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Future Perspectives of the Bonn Polarized Target: A Legacy of Excellence

Since the mid-1980s, Bonn has excelled in the field of polarized solid targets, especially in hardware like the GDH cryostat. However, the development of software, i.e., polarizable target materials, is crucial and requires reestablishment of the material research branch. Collaboration opportunities exist between the Bonn Polarized Target group and the Radiation Safety Officer of the Physics Institut. Topics include Maximum Polarization, FS Relaxation Time, Dilution Factor, Preparation & Handling, Radiation Resistance, and Figