Division Particle & Astroparticle Physics
 
 

Research: NUCIFER

Original motivation

The large amounts of electron antineutrinos produced in nuclear reactors provide information related to the isotopic composition of the reactor core and its thermal power. There is an interest in using antineutrino detectors as a potential safeguard tool. Therefore the studies within the NUCIFER project [1] are dedicated to a large extent to safeguard and non-proliferation applications. For example, the detection of a change in the antineutrino spectrum consistent with the removal of a large quantity of 239Pu from the reactor would raise suspicions. The NUCIFER experiment was proposed to IAEA (International Atomic Energy Agency) in October 2008 [2]. To allow that the antineutrino detector can be placed very near to the reactor core (ca. 10 m) the detector should be compact, remote controlled, safe and moveable. The detector is currently operated at the OSIRIS research reactor at CEA-Saclay, France.

Do sterile neutrinos exist?

Recently a possible new application for this experiment of major scientific impact appeared. The NUCIFER experiment could investigate an anomaly observed in the data of several reactor neutrino experiments around the world. Measured values of the electron antineutrino flux appear to be only 94% of the value expected from theory [3]. So far, it is unknown whether this is due to unknown physics that might involve weak mixing with a sterile neutrino or due to an overseen issue either related to the experimental measurements or the theoretical flux calculations.

Detector design

The detector target is a 850 liter Gadolinium doped liquid scintillator filled into a cylindrical stainless steel vessel. As in other reactor neutrino experiments as Double Chooz the antineutrinos are detected via the inverse beta decay on Hydrogen nuclei of the target scintillator resulting in a coincidence signal (separated by several microseconds) of a prompt (positron energy) and delayed (neutron capture on Gadolinium isotopes) event. The scintillation light produced in the prompt and delayed signal is detected by 16 photomultiplier tubes (PMTs) on top of the detector. Between the PMTs and the target liquid there is a 25 cm thick acrylic buffer disk. Layers of polyethylene (15 cm) and lead (10 cm) protect the target liquid against external radioactivity mainly originating from the nearby research reactor. There is also an active veto made of 5 cm thick plastic scintillator panels. The data acquisition system (DAQ) is build with commercial VME and NIM modules and it is operated with a software interface written in LabView. Regular calibrations allow to monitor detector performance and stability.

NUCIFER at the MPIK

MPIK provides the Gadolinium loaded organic target scintillator for the NUCIFER experiment. The main challenge in developing metal loaded scintillator is to ensure long term stability of the optical parameters as light yield and transparency. Similar methods as for the production of the Double Chooz target scintillator [4] are applied and identical components are used. The concentrations of the individual components were tuned to optimize background reduction in NUCIFER. In particular the target liquid was tuned to allow for a pulse shape discrimination of fast neutron events, a main background source in the experiment, and the coincidence time window is shortened due to an increased Gd-concentration. Our group will also contribute to the analysis of the experiment, especially to learn more about the reactor neutrino anomaly described above.

Future goals

In the future the NUCIFER detector might be used at a commercial reactor in France as well. Concerning the search for sterile neutrinos new detectors are planned optimized for the needs of such an experiment. The design and results of the NUCIFER experiment provide important input information for such expermiments trying to solve the reactor neutrino anomaly.


References

[1] A. Porta for the NUCIFER collaboration, "Reactor Neutrino Detection for Non Proliferation with the NUCIFER Experiment", IEEE proceedings, 10.1109/ANIMMA.2009.5503653 (2009).
[2] Focused Workshop on Antineutrino Detection for safeguard Applications, Final Report of IAEA Workshop, IAEA Headquarters, Vienna (2008).
[3] G. Mention et al., Phys. Rev. D83, 073006 (2011).
[4] C. Aberle et al., JINST, 7, P06008 (2012).


Contact:

  • Dr. Christian Buck
    Tel: 06221 516829
    E-Mail: Christian.Buck@mpi-hd.mpg.de
  • Prof. Dr. Manfred Lindner
    Tel:06221 516800
    E-Mail: manfred.lindner@mpi-hd.mpg.de
 
 


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