Recent results in accelerator mass-spectrometer construction at BINP
Present status of the accelerator mass spectrometry facility at BINP is described. The results of first experiments for ¹⁴C selection and background measurements are presented.
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| Zitieren: | Recent results in accelerator mass-spectrometer construction at BINP / S.A. Rastigeev, N.I. Alinovsky, A.D. Goncharov, V.F. Klyuev, S.G. Konstantinov, A.M. Kryuchkov, V.V. Parkhomchuk, M.V. Petrichenkov, V.B. Reva // Вопросы атомной науки и техники. — 2008. — № 5. — С. 8-11. — Бібліогр.: 6 назв. — англ. |
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irk-123456789-1114542017-01-11T03:02:26Z Recent results in accelerator mass-spectrometer construction at BINP Rastigeev, S.A. Alinovsky, N.I. Goncharov, A.D. Klyuev, V.F. Konstantinov, S.G. Kryuchkov, A.M. Parkhomchuk, V.V. Petrichenkov, M.V. Reva, V.B. Физика и техника ускорителей Present status of the accelerator mass spectrometry facility at BINP is described. The results of first experiments for ¹⁴C selection and background measurements are presented. Розглянуто поточний стан робіт з створення у ІЯФ ім. Г.І. Будкера прискорювального мас-спектрометричного комплексу (AMS). Наведено результати перших експериментів по виділенню ¹⁴С і виміру фону. Рассмотрено текущее состояние работ по созданию в ИЯФ им. Г.И. Будкера ускорительного масс-спектрометрического комплекса (AMS). Приведены результаты первых экспериментов по выделению ¹⁴С и измерению фона. 2008 Article Recent results in accelerator mass-spectrometer construction at BINP / S.A. Rastigeev, N.I. Alinovsky, A.D. Goncharov, V.F. Klyuev, S.G. Konstantinov, A.M. Kryuchkov, V.V. Parkhomchuk, M.V. Petrichenkov, V.B. Reva // Вопросы атомной науки и техники. — 2008. — № 5. — С. 8-11. — Бібліогр.: 6 назв. — англ. 1562-6016 PACS: 29.30.Aj http://dspace.nbuv.gov.ua/handle/123456789/111454 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Физика и техника ускорителей Физика и техника ускорителей |
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Физика и техника ускорителей Физика и техника ускорителей Rastigeev, S.A. Alinovsky, N.I. Goncharov, A.D. Klyuev, V.F. Konstantinov, S.G. Kryuchkov, A.M. Parkhomchuk, V.V. Petrichenkov, M.V. Reva, V.B. Recent results in accelerator mass-spectrometer construction at BINP Вопросы атомной науки и техники |
| description |
Present status of the accelerator mass spectrometry facility at BINP is described. The results of first experiments for ¹⁴C selection and background measurements are presented. |
| format |
Article |
| author |
Rastigeev, S.A. Alinovsky, N.I. Goncharov, A.D. Klyuev, V.F. Konstantinov, S.G. Kryuchkov, A.M. Parkhomchuk, V.V. Petrichenkov, M.V. Reva, V.B. |
| author_facet |
Rastigeev, S.A. Alinovsky, N.I. Goncharov, A.D. Klyuev, V.F. Konstantinov, S.G. Kryuchkov, A.M. Parkhomchuk, V.V. Petrichenkov, M.V. Reva, V.B. |
| author_sort |
Rastigeev, S.A. |
| title |
Recent results in accelerator mass-spectrometer construction at BINP |
| title_short |
Recent results in accelerator mass-spectrometer construction at BINP |
| title_full |
Recent results in accelerator mass-spectrometer construction at BINP |
| title_fullStr |
Recent results in accelerator mass-spectrometer construction at BINP |
| title_full_unstemmed |
Recent results in accelerator mass-spectrometer construction at BINP |
| title_sort |
recent results in accelerator mass-spectrometer construction at binp |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2008 |
| topic_facet |
Физика и техника ускорителей |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/111454 |
| citation_txt |
Recent results in accelerator mass-spectrometer construction at BINP / S.A. Rastigeev, N.I. Alinovsky, A.D. Goncharov, V.F. Klyuev, S.G. Konstantinov, A.M. Kryuchkov, V.V. Parkhomchuk, M.V. Petrichenkov, V.B. Reva // Вопросы атомной науки и техники. — 2008. — № 5. — С. 8-11. — Бібліогр.: 6 назв. — англ. |
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Вопросы атомной науки и техники |
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| fulltext |
RECENT RESULTS IN ACCELERATOR MASS-SPECTROMETER
CONSTRUCTION AT BINP
S.A. Rastigeev, N.I. Alinovsky, A.D. Goncharov, V.F. Klyuev, S.G. Konstantinov,
A.M. Kryuchkov, V.V. Parkhomchuk, M.V. Petrichenkov, V.B. Reva
BINP, Novosibirsk, Russia
E-mail: S.A.Rastigeev@inp.nsk.su
Present status of the accelerator mass spectrometry facility at BINP is described. The results of first experiments
for 14C selection and background measurements are presented.
