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A 2nd-generation gravitational neutron spectrometer

The GRANIT project consists of designing and building a second-generation gravitational neutron spectrometer with ultra-high resolution. Its key property is the storage of UCN in a selected gravitationally bound state for extended period of time using a closed specula trap. The high quality of mirrors needed for the trap is at the edge of modern technology.

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Description

The existence of quantum states of matter in the gravitational field has been demonstrated for the very first time at the ILL by a series of ground-breaking experiments 1-3 with ultracold neutrons (UCN). The GRANIT 4 instrument is the follow-up project based on a second-generation UCN gravitational spectrometer with ultra-high energy resolution. It will provide more accurate studies of/with the quantum states as well as measurements of the resonant transitions between them 5. It will benefit from a dedicated UCN source 6 delivering UCN to GRANIT with no significant dilution of the phase-space density 7-8.

Instrument layout

Instrument team

NESVIZHEVSKY Valery

Scientific project leader

nesvizhevsky(at)ill.eu

+33 4 76 20 7795/7689


KREUZ Michael

Technical project leader

kreuz(at)ill.eu

+33 4 76 20 786


The project

The GRANIT project consists of designing and building a second-generation gravitational neutron spectrometer with ultra-high resolution. Its key property is the storage of UCN in a selected gravitationally bound state for extended period of time using a closed specula trap. The high quality of mirrors needed for the trap is at the edge of modern technology 9. According to the uncertainty principle, longer observation time corresponds to better defined energy of a state. Resonant transitions between the states allow us to measure energy precisely. Such precision measurements constrain acceptable external perturbations, such as vibrations or magnetic fields. As the fraction of gravitationally bound neutrons is extremely small, we develop neutron detectors with extremely low backgrounds, UCN sources with maximum neutron density, and neutron transport systems with minimal losses. Nearly every component of the GRANIT spectrometer is constructed for the first time and has no analogs.    
 The GRANIT spectrometer will be a unique tool for carrying out a wide range of investigations in particle fundamental physics (neutron electric charge, spin-dependent or spin-independent short-range forces), foundations of quantum mechanics, in surface physics, as well as for development of experimental techniques and their applications 4, 10, 11.
The GRANIT project is being constructed in the framework of ANR (Agence Nationale de la Recherche, France) grant of 600 K€ received in 2005 by a joint collaboration ILL-LPSC-LMA. The physical program to be carried out using the GRANIT spectrometer involves a number of scientific institutions from France, USA, Germany, and Russia.

References

  1. V.V.Nesvizhevsky, H.G.Börner, A.K.Petukhov, H.Abele, S.Baeßler, F.J.Rueß, Th.Stöferle, A.Westphal, A.M.Gagarsky, G.A.Petrov, and A.V.Strelkov (2002). "Quantum states of neutrons in the Earth's gravitational field." Nature 415: 297-299.
  2. V.V.Nesvizhevsky, H.G.Börner, A.M.Gagarski, A.K.Petukhov, G.A.Petrov, H.Abele, S.Baeßler, G.Divkovic, F.J.Rueß, T.Stöferle, A.Westphal, A.V.Strelkov, K.V.Protasov, A.Yu.Voronin (2003). "Measurement of quantum states of neutrons in the Earth's gravitational field." Physical Review D 67: 102002(1-9).
  3. V.V.Nesvizhevsky, A.K.Petukhov, H.G.Börner, T.A.Baranova, A.M.Gagarski, G.A.Petrov, K.V.Protasov, A.Yu.Voronin, S.Bäßler, H.Abele, A.Westphal, and L.Lucovac (2005). "Study of the neutron quantum states in the gravity field." European Physical Journal C 40(4): 479-491.
  4. V.V.Nesvizhevsky, and K.V.Protasov (2006). "Quantum states of neutrons in the earth's gravitational field: state of the art, applications, perspectives. Edited book on Trends in quantum gravity research." D. C. Moore. New York, Nova science publishers: 65-107.
  5. M. Kreuz, V.V. Nesvizhevsky, P. Schmidt-Wellenburg, T. Soldner, M. Thomas, H.G. Boerner, F. Naraghi, G. Pignol, K.V. Protasov, D. Rebreyend, F. Vezzu, R. Flaminio, C. Michel, L. Pinard, A. Remillieux, S. Baessler, A.M. Gagarski, L.A. Grigorieva, T.M. Kuzmina, A.E. Meyerovich, L.P. Mezhov-Deglin, G.A. Petrov, A.V. Strelkov, A.Yu. Voronin (2009). "A method to measure the resonance transitions between the gravitationally bound quantum states of neutrons in the GRANIT spectrometer." arXiv: physics.ins-det/0902.0156.
  6. P. Schmidt-Wellenburg, K.H. Andersen, P. Courtois, M. Kreuz, S. Mironov, V.V. Nesvizhevsky, G. Pignol, K.V. Protasov, T. Soldner, F. Vezzu, and O. Zimmer (2008). "Ultracold-neutron infrastructure for the gravitational spectrometer GRANIT." nucl-ex/arXiv:0811.1635.
  7. P. Schmidt-Wellenburg, J. Barnard, P. Geltenbort, V.V. Nesvizhevsky, C. Plonka, T. Soldner, O. Zimmer (2007). "Efficient extraction of a collimated ultra-cold neutron beam using diffusive channels." NIM A 577(3): 623-625.
  8. J. Barnard, and V.V. Nesvizhevsky (2008). "Analysis of a method for extracting angularly collimated UCNs from a volume without losing density inside." NIM A 591: 431-435.
  9. G. Pignol, K.V. Protasov, D. Rebreyend, F. Vezzu, V.V. Nesvizhevsky, A.K. Petukhov, H.G. Börner, T. Soldner, P. Schmidt-Wellenburg, M. Kreuz, D. Forest, P. Ganau, J.M. Mackowski, C. Michel, J.L. Montorio, N. Morgano, L. Pinard, A. Remillieux, A.M. Gagarski, G.A. Petrov, A.M. Kuzmina, A.V. Strelkov, H. Abele, S. Bäßler, A.Yu. Voronin (2007). "GRANIT project: a trap for gravitational quantum states of UCN." arXiv: physics.quant-ph/0708.2541.
  10. S.Bäßler, V.V.Nesvizhevsky, K.V.Protasov, and A.V.Voronin (2007). "Constraint on the coupling of axionlike particles to matter via an ultracold neutron gravitational experiment." Physical Review D 75(7): 075006(1-4); constrains for axions in the Particle Data Group.
  11. V.V. Nesvizhevsky, G. Pignol, and K.V. Protasov (2008). "Neutron scattering and extra-short-range interactions." Physical Review D 77(3): 034020(8).