T Ü R K İ Y E A T O M E N E R J İ S İ K U R U M U
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ÇEKM ECE N Ü K LEER ARAŞTIRMA VE EĞİTİM MERKEZİ
Ç.N.A.E.M.
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A . R - 247ABSOLUTE NEUTRON YIELD DETERMINATION OF AN ACCELERATOR
*
NEUTRON SOURCE BY USING THE ASSOCIATED PARTICLE METHOD
Metin Subaşı
Physics Department
May 1988
T Ü R K İ Y E A T O M E N E R J İ S İ K U R U M U ÇEKM ECE N Ü K LEER ARAŞTIRMA VE EĞİTİM MERKEZİ
Ç.N.A.E.M. - A . R - 247
ABSOLUTE NEUTRON YIELD DETERMINATION OF AN ACCELERATOR
NEUTRON SOURCE BY USING THE ASSOCIATED PARTICLE METHOD
Metin Subaşı
Physics Department
May 1988
A B S O L U T E N E U T R O N Y I E L D D E T E R M I N A T I O N OF AN A C C E L E R A T O R * N E U T R O N S O U R C E B Y U S I N G T H E A S S O C I A T E D P A R T I C L E M E T H O D M e t i n Subaşı P h y s i c s D e p a r t m e n t M a y 1988
* This w o r k was p e r f o r m e d in the I n s t i t u t e of R e a c t o r D e v e l o p m e n t at J u e l i c h N u c l e a r R e s a e r c h Centre, F e d a r a l R e p u b l i c of Germany.
m m s i The a b s o l u t e 14 M e V n e u t r o n o u t p u t of a n e u t r o n g e n e r a t o r (Sames TB8) was d e t e r m i n e d b y u s i n g t h e a s s o c i a t e d p a r t i c l e method. The a l p h a p a r t i c l e s a s s o c i a t e d w i t h n e u t r o n s f r o m t h e 3H(d, n ) 4 H e r e a c t i o n w e r e c o u n t e d b y a small r u g g e d i z e d s u r f a c e b a r r i e r d e t e c t o r (R S B D ). A thin A l - c o a t i n g on the a c t i v e s u r f a c e of th i s d e t e c t o r p r o v i d e d e x c e l l e n t d i s c r i m i n a t i o n n o t o n l y a g a i n s t t h e a s s o c i a t e d alphas f r o m t h e other c o m p e t i n g r e a c t i o n products, but, al s o the low e n e r g y p a r t i c l e s (tritons, 3He- par t i c l e s ) fr o m t h e b a c k g r o u n d or n o i s e at low d e u t o r o n en e r g i e s (<100 k e V ) . Hence, in a d d i t i o n t o t h e p r e c i s e d e t e r m i n a t i o n of t h e a b s o l u t e 14 M e V n e u t r o n output, t h e total n e u t r o n o u t p u t fr o m t h e 2H(d, n ) 3 H e r e a c t i o n w h i c h a c c o u n t s for t h e c o n t a m i n a t i o n of t h e t r i t i u m t a r g e t d u e t o d e u t o r o n b u i l t - u p w a s a l s o monitored. F o r comparison, t h e 14 M e V - n e u t r o n y i e l d of t h e n e u t r o n g e n e r a t o r was a l s o d e t e r m i n e d b y t h e foil a c t i v a t i o n m e t h o d u s i n g t e f l o n and ni c k e l as s t a n d a r t materials. The r e s ults o f t h e b o t h m e t h o d s a g r e e d well w i t h i n t h e e x p e r i m e n t a l uncertainties.