PACS: 29.30.Aj
1. INTRODUCTION
The accelerator mass spectrometry is an ultra-
sensitive method of isotopic analysis for archaeology,
environment science and another fields. It’s based on
measurements of the ratio between isotopes.
The AMS system consists of the ion source, low en-
ergy channel, tandem accelerator and high-energy chan-
nel [1,2]. The tandem accelerator is a folded type verti-
cal machine. The low energy beam line is used for ini-
tial isotopes selection. The tandem accelerator is applied
for rejection of the molecular ions and of course for
obtaining necessary beam energy for radioisotopes de-
tector. The high-energy beam line is used for the subse-
quent ions selection and for radioisotopes detection.
The negative ion beam is horizontally extracted from
the ion source [3]. Then the beam is vertically injected into
the low energy accelerating tube through injection channel
with 90° LE magnet. The negative ions are accelerated to
the positively charged high voltage terminal and stripped to
plus charge state in magnesium vapors stripper. Then they
pass through the 1800 electrostatic bend and then again are
accelerated vertically into the high energy accelerating tube
to the ground potential. The extracted radioisotope ions are
horizontally put to the final detector through high-energy
channel with 90° HE magnet.
Now the AMS facility is being constructed at BINP.
The construction works in specialized building for AMS
(Dating Center) will be finished next year. The accelera-
tor will be placed into underground room with radiation
shielding. The inner size of the room will be 6x6x7.5 m.
In this Center equipped with radiation shielding, we
plan to use ~ 2MV tandem voltage for optimum 3+
charge state transmission.
The most distinguishing features of our AMS ma-
chine is the use of the middle energy separator of ion
beams and the magnesium vapors target as a stripper.
The aim of this innovations was described in details
earlier [1].
2. PRESENT STATUS
The main parts of tandem accelerator have been in-
stalled and in operation. The 500 kV terminal voltage
was achieved in air medium (without insulating gas).
The electrical power required in the HV terminal is gen-
erated by the 500 W gaseous turbine.
The previous experimental results have demon-
strated, that the negative carbon ion beam can be accel-
erated and stripped into high voltage terminal of BINP
AMS facility. The charge state fractions of carbon beam
stripped by the magnesium vapors stripper was obtained
[4]. Recently, the first accelerated beam was observed at
the exit of HE magnet [5]. The beam was focused to a
spot diameter of about 3 mm on the detector surface.
The photo from CsI crystal and two transverse profiles
from single wire monitor of carbon beam after HE mag-
net are presented in Fig.1.
Fig.1. Beam profile at the exit of AMS
In this paper the first tests for mass-14 isotope selec-
tion are presented. During the experiments, the injection
energy of carbon beam was 10 keV. The sputter ion
source was used for negative carbon ions production
from graphite sample. The carbon beam current was
1 uA. The terminal voltage was 250 kV. The ions trans-
missions of AMS system at this energy are about 10%,
1% and 0.02% for 1+, 2+ and 3+ charge states, respec-
tively. The current of accelerated beam was measured
by a silicon surface barrier detector or by Faraday cup
placed at the exit of HE magnet. The vacuum in the
beam line was about 10-6 Torr.
