DSpace at VNU: Some results of interfacing the r-r coincidence spectrometer and computer

VNU JOURNAL OF SCIENCE, Mathematics - Physics. T .XVIII, No3 - 2002

S O M E R E S U L T S O F IN T E R F A C IN G

THE 7 - 7

C O IN C ID E N C E S P E C T R O M E T E R A N D C O M P U T E R

C h u D u e T r i n h . N g u y e n V in h Q u a n g
F a c u lty o f Technology', V N V
N g u y e n D a n g L a m , P h a m D in h K h a n g
D e p a r tm e n t o f P h y s ic s, C o lleg e o f S cien ce, V N V

1 . I n tr o d u c tio n
T h e c o n stru c tio n o f th e s p e c tro m e te r b a se d on S A C P m e th o d (S u rm n atio n o f A m ­
p litu d e s o f coinciding of pulses) h a s lead to th e n eed o f th e in terface c a rd to exchange d a ta
wit h c o m p u te r. T h e in terface c a rd h a s b e e n co m p leted at t he facu lty o f technology. V iet­
n a m N a tio n a l U niversity. H anoi. W ith sim ple design, th e card w orked co m p letely sta b ility
in th e long w ork p erio d . M any m e asu rin g e x p erim en ts w ith th is c a rd have b een done a t
D alat n u clear re sea rc h In s titu te . P ro cessin g in d ep en d en tly , th e re su lts o f ex p erim en ts at
H anoi a n d D u b n a p o in te d out th e good o p e ra tio n o f th e s p e c tro m e te r a n d th e in terface
card .
2. O v e r v ie w

T h e e x p e rim e n ta l research o i l th e n u clear s tru c tu re tru th fu lly is m easu rin g (by th e
different m e th o d s ) som e p a ra m e te rs su ch as cross-section, en erg y o f th e excited states,
p ro b a b ility of th e tra n s itio n s b etw een th e e x cited s ta te s . F rom th e m e asu rin g p a ra m e te rs
it is possible c alc u la te q u a n tu m p a ra m e te rs o f th e s ta te s . T h e e x p e rim e n ta l re su lts a re th e
b ases to e s tim a te , to co rrect a n d to c o m p lete th e n u clear th e o ry a n d th e o th e r a p p licatio n s
o f technology.
T h e s tu d ie s call be c a rrie d o u t on th e e q u ip m e n t such a s th e re a c to r, accelerator.

G enerally, th e layout, of th e e x p e rim e n t is show ed on F ig .l.

dQ
CỈƠ

1«

dn

-------------------- ►
-------------------- ►
-------------------- ►

In c id e n t beam

T a rg e t
Fig. 1. S tu d y in g n u clear s tru c tu re by th e n u c lea r re a c tio n s

T y p e s e t b y ^ A / j iS - T f e X

57


C h u D u c T r in h , N g u y e n

58

V in h Q u a n g ..

T h e p o ssib ility o f th e gam m a-ray d eca y o f th e n u clei (b ein g sh o t by p article b eam

o f th e accelerator or n eu tron b ea m o f th e reactor) is th e h ig h est.

For th e reason, th e

.gam m a sp ectro m eter w as u sed to o b ta in th e most, in fo rm a tio n o f th e stu d ie d nucleus. T h e
use o f th e so lid -sta te d etecto rs w ith h ig h -en erg y reso lu tio n a n d h ig h sp e e d en h an ced th e
accuracy o f th e m easuring.
H ow ever, th e effects su ch as th e C o m p to n -sc a tte r in g , e le c tio n -p o sitio n pair form a­
tion in the in tera ctio n o f g a m m a ray w ith d etecto r h a d a b ad effect o n the rad iative
sp ectru m and red u ced th e a b ility o f o b ta in in g in form ation .
T h e use o f th e sp ectro m eter w ith o p p o sin g C o m p to n -sca tterin g p e r m it o f red u cing
30% o f th e background g en era ted by th e C o m p to n -sca tterin g . In order to reduce com ­
p letely th e C o m p to n background, th e m eth o d o f su m m a tio n o f a m p litu d e s o f coincidence
p u lses m u st be used. Today, there is o n ly such sp ectro m eter a t J IN R (th e Joint In stitu te
for N u clear R esearch, D u b n a ). Prom th e resu lts o b ta in ed by th e u se o f th e sy stem , the
q u an tity o f the u sefu l in fo rm a tio n in creased m an y tim es.