B i r n ö t r o n ü r e t e c i n i n (Sames TB 8) m u t l a k 14 M e V - n ö t r o n çıkışı o r t a k t a n e c i k s a y m a y ö n t e m i y l e saptanmıştır. 3 H ( d , n ) 4 H e r e a k s i y o n u n d a n ö t r o n l a r l a b i r l i k t e o r t a y a ç ı k a n a l f a t a n e c i k l e r i k ü ç ü k ve d a y a n ı k l ı bir y ü z e y enge l l i d e d e k t ö r l e sayılmıştır. Bu d e d e k t ö r ü n e t k i n yü z e y i ü z e r i n d e k i ince a l ü m i n y u m k a p l a m a sayesinde, sa d e c e a lfaları d i ğ e r r e a k s i y o n ü r ü n l e r i n d e n a y ı r m a k k olaylaşmamış, 100 k e V d e n d ü ş ü k d ö t o r o n e n e r j i l e r i n d e d ü ş ü k en e r j i l i t a n e c i k l e r i (triton, 3 H e - t a n e c i k l e r i gibi.,) de b a c k g r o u n d v e g ü r ü l t ü d e n a y ı r a r a k s a y m a k m ü m k ü n olmuştur. Böylece, 14 M e V - n ö t r o n ç ı k ı ş ı n ı n d u y a r l ı b i r ş e k i l d e m u t l a k s a p t a n m a s ı yanısıra, d ö t e r y u m b i r i k m e s i n e d e n i y l e olu ş a n t r i t y u m h e d e f k i r l e n m e s i d e izlenmiştir. K a r ş ı l a ş t ı r m a k amaciyle, n ö t r o n ü r e t e c i n i n 14 M e V - n ö t r o n çıkışı, s t a n d a r t m a d d e o l a r a k t e f l o n ve n ikel k u l l a n ı l a r a k foil a k t i v a s y o n u y ö n t e m i u y g u l a n a r a k t a bulunmuştur. H e r iki y ö n t e m l e b u l u n a n s o n u ç l a r d e n e y s e l b e l i r s i z l i k s ı n ı r l a r ı içinde u y u ş m a k t a d ı r 1a r .
CONTENTS
1. Introduction... 4
2. Determination of the 14 MeV-neutron yield....6
2.1 Calculating the neutron yield in the A P M ... 6
2.2 Counting the alpha particles... 10
2.3 Foil activation measurements... 12
3. Results and Conclusion... 13
ii introduction
In various experiments involving accelerator neutrons the absolute neutron yield of the target is an important parameter. For example, total number of the 14 MeV-neutrons from the target of a neutron generator must be accurately known in a fusion blanket experiment or in an activation analysis measurement so that the integral parameters of interest (e.g. the neutron flux, tritium production rate, etc.,) or the reaction rate in a foil can be expressed per source neutron.
Since the early measurements of fast neutrons by a BF gas 3
counter placed in a moderating material(paraffin) /1/, two methods have been mainly used for neutron yield determination. These include the measurements of the induced activity/2-9/, and the yield of an associated reaction product/10-19/. In the activation method, a standart material is irradiated with the target and induced activity of the reaction product by the neutron capture is measured via the associated gamma ray from its decay by a Nal(Tl) or Ge(Li) detector assembly. The standart is usually in the form of a thin foil (In, F, Cu, Ni, Zr, etc.,) but, liquid solutions (e.g. Magnesium Sulfate or Vanadyle S u l fate)/4,5/ have been also used"in a container surrounding the target. Although the foil activation is very attractive in application due to its simplicity, it suffers from the uncertainties in cross section values as well as the errors associated with the target absorption and scattering. In comparison to the foils, the liquid baths have, so far, found little application for accelerator sources due to the additional
disadvantages of background and residual activity problems.
The other widely used method of neutron yield determination meant above is the associated particle method (APM) which requires one to determine the number of particles produced simultaneously with the neutrons in a neutron producing reaction
3 4 2 3
( H(d, n) He or H(d, n) He). In practice, these particles are counted by a small detector located in the target chamber under vacuum. The detector is usually a SBD, but, a thin plastic scinti 1lator/17/ or a proportional gas counter/13/ has been also used. As a matter of fact, considering the requirements from such a detector -small size and mass, high detection efficiency and resolution, stable response, no-maintainance problem, etc.,- a SBD seemes to be the most appropriate. However, measurement of the charged particles with this detector should be performed very carefully in the target chamber considering the interferences from the following sources;
- the photons and the scattared deutorons coming from the t a r g e t ,
- the lower energy neutrons resulting from the scattarino of
2 3
the source neutrons or from the reaction H(d, n) He because of the deuterons accumulated on the target during previous operat i o n s ,
- the competing reactions products, - the geometrical factors.