Fig.2. Mass spectrums of the injected (upper curve) and
accelerated (lower curve) beams
____________________________________________________________
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2008. № 5.
Series: Nuclear Physics Investigations (50), p.8-11.
8
3. RESIDUAL BACKGROUND
INVESTIGATION
The scattering and charge exchange processes allow
the unwanted particles to pass through electrostatic and
magnetic filters. The ions can interact with molecules of
residual gas and parts of vacuum chamber.
The Fig.2 (upper curve) shows the typical mass
spectrum of the graphite target at the exit of LE magnet.
It is seen that the intensity of the mass 13 peak is about
2% per stable carbon isotope, but the natural abundance
of 13C is 1.1%. It is because, the 13C and 12CH1 ions can
not be separated by LE magnet. The mass-14 is nearly
invisible. The intensities of the molecular beams are
changed in time. It depends on vacuum conditions in ion
source and sample quality. The beam spectrum at the
exit of HE magnet is also shown in Fig.2. Scanning was
carried out with mass 14 injected into tandem accelera-
tor with AMS settings appropriate for charge state 2+.
The magnesium vapors stripper was heated for obtain-
ing the equilibrium charge state distribution, but not
more. The basic peaks have the same order values, but
masses 12,13,16 peaks are reduced by 6…8 orders of
magnitude. Therefore the mass-14 is clearly visible and
separated. At these settings, the mass-14 ions are mainly
the isobaric molecular ions. The peaks have a flat-top
intensity profiles, because the beam spot size was about
ten times smaller than detector window.
Fig.3. The scan of the tandem bend
Fig.4. The scan of the electrostatic field of Wien filter
(upper part) and of the180° tandem bend (lower part)
for mass-13 and mass-14
To test the terminal 180° bend selection, the mass-
14 beam was accelerated and passed through HE mag-
net which was set for ions with mass-14 and charge
state 2+. Main ion peak 14M2+ and peaks from the frag-
ments of molecules is presented in Fig.3 by tandem
bend scanning. The velocities of fragments and primary
ions are equal in tandem terminal position. So the frag-
ments should be filtered by HE magnet, but after the
second stage of acceleration they pass through HE mag-
net at settings appropriate for mass-14 by recharging
into electric field. These fragments of the destructed
molecular ions are filtered by tandem bend at opera-
tional bend value “1”, and can not take part in charge-
exchanging process in HE accelerator tube. The primary
ions with charge not equal to 2+ are also filtered by tan-
dem 180° bend system. We also have noted, that this
bend is very important for the isobaric background fil-
tration, because the positive nitrogen ions are generated
from negative NH– ions, while negative nitrogen ions
are unstable.
Fig.5. The ions energy (upper part) and detector count
rate (lower part) for different HE magnet settings
Fig.6 The coordinate signals (upper part) and ions posi-
tion (lower part) for different HE magnet settings
To investigate the background nature, the Wien filter
was added to the injection line. The intensity of peak
mass-14 and mass-13 as functions of the electrostatic
field in Wien filter are shown in Fig.4 (top part). The
field value “1” corresponded to optimal mass-14 pass-
ing. The settings of HE magnet corresponded to meas-
ured mass. It is seen that mass-13 background consists
of two parts. The HE part can be filtered by Wien filter.
This background is due to HE tails from mass-13 peak
9
energy distribution, which have the same momentum as
mass-14 for injection magnet passing. With using of the
Wien filter set to mass-14, the mass-13 ions are gener-
ated between the LE magnet and the LE accelerator
tube, by breaking of the mass 14 molecules. The energy
of mass-13 beam is smaller than of mass-14 beam, as it
is shown in Fig.4 (in lower part). The energy difference
is about 1/14 of injection energy. Experiments, when the
pump after LE magnet was turned off, showed, what
mass-13 current increased by two times, while the vac-
uum worsened by five times.
