⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus
The reaction of two-particles nitrogen nucleus photodisintegration with ⁷Li and ⁷Be in the final state are investigated using diffusion chamber, which is placed into the magnetic field and filled with 15% nitrogen and helium compound. Chamber was irradiated with gamma rays from electron accelerator....
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| Zitieren: | ⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus / M.S. Glaznev, E.S. Gorbenko, A.L. Bespalov, R.T.Murtazin, A.F. Khodyachikh // Вопросы атомной науки и техники. — 2014. — № 5. — С. 31-34. — Бібліогр.: 8 назв. — англ. |
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irk-123456789-805022015-04-19T03:01:57Z ⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus Glaznev, M.S. Gorbenko, E.S. Bespalov, A.L. Murtazin, R.T. Khodyachikh, A.F. Ядерная физика и элементарные частицы The reaction of two-particles nitrogen nucleus photodisintegration with ⁷Li and ⁷Be in the final state are investigated using diffusion chamber, which is placed into the magnetic field and filled with 15% nitrogen and helium compound. Chamber was irradiated with gamma rays from electron accelerator. The method of extraction of the reaction from the background two-particle reactions with multi-charged ions in the final state was created. Differential, full and integral cross-section of the reaction were measured. The results were compared with experimental data, where the full isotope ⁷Be output at ¹⁴N photodisintegration reaction was measured Реакция двухчастичного фоторасщепления ядра азота с выходом изотопов ⁷Li и ⁷Be исследована с помощью диффузионной камеры, заполненной 15% смесью азота с гелием и помещенной в магнитное поле. Камера облучалась тормозными γ-квантами от линейного ускорителя. Разработан метод выделения реакции из фоновых двухчастичных реакций с многозарядными ионами в конечном состоянии. Измерены дифференциальные, полные и интегральное сечения реакции. Проведено сравнение результатов с данными эксперимента, в котором измерен полный выход изотопа ⁷Be при фоторасщеплении ядра ¹⁴N . Реакцiю двочасткового фоторозщеплення азоту з виходом iзотопiв ⁷Li та ⁷Be дослiджено за допомогою дифузiйної камери, яку заповнено 15% сумiшшю азоту та гелiю i розмiщено у магнiтному полi. Камера опромiнювалася гальмiвними γ-квантами вiд лiнiйного прискорювача. Розроблено метод видiлення реакцiї з фонових двочасткових реакцiй з багатозарядними iонами в кiнцевому станi. Вимiряно диференцiйнi, повнi та iнтегральне перерiзи реакцiї. Проведено порiвняння результатiв з даними експерименту, в якому вимiряно повний вихiд iзотопу ⁷Be при фоторозщепленнi ядра ¹⁴N . 2014 Article ⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus / M.S. Glaznev, E.S. Gorbenko, A.L. Bespalov, R.T.Murtazin, A.F. Khodyachikh // Вопросы атомной науки и техники. — 2014. — № 5. — С. 31-34. — Бібліогр.: 8 назв. — англ. 1562-6016 PACS: 25.20.-x http://dspace.nbuv.gov.ua/handle/123456789/80502 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Ядерная физика и элементарные частицы Ядерная физика и элементарные частицы |
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Ядерная физика и элементарные частицы Ядерная физика и элементарные частицы Glaznev, M.S. Gorbenko, E.S. Bespalov, A.L. Murtazin, R.T. Khodyachikh, A.F. ⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus Вопросы атомной науки и техники |
| description |
The reaction of two-particles nitrogen nucleus photodisintegration with ⁷Li and ⁷Be in the final state are investigated using diffusion chamber, which is placed into the magnetic field and filled with 15% nitrogen and helium compound. Chamber was irradiated with gamma rays from electron accelerator. The method of extraction of the reaction from the background two-particle reactions with multi-charged ions in the final state was created. Differential, full and integral cross-section of the reaction were measured. The results were compared with experimental data, where the full isotope ⁷Be output at ¹⁴N photodisintegration reaction was measured |
| format |
Article |
| author |
Glaznev, M.S. Gorbenko, E.S. Bespalov, A.L. Murtazin, R.T. Khodyachikh, A.F. |
| author_facet |
Glaznev, M.S. Gorbenko, E.S. Bespalov, A.L. Murtazin, R.T. Khodyachikh, A.F. |
| author_sort |
Glaznev, M.S. |
| title |
⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus |
| title_short |
⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus |
| title_full |
⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus |
| title_fullStr |
⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus |
| title_full_unstemmed |
⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus |
| title_sort |
⁷be generation in the reaction of two-particle photodisintegration of ¹⁴n nucleus |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2014 |
| topic_facet |
Ядерная физика и элементарные частицы |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/80502 |
| citation_txt |
⁷Be generation in the reaction of two-particle photodisintegration of ¹⁴N nucleus / M.S. Glaznev, E.S. Gorbenko, A.L. Bespalov, R.T.Murtazin, A.F. Khodyachikh // Вопросы атомной науки и техники. — 2014. — № 5. — С. 31-34. — Бібліогр.: 8 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-06T04:30:52Z |
| last_indexed |
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| fulltext |
7Be GENERATION IN THE REACTION OF TWO-PARTICLE
PHOTODISINTEGRATION OF 14N NUCLEUS
M.S.Glaznev, E.S.Gorbenko, A.L.Bespalov, R.T.Murtazin∗,
A.F.Khodyachikh
National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine
(Received July 1, 2014)
The reaction of two-particles nitrogen nucleus photodisintegration with 7Li and 7Be in the final state are investigated
using diffusion chamber, which is placed into the magnetic field and filled with 15% nitrogen and helium compound.