In counter
this study, performance of a RSBDl'Ortec) as the alpha was investigated in the application of the APM to
determine the absolute 14 MeV-neutron yield of the Sames TB 8 neutron generator in the institute of Reactor Development at Juelich Nuclear Resaerch Center,FRG. Additionally, the foil activation method was applied to compare the results.
Determination of the 14 MeV-Neutron Yield 2^1 Calculating the neutron Yield in the APM
3 4
For the H(d, n> He reaction, total number of 14 MeV- neutrons produced in the target and the number of alpha particles
counted by the detector may be inter-related with the equation
N =N . < 4İÎ fSL ) .RCE , 0 ) Cl)
n a d a
where £L is the solid angle subtended by the alpha detector and RCE , 0 ) is the anisotropic correction factor. The anisotropy
d a
factor which is a function of the incident deuteron energy E , d and the mean alpha particle emission angle, 0 ,is given by the
a relation/13/ RCE d 0 )
I
CTCE).nCE).CdE/dx) dE / ' -1 CTCE) .nCE) . Cdw /dw ) CdE/dx)CM LAB
C 2 )
where
CTCE) is the differential cross section for the D-T reaction in the center of mass CCM) system,
dE/dx is the rate of energy loss of deuterons in the target material,
dw /dw is the solid angle conversion factor from the CM LAB
n(E) is the local tritium atom density in the target at a depth where the deuterons have energy E.
In the relation above it is assumed that
- the reaction products are isotropically distributed in the center of mass system for the incident deuteron energies up to 300 keV,
- the target has been loaded homogeneously with tritium atoms to a depth thick enough to stop the incident deuterons,
- the deuterons are not scattered from the target,
- dE/dx is fairly well known for the deuterons in the energy range from 0 to 300 keV.
The conversion term, dw /dw , which primerly depends on CM LAB
the laboratory angle of emission of alpha particles, 0 , may be a
derived from simple kinematic consideration of the D-T reaction/12/;
2 2 1 / 2
b(Cos & + (1/b -Sin 0))
dw /dw --- (3)
CM LAB 2 2 1 / 2
(1/b -Sin 0)
2
where 1/b =(m /m )<(m +ra )/m )(m /<m +m )+Q/E > ;Q is the Q walue
n a d t d t d t d
of the reaction, E is the incident deuteron energy, m , m , m ,
d d t n
m are masses of deuteron, triton, neutron, and alpha particles a
respectively. Thus, the source strength, N , may be connected to n
the number of alpha particles measured experimentally when R(E , d 0 ) is calculated from the expression given above. Evidently, the
a •
uncertainties associated with the measurement of alphas and the calculation of the anisotropy factor will determine the accuracy
of this evaluation. Exceptionally, when the alpha detector İS positioned at 90 deg to the incident deuteron beam direction then the value of dw /dw at this angle, as clearly seen in fig.l,
CM LAB
is almost independent from the variations in the deuteron energy and thus, the anisotropy factor is not influenced from the non-uniform tritium loading on the target and from the uncertainties in the cross section values. Therefore, for precise monitoring of the alpha particles, especially, in the absence of certain target information, it is recommended that the alpha counter is to be positioned perpendicular to the deuteron beam direction. However,
in some experimental set-ups like ours where the 90 deg configuration is not allowed physically, one should calculate the anisotropy factor for the particular angle under consideration. So, it was calculated in our case (© =176 ) by writing the
a
integral equation (2) in a simple discrete form:
7 CTCE) .n(E) . CdE/dx>
R ( E , 0 ) --- -1 (4) d a S <T(E> .n<E> . (dw /dw ). <dE/dx>
CM LAB
or remembering the homogeneity assumption for tritium loading on the target R C E , d 0 ) = a ^CTCE) . (dE/dx) yT(X<E>.(dw /dw >. (dE/dx) U CM LAB ( 5 > 4 3 Fortunately, the cross section v a l u e » for the H(d, n> He reaction are fairly well known in the 1 i t e rature/21,22 / ,
errors associated with these values, even if considerable, do not fully appear in the value of the anisotropy factor in eq(5) since the cross section occurs in both the numerator and denominator. The same argument also holds for the term (dE/dx). However, the main difficulty comes from the fact that there are no-available experimental data on the rate of energy loss of deuterons in either titanium or tritium for the required energy range. Therefore, in order to estimate the value of (dE/dx) for deuterons in these materials we made use of the experimental data on the rate of energy loss of protons since
(dE/dx) = (dE/dx)
proton(E) deuteron(2E)
( 6)
In addition, we have calculated the value of (dE/dx) for deuterons in titanium tritide (TiT) by assuming that Bragg's law holds (i.e. that the energy loss in a compound is the sum of the energy losses in its seperate constituents).
