=Paper=
{{Paper
|id=Vol-2507/341-346-paper-62
|storemode=property
|title=Experiments with GABRIELA Detector System
|pdfUrl=https://ceur-ws.org/Vol-2507/341-346-paper-62.pdf
|volume=Vol-2507
|authors=Alena Kuznetsova,Alexander Yeremin,Andrey Popeko,Oleg Malyshev,Alexandr Svirikhin,Andrey Isaev,Yuriy Popov,Viktor Chepigin,Maksim Chelnokov,Araseli Lopes-Martens,Karl Hauschild,Oliver Dorvaux,Benua Gall
}}
==Experiments with GABRIELA Detector System==
https://ceur-ws.org/Vol-2507/341-346-paper-62.pdf
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
EXPERIMENTS WITH GABRIELA DETECTOR
SYSTEM
A. Kuznetsova1,a, A. Yeremin1,b, A. Popeko1, O. Malyshev1, A. Svirikhin1,
A. Isaev1, Yu. Popov1, V. Chepigin1, M. Chelnokov1, A. Lopes-Martens2,
K. Hauschild2, O.Dorvaux3, B. Gall3
1
FLNR, JINR, 141980 Dubna, Russia
2
CSNSM, IN2P3-CNRS, UMR 8609, F-91405 Orsay, France
3
IPHC-DRS/ULP, IN2P3-CNRS, F-67037 Strasbourg, France
E-mail: aaakuznetsova@jinr.ru, beremin@jinr.ru
For several years, more dozen experiments was carried out on SHELS (Separator for Heavy
ELements Spectroscopy), aimed to investigation of characteristics of heavy elements and discover
new isotopes. Perfect data acquisition system GABRIELA allows to investigate single particle states
behavior, as well as the structure of little known elements in the Z = 102–105 and N = 148–162
region. Complex of DSSSD detects 70% alpha particles and 90% spontaneous fissions; a system of 5
coaxial Ge-detectors in 4π geometry has efficiency of gamma-quanta registration of 34–14% by scale
~ 100–1000 keV.
Keywords: SHELS/VASSILISSA, heavy elements, spectroscopy.
Alena Kuznetsova, Alexander Yeremin, Andrey Popeko, Oleg Malyshev, Alexandr
Svirikhin, Andrey Isaev, Yuriy Popov, Viktor Chepigin, Maksim Chelnokov,
Araseli Lopes-Martens, Karl Hauschild, Oliver Dorvaux, Benua Gall
Copyright © 2019 for this paper by its authors.
Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
341
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
1. Separator for Heavy Elements Spectroscopy (SHELS)
Flerov Laboratory of Nuclear Reactions (FLNR) at JINR is well-known in researches of heavy
and superheavy elements (SHE). There are synthesized new elements with Z = 113–118 and a lot of
isotopes of SHE with Z = 104–118. The last chemical element in Mendeleev table was named
Oganesson (118, Og) in honor of academician Yu. Ts. Oganessian.
Studies of reaction products and their levels structure are produced via VASSILISSA [1] set-
up. Due to upgrades of VASSILISSA at 2013 years, the kinematic separator was remade in velocity
filter SHELS [2], thereby a yield of facility is increased in times.
SHELS consists of the following elements (fig. 1):
● Target wheel: radius is 12 cm. The metal wheel divided by segments. In each segment was
implanted target’s substance on 1.5-2 μm Ti foil.
● Two triplets of quadrupole lenses: maximum field gradient is 13 T/m, effective length of 38
cm and aperture radius of 10 cm.
● Two high voltage electrostatic deflectors: effective length of 65.7 cm, distance between plats
is 10–20 cm, maximum field gradient of 40 kV/cm and rated deflection angle is 8°.
● Three dipole magnets: effective length of 59.7 cm, dipole aperture of 13.5 cm, maximum field
gradient is 0.8 T. Two magnets have rated deflection angles of 21.8°, and one of 8°.
● Time of Flight system (ToF).
● Detector system GABRIELA.
Figure 1. Separator for Heavy Elements Spectroscopy
The accelerated beam provides by the U-400 cyclotron, its intensity 0.5–1.5 μpA in depends of
study reactions. There are use projectiles from 22Ne to 54Cr. Efficiency of the transmission of recoils
nuclei (εtr) through the facility reaches 45%. This value is different for various asymmetric reaction, as
an example, the reaction of 22Ne + 197Au has εtr = 6.5%. If compared to εtr from old facility, its value
was 3% (tab. 1). For other reactions εtr were notably changed.
342
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
Table 1. Efficiency of the recoils nuclei transmission (εtr) for VASSILISSA and SHELS
Target thick., εtr, % εtr, %
Reaction Ebeam, MeV
mg/cm2 VASSILISSA SHELS
22
Ne(197Au,4n)213-215Ac 120 0.25 3 6.5
22
Ne(198Pt,5-7n)213-
215 115-125 0.25 3.5 3.5–5
Ra
50
Ti(164Dy,4-5n)209Ra 240 0.3 30 40
50
Ti(208Pb,2n)256Rf 237 0.36 25 20–40
2. Detection system
After selection in separator the interest products pass through a ToF detector composed of 2 or
3 emissive polycarbonate foils and 4 large-size (70×90mm2) microchannel plates (production by
BASPIK). Foils have gold or graphite sprayed on it, and installed in metal frame. Thickness of
polycarbonate is 0.4 mg, gold of 0.35–0.45 mg. Active area of plate is 86×66 mm, thickness of 1 mm,
as well as pore size is 15 μm, a channel pitch of 19 μm and bias of 8°. A new ToF detector has more
compact geometry. The main purpose of this system is giving a marker to the recoil nucleus, which
used in data analysis.
In the next step, the particles enter the detection system. The separator can use two kinds of
detector arrays:
● Neutron barrel (fig. 2).
● Gamma Alpha Beta Recoil Investigation with the Electromagnetic Analyzer (GABRIELA)
(fig. 3).
The assembly of the focal detector for neutron barrel is positioned in a cylindrical vacuum
chamber surrounded by three layers of neutron counters (3He at pressure of 7 atm) placed in the
volume of the retarder. The neutron assembly is surrounded by six plates of Ba-doped polyethylene to
protect against background neutrons [3]. The TKE of fragments and their half-lives were measured in
the experiment. The signals from fission fragments trigger interrogation of the neutron counters
positioned around the vacuum chamber of the focal detector, ensuring reliable measurements of the
number of neutrons accompanying each fission event. The average lifetime of fission neutrons in the
detector is 23–30 μs, and the efficiency of single neutron registration is 43–45% (measurements are
made using a 248Cm source). It should be noted that the background conditions were quite favorable in
all experiments: the count of background neutrons in the room with detectors did not exceed 100
random counts per second.
Figure 2. Neutron barrel
343
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
The GABRIELA [4] detects the evaporation residues with their subsequent α decay or fission,
as well as γ-rays, X-rays and conversion electrons. At 2013-2015 for GABRIELA was upgraded, and
now it has another view (fig. 3). New content includes of the one box of DSSD and 5 Ge-detectors,
which demonstrate more efficient work, than one Si-box and 7 Ge-detectors (in old version).
Figure 3. GABRIELA
The box of detectors consists of large 10×10cm2 double-sided silicon strip detector (DSSSD)
(fig. 4), 128×128 strips (16384 pixels) and thickness is 500 μm. This is focal plane detector, which
surrounded of 8 plats 50×60mm2 DSSD (thickness of 700 μm), 32×32 strips (4096 pixels). Alpha
particles registration efficiency εα = 70% and the resolution energy is 15-20 keV for α in the range of
5–7 MeV.
Figure 4. Focal detector 128×128 strips
344
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
The Ge array consists of a large Clover installed just behind the focal plane DSSSD and 4
coaxial Ge detectors forming a cross around the DSSD. All Ge detectors are equipped with BGO
shields. This configuration is more efficient! The calibration of the Ge detectors was performed using
standard sources such as 152Eu and 133Ba. Registration efficiency is 38–14% by gamma-quanta energy
scale from 100 keV to 1000 keV.
3. Conclusions
As for recoils registration efficiency (εreg), then achieved good results. In hot fusion reaction
40
Ar + 180Hf formed compound nuclei 220Th*, by energy beam 220 Mev (fig. 5). There was integral
flux of 6.2·1017 particles. Value of registration efficiency εreg was calculated by peak of 215Ac, which
created through p4n-channel. Nuclide of 215Ac has short half-life time 0.17 s, it was convenient to used
for calculate. Ratio of number of Rec-α correlations by number of α-particles from 215Ac peak it is εreg
= 87.4%.
Figure 5. Spectrum of α-particles decays of Th isotopes
In experiments was studied heavy nuclei with Z=102–106 (tab. 2). System of detectors
demonstrated good performance.
Table 2. Experiments 2017–2019 years
Z Reaction Isotopes Results
22
Ne+238U 256
No
102 48 New metastable states of No isotopes.
Ca+204,206,208Pb 250
No, 252No, 254No
254
50 Rf, 255Rf,256Rf,
104 Ti+206,208Pb [3] 257 New information about levels structure.
Rf
50 More chains of decay Db isotopes and 3
105 Ti+209Bi [5] 256
Db, 257Db, 258Db
events “fast” fission from 258Rf (p0n).
54 Test for future experiments with Cr
106 Cr+208Pb 262-xn
Sg
beam.
The plans are another upgrade of the SHELS. Instead quadrupole lenses will be install lenses
with more apertures of 300 mm. All Ge-detectors will be replaced on Clovers, and small DSSD on
10×10cm2 DSSSD. Also diameter of target wheel will increase before 24 cm.
345
Proceedings of the 27th International Symposium Nuclear Electronics and Computing (NEC’2019)
Budva, Becici, Montenegro, September 30 – October 4, 2019
References
[1] A. V. Yeremin, A. N. Andreev, D. D. Bogdanov, V. I. Chepigin, V. A. Gorshkov, A. I. Ivanenko,
A. P. Kabachenko, L. A. Rubinskaya, E. M. Smirnova, S. V. Stepantsov, E. N. Voronkov, and
G. M. TerAkopian, The VASSILISSA facility for electrostatic separation and study of complete fusion
reaction products // Nucl. Instrum. Methods Phys. Res., Sect. A 274, 528–532, 1989.
[2] A.V. Yeremin, A.G. Popeko, O.N. Malyshev, A. LopezMartens, K. Hauschild, O. Dorvaux,
B. Gall, V.I. Chepigin, A.I. Svirikhin, A.V. Isaev, E.A. Sokol, M.L. Chelnokov, A.N. Kuznetsov,
A.A. Kuznetsova, A.V. Belozerov, K. Rezynkina, F. Dechery, F. Le Blanc, J. Piot, J. Gehlot,
D. Tonev, E. Stefanova, D. Pantelika, C. Nita, B. Andel, S. Mulins, P. Jones, S. Ntshangase. First
Experimental Tests of the Modernized VASSILISSA Separator // Physics of Particles and Nuclei
Letters, 2015, Vol. 12, No. 1, pp. 35–42.
[3] A.I. Svirikhin, A.V. Yeremin, A.V. Andreev, I.N. Izosimov, A.V. Isaev, A.N. Kuznetsov,
A.A. Kuznetsova, O.N. Malyshev, A.G. Popeko, Y.A. Popov, E.A. Sokol, M.L. Chelnokov,
V.I. Chepigin, T.M. Schneidman, B. Gall, O. Dorvaux, P. Brione, K. Hauschild, A. Lopez-Martenz,
K. Rezynkina, S. Mullins, P. Jones, P. Mosat, B. Andel, Z. Kalaninova, M.Z. Asfari, N. Yoshihiro,
J. Piot, E. Stefanova, D. Tonev. Short-lived Isotopes of transfermium elements: studying
characteristics of spontaneous fissioning // Bulletin of the Russian Academy of Sciences: Physics,
2018, Vol. 82, No. 6, pp. 632–636.
[4] K. Hauschild, A. Yeremin, O. Dorvaux, A. Lopez-Martens, A. Belozerov, Ch. Briancon,
M. Chelnokov, V. Chepigin, S. Garcia-Santamaria, V. Gorshkov, F. Hanappe, A. Kabachenko,
A. Korichi, O. Malyshev, Y. Oganessian, A. Popeko, N. Rowley, A. Shutov, L. Stuttgé, A. Svirikhin.
Gabriela, A new detector array for γ -ray and conversion electron spectroscopy of transfermium
elements // Nucl. Instrum. Methods Phys. Res., Sect. A, Accel. Spectrom. Detect. Assoc. Equip. 560
(2) (2006) 388–394, https://doi.org/10.1016/j.nima.2006.01.107.
[5] A. Lopez-Martens, A.V. Yeremin, M.S. Tezekbayeva, Z. Asfari, P. Brionnet, O. Dorvaux,
B. Gall, K. Hauschild, D. Ackermann, L. Caceres, M.L. Chelnokov, V.I. Chepigin, M.V. Gustova,
A.V. Isaev, A.V. Karpov, A.A. Kuznetsova, J. Piot, O.N. Malyshev, A.G. Popeko, Yu.A. Popov,
K. Rezynkina, H. Savajols, A.I. Svirikhin, E.A. Sokol, P. Steinegger. Measurement of proton-
evaporation rates in fusion reactions leading to transfermium nuclei // Physics Letters B 795, 2019,
pp. 271–276.
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