Chamber was irradiated with gamma rays from electron accelerator. The method of extraction of the reaction from
the background two-particle reactions with multi-charged ions in the final state was created. Differential, full and
integral cross-section of the reaction were measured. The results were compared with experimental data, where the
full isotope 7Be output at 14N photodisintegration reaction was measured.
PACS: 25.20.-x
1. INTRODUCTION
Photodisintegration reactions of light nuclei are
interesting in nuclear physics. At low energies they
give information about few-nucleon systems behav-
ior and upper states of nuclei in the giant reso-
nance area [1]. Photonuclear reactions are caused by
the well known electromagnetic interactions. That’s
why their investigation gives important information
about fundamental properties of nuclear forces, such
as nucleon-nucleon interactions and exchange meson
currents for nuclear physics [2].
Investigation of lithium and beryllium isotopes in-
teraction at low energies is important for understand-
ing of certain astrophysics and inner stars structure
problems [3]. But experimental investigation of their
interactions at low energies is difficult. That’s why
reverse reactions, such as photodisintegration of nu-
clei with listed isotopes generation, are useful for un-
derstanding of existent processes. Photonuclear re-
actions are important factor in nuclear fusion and
astrophysical processes [3, 4].
The monitoring of radionuclide content in near-
ground atmospheric shell is an important part of in-
formation about nuclear reactions. 7Be short-lived
isotope gives significant contribution in air radioac-
tivity. It is considered that in the atmosphere 7Be
generates in reactions of cosmogenic and solar pro-
ton and neutron interaction with nitrogen and oxy-
gen nuclei[5]. But it is shown in paper [6], that pho-
tonuclear reactions, which were not considered until
now mainly because of a lack of experimental data in
the literature, can give significant contribution into
7Be isotope generation. 7Be nucleus is interesting
not only from the perspective of its radioactive influ-
ence on the biological systems, but as an indicator of
a pollutants accumulation by environment.
In this paper the results of research findings of
photodisintegration reaction of 14N nucleus with 7Li
and 7Be in the final state are shown.
2. EXPERIMENTAL METHOD
Experiment was held on a diffusion chamber,
placed in the 15 kOe magnetic field, exposed with
bremsstrahlung from Kharkov 300MeV electron lin-
ear accelerator with 150MeV peak energy. The
chamber filled with 15% nitrogen with helium mix-
ture at pressure of 2 at. Nitrogen nucleus photodis-
integration event was separated visually with ease.
Low pressure in the chamber and target and detec-
tor matching made possible to investigate reactions of
nitrogen photodisintegration basically from reaction
threshold. The reactions with two particles in the
final state were selected for studying. The conclu-
sion about particle stopping in the working space of
the chamber and about that fact if its mass is heav-
ier than deuteron mass was made by track density
changing. The reactions of two-particle photodisin-
tegration of nucleus listed below are matching these
criteria:
γ + 14N → 7Li+ 7Be , (1)
γ + 14N → 4He+ 10B , (2)
γ + 14N → 3He+ 11B , (3)
γ + 14N → 3H + 11C . (4)
Only in the fourth reaction tritium ran out the work-
ing space of the chamber, all products of the other
reactions stopped in the chamber.
∗Corresponding author E-mail address: rumurtazin@gmail.com
ISSN 1562-6016. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2014, N5 (93).
Series: Nuclear Physics Investigations (63), p.31-34.