48 3N
(dE/dx) (dE/dx)
TiT 48+3N Ti 48+3N
(dE/dx) (7)
3
where N is the target loading ratio defined as (Ti/ H ) . For N=1.8 which is the value given in the specifications of the TiT-targets used in our experiments eq(7) reduces to
(dE/dx) = 0 .8989(dE/dx) + 0 . 1010(dE/dx) (8)
TiT Ti T
In table(l) we used the values of (dE/dx) and (dE/dx) given
Ti T
in the reference/12/ and calculated (dE/dx) from eq(8). TiT
2 ± 2 C o u n t i n g the A l p h a P a r t i c l e s
F i g u r e . 2 is a schematic representation of the a.p. m o n i toring system together with the block diagram of the related electronics. The alpha detector used was an Ortec R-Series SBD -2 covered with a thin <1ight-tight) aluminium coating (50 g. cm >
2
on its active surface <300 mm ). The detector was placed in the target chamber 100 cm away from the target to avoid pulse pile- up/19/, and as mentioned earlier, positioned at an angle of 176 deg with respect to the incident deuteron beam direction.
Before attempting to monitor the alpha particles
3 4
associated with the 14 MeV-neutrons from the H(d, n) He reaction, the detection efficiency of the eC-detector (unity) was precisely tested in the actual experimental geometry by replacing
241
the accelerator target with a calibrated alpha source ( Am : 1.52 ^aC İ ). Meanwhile, the energy calibration of the Multi-Channel Analyzer (MCA) used in the caunting system (Canberra 60) was
241
checked by the 5.48 MeV-alphas from the Am-source. On the otherhand, a neutron detector (Ne 102A, plastic scintillator) was placed behind the target and used to detect the genuine alpha particles by detecting the associated neutron pulses in coincidance. In order to minimize the rate of the false coincidance pulses caused by the room scatterred background neutrons reaching the detector, and to provide neutron collimation, the detector was shielded by means of a coaxial iron cylinder, as illustrated in fig.2. To optimize the coincidance count rate,the detector to beam angle was determined during the
measurements. That is, the neutron detector was so positioned that it constituted an angle with the deuteron beam which equals to the neutron emission angle from the target. Furthermore, the resolvinq time of the coincidance unit (Ortec 414A) was adjusted according to the distribution of delay times between the n and the oi signals measured by a Time to Amplitude Convertor (TPHC) un it (<100 ns).
Figure 3 shows three a. p. spectra taken with different targets; each was obtained with a deuteron beam of 100 keV energy and a target current of a few pA. The spectrum at the top was taken with a new tritium target. As expected, the only visible
3 4
peak is due to the alphas from the H(d, n) He reaction.Surprisingly.it exhibits a doublet structure with two energy maximums.The fact that both maximums resulted from the alphas was experimentally verified by counting the alphas in coincidence with the associated 14 MeV-ne u t r o n s . Additionaly, kinematic computations assuming a molecular deuteron beam gave the same energy values for the two alpha peaks corresponding the 50 and 100 k e V-deuterons. So, the higher energy peak is probabily
+
due to d content of the deuteron beam as the alphas from the D-T
2 +
reactions resulting from the d beam component have a higher
2 '
recoil energy into backward direction than the recoiling alphas from the more energetic mono-atomic deuteron beam component /16/. The tail at low energies of this spectrum is probabily due to Coulomb scatterred d e u t o r o n s .