T h e resu lts o b ta in ed by the

oth er m eth o d are also th e sa m e in th e en erg y region o f 0 to 8 M ev.

I n V ie tn a m
The nuclcar reaction studies are carricd out at two centers:
- O il th e accelerator o f th e n uclear cen ter, p h y sic in s titu te , T h e N a tio n a l Science
and T ech n ology center.
- At th e Dalat, nuclear R esearch I n s titu te w ith th e te s ts o n th e n eu tron b eam to
define th e rea ctiv e cro ss-sectio n o f th e so m e nuclear iso to p e s.

N ow , th e m ost m odern

gainm a-ray sp ectro m eters are th e m o n o -cry sta l gam in a-ray sp ectro m eter . T h e reduction
o f the C o m p to n -sca tterin g back grou n d is n o t s till o p tim a l b eca u se o f u sin g the passive
m eth o d s such as covering, m ak in g o f c o llim a tio n block or th e a ctiv e m e th o d s w ith using
th e a n ticoin cid en ce sy ste m a n d d etecto rs su ch as G eiger-M tiller co u n ter or scin tillation
d etector.

3. S p e c t r o m e t e r o f S u m m a t i o n o f a m p l i t u d e s o f c o i n c i d e n c e p u l s e s

Fig. 2. T h e sch em a o f th e selec ted sy ste m at D a la i a fter m an y o f different te sts.


S o m e r e s u lts o f in te r fa c in g

The

7

—

7

c o in c id e n c e

59

D1 a n d 1)2 a n ' sem ico n d u c to r d e te c to rs. SA1 a n d SA2 a rc s p e c tru m am plifiers;
A IX ’l a n d A D C 2 un', th e IK a n alo g to d ig ita l c o n v erters o f successive a p p ro x im atio n .
T h e y w ere m a n u fa c tu re d a t D alat. n u clear R esearch In s titu te .
F ro m 1996, I ho ideas o f ex am in in g a n d c o n stru c tin g th e sy ste m o f S A C P to use th e
n e u tro n b e am at t ho I )a la t n u c le a r re a c to r h a s b een carrie d o u t. U p to now , a fte r m any of

test ing a n d ex am in in g the first p e rio d o f b u ild in g sy stem h a s b e en co m p leted . T h e second
p e rio d o f using t h e sy stem t o research th e n u c lea r s tru c tu re o n th e n e u tro n b e a m h as been
s ta rte d . T h e schem a o f t h e sy ste m is o n F ig.2
T h e fast a n d slow coincidence blocks w ere m ad e a t physic Faculty, N a tu ra l Sci­
ences In s titu te . T h e in terface c a rd w as m ad e a t F acu lty o f Technology, Viet n am N atio n al
U niversity, H anoi.
O p e r a tio n a l p r in c ip le o f th e s y s t e m is fo llo w e d

T h e ta rg e t nuclei c a p tu re d t h e rm a l n e u tro n lives ill th e e x cited s ta te s h o rtly (1 0 “ 17 —
s) a n d it will decay by cascade. T w o so lid -sta te d e te c to rs c a p tu re p a irs of gam m a.