31
The reaction was considered as two-particle one
if the ions and γ-quantum momentums were situated
in the same plane. An angle of the tracks coinci-
dence with the plane was measured with 10◦ accu-
racy for every event. An event was rejected if this
angle was above 15◦. Since light ions have differ-
ent energies, then it is impossible to identify them
by ionization. Width and density of the heavy ions
tracks almost didn’t distinguish from those parame-
ters of the light ions. Calculations show that in the
reactions 2...4 a light ion with any γ-quantum energy
and outlet angle has longer track. In the first reac-
tion the path of the 7Li ion is shorter then the pass
of the 7Be ion at γ-quantum energy less than 2MeV
above reaction threshold and at outlet angle greater
than 90◦. The main criteria for reaction identification
were track length data, scaled to the standard con-
ditions. During scaling it is also changes of density
of the mixed gases because of temperature changes
with increasing the distance between track and me-
dian plane counted. An obtained value was called
track path length.
Because of different charges and masses of ions, it
would be excepted a difference in track path lengths
ratio η in the reactions. With assumption that all
events refer to the first reaction there was distribu-
tion of η calculated. For this purpose the kinetic en-
ergy and the absolute value of momentum of the first
ion was defined from its path using path-to-energy
relation tables. The momentum direction in space
was defined from the track coordinates. Since the
reaction is two-particle one, then the γ-quantum en-
ergy and the kinematical parameters of the second
ion was calculated using the parameters of the first
one. From the kinetic energy of the second ion it is
possible to get its path and calculate the value of η
On Fig.1 events distribution from η is shown
with filled circles. Thus if η is lower 2.5, then
an event concerns to the first reaction. Com-
paring experimentally measured η and calculated
one it is possible to determine the first reaction.
0 2 4 6 8 10
0
400
800
1200
N
Fig.1. Number of events distribution versus η
The filled triangles show the second reaction events
distribution. The distribution begins at η value
greater then 2.5 and continues till 7.0. The distribu-
tion for the third reaction is shown empty circles. It
begins at η greater 2.5 and lasts till 8.0. The events
of the second and the third reactions are situated in
this interval. Comparing experimentally measured η
and calculated one it is possible to determine these
reactions. The curve with empty triangles shows the
fourth reaction distribution. 3H ion is single-charged
therefore it has much longer path then 3He ion with
the same energy. Therefore the curve starts at η = 6
and lasts till η = 30.
An event considered identificated, if the measured
ratio matched with calculated one within the limits
of errors. But because of measurement errors of path
lengths of heavy ions, the ratio comparison not al-
ways gave an opportunity to identificate the reaction.
That’s why the other data were used. The length
of the short measured track with its calculated value
was compared. It is possible to determine γ-quantum
energy from the parameters of each ion. For each one
of the four reactions the difference δE = E1−E2 was
calculated, where E1 is a γ-quantum energy, deter-
mined from the longer track, and E2 is from the short
one. The lowest value of δE determined the reaction,
if the previous two criteria didn’t allow doing this.
Diffusion chamber was placed in the magnetic
field. Momentum, which is defined from track’s cur-
vature, is an average of its length. Its compari-
son with an average momentum determined by path,
helps to identificate reaction if the track path length
is enough. Because of ion recharge with medium, the
ion charge is decreasing. According to tables [7] the
proton and ion path length ratio at equal kinetic en-
ergy is greater on one nucleon then 5MeV equal to
A/z2, where A – atomic number of the ion, z – its
charge. Ion path increasing comparing to A/z2 mul-
tiplied proton path at low energies of ion can be ex-
plained by ion charge decreasing. Paths ratio allowed
determining coefficients of charge decreasing for all
ions. They don’t have much changes with energy and
on average is equal to 0.85 and 0.71 respectively for
helium and lithium ions at energies to 2MeV . The
charge decreasing is considered in momentum deter-
mination by track curvature.
Path-energy relation [7] for light ions was exam-
ined by comparing with the experimental data and
the data from literature. Energy of heavy ions was
determined from light ions data. An energy depen-
dence form path length changing was plotted. A sat-
isfactory correlation of dependence with data was ob-
tained [7] at energies up to 2MeV .
An error of a track length measurement is
0.025 cm, of a noncomplanar angle 10◦, of a polar
angle of the long tracks 1.0◦ and 2.0◦ for short tracks.
3. THE RESULTS OF THE EXPERIMENT
The γ-quantum energy was determined from kine-
matical parameters of the light ion, which were mea-
sured with the better accuracy due to longer track.
32
The events considered to the first reaction were dis-
tributed by the γ-quantum energy. The histograms
with 1MeV step were plotted. All results are rep-
resented with points, placed in the middle of a step.