The spectrum of a rather old tritium target is shown in
3 4
reaction, this spectrum also contains the peaks of proton,
3 2 3
triton, and He-particles that result from the H(d, n) He and
2 3
H(d, p) H twin reactions in the target due to the built-up d e u t e r o n s .These particles were identified by comparing this spectrum with the spectrum(c) below which was obtained with a deuterium target without changing the amplifier's gain settings used before. As in the alpha peak of the spectrum(a) it is again seen that all the peaks in the spectra of (b) and (c) show a doublet structure since the deuteron beam is molecular.
2^3 Foil Activation Measurements
For comparison, the absolute 14 MeV neutron yield of the neutron generator was also determined by the foil activation method. This method was applied by irradiating teflon and nickel foils surrounding the Al-target holder as depicted in fig.4. The properties of the activation detectors used are given in
19 18
table(2). The activities due to the both F(n, 2n) F and
58 57
Ni(n, 2n> high threshold O i l MeV) reactions may be counted directly after the irradiation since no competing activities can be established. Thus, the activities of radionuclides produced in these reactions were easily determined by a Ge(Li) detector assembly shown in the block diagram of fig.5. Number of the 14 MeV-neutrons produced in the target during the irradiation was
then calculated from the well known relation
2
$ = 4 TT r . AS / < A • N .t.F(t)) (9)
where r is the source to foil distance, AS is the measured s a t u r a t i o n a c t i v i t y , A is t h e d e c a y c o n s t a n t of t h e p r o d u c e d radionuclide, N is the number of the detector atoms of interest
t
which is determined by weighing the foil, T is the irradiation time, and F(t) is the time correction factor to take into account the variations in the neutron output during the irradiation period ;
A • exp ( A t >
F(t)= --- (1 0) < 1 -exp ( - A t ) C l-exp( - A T )
m
In this formula, t is equal to <T+t -t), where t is the time
w d d
between the end of the irradiation and start of the counting, t m is the measuring time. Some typical results and the related uncertainties in the application of this method are given in the next paragraphs in comparison with those of the APM.
3. Results and Conclusion
It should be emphesized that the a. p. spectra considered in the section<2.2) had been obtained with a 'bare' RSBD when the n-generator was operated with a relatively low accelerating
8 - 1
voltage(100 kV) for a neutron output of the order of 10 n.s In these measurements, response of the RSBD to the charged particles was quite typical concerning the stability of the a.p.spectra o b t a i n e d .B u t , when the neutron output was increased
9 -1
beyond the order of 10 n.s , it was changed in time significantly manifesting itself as a continuous decrease in the detector's gain. Then, accurate analysis of the peaks became almost impossible because a stable spectrum could not be recorded
in the
MCA.
Figure6
shows sucha. situation with the three
spectra taken at successive time intervals during the operation of the n-generator for a constant neutron output. It is clearly seen that 0C -peak shifted in time towards the lower energies of the spectrum. This was atributed to a probable radiation damage in the solid state detector/20/ caused by the intense beam of the heavy perticles (scattered energetic deuterons, alphas, neutrons, etc.,) hitting on its surface. Although deterioration of the detector was temporary in our case, a SBD to be used in the associated particle measurements, even if it is from a ruggedized type, must be sufficiently protected against the heavy particles to avoid such a radiation damage. The usual way of doing this, as widely applied in practice, is to place a thin foilCAl, Ni, etc.,) in front of the detector. However, care should be taken in selecting the foil thickness because it may critically effect the peaks' positions in an a .p .s p e c t r u m . For example, in the case of old tritium targets, it will be difficult to discriminate the alpha particles from the interferring protons
2 3
due to the H(d,n) H reaction if an Al-foil of 2 jim thickness is used. The reason is that the both particles have almost the same energy ( rsj 3 MeV) after passing through the foil. A 5 jam foil,
instead, will even make this discrimination easier as shown in the spectra of fig.7.
