مجال التميز
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تميز دراسي و بحثي + جائزة تفوقية
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البحوث المنشورة
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البحث(1):
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عنوان البحث:
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Lifetime
measurement of neutron-rich even-even molybdenum isotopes
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رابط إلى البحث:
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Click Here
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تاريخ النشر:
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08/03/2017
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موجز عن البحث:
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Background: In the neutron-rich A≈100 mass region, rapid shape
changes as a function of nucleon number as well as coexistence of prolate,
oblate, and triaxial shapes are predicted by various theoretical models.
Lifetime measurements of excited levels in the molybdenum isotopes allow the
determination of transitional quadrupole moments, which in turn provides
structural information regarding the predicted shape change.
Purpose: The present paper reports on the experimental setup, the method
that allowed one to measure the lifetimes of excited states in even-even
molybdenum isotopes from mass A=100 up to mass A=108, and the
results that were obtained.
Method: The isotopes of interest were populated by secondary knock-out
reaction of neutron-rich nuclei separated and identified by the GSI fragment
separator at relativistic beam energies and detected by the sensitive
PreSPEC-AGATA experimental setup. The latter included the Lund-York-Cologne
calorimeter for identification, tracking, and velocity measurement of
ejectiles, and AGATA, an array of position sensitive segmented HPGe
detectors, used to determine the interaction positions of the γ ray
enabling a precise Doppler correction. The lifetimes were determined with a
relativistic version of the Doppler-shift-attenuation method using the
systematic shift of the energy after Doppler correction of a γ-ray
transition with a known energy. This relativistic Doppler-shift-attenuation
method allowed the determination of mean lifetimes from 2 to 250 ps.
Results: Even-even molybdenum isotopes from
mass A=100 to A=108 were studied. The decays of the
low-lying states in the ground-state band were observed. In particular, two
mean lifetimes were measured for the first time: τ=29.7+11.3−9.1 ps
for the 4+ state of 108Mo and τ=3.2+0.7−0.7 ps
for the 6+state of 102Mo.
Conclusions: The reduced transition strengths B(E2), calculated from
lifetimes measured in this experiment, compared to beyond-mean-field
calculations, indicate a gradual shape transition in the chain of molybdenum
isotopes when going from A=100 to A=108 with a maximum
reached at N=64. The transition probabilities decrease
for 108Mo which may be related to its well-pronounced triaxial
shape indicated by the calculations.
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البحث (2):
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عنوان البحث:
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Shape Coexistence
Along N = 40 Studied with Isomer and Beta Decay
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رابط إلى البحث:
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تاريخ النشر:
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26/06/2016
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موجز عن البحث:
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In 68Ni the presence of a high-lying 2+ state with small transition
probability to the ground state is a result of the N = 40 harmonic oscillator
shell gap between the fp shell and the g9/2 orbital. This shell gap is
reduced as protons are removed in Fe and Cr isotopes [1]. Collective behavior
is caused by quadrupole correlations which favour energetically the deformed
intruder states involving the neutron g9/2 and d5/2 orbitals and proton
excitations across the Z=28 subshell gap [2] leading to rather low-lying
first 2+ states and large B(E2) values. Limited experimental data is still
available for the low spin states of the region of deformation that develops
south of 68Ni. The trend of the ratio E4+ /E2+ towards N = 40 in Cr isotopes
suggests a transition from spherical (at N = 32) to deformed shapes, that
approach better the gamma-unstable regime than the axially deformed one,
while Fe isotopes lie at the O(6) limit from N = 30 to N = 42 [3]. To better
understand the structure of these nuclei, the knowledge of other states at
low excitation energy is needed. The large difference in angular momentum
between the p1/2 , f5/2 and d5/2 , g9/2 orbitals around the Fermi surface in
N ≈ 40 nuclei leads to the occurrence of several isomeric states. In the Cr
and Ti nuclei with N = 39 and N = 41 similar configurations should also lead
to long-lived states. Observation of isomers at N = 39 will allow us to draw
conclusions on the location and evolution of intruder orbitals towards 60Ca.
Theoretical and experimental investigations show that the collective behavior
observed in 64Cr, with its small E(2+) energy and large B(E2) value, is
restored approaching 60Ca [2, 4]. To study the properties of the these nuclei
in the N = 40 region by means of gamma-ray spectroscopy following beta-decay,
an experiment has been proposed within the EURICA γ-spectrometer campaign and
it has been performed at the Radioactive Isotope Beam Factory RIBF at RIKEN
Nishina Center, Japan in June 2016. In this report we describe the
BigRIPS-AIDA-EURICA setup and we present some preliminary experimental
results.
