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Institut Laue-Langevin

A selection of recent workshops and symposiums held at ILL

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Past events

The GRANIT-2010 Workshop

The Workshop GRANIT-2010 on experimental and theoretical approaches to quantum states of neutrons in gravitational field took place in Les Houches, France, 14-19 February 2010. The aim of this workshop consisted in discussing the scientific program with the new GRANIT spectrometer in a broad context of behavior of ultracold neutrons (UCN) in gravitational field in GRANIT and in alternative experiments, as well as applications of this phenomenon/spectrometer to various domains of physics, ranging from short-range interactions to neutron quantum optics and reflectometry using UCN. Topics were the scientific issues, instrumental and methodical developments, alternative methods, new ideas. This is a follow-up for the GRANIT-2006 Workshop (http://lpsc.in2p3.fr/congres/granit06/index.php), and preceding annual meetings of the collaboration on measurement of the quantum states of neutrons in gravitational field.

Over 50 participants from 12 countries in 4 continents attended the Workshop. The first day was devoted to detailed presentations of the new GRANIT spectrometer covering the engineering and methodical aspects as well as theoretical principles of its operation and first measurements to carry out as soon as first UCN will be delivered to the spectrometer. During second day, we were discussing various new methodical developments to be used in GRANIT at further stages, such as real-time position-sensitive detectors, nanoparticle neutron reflectors, the new concept of “virtual cold neutron source” for producing extremely high UCN densities, an option to use GRANIT as a general-purpose UCN reflectometer. The presentation during third day concentrated on fundamental applications of GRANIT, in particular on short-range forces; all competing approaches were presented as well. A broad range of various alternative quantum phenomena and experiments in gravitational field were analyzed during forth day. Finally, a recently observed phenomenon of the centrifugal quantum states of neutrons (neutron whispering gallery) was presented during the last day of the Workshop.       

GRANIT spectrometer

The existence of quantum states of matter in gravitational field was demonstrated recently by a series of experiments with UCN in the ILL. The GRANIT spectrometer is a follow-up project based on a second-generation spectrometer with ultra-high energy resolution. It will provide more accurate studies of/with the quantum states as well as measurements of resonance transitions between and interference of the quantum states. It will benefit from a dedicated 4He UCN source delivering UCN to the spectrometer with no significant dilution of the phase-space density.

The key property of GRANIT is UCN storage in selected gravitational bound states for extended period of time using a closed specular trap. According to the uncertainty principle, longer observation time corresponds to better defined energy thus higher measurement precision. External perturbations, such as vibrations or magnetic fields, have to be minimized. As the fraction of gravitationally bound neutrons is extremely small, we develop neutron detectors with extremely low backgrounds, UCN sources with maximum neutron phase-space density, and neutron transport systems with minimal losses.


The GRANIT spectrometer will be a unique tool for carrying out a wide range of investigations in particle fundamental physics, in foundations of quantum mechanics, in surface physics, as well as for development of experimental techniques and their applications. The physical program to be carried out using the GRANIT spectrometer involves a number of scientific institutions from all over the world; also we are open for new ideas and collaborations.


The GRANIT project is being constructed in the framework of ANR (Agence Nationale de la Recherche, France) grant received in 2005 by a joint collaboration ILL-LPSC-LMA. Permanent installation of GRANIT at the ILL high-flux reactor is financed by the ILL and IN2P3 institutes.