On the other hand, besides the advantage of protection, the foil has also a big disadvantage concerning the analysis of the a.p spectra. The energy loss of the low energy particles in the foil make their detection even more difficult since the
background or noise is rather high at these energies. This is 3
especially true for the He-particles because of their relatively heavier masses and lower energies as compared with the other
reaction products. So, they are usually not observed distinquishably in the experimental a. p. spectra.
As noted before, presence of two maximums in the peaks of the a.p.spectra is an advantage as it may be used to monitor the deuteron beam composition of the neutron generator. In refe r e n c e /23/, the alpha particles' yields from the D-T reaction for monatomic and diatomic deuteron ion beams of equal intensity was shown to be 1:2,5 . For the Sames- TB8 generator which had a duoplasmatron ion source, the relative alpha particle yields were 1,67 to 1. When this information was combined it showed that diatomic ions constituted 34% of the total beam.
The uncertainties on the evaluation of the 14 MeV-neutron yield of a neutron generator using the associated particle counting and the foil activation techniques were given in Table 3 and 4, respectively. It should be noted that the greatest uncertaintyC2%) in the application of the APM is related to the solid angle calculation. The reason of this is the difficulty in measuring the distance between the detector and the target, and also the active area of the SBD sensitevely.
Finally, some typical neutron yield values obtained by the two methods are given in table.5. It is seen that most significant discripiency between the results is 8% which is in the limits of the experimental uncertainties.
Acknowledgement
The author wishes to thank to Prof. R. Hecker for his kind interest and encouragement during the work. He wishes to express his gratitudes to Dr. V. Drueke and to Mr. N. Paul for their valuable assistances in performing some measurements, and to Mr. H, Adamietz for his excellent handling the neutron generator during the experiments. The author is finally indebted to both the Turkish Atomic Energy Authority and the International Atomic Energy Agency for financing his stay in the Federal Republic of Germany.
/ 1 / / : ' 7.H . G i b b o n s a n d R . L .M a e k l i n , P h y s . R e v . 1 1 4 , p . 5 7 l 1 1 9 5 9 ) H . A .H o w e , P h y s . R y v . 1 0 9 , p . 2 0 8 3 ( 1 9 5 7 ) / .7 L . F . Ü a n s e n , R . C . J o p s o n , H . M a r k a n d C . L 7 . S w ı f t , N u c l . P h y s . 90, p. 3 9 9 ( 1 9 6 2 ) / 4 / M . C . S c o t t , .7. Nur. 1. E n e r g y , 2 5 , p. 4 0 5 ( 1 9 7 1 ) /5 / M . A . A t t a a n d M . C . S c o t t , J. N u c l . E n e r g y 2 7, p . 8 7 5 ( 1 9 7 3 ) / 6/ P r o c . C o n s u l t a n t e M e e t i n g 1 9 7 3 , I N D C ( N D S ) - 5 6 / n , I A E A / / / L . K u ı j p e r s . K F A - . 7 u e l ı c h 1 3 5 6 , p . 4 2 ( 1 9 7 6 ) / 8 / K . W . G e i g e r a n d G . N . W h y t e , C a n . J. R h y s . 3 7, p . 2 5 6 ( 1 9 5 9 ) / 9 / E . J . A x t o n a n d P . C r o s s , N u c l . E n e r g y 15. p . 2 2 ( 1 9 6 1 ) / 10 / K . E . L a r s s o n , A r k . P h y s . 9, p . 