4 PhD positions at ILL Grenoble

Institut Laue-Langevin in Grenoble has 4 open PhD positions in the nuclear and particle physics group:

1. Theoretical and experimental investigation of shape coexistence around N=60 with EXILL
2. Shape coexistence at N=60 with EXILL and detector development for the full identification of fission fragments
3. Search for sterile neutrinos by the short-baseline reactor neutrino oscillation experiment STEREO
4. A direct measurement of the energy equivalent of the atomic mass unit

Short job descriptions are given below. More details including contact addresses and collaborating labs can be found here:
http://www.ill.eu/careers/opportunities/phd-recruitment/open-phd-programme-positions/

1. Theoretical and experimental investigation of shape coexistence around N=60 with EXILL

Today there are several indications of a rapid onset of quadrupole deformation around the neutron number N=60. This shape change has made of the neutron-rich A=100 region a very active area of experimental and theoretical studies. In particular, nuclear spectroscopy measurements have shown shape coexistence in most of the neutron-rich N=59 isotones. Certain theoretical predictions indicate that yet another shape change should occur when going to lower Z values. Nuclear spectroscopy of very neutron-rich isotopes can be performed via γ-γ or γ-γ-γ coincidences with efficient Ge detector arrays such as EXOGAM. Mass and nuclear charge are usually identified via coincidences with known γ-rays of complementary fragments. In December 2012, the EXOGAM array was used at the ILL (EXILL campaign) to measure γ-rays emitted from various fission fragments that are produced in the thermal neutron induced fission of 235U. The primary aim of the proposed PhD project is to analyze the 235U EXILL data to investigate excited states in 88-89Se and 91-92-93Br. In the second half of the PhD thesis, the student will participate actively in the interpretation of the obtained experimental data using several theoretical models including Quasi Particle-phonon Model (QPM) or the Interacting Boson Model (IBM) and its extensions for even-odd and odd-odd nuclei (IBFM and IBFFM respectively). Applicants should have a degree in physics with specialisation in nuclear physics.

2. Shape coexistence at N=60 with EXILL and detector development for the full identification of fission fragments
Today there are several indications of a rapid onset of quadrupole deformation around the neutron number N=60 in the neutron-rich Zr and Sr isotopes. In addition to this shape change, shape coexistence scenarios are suggested which would reflect the competition between the spherical and deformed configurations. Below the isotopic chain of Sr, at the limit in proton number of this phenomenon, the spectroscopy of neutron rich Kr isotopes at N=60 remains extremely scarce and still under debate. In particular, the seemingly contradictory spectroscopic experimental data for 96Kr isotopes underlines the need for more experimental data on this nucleus. Nuclear spectroscopy of very neutron-rich isotopes can be performed via γ-γ or γ-γ-γ coincidences with efficient Ge detector arrays such as EXOGAM. Mass and nuclear charge are usually identified via coincidences with known γ -rays of complementary fragments. In December 2012, the EXOGAM array was used at ILL (EXILL campaign) to measure γ-rays decaying from various fission fragments from the thermal neutron induced fission of 235U. The first half of the proposed PhD project will be dedicated to the 235U EXILL data analysis to investigate higher lying states in 96Kr helping elucidating the much discussed shape change around N=60.
When γ-γ-γ coincidences are not possible, an additional mass information from an ancillary spectrometer can improve the overall resolving power to identify new, weak γ-rays. In this context, FIPPS a new FIssion Product Prompt γ-ray Spectrometer is being developed at the ILL. The ambitious goal of FIPPS is to combine a high-resolution γ-ray spectroscopy together with a large acceptance and high resolution recoil spectrometer. The FIPPS spectrometer is based on a combination of a Gas-Filled Magnet (GFM) and a Time Projection Chamber (TPC) for individual 3D tracking of the fragments. The second part of the PhD project aims at developing the tracking system based on Micromegas detectors developed at CEA-Saclay for the FIDIAS (FIssion Detector at the Interface with Astrophysics) project. Applicants should have a degree in physics with specialisation in nuclear physics.

3. Search for sterile neutrinos by the short-baseline reactor neutrino oscillation experiment STEREO

New analyses of reactor antineutrino oscillation experiments revealed a deficit in detected electron-antineutrinos at short baseline. This deficit cannot be explained by oscillations to other neutrinos of the standard model and is called "reactor neutrino anomaly". Similar deficits were observed by calibrating the solar neutrino detectors GALLEX and SAGE. This may indicate the existence of a light neutrino that does not participate in weak interaction and is called "sterile neutrino". The STEREO collaboration will search for reactor antineutrino oscillations at very short baseline. The detector features a multi-chamber setup allowing to observe an oscillation by differences in the spectra between the chambers. It will be installed at the research reactor of the ILL Grenoble. Data taking is scheduled for the period 2015-2016. The PhD student will participate in all phases of the project: experiments to optimise detector components, characterisation of background by simulations and measurements, detector installation, data taking and analysis. The student will be located at the ILL. Applicants should have a degree in physics with specialisation in particle or nuclear physics.

4. A direct measurement of the energy equivalent of the atomic mass unit

A re-definition of the kilogram mass via fundamental constants can be followed via two routes: i) answering the question of how much electrical power is needed to lift/move a macroscopic mass of one kilogram or ii) answering the question of how many atomic mass units are contained in one kilogram of mass. The first route, followed by the Watt Balance projects, links the kilogram to the Planck constant while the second route, followed by the Avogadro project, links the kilogram to the Avogadro constant and the atomic mass unit. At present both routes show an inconsistency in the order of 10-7 in their results, which is an order of magnitude too large if compared to the published relative uncertainties of each individual measurement. An energy equivalent of the atomic mass unit represents an independent verification.

The PhD project aims at directly determining the energy equivalent of the atomic mass unit with a relative uncertainty of 10-8. This can be done by measuring the energy of gamma rays after a neutron capture reaction very accurately. From the gamma ray energies the neutron binding energy can be calculated and compared to the mass difference of the mother and daughter isotopes, which need to be measured with precision Penning traps. The PhD project involves energy measurements at the world’s most precise gamma ray spectrometer GAMS6 at the ILL in Grenoble and the penning trap PENTATRAP at the MPKI Heidelberg. Applicants should have a degree in physics or engineering with experience in precision measurements.

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