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Future Perspectives of the Bonn Polarized Target

Future Perspectives of the Bonn Polarized Target. Since the mid 1980‘s: Bonn is a place of excellence in the field of polarized solid targets ! Still valid today, especially concerning the ‚ hardware ‘ !  Famous ‚GDH cryostat‘, now used for CB ELSA

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Future Perspectives of the Bonn Polarized Target

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  1. Future Perspectives of the Bonn Polarized Target Since the mid 1980‘s: Bonn is a place of excellence in the field of polarized solid targets ! Still valid today, especially concerning the ‚hardware‘ !  Famous ‚GDH cryostat‘, now used for CB ELSA But: Development of the ‚software‘ = Polarizable target materials ! Needed: Reestablishment of the material research branch Chance : Collaboration between the Bonn Polarized Target group and the Radiation Safety Officer of the Physics Institut

  2. Maximum Polarization FS Relaxation Time Dilution Factor Preparation & Handling Radiation Resistance Figure of Merit ~ P2 f2 Beam Intensity The Material Economy Availability large amounts Special Requirements Thermal Conductance Target Set-Up Experiment

  3. Special Requirements • by the target (cryostat) • Loading temperature •  Temp. stability of the • unpaired electrons • ‚Enhanced‘ base temperature •  Particularly long • FS relaxation times • Internal polarization magnet •  Reduced sensitivity on • magn. field parameters • by physics experiment • Background nuclei •  Polarized ? •  Light nuclei needed ? • Low energy reaction products •  Target = Detector •  Polarizable szintillator • ‚Active Target‘

  4. Target material development & Possible Experiments • The period of the ‚gold diggers‘, the phenomenological period: • Radiation Hardness & Dilution Factor • ~ 1960: First target material LMN proposed by Abragam/Jeffries 1010/cm2 • 1962: 70% proton polarization, used in > 40 Exp. since 1968 ~ 3% • 1966: Invention of the alcohols (butanol !) by S. Mango * 103 •  First pol. experiments with electromagnetic probes ~ 13% • 1970‘s: Development of a ammonia (NH3, ND3) by Niinikoski/Meyer * 101 •  First pol. electron scattering exp. (SLAC/EMC) ~ 17% • 1980: Proposal of the Lithium Hydrides (6LiD/7LiH) by A. Abragam * 101 • ~ 50% • 1990‘s: Development of a reproducible preparation method (Saclay, • Bonn, Bochum), used in E155@SLAC, COMPASS@CERN, GDH@ELSA

  5. Target Material Development & Possible Experiments (Bonn and Bochum 1990-today) B) The period of the ‚pea counters‘, the systematical period: DNP & Max. Polarization 1990‘s: Spin temperature theory and the DNP of LiD/LiH 2000 : Preparation of 1 liter 6LiD for COMPASS@CERN (± 55%) 2000+: Further systematical investigations Properties of the electron centers  Polarization behaviour  Understanding the magnetic field behaviour of d-butanol  Irradiated d-butanol: 70% @ 5T  Trytil doped deuterated alcohols & diols: ~80% @ 2.5T

  6. Necesseties for fruitfull material research activities • Experience  • Intense collaboration with our Bochum colleagues • Equipment  • Simple to operate polarization apparatus for material tests •  currently under construction • NMR system for polarization measurement •  PhD position, advertized with positve resonance • EPR system for studying the DNP active electron centers •  Collaboration with the Sync. Rad. Group of ELSA • Man power  • Lots of enthusiastic students !!!

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