2 9 3 ( 1 9 5 5 > / İ l / L .R u b y a n d R . B .C r a w f o r d , N u c l . I n s t r u m . M e t h . 2 4, p . 4 1 3 ( 1 9 6 3 ) / 1 2 / T . R . F e w e l l , N u c l . I n s t r u m . M e t h . 6 1 , p . 6 1 ( 1 9 6 8 ) / 1 3 / J .B e n v e n i s t e , A .C .M i t c h e l 1, C . D . S c h r a d e r a n d J. H. Z e n g e r , N u c l . I n s t r u m . M e t h . 7, p . 3 0 6 ( 1 9 6 0 ) / İ l / R . C e d e r l a n d , A . H o r n a n d M . S c o l n i c k , N u c l . I n s t r u m . M e t h . 13, p . 3 0 5 ( 1 9 6 1 ) / 15 / J .C .R o b e r t s o n a n d K . J . Z i e b a , N u c l . I n s t r u m . M e t h . 4 5, p . 1 7 9 ( 1 9 0 6 ) / 1 O / N . E . H e r t e l a n d B . W . W e h r i n g , N u c 1 . I n s t r u m .M e t h . 1 7 2 , p . 5 0 1 < 1 9 8 0 ) ! 1 7 ! N . E v a n s , I . R . B r e a r l e y a n d M . C . S c o t t , N u c l . I n s t r u m . M e t h . 1 6 0 , p . 4 6 5 ( 1 9 7 9 ) / 1 8 / P . K u i i p e r a n d D . S p a a r g a r e n , N u c 1 . I n s t r u m .M e t h . 9 8 , p . 1 7 3 ( 1 9 7 2 )
/19/ U .Fri t s e h e r , F.Kappler and D.Rusch, N u c l .Instrum.Meth. 153, p.563 (1978)
/20/ J.B.England, Techniques in Nuclear Structure Physics, MacMillan Press Ltd. London, p.74 (1974)
/21/ H.Liskien and A.Paulsen, Nuclear Data Tables, 11, N o . 7 , p.601 (1973)
12.21 R.T.Santoro and J.Barish, Nucl. Sci. Eng. 59, p.189
(1976)
1221 H .M iL o e b e n s tein and Y.Gazit, Nue 1 . I n s t r u m .M e t h . ,108,p .387 (1972)
Figure Captions
Fig . 1 systems of the deuteron
The ratio of solid angles in the center of mass and lab into which the alpha particle is produced as a function alpha particle lab angle, 0 , for several incident e n e r g i e s , E .
a d
F i g . 2 Schematic representation of the associated particle counting system and the block diagram of electronic circuitry used in monitoring the alpha particles. The arrows indicate the flow of information through the circuit.
F i g . 3 The pulse hight spectra obtained with the ruggedized silicon surface barrier detector during the operations of the n- generator with different targets at a deuteron beam energy of 100 keV. (a) New tritium target, (b) Old tritium target, (c) Deuterium target.
F i g . 4 Arrangement used for the measurement of the neutron source output by irradiating foil detectors.
F i g . 5 The block diagram of the electronic circuitry used for measuring the saturation activities from the irradiated foils. Fig.6 The alpha peak shift in the pulse height spectrum of a bare RSBD caused by the radiation damage of the heavy particles
10
in the case of high neutron flux(at the order of 10 )
F i g . 7 The pulse hight spectra obtained with a RSBD during the operation of the neutron generator at 300 keV deuteron beam energy when there was a protecting Al-foil of, (a) 2 jim or (b) 5
um thicness in front of the detector.
Table Captions T a b l e . Table. Table. T a b 1e . Table.
Experimental values used in the calculations.
Properties of the activation foil detectors used in the measurements of the 14 MeV neutron source output. Estimated errors in the application of the APM to determine the 14 MeV neutron source output.
Estimated errors in the application of the foil activation method to determine the 14 MeV neutron source output.
Some comparative results of the APM and the foil activation measurements.
