faraday cup to be maximal, and the current on the diafragm D to be minimal.
5. Applications The result of an experiment performed with this system is given in fig. 5. To measure the half-life of 58Cu a nickel target was irradiated for 5 sec with 18 MeV protons. The decay of the 511 keV annihilation radiation was followed with a 3"× 3" NaI(T1)-crystal and a multiscale unit. The pulses were stored in a 1024 words Nuclear Data 160 memory. The detector was placed at the position as indicated in fig. 3. The counting was started at the end of the irradiation. In fig. 5 one can see that the rabbit arrives within 6 sec at the receiver station3). The resulting half-life of the short-lived component is (3.2 + 0.2) sec and has to be assigned to the t + decay of SSCu 4). In development are still on-line connections of the receiver station to an isotope separator and to a chemical separation equipment. We greatly appreciate stimulating and encouraging discussions with and assistance of many people in our laboratory during the development and test-runs of this system. Especially we wish to express our gratitude to dr. J.
A RAPID TRANSFERSYSTEM Rethmeier and his cyclotron staff, to messrs. W. Jongsma, W. F. L. R o o d a and their collaborators of the mechanical w o r k s h o p and to messrs. J. K n o l and B. Bakker of the electronical workshop. This w o r k has been supported in part by the F o u n d a tion of F u n d a m e n t a l Research o f Matter (F.O.M.), financially supported by the Netherlands Organization of Pure and Scientific Research (Z.W.O.).
55
References 1) C. C. Jonker, IEE Trans. Nucl. Sci. NS-13 (1966) 446. 3) j. Rethmeier, J. G. Nijenhuis and R. Langkau, Nuel. Instr. and Meth. 68 (1969) 135. a) C. E. Bemis, Jr. and J. W. Irvine, Jr., Nucl. Instr. and Meth. 34 (1965) 57. 4) C. M. Lederer, J. M. Hollander and I. Perlman, Table of Isotopes (Wiley, New York, 1967).