Errors are statistical. In order to get full cross-section
a calculated γ-quantum spectrum was taken. It has
a shiff form. A soft component was removed by the
beryllium filter with 2.5 radiation unit length.
Full cross-section dependence versus energy is
shown on Fig.2. Near threshold the cross-section is
increasing rapidly, then it is decreasing smoothly with
energy. This reaction cross-section didn’t measured
earlier. In the energy interval from 28 to 39MeV an
integral cross-section σint = (1.49 ± 0.21)mbn·MeV
26 28 30 32 34 36 38 40
0,0
0,2
0,4
, m
bn
E , MeV
Fig.2. Full cross-section dependence versus energy
The differential cross-sections are plotted ver-
sus angle in the centre-of-mass system with 20◦
step in Fig.3, using events in all energy in-
terval. The points are placed in the mid-
dle of a histogram. The errors are statistical.
0 30 60 90 120 150 180
0
4
8
12
d
/d
, a
rb
itr
ar
y
un
its
, degree
Fig.3. The differential cross-section
The angle cross-section dependence is not
isotropic an it has a distinct asymmetry relative to
90◦, which is caused by electrical quadrupole transi-
tion contribution. The total cross-section dependence
with respect to the polar angle θ approximated with
function:
dσ/dΩ = a+ b · sin2 θ + c · sin2 θ cos θ
As the result, the coefficients were obtained: a =
2.2± 1.1, b = 3.8± 1.7, c = 5.9± 2.4.
4. THE RESULTS AND DISCUSSIONS
In paper [8] aluminum nitride targets, con-
tained 0.3 g/cm2 of nitrogen, were radiated with
bremsstrahlung from electrons with energies 40, 50,
60, 70, 80 and 90MeV . The converter was a tan-
talum bars with total thickness 4mm. The expo-
sure lasted for 12.5 hours with 1mkA current. The
bremsstrahlung spectrum was calculated for every
energy using electron transmission through the con-
verter and the target modeling. The target activ-
ity, corresponded to unstable 7Be nuclei disintegra-
tion from unknown reactions 14N(γ, X)7Be for all
six electron energies, was measured.
Using the reaction 14N(γ,7 Li)7Be cross-section
and the bremsstrahlung spectra for each electron en-
ergy, the number of 7Be nuclei N0 was obtained,
which were generated in the target at the time
of each exposition. The number of 7Be nuclei,
which are disintegrating per second N = λN0e
−λt,
where λ = ln2/T0, half-life period T0 = 53.3 days.
Since t≪T0, then e−λt≈1, and the activity of the
target N = λN0. At energy of the electrons
40MeV the calculated activity is 2.4 kBq, which is
2.5 times as much as experimental value. Calcu-
lated activity versus electron energy dependence is
shown with solid curve in Fig.4. The points shows
the results of activity measurements in paper [8].
The curve is normalized on the first point. The
increasing disagreement with energy testifies that
14N(γ,7 Li)7Be is not single photonuclear reaction
on nitrogen, in which 7Be nucleus is generation.
40 50 60 70 80 90
0
3
6
9
12
15
A
ct
iv
ity
, k
B
q
Ee, MeV
Fig.4. 7Be activity
Authors express their sincere gratitude to
O.S.Deiev and B.I. Shramenko for the useful discus-
sion of the paper results and bremsstrahlung spectra
submitting.
33
References
1. V.V.Varlamov, B.S. Ishkhanov, I.M.Kapitonov.
Photonuclear reactions. Present status of exper-
imental data. Moscow: MGU, 2008, 304 p. (in
Russian).
2. Q. Ellerkmann, W. Sanhas, et al. Integral equa-
tion calculations for the photodisintegration pro-
cess 4He(γ, n)3He // Phys. Rev. 1996, v. C 53,
p. 2638-264.
3. Y.Nagai, S.Migamoto, S.Amano, et al. Experi-
mental study of nuclear astrophysics with photon
beams // The 10th international symposium on
original of matter and evolution of Galaxies. AIP
Conf. Proc. 2010, p. 72-81.
4. T. Shima. Experimental nuclear astrophysics
with real photon beams // The 10th international
symposium on original of matter and evolution of
Galaxies. AIP Conf. Proc. 2010, p. 207-214.
5. M.Yoshimori. Production and behavior of beryl-
lium 7 radionuclide in the upper atmosphere //
Advances in space research. 2005, v. 36, p. 922-
926.
6. M.V.Bezuglov, V.S.Malyshevsky,
T.V.Malykhina, et al. Photonuclear chan-
nel of cosmogenic 7Be production in the
terrestria atmosphere // Yad. Fiz. 2012, v. 75,
N4, p. 427-443 (in Russian).