0 ( D E G R E E )
CM tî>
(A)
(B)
e* < à. > m 4 9 0
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i
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a ch. 530 *t.C IHT » 3 ) 0 ) » ÇFS • • » * .* üt*( e )
HEfiSUREMENT C M-TAGMRD 944 ) 3IF>
(A)
(B)
Ed o/i*rr CdE/dx) T1 ( dE/dx) . ( dE/d x )TİT dwen /dwla b OceV) ( b/s te r a d ) ng/cmkeV , Bg/cı»keV ,
keV , u g /c n f o r 9 s l 76* a 10 1 ,5 ı o ' 4 82 660 1 3 8 ,3 5 0 ,9 6 1 20 6 ,3 1 0 " 5 115 786 1 8 2 ,5 6 0 ,9 1 7 30 2 ,2 İO" 2 161 896 217 0 ,8 9 9 <♦0 5 ,7 İO' 2 163 980 265 0 ,8 8 6 50 1 ,1 10* * 183 1066 2 6 9 ,9 6 0 ,8 7 1 60 1 ,7 3 1 0 *1 200 1116 2 9 2 ,2 9 0 ,8 5 9 70 2 ,6 3 1 0 * 1 216 1172 3 1 0 ,7 6 0 ,8 6 8 8o 3 ,1 1 0 *1 226 1216 3 2 5 ,9 7 0 ,8 3 8 90 3 ,6 1 0 "1 236 1250 3 3 8 ,6 0 0 ,8 2 9 100 3 ,9 5 1 0 *1 265 1270 3 6 8 ,5 0 0 ,8 2 0 110 4 , o ı o * 1 251 1286 3 5 5 ,3 1 0 ,8 1 2 120 3 ,9 5 1 0 * 1 257 1286 3 6 0 ,7 0 0 ,8 0 6 130 3 ,7 5 1 0 " 1 262 1278 3 6 6 ,5 9 0 ,7 9 7 160 3 ,5 1 0 " 1 266 1268 3 6 7 ,1 8 0 ,7 9 0 150 3 ,2 1 0 '1 270 1256 3 6 9 ,5 6 0 ,7 8 3 160 2 ,9 1 0 "1 273 1260 3 7 0 ,6 6 0 ,7 7 7 170 2 , 6 5 ’ 1 0 "1 276 1226 3 7 1 ,7 2 0 ,7 7 0 180 2 ,5 1 0 " 1 277 1206 3 7 0 ,6 0 0 ,7 6 6 190 2 ,3 İO* 1 279 1186 3 7 0 ,6 0 0 ,7 6 0 200 2 ,1 İO" 1 280 1166 3 6 9 ,6 6 0 ,7 5 6 Tabie.1 m a t e r i a l t h i c k n e s s ( m m ) r e a c t i o n o f i n t e r e s t i s o t o p i c a b u n d a n c e w h a l f -l i f e ^ - e n e r g y ( M e V ) T ’- a b u n d a n e e . ( * ) F ( t e f l o n ) 1 . 0 1 9 F ( n , 2 n ) 1 8 F 1 0 0 . 0 1 0 9 . 7 m i n 0 , 5 1 1 1 9 4 N i 0 , 3 5 8 N i ( n , 2 n ) 5 7 N i 6 7 , 9 3 6 . 0 h 1 , 3 7 8 6
1 ) Uncertainties in the evaluation of R(Ed,U) due tos
a) non-analysed deuteron beam (assuming 34% Dl+66% D2)
± 1.0%
b) non-iniform tritium distribution in
the TiT~ta<rget + 0.5%
c) scattering of deuterons from the target
without causing reaction 4* 0.025%
d) variations in the «-emission angle# neqli qi ble
2) U ncertainties in the <r (E) and dE/dx values + 5.0%
3) Uncertainties in the calculation of the «-
detector solid angle 4- 2.0%
4) Uncertainties in counting the alphas caused
by the interferences from the competing reactions' products(excluding deuterium
b u i 11— u p ) ± 0.5%
Total + 5.5%
Tabi e.3
İ ) Unc e r t a i n t ies in di stances between the center of the
the measurements of the foil detectors
1 tritium target the and the 4 0.2% 2) Uncertainty in measurements
the saturation activity
£ 3.0%
3) Uncertai nti es i n the cross-section values £ 5.0%
4) Uncertai nti es
detectors
i n weighting the foil
£ 0.1 %
5) U n c e r t a i n t ies i n the measurements of time £ 0.01%
Ik MeV-Neutron Yield Target (TiT) Deuteron Energy (keV) Targe t Current (uA) Foil Thickness (ura)
from the APM (n.s”1 )
from the foil activation (n.s” 1 )