The ions energy can be measured by silicon detector.
Fig.5 shows the measured ions energy (upper part) and
detector count rate (lower part) for different HE magnet
settings. The three reference energy points can be se-
lected:
10
( )1 1 3 1010t injW e V W= + ⋅ ⋅ + = keV
( )2
2 2 6773 t injW e V W= + ⋅ ⋅ + = keV
( )3 1 2 760t injW e V W= + ⋅ ⋅ + = keV , (1)
where Vt is the terminal voltage, Winj is the beam injec-
tion energy. The system was adjusted for charge state
3+ transmission. The primary beam is located at magnet
settings of 37 A, with average beam energy W1. The
ions corresponding to 44 A current in HE magnet have
the energy W2. These particles pass through the system
with charge 2+, but in front of terminal bend they
should have a smaller energy for bend passing. They are
recharged from “1–” to “0” state in the LE accelerator
tube. The ions of 48-57A range have energy from W3 to
W1. These particles passed through the terminal bend
with charge 3+, but recharged into 2+ state along the
HE accelerator tube. All these peaks which are resulted
from one step recharging in accelerator tubes are clearly
visible in experiments. These peaks with large energy
difference are filtered easily by HE magnet. The ions
background can pass through the HE magnet by two
steps recharging process, but it is below our detectable
level. If the background decreasing will be required, the
vacuum in the accelerator tubes will be improved by
tube heating, or by additional pumps. The magnesium
vapors stripper had no the observable influence on vac-
uum condition.
The position of each ion can be measured by the de-
tector being used. Fig.6 shows the coordinate signals
from detector (upper part) and ions position (lower part)
for different HE magnet settings. This data is presented
without selection particles by their energy by silicon
detector. The data in Figs.5,6 are obtained in the same
scan. Previously, the 0.4 mm space resolution was
achieved in tests with the alpha-particles source [1].The
space resolution information will be used for additional
particle identification.
The background in AMS with middle energy separa-
tor, located in tandem terminal is filtered below our cur-
rent detectable level. When we’ll work with higher ter-
minal voltage (~2 MV) the AMS sensitivity will be im-
proved. The background investigations based on the
described results will be continued.
4. MOLECULES DESTRUCTION
The molecular background can be suppressed by
many orders of magnitude by the stripping process in
the magnesium target. For this aim the target thickness
must be increased by increasing temperature of magne-
sium stripper. In test of the molecule destruction proc-
ess, the target was heated up to 5000C. During target
surface heating the temperature inside the magnesium
target reaches its preset value after some delay time.
The effective inner temperature (Tin) of target and the
target surface temperature (Tout) as a functions of time
are presented in the upper part of the Fig.7. The surface
temperature is controlled by thermocouples. The inner
temperature was obtained by numerical solution of the
thermal equation:
( ) τinout
in TT
dt
dT
−= (2)
The left part of the equation is a heat required to raise
temperature, and the right part of the equation is a heat-
ing by thermal conduction from the target surface. The
delay time τ is obtained from ion stripping efficiency by
using experimental data, which are presented in the
lower part of the Fig.7. There the beam current curves
as a functions of the Tout (curve 1) and Tin (curve 2) with
430 s delay time are given. During the experiments, the
temperature increased from 4300C to 5000C within
~ 15 minutes and then dropped again during the same
time. One can see that the beam current dependence
function on Tout have a hysteresis form, but the beam
current dependence function on Tin have the same form
with increasing and decreasing temperature. It is im-
plied that Tin is a temperature of magnesium vapor. The
delay time is nearly independent on the temperature
increase rate.
Fig.7. The time dependence of the temperatures of the
magnesium vapor and of the container (upper part), the
beam current (lower part) as functions of the container
temperature (1) and of the vapor temperature (2) during
heating and cooling
The molecular destruction process is presented in the
Fig.8. The 2+ charge state mass-14 ions were used. The
target thickness is obtained from the temperature by use
of temperature-pressure data [6], with 30 cm target
length. The 5.5⋅10-16 cm2 destruction cross section is
used for fitting in Fig.8. The equilibrium charge state
distribution of ions passing through the target is reached
with about 4⋅1015 1/cm2 (4300C) target thickness.