10“

T h e signals from Ỉ he tim e o u tp u ts o f th e d e te c to rs are led to th e fa st am plifiers a n d the
d isc rim in a to r a n d th e n 1.0 th e in p u ts o f th e coincidence block. At th a t tim e , th e signals
from th e a m p litu d e o u tp u ts OÍ th e two d e te c to rs a re also led to th e s p c c lru m am plifiers. Ill
t he case o f two tim e signals b e in g co in cid en t, th e re is a pulse a t o u tp u t o f th e coincidence
block. T h e pulse will en ab le th e A D C s to o p e ra te .
Rise slope o f th e p u lses also have d u ty of e ra sin g th e d a ta o f th e last conversion if
th e c o m p u te r d id not take th e m . A fter co n v ertin g tw o pu lses to d ig ita l form , th e A D C s
will g en erate th e signal o f ” D a ta re a d y ” to c o m p u te r to sen d d a ta .
A fter receiving d a ta , P C w ill g e n e ra te a co m m an d to erase th e d a t a in two A D C s
a n d continues th e new cycle.
T h e in fo rm atio n w as s to re d in P C u n d e r form of a tw o-dim ension m a trix E \ (n )
a n d E 2 (rc). E l (n ) a n d E 2 (71) a re th e d ig ita l a m p litu d e o f th e pu lses o f d e te c to r 1 an d
d e te c to r 2. II is th e o rd in al n u m b e r o f th e coincident fact co u n ted from th e s ta r t lim e.
T h u s, th e interface card h a s d u ty of in fo rm in g two A D C ’s d a ta read y , talking d a ta to P C
a n d g e n eratin g th e c o m m a n d to erase d a ta in two A D C ’s buffer.
T h e in terface card is c o m p le ted from IC s-8255. T h e m e a su rin g re s u lts w ith source
C 06 O a re show ed in Fig. 3.

3UÜ
250

*00
150

S e r ie s I

'Ả ị.-ỉiịĩ.

ỉẫm

100

^ ° *
is p p 1
p

50

11VAw * vrrr*TT*»

0
68

135 202 2 6 9 3 3 6 4 0 3 4 7 0 5 3 7 6 0 4 671 7 3 8 8 0 5 8 7 2

F ig .S . T h e p a tte r n o f s p e c tra C o° o b ta in e d by th e in terface

60

C h u D u c T r in h , N g u y e n

V in h Q u a n g ..

From Fig.3, it is possible to say th at the system operates very well; the Co 60
gamma spectrum of each detector is completely like w ith th a t of m ono-crystal gamma ray
spectrom eter. T he above results m ean th a t the address decode, the d a ta transmission are
good and stability. Some calculates of the energy and tim e resolution has been carried out
and the obtained results are very good.
W ith the obtained database and after the processing, the sum m ation and differential
spectra of source CoC)0 are given in Fig.4.

Fig. 4‘ The sum m ation and differential spectra of source C o 60
From the differential spectrum , it is possible to say th a t the Com pton-scattering
background has been erased completely.
4. E s tim a tio n o f th e in te rf a c e o p e ra tio n
From the obtained results, it is clear th at the system of SACP operates very well
and can be used to study the nuclear structure on the neutron channel of the reactor.
T he system operates effectively like the system of JIN R (the Joint In stitu te for Nuclear
Research, Dubna) although it is simple.
Interface card has good ability of the inform ation transmission. Although the num­
ber of the m easuring fact ill a tim e unit is not much (about 100 counts per second) but
the time of one conversion is very short about 25 ịis and the transm ission rate is about
In the near future, besides using the system to study the nuclear structure the
system will be enhanced w ith íbiư analog inputs.
T he authors would like to thank the Hanoi national University for the financial

support in this research.
R e fe r e n c e s

1. Boueva S.T. et. al., Physics of Elementary Particles and Atomic Nuclei, V.22, Part.
2, 1991, p. 479.
2. Boueva ST. et al., Physics of Elementary Particles and Atomic Nucleif V.22, P art
6 , 1991, p. 1431.
3. P h a m D in h K hang, R esearch o n th e C a sca d e - 7 d eca y o f th e N u clei Y b 170 and G d 158,
P h .D thesis, H anoi, 1994.
4. N g u y e n Vinh Q u an g, e t al., S om e R esu lts o f th e S p ectro m eter b a sed on S A C P
m e th o d at D a la i and H anoi, The articltj the N ational Coference on P hysics , 2001.
5. P h a m D in h Kharig e t al., T h e 7 — 7 co in cid en ce S p ectro m eter and te stin g w ith ra­
d io a c tiv e S ource C q°, Proceedings o f The N ational Coference on the nuclear physic,
2001.