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NEUTRONS FOR SCIENCE

NEUTRONS FOR SCIENCE. STORAGE OF ULTRACOLD NEUTRONS IN A TRAP MADE OF PERMANENT MAGNETS.

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NEUTRONS FOR SCIENCE

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  1. NEUTRONS FOR SCIENCE STORAGE OF ULTRACOLD NEUTRONS IN A TRAP MADE OF PERMANENT MAGNETS V.F. Ezhov1, B.A.Bazarov1, P. Geltenbort2, F.J. Hartmann3, N.A. Kovrizhnykh4, A.Z. Andreev1, A.G. Glushkov1, M.G. Groshev1, V.A. Knyazkov1, G.D. Krygin1, A.R. Müller3, S. Paul3, R. Picker3, V.L. Ryabov1, A.P. Serebrov1 & O. Zimmer3 1 Petersburg Nuclear Physics Institute, Gatchina, Russia 2 Institut Laue-Langevin, Grenoble, France 3 Technical University, Munich, Germany 4 Research Institute of Electrophysical Apparatus Saint Petersburg, Russia P. Geltenbort

  2. Institut Laue-Langevin (ILL) (High Flux Reactor) ESRF (6 GeV) P. Geltenbort

  3. The UCN/VCN facility PF2 at the ILL NEUTRONS FOR SCIENCE ~50 cm-3 Properties of UCN Ekin (~ 5 ms-1) = 100 neV (10-7 eV) Neutron turbine A. Steyerl(TUM/ILL - 1985) λUCN ~ 1000 Å TUCN ~ 2 mK UCN are totally reflected from suitable materials at any angle of incidence, hence storable! Vertical guide tube Cold source Long storage and observation times possible (up to several minutes)! High precision measurements of the properties of the free neutron (lifetime, electric dipole moment, gravitational levels, …) Reactor core P. Geltenbort

  4. NEUTRONS FOR SCIENCE The free neutron lifetime: plenary talks of M. Ramsey-Musolf B. Filippone Together with measurements of asymmetry coefficients in neutron decay Weak interaction theory Neutrino induced reactions: Neutrino physics Cosmology Extraction of gV,gA and Vud Neutrino detectors: Test of Conserved Vector Current (CVC: ‘gV’ = 1) Solar pp-process: Test of Unitary ofCKM matrix (Vud2+ Vus2 + Vub2 = 1) Big bang: Primordial elements’ abundances Necessary to understand matter abundance in the Universe Important input parameter for tests of the Standard Model of the weak interaction Necessary to calibrate Neutrino Detectors and to predict event rates P. Geltenbort (C. Plonka)

  5. 885.4  0.9stat0.4sys P. Geltenbort (O. Zimmer)

  6. Scheme of “Gravitrap”, the gravitational UCN storage system • 1 – neutron guide from UCN Turbine; • 2 – UCN inlet valve; • 3 – beam distribution flap valve; • 4 – aluminium foil (now removed); • 5 – “dirty” vacuum volume; • 6 – “clean” (UHV) vacuum volume; • 7 – cooling coils; • 8 – UCN storage trap; • 9 – cryostat; • 10 – mechanics for trap rotation; • 11 – stepping motor; • 12 – UCN detector; • 13 – detector shielding; • 14 – evaporator for LTF (Low Temperature Fomblin) P. Geltenbort (A. Serebrov)

  7. Quasi-elastic UCN scattering on LTF P. Geltenbort (A. Serebrov)

  8. Neutron lifetime: world average and new result n=6.5 P. Geltenbort (A. Serebrov)

  9. CKM Summary: Other? New tn !! UCNA courtesy of B. Filipponi

  10. Neutron Storage Bottlemade of permanent magnets 1 – permanent magnet 2 – magnetic field guide 560 permanent magnets (1 cm broad) horizontal magnetization Br ≥ 1.2 T ; gradient ~ 2T/cm FeCo poles between the magnets twenty-pole magnetic system P. Geltenbort (V. Ezhov)

  11. Permanent magnets PNPI — ILL — TUM (2003) small storage volume: 3.6 l (diam. 200,h 100 mm) proof of principle! Storage lifetime (882 ± 16) s P. Geltenbort (V. Ezhov)

  12. 2004 increase storage volume from 3.6 l to 15 l P. Geltenbort (V. Ezhov) P. Geltenbort (V. Ezhov) PANIC05, Santa Fe, NM (USA), October 27, 2005 12

  13. To control the depolarization of stored UCN the inner walls of the trap are covered with a thin layer of fomblin that reflects depolarized UCN. Therefore, those depolarized UCN can penetrate the magnetic barrier created by the solenoid and are measured in an UCN detector which is installed below the solenoid. Hence this detector serves as a monitor for depolarization losses during the storage of UCN in the magnetic trap. Experimental scheme storage lifetime (878  6) s leakage time (24100 ± 1400) s P. Geltenbort (V. Ezhov)

  14. Cleaning larger guide Magnetic wall is an ideal mirror, as a result there are stationary trajectories Switching on the shutter heating Polarization of leaking neutrons monitor Problems P. Geltenbort (V. Ezhov)

  15. neutron elevator sensitive to both polarizations P. Geltenbort (V. Ezhov)

  16. neutron elevator sensitive to both polarizations P. Geltenbort (V. Ezhov)

  17. 2000 UCN Elevator moves down Elevator in lowest position P. Geltenbort (V. Ezhov)

  18. Statistical treatment statistical error: 1.6 s background: 0.004 s-1 Main problem: Detection efficiency of losses? Decreasing of cleaning time (by using a neutron guide of larger cross section) P. Geltenbort (V. Ezhov)

  19. very preliminary result: storage lifetime ( 874.6 ± 1.6stat) s leakage time (23900 ± 1500) s P. Geltenbort (V. Ezhov)

  20. 2003 small trap 3.6 l storage lifetime (882 ± 16) s 2004 bigger trap 15 l storage lifetime (878  6) s Storage of UCN in a trap made of permanent magnetsPNPI – ILL - TUM 2005 trap (as in 2004) 15l + neutron elevator storage lifetime (874.6 ± 1.6) s • Outlook • larger neutron guide (cross section x 10) • precision about1 s • increase the trap volume (about 10 times) • precision about 0.3 s P. Geltenbort (V. Ezhov)

  21. future neutron lifetime projects NEUTRONS FOR SCIENCE • S. Dewey, NIST improvements in n flux measurement • V. Ezhov, PNPI (ILL) bottle made of permanent magnets • A. Steyerl, URI (ILL) LTF coated “accordion” • V. Morozov, KI (ILL) LTF coated teflon bottle • A. Serebrov, PNPI (ILL) big gravitational trap coated with LTF • P. Huffman, NSCU (NIST/SNS) sc magnet and sfHe • measure decay • S. Paul, TUM (ILL,FRM-II) bottle made of superconducting magnets • measure storage and decay • Y. Masuda, KEK (RCNP,J-PARC) bottle made of quadrupoles • measure decay • D. Bowman, LANL presented at PMSN, NIST, April 2004 bottle made of quadrupoles • now also with permanent magnets! • A. Pichlmaier, PSI (PSI) “insider” information bottle made of permanent magnets • measure storage and decay P. Geltenbort

  22. I hope I could convince you that storage of ultracold neutrons in a bottle made of permanent magnets can help to clarify the neutron lifetime puzzle! Thank you, merci beaucoup and besten Dank for your attention! P. Geltenbort

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