7. O.F.Nemets, Yu.V.Gofman. Spravochnik po
yadyernoi fizikye. Kiev: ”Naukova Dumka”, 1975
(in Russian).
8. A.N. Dovbnya, O.S.Deyev, V.A.Kushnir, et al.
Experimental cross-section evaluation data for
7Be photoproduction by 12C, 14N , 16O nuclei
in the energy range between 40. . . 90 MeV //
Problems of Atomic Science and Technology. Ser.
“Nuclear Physics Investigations”. 2013, N6(88),
p. 192-195.
ÎÁÐÀÇÎÂÀÍÈÅ 7Be  ÐÅÀÊÖÈÈ ÄÂÓÕ×ÀÑÒÈ×ÍÎÃÎ ÔÎÒÎÐÀÑÙÅÏËÅÍÈß
ßÄÐÀ 14N
Ì.Ñ.Ãëàçíåâ, Å.Ñ.Ãîðáåíêî, À.Ë.Áåñïàëîâ, Ð.Ò.Ìóðòàçèí, À.Ô.Õîäÿ÷èõ
Ðåàêöèÿ äâóõ÷àñòè÷íîãî ôîòîðàñùåïëåíèÿ ÿäðà àçîòà ñ âûõîäîì èçîòîïîâ 7Li è 7Be èññëåäîâàíà ñ
ïîìîùüþ äèôôóçèîííîé êàìåðû, çàïîëíåííîé 15% ñìåñüþ àçîòà ñ ãåëèåì è ïîìåùåííîé â ìàãíèòíîå
ïîëå. Êàìåðà îáëó÷àëàñü òîðìîçíûìè γ-êâàíòàìè îò ëèíåéíîãî óñêîðèòåëÿ. Ðàçðàáîòàí ìåòîä âûäå-
ëåíèÿ ðåàêöèè èç ôîíîâûõ äâóõ÷àñòè÷íûõ ðåàêöèé ñ ìíîãîçàðÿäíûìè èîíàìè â êîíå÷íîì ñîñòîÿíèè.
Èçìåðåíû äèôôåðåíöèàëüíûå, ïîëíûå è èíòåãðàëüíîå ñå÷åíèÿ ðåàêöèè. Ïðîâåäåíî ñðàâíåíèå ðåçóëü-
òàòîâ ñ äàííûìè ýêñïåðèìåíòà, â êîòîðîì èçìåðåí ïîëíûé âûõîä èçîòîïà 7Be ïðè ôîòîðàñùåïëåíèè
ÿäðà 14N .
ÓÒÂÎÐÅÍÍß 7Be Ó ÐÅÀÊÖI� ÄÂÎ×ÀÑÒÊÎÂÎÃÎ ÔÎÒÎÐÎÇÙÅÏËÅÍÍß ßÄÐÀ 14N
Ì.Ñ.Ãëàçí¹â, �.Ñ.Ãîðáåíêî, O.Ë.Áåñïàëîâ, Ð.Ò.Ìóðòàçií, O.Ô.Õîäÿ÷èõ
Ðåàêöiþ äâî÷àñòêîâîãî ôîòîðîçùåïëåííÿ àçîòó ç âèõîäîì içîòîïiâ 7Li òà 7Be äîñëiäæåíî çà äîïîìî-
ãîþ äèôóçiéíî¨ êàìåðè, ÿêó çàïîâíåíî 15% ñóìiøøþ àçîòó òà ãåëiþ i ðîçìiùåíî ó ìàãíiòíîìó ïîëi.
Êàìåðà îïðîìiíþâàëàñÿ ãàëüìiâíèìè γ-êâàíòàìè âiä ëiíiéíîãî ïðèñêîðþâà÷à. Ðîçðîáëåíî ìåòîä âèäi-
ëåííÿ ðåàêöi¨ ç ôîíîâèõ äâî÷àñòêîâèõ ðåàêöié ç áàãàòîçàðÿäíèìè iîíàìè â êiíöåâîìó ñòàíi. Âèìiðÿíî
äèôåðåíöiéíi, ïîâíi òà iíòåãðàëüíå ïåðåðiçè ðåàêöi¨. Ïðîâåäåíî ïîðiâíÿííÿ ðåçóëüòàòiâ ç äàíèìè åêñ-
ïåðèìåíòó, â ÿêîìó âèìiðÿíî ïîâíèé âèõiä içîòîïó 7Be ïðè ôîòîðîçùåïëåííi ÿäðà 14N .
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