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The PSI UCN source. Status summer/autumn 2007: 1) Introduction 2) Source principle 3) R & D experiments UCN storage, losses and depolarization UCN production in solid deuterium 4) Some impressions. Zürich - Vancouver. Zürich - Vancouver. Switzerland. PSI.

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The PSI UCN source


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    1. The PSI UCN source Status summer/autumn 2007: 1) Introduction 2) Source principle 3) R & D experiments UCN storage, losses and depolarization UCN production in solid deuterium 4) Some impressions

    2. Zürich - Vancouver

    3. Zürich - Vancouver

    4. Switzerland PSI

    5. Paul-Scherrer-Institut 600 MeV p cyclotron 2 mA, 1.2 MW, since 1974 Upgrade  2 MW (2009) PSI: 1200 employees 1000 external users SINQ: n SR: , UCN: n Proton cyclotron for medical application: p SLS: 

    6. Proton accelerator @ PSI Ring cyclotron: 600MeV, 2mA 1.2MW (unique!) UCN Source nEDM experiment

    7. 600 MeV How do we make neutrons at PSI?

    8. PSI UCN source 2.5 m 2m3 1.2 MW p beam spallation target

    9. Spallationsprozess

    10. PSI UCN source 2.5 m 2m3 heavy water moderator

    11. PSI UCN source Lebensdauer in D2O: 5 ms v = 2200 m/s Reichweite: ~10 m 2.5 m 2m3 heavy water moderator

    12. Neutron production at PSI (SINQ, UCN) Spallation target: lead (82p + 126n) Proton beam: 2mA (or more!)  1016 p/s 1 proton  10 neutrons  1017 n/s ~10 s Puls  1018 n/puls Average neutron energy 2MeV  20’000 km/s After ca. 30 bounces ~25 meV  2200 m/s

    13. Φ0 Thermal flux 0.2 • 1013/cm2/mA 0.4 0.8 1.0 2.0 4.0 6.0 8.0 10.0 sD2 Pb Neutron flux at PSI UCN source sD2 near target! 8 s-puls (1.2 MW): 5 K  8 K 800 s no beam 8 K  5 K

    14. Pulsed UCN source 800s 8s

    15. Pulsed UCN source 800s 8s

    16. Pulsed UCN source 800s 8s

    17. b a Cu Be, DLC UCN cold source h = 2.5 m V = 2m3 v = 0 – 7 m/s Coherent strong interaction surface potential of solid deuterium (106 neV  4.5 m/s) v = 5 – 9 m/s cold source Needs: storage volume coating ( storable neutrons ~vc3!)

    18. "bad" 58Ni Cu Fe Ni 65Cu BeO Al C Be 300 K Pb Be 70 K DLC Diamond "good" Storage materials low wall loss probability µ long storage time high Fermi potential more UCN (v3)

    19. wall material: loss and depolarization Detector count rate: 105 1 Sample B Magnet 100 % 0 B 0 100 200 300 400 time [s] UCN from ILL-turbine Detector

    20. Diamondlike carbon Wall loss coefficient  [1 / wall collision] x 10-4 DLC is a good choice  also for  (DLC)=1•10-6,  (Be)=10•10-6 F. Atchison et al., Phys. Lett. B 625, 19 (2005). T. Brys et al., Nucl. Instr. and Meth. in Phys. Res. A 550, 637 (2005).

    21. vc(Be) = (6.9  0.1) m/s vc(DLC) = (6.9 0.1) m/s UCN transmission: Fermi potential F. Atchison et al., NIMB 260, 647 (2007), Phys. Lett. B 642, 24 (2006).

    22. DLC: (6.9 ±0.2)m/s F. Atchison et al., NIMB 260, 647 (2007). PLB 642, 24 (2006). Be: (6.8 ±0.2)m/s UCN transmission: Fermi potential

    23. solid D2: Motivation Need to know for solid Deuterium: • UCN production cross section • theoretical: Golub and Böning, ZPB51(1983)95 • experimental: F. Atchison et al., PRC 71, 054601 (2005). • UCN lifetime • theoretical: Liu et al., PRB62(2000)R3581 • experimental: Morris et al., PRL89(2002)272501 • UCN mean free path • theoretical: incoherent cross section, sinc = 4.1 barn • experimental: F. Atchison et al., PRL 95, 182502 (2005).