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البحث (3):
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عنوان البحث:
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First spectroscopy of 61Ti and the transition to the
Island of Inversion at N = 40
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رابط إلى البحث:
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تاريخ النشر:
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14 March 2019
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موجز عن البحث:
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Isomeric states in 59, 61Ti have been populated in the
projectile fragmentation of a 345 MeV 238U beam at the
Radioactive Isotope Beam Factory. The decay lifetimes and delayed γ-ray
transitions were measured with the EURICA array. Besides the known isomeric
state in 59Ti, two isomeric states in 61Ti
are observed for the first time. Based on the measured lifetimes, transition
multipolarities as well as tentative spins and parities are assigned.
Large-scale shell model calculations based on the modified LNPS interaction
show that both 59Ti and 61Ti belong to the
Island of Inversion at N=40 with ground state configurations dominated by
particle-hole excitations to the g 9/2 and d 5/2 orbits.
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البحث (4):
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عنوان البحث:
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α-spectroscopy studies of the new nuclides 165Pt
and 170Hg
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رابط إلى البحث:
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تاريخ النشر:
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8 July 2019
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موجز عن البحث:
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The new nuclides 165Pt and 170Hg were
produced in the reactions 92Mo (78Kr, 5n)
and 96Ru (78Kr, 4n) at bombarding energies of 418,
MeV and 390, MeV, respectively. For 170Hg an α-particle
energy of {Eα}= 7590 (30), keV and half-life of {t1/2}=
0.08− 0.04+ 0.40, ms were deduced, while for 165Pt the
corresponding values were 7272 (14), keV and 0.24− 0.08+ 0.30, ms. Comparison
of the reduced α-decay widths with systematics indicates that both α decays
are unhindered. Although combining the measured α-decay Q values with
extrapolated masses suggests that both new nuclides are unbound to 2-proton
emission by more than 1 MeV, their α-decay half-lives are too short for this
decay mode to compete. Improved data were also obtained for 166,
167Pt, produced via the 96Ru (78Kr,3 n)
reactions at bombarding energies of 390 MeV and 418 MeV.
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المؤتمرات
العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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IOP Nuclear Physics
conference 2017
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تاريخ الإنعقاد:
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03/04/2017
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مكان الإنعقاد:
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Birmingham, UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Optimising AIDA for proton-decay studies using Geant4
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ملخص المشاركة:
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Nuclear structure study is a key to understanding the world around us
and the development of the universe. Exploring the limit of nuclear existence
at the proton drip line in the highly neutron-deficient region between Z = 50
and 82 is the main focus of this study. Accessing this region is challenging
and requires advanced techniques, including high-energy accelerators with
high-resolution separators combined with an efficient detection system.
Separating fragments of a 1GeV 238U beam via the FRagment Separator (FRS), at
GSI in Germany, following implantation in the Advanced Implantation Detector
Array (AIDA), is one of these possible production mechanisms. Optimising AIDA
beforehand, which is the aim of this work, would help in planning experiments
to search for new cases of proton radioactivity.
A Monte Carlo approach has been used to model AIDA using Geant4. A
silicon detector has been constructed and its energy response for charged
particles emitted within it has been simulated. The absolute detector efficiency
has been calculated for different detector thicknesses and for a range of
proton energies, while the background energy spectrum arising from
beta-delayed protons has also been simulated to evaluate the optimum silicon
detector thickness for proton-decay studies. The results of this study will
be presented
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المؤتمر(2):
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عنوان المؤتمر:
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IOP Nuclear Physics
conference 2018
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تاريخ الإنعقاد:
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04/04/2018
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مكان الإنعقاد:
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Paisley, UK
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طبيعة المشاركة:
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Oral presentation
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عنوان المشاركة:
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Decay Spectroscopy of the Proton-Emitting Isotopes 177,176Tl
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ملخص المشاركة:
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The preliminary results of the PhD project titled of “Decay
Spectroscopy of the Proton-Emitting Isotopes 177,176Tl” which is done in
Finland, Jyvaskyla laboratories.
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المؤتمر (3):
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عنوان المؤتمر:
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International Conference on Proton-Emitting Nuclei (PROCON2019)
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تاريخ الإنعقاد:
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03 – 07 June 2019
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مكان الإنعقاد:
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Michigan, USA
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طبيعة المشاركة:
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Oral presentation
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عنوان المشاركة:
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Decay Spectroscopy of the Proton Rich Isotopes 176,177 Tl
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ملخص المشاركة:
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Measurements of proton-decay properties provide an important source of
spectroscopic information at the limits of known nuclei. Spherical
proton emitters are important for testing models of proton emission. The most
nearly spherical cases are expected to be the Ta nuclei closest to N= 82 and
the proton-emitting isotopes 176,177Tl that lie just on
proton below the Z= 82 shell closer. These nuclei are the focus of this study
which was performed at the Accelerator Laboratory of the University of
Jyväskylä. The 176,177Tl nuclei were produced in
fusion-evaporation reactions induced by a beam of 78Kr ions
bombarding a102Pd target at energies of 397 MeV and 376 MeV. The
fusion products were separated in flight using the newly commissioned recoil
mass separator MARA and implanted into a double-sided silicon strip detector.
The proton and alpha decays of the ground and isomeric states of 177Tl
were remeasured and found to be consistent with previous studies [1,
2]. In addition, proton emission from the ground state of 176Tl
was confirmed. The previously unobservedαdecay from this state was identified
through correlations withαdecays of 172Au. The decays of the
isomeric state in176Tl were also observed for the first time.
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المؤتمر (4):
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عنوان المؤتمر:
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International Nuclear Physics Conference (INPC 2019)
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تاريخ الإنعقاد:
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29 July – 02 August
2019
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مكان الإنعقاد:
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Glasgow, UK
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طبيعة المشاركة:
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Poster presentation
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عنوان المشاركة:
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Decay Spectroscopy of the Proton-Rich Thallium Isotopes 177,176Tl
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ملخص المشاركة:
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Measurements of proton-decay properties provide an important source of
spectroscopic information at the limits of known nuclei. The decay energies
can be compared with proton separation energies predicted by mass models and
in some cases atomic masses can be determined by linking decay chains to
known masses, allowing direct comparisons with models to be made. The
orbitals from which the protons are emitted can also be deduced from
comparing partial proton-decay half-lives with predictions of theoretical models
using the measured proton energies. Spherical proton emitters are important
for testing models of proton emission and the most nearly spherical cases are
expected to be the Ta nuclei closest to N= 82 and the proton-emitting
isotopes176,177Tl that lie just 1 proton below Z= 82 shell closure and are
the focus of this study. The 176,177Tl nuclei were produced in
fusion-evaporation reactions induced by beam of 78Kr ions bombarding a102Pd
target using two bombarding energies of 397MeV and 376MeV. The fusion
products were separated in-flight using the evacuated mass recoil separator
MARA and implanted into a double-sided silicon strip detector. A new
alpha decay was observed for the first time from the ground and the isomeric
states of 176Tl followed by decay of the alpha emitter 172Au.
Correlated charged-particle included events assigned to proton emission from
the ground state of 176Tl followed by decays of the alpha emitter
175Hg. Both ground and isomeric states of the proton emitter 177Tl were
identified. The alpha-particle emission from the isomeric and ground state of
this isotope and the following alpha decay of 173Au were observed. The
resulting values were consistent with previous studies.
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جوائز التكريم:
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الجائزة (1):
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مسمى الجائزة:
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Best Talk Prize
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الجهة المانحة:
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Institute of
Physics (IOP)
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تاريخ الجائزة:
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06/04/2018
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مجال التكريم:
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The top prize for the best student presentation out of 44. The
presentation was a brief talk about the preliminary results of the PhD
project titled of “Decay Spectroscopy of the Proton-Emitting Isotopes
177,176Tl” which is done in Finland, Jyvaskyla laboratories.
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الجائزة (2):
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مسمى الجائزة:
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1st Place Poster Prize
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الجهة المانحة:
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International
Nuclear Physics Conference (INPC)
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تاريخ الجائزة:
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28/07/2019
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مجال التكريم:
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1st prize for a poster titled “Decay Spectroscopy of
the Proton-Rich Thallium Isotopes 177,176Tl” at the
International Nuclear Physics Conference in Glasgow, UK.
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