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İsmail Boztosun
Photofission of 238-U Nuclei
This research has been supported by TÜBİTAK with grant number 114F220
International Thorium Energy Conference - ThEC18,
29-31st of October 2018, Belgium
Motivations
i. Personal: From Theory to Experiment
ii. No dedicated research accelerators in developing world: Use of medical Linacs
- Advantages of having Good total photon flux
i. Fundamental Nuclear Science
ii. Aplication of Nuclear Tecniques
iii. Tranining & education facility for the PhD and MSc students
OUTLINE
• A New Landscape for developing countries,
• Nuclear Reactions & structure
• Proton Rich Nuclei and PR and GDR
measurements
• Photonuclear and Photofission Reactions,
• Experimental setup
• Electron Linac
• Detectors
• Results
• Summary & Outlook
• NUBA
Stable nuclei less than 300 !
~2000 KNOWN NUCLEI
Limits of existence
mass, charge & ratio N/Z
spin & temperature
extremes shapes
pro
tons
neutrons
The nucleus : a laboratory for
fundamental interactions and symmetries
Shell structure and Isospin
Spin and shapes
82
50
28
28
50
82
20
8 2
2
8
20
126
Key nuclei for
stellar processes are far
from stability
A landscape for Nuclear Reseach at Developing Countries with Medical Linacs
• High energies - Current Accelerators • Still interesting research for low energy charged particle and photon reactions
PHOTONUCLEAR REACTIONS
A B
target
projectile
B + b
product
ejectile
a
b
h • n
delayed
Target nuclide
“Compound nucleus”
Product nuclide
level
Prompt Neutron Gamma
Ga Ga Ga
Medical Electron Linear Accelerator
Bremsstrahlung photons for photonuclear reactions are obtained using a
Electa TM Synergy TM accelerator, SLi-25.
Primary electron beam is generated by an electron gun with 50 keV
electrons.
Then the beam accelerated in a copper cavity by a 3 GHz (2856MHz to be
exact) radio-frequency with peak power of about 5 MW.
The typical average electron current is about 30 μA for an electron energy
of about 10 MeV,
The SLi-25 is a pulsed linear accelerator with 400 pulses per second and a
pulse length of 3 micro seconds.
The steering and focusing of the beam is achieved by standard magnetic
and electrostatic devices.
e-
h·
The bremsstrahlung field; lateral homogeneity
Spatial beam uniformity at y=0 along
the x-axis
Measurement performed with a matrix
of 32x32 ion chambers for 2 s.
Longer measurement times reduce
the variations.
Bremsstrahlung spectrum at sample position
DETECTORS
A p-type, coaxial, electrically cooled, HPGe gamma-ray spectrometer
40% relative efficiency and 768 eV FWHM at 122 keV for 57Co and 1.85 keV
FWHM at 1332 keV for 60Co
Connected to a NIM consisting of ORTEC bias supply, spectroscopy
amplifier, analog to digital converter and a computer.
Placed into a 10 cm thick lead shield with an inner surface covered by a 2
mm thick copper foil to shield from the X-rays originating in lead
Emitting gamma rays in the energy range between 47 and 1836 keV is
rutinely used for energy calibration.
Configured with 16383 channels and the gain is adjusted: energy resolution
is about 0.18 keV giving a range of detected energies up-to about 3000 keV.
DATA ACQUISITION
PHOTONUCLEAR REACTIONS
Ga-69: 60.1%
Ga-71: 39.9%
THE GALLIUM EXPERIMENT: GAMMA SPECTRUM
THE GALLIUM EXPERIMENT: ENERGY LEVELS
THE PRASEODYMIUM EXPERIMENT:
ENERGY LEVELS
THE SCANDINIUM EXPERIMENT:
ENERGY LEVELS
HALF-LIFE FITS
Secular equilibrium is assumed i.e. T1/2 parent >> T1/2 daughter
min, h, d >> ns, ps
Isotope NUDAT T1/2
σNUDAT
T1/2
σ
68Ga 67.71 m 0.09 67.5 m 0.9 72Ga 14.10 h 0.02 13.9 h 0.2 140Pr 3.39 m 0.01 3.38 m 0.06
142Pr 19.12 h 0.04 20.3 h 0.7 44Sc*(1157) 58.61 h 0.10 59 h 6 44Sc(1157) 3.97 h 0.04 4.04 h 0.02
44Sc*(271) 58.61 h 0.10 60.3 h 1.5
HALF-LIFE RESULTS
for multi-isotop elemements (Ga) we get some systematic
error ~10% for single isotop elements (Pr, Sc) we are in agreament with
the literature and can have similar uncertanties
THE DECAY OF SCANDİNİUM:
(No-secular equilibrium!)
Photo-fission of Uranium-238 Materials
Photo-fission of Uranium-238
Stage 1- To perform photo-fission of the target nuclei Uranium-238, inside compound UO2(NO3)2, was prepared with appropriate geometry for irradiation and detection of the yield with the HPGe detector.
Stage 2- The target was irradiated for 1 hour with 18 MeV bremsstrahlung photons obtained from e-linac.
Stage 3- Fission yield data resulted from photo-nuclear reaction were counted for two days with HPGe.
Stage 4- The spectrum was analyzed to identify the photo-fission yields. The energy and the area of the each peak and half lives of the nuclei of the peaks were determined.
Results
Photo-Fission Yields Energy
(keV)
134Te 210.573
94Y 917.7587
136Pr 999.8549
142Ba 255.0362
142Ba 364.21
142Ba 1093.1321
142Ba 1202.1
138Xe 258.2187
138Xe 396.2359
104Tc 357.632
104Tc 529.4958
104Tc 792.627
Yield identification continues…
SUMMARY & OUTLOOK A unique research center having an accelerator that is capable of
performing spectroscopy and instrumentation
Important to promote Nuclear Science at devoloping countries
Tranining and education facility for the PhD and MSc students: i.e. For the case of Turkey, CERN membership, Nuclear & HEP
studies
Material hardening, space radiation and detector studies: compton background test for AGATA and ELI-NP
Nuclear Reactions: (,n) (,p) (, ) and (, ’) for PR and GDR
Energy Levels and Half-life measurements for proton rich nuclei: Better results
Nuclear structure: level densities and transitions
Nuclear structure: Shape-Phase transitions
Nuclear Astrophysics: Nucleosynthesis for early universe
Applications of Nuclear Techniques from Archeology, Engineering to Agriculture for devoloping countries
Outcomes: First photonuclear paper with local resources
• 2221 Visiting Scientists/researchers on Long term Long-term fellowships fund is available for the following activities in Turkey: Conducting research and development (R&D) • Scientists/researchers on SABBATICAL LEAVE (3 to 12 months): Scholars or academic staff on SABBATICAL LEAVE planning to come to any Turkish university/institution is also funded • Requirements for Beneficiaries: Fellows can be citizen of any country. Fellows should have a PhD degree (or equivalent) • Fellowship Details: A monthly stipend of up to 3.000 US$ for Visiting Scientists. A monthly stipend of up to 3.500 US$ for Visiting Scientists on Sabbatical Leave Travel costs (round trip) and health insurance premiums.
TUBITAK VISITING SCIENTIST PROGRAMME http://www.tubitak.gov.tr/
This research has been supported by TÜBİTAK with grant number 114F220