ACKNOWLEDGMENTS
This work is financial supported by FASIE* founda-
tion. We wish to thank A.S. Popov from BINP for crea-
tion and support of the silicon detector system.
REFERENCES
1. N. Alinovsky, et al. The project of accelerator
mass-spectrometr at BINP // EPAC 2004, Lucerne,
Switzerland, 2004, p.2386-2388.
2. N. Alinovsky, et al. Status of an accelerator mass–
spectrometr project for SD RAS // Problems of
Atomic Science and Technology. Series “Nuclear
Physics Investigations” (46). 2006, №2, p.34-36.
Fig.8 The destruction of the molecules 3. N. Alinovsky, et al. The negative carbon ion
sources for accelerator mass–spectrometer // Prob-
lems of Atomic Science and Technology. Series
“Nuclear Physics Investigations” (47). 2006, №3,
p.72-74.
Thus, the magnesium vapors target thickness neces-
sary for molecular ions destruction is about ten times
more than for ion stripping. The primary beam current is
decreased by two times by angular scattering of the ions
on the denser target. The graphite sample used in the ion
source was a “dead” sample with low radiocarbon con-
centration. The achieved 10-13 level of mass-14 intensity
is about one order smaller then the radiocarbon concen-
tration in modern sample.
4. N. Alinovsky, et al. Status of the Russian accelera-
tor mass spectrometer // EPAC 2006, Edinburgh,
Scotland, 2006, p.2391-2393.
5. A. Goncharov, et al. Status of BINP AMS Facility
// APAC 2007, Indore, India, 2007.
6. A. Babichev, et al. Physical Magnitudes Handbook.
M.: “Energoatomizdat”, 1991, p.257 (in Russian).
* www.fasie.ru
Статья поступила в редакцию 06.09.2007 г.
SUMMARY
The main parts of AMS facility have been installed
and in operation. Initial research was focused on back-
ground filtration. The different components of the ion
background were considered. The ten percent back-
ground level was achieved at 250 kV tandem accelerator
voltage.
РЕЗУЛЬТАТЫ ПО СОЗДАНИЮ УСКОРИТЕЛЬНОГО МАСС-СПЕКТРОМЕТРА В ИЯФ СО РАН
С.А. Растигеев, Н.И. Алиновский, А.Д. Гончаров, В.Ф. Клюев, С.Г. Константинов,
А.М. Крючков, В.В. Пархомчук, М.В. Петриченков, В.Б. Рева
Рассмотрено текущее состояние работ по созданию в ИЯФ им. Г.И. Будкера ускорительного масс-
спектрометрического комплекса (AMS). Приведены результаты первых экспериментов по выделению 14С и
измерению фона.
РЕЗУЛЬТАТИ ПО СТВОРЕННЮ ПРИСКОРЮВАЛЬНОГО МАС-СПЕКТРОМЕТРА У ІЯФ СВ РАН
С.А. Растигєєв, Н.І. Аліновський, А.Д. Гончаров, В.Ф. Клюєв, С.Г. Константинов,
А.М. Крючков, В.В. Пархомчук, М.В. Петриченков, В.Б. Рева
Розглянуто поточний стан робіт з створення у ІЯФ ім. Г.І. Будкера прискорювального мас-
спектрометричного комплексу (AMS). Наведено результати перших експериментів по виділенню 14С і
виміру фону.
11
РЕЗУЛЬТАТЫ ПО СОЗДАНИЮ УСКОРИТЕЛЬНОГО МАСС-СПЕКТРОМЕТРА В ИЯФ СО РАН
РЕЗУЛЬТАТИ ПО СТВОРЕННЮ ПРИСКОРЮВАЛЬНОГО МАС-СПЕКТРОМЕТРА У ІЯФ СВ РАН
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