    24. solid D2: Motivation mfp, t t ~ 30ms R h ~ 150mm v = 5 m/s = 150 mm / 30 ms

    25. Transmission experiments UCN, VCN cold very-cold ultra-cold 1000 – 100 m/s 100 – 10 m/s 10 – 0 m/s

    26. Preparation of sD2(T = 18 K) 12 hours Liquid Solid

    27. Thermal stress

    28. Cross sections Thermal stress IV Mean free path 1 cm2 cm 8 cm UCN F. Atchison et al., PRL 95, 182502 (2005).

    29. UCN production at SINQ, PSI F.Atchison et al., PRC 71, 054601 (2005). UCN CN UCN + CN sD2 Detector

    30. UCN production at SINQ, PSI F. Atchison et al., PRC 71, 054601 (2005). Empty cell solidD2 liquid D2 and gaseous D2

    31. UCN production at PSI Our experiment:F.Atchison et al., PRC 71, 054601 (2005). Rsolid,8K = (1.11±0.23) x 10-8 cm-1 • in agreement with Z.-Ch. Yu et al., ZPB62(1986)137 Estimate for PSI UCN source: - FCN ~ 2 x 1013 cm-2s-1mA - tUCN ~ 30 ms • 50% of equilibrium density after 4s proton pulse rUCN = Rsolid,8K x FCN x tUCN x 0.5 ≈ 5000 cm-3 2000 cm-3 in storage, 1000cm-3 in experiments In Grenoble: ρ(UCN) = 10 UCN cm–3

    32. Where is the UCN source Ring cyclotron: 600MeV, 2mA 1.2MW (unique!) UCN Source nEDM experiment

    33. Proton beam

    34. Proton beam 1000 A (10 ms) test beam September 6, 2007 UCN source Proton beam line

    35. Experimental areas EDM  > 1000 UCN/cm3 Test beam 1000 A, 10 ms September 6, 2007 target n 1.2 MW proton beam, UCN source, Exp. Areas

    36. test beam dump

    37. Harp monitors Quadrupole collimator D2O circuit Proton beam Existing Experimental floor

    38. Proton beam Proton beam line

    39. 50 cm Dome Torus PSI UCN source Relative Masses: Flat foil 100 % Torus 110 % Dome 131 % 2.5 m 2m3 Cold source spallation target 1.2 MW p beam

    40. UCN tank fabrication

    41. Vacuum box of UCN tank system

    42. spallation target target head iron shielding lead block target water pipes

    43. D2 hut 30 m3 He liquefier D2 Gas System D2 tanks

    44. Gas handling boxes

    45. UCN-Tanksystem: Schwerwasser 8m3 Heat exchangers D2O-Tanks Pumpe (25 l/s) Ion exchangers

    46. Papers in 2003/04 • Ortho-para equilibrium in a liquid D2 neutron moderator under • irradiation PRB 68, 094114 (2003). • Spallation yields of neutrons produced in thick lead/bismuth targets • by protons at incident energies of 420 and 590 MeV • NIMB 217, 202 (2004). • An apparatus for the investigation of solid D2 with respect to • ultra-cold neutron sources NIMA 533, 491 (2004).

    47. Papers in 2005 1) The simulation of ultracold neutron experiments using GEANT4 NIMA 552, 513 (2005). 2) On the use of lead/tin alloys as target material for the production of spallation neutrons NIMA 539, 646 (2005) 3) A fast kicker magnet for the PSI 600 MeV proton beam to the PSI ultracold neutron source NIMA 541, 598 (2005) 4) Magnetron sputtered Be coatings as reflectors for ultracold neutrons NIMA 551, 429 (2005). 5) Measured Total Cross Sections of Slow Neutrons Scattered by Gaseous and Liquid 2H2 PRL 94, 212502 (2005) 6) Production of ultracold neutrons from a cold neutron beam on a 2H2 target PRC 71, 054601 (2005) 7) Magnetic field stabilization for magnetically shielded volumes by external field coils NIMA 554, 527 (2005). 8) A novel apparatus for the investigation of material properties for the storage of ultracold neutrons NIMA 550, 637 (2005)

    48. Papers in 2005/06/07 • First storage of ultracold neutrons using foils coated with • diamond-like carbon Phys. Lett. B 625, 19 (2005). • Measured total cross sections of slow neutrons scattered by solid • deuterium and implications for ultracold neutron sources • Phys. Rev. Lett. 95, 182502 (2005). • 3) Storage of ultracold neutrons in a volume coated with diamondlike carbon Phys. Rev. C 74, 055501 (2006). • 4) Diamondlike carbon can replace beryllium in physics with ultracold neutrons Phys. Lett. B 642, 24 (2006). • 5) The spallation target of the ultra-cold neutron source UCN at PSI • NIMA 564, 51 (2006). • 6) A time-of-flight chopper for ultracold neutrons • NIMA, 557, 572 (2006). • 7) Structural characterization of diamond-like carbon films for ultracold • neutron applications Diamond & Related Materials, 16, 334 (2007). • 8) Measurement of the Fermi potential of diamondlike carbon and other materials NIMB 260, 647 (2007).

    49. On the way to the top! Schedule: 1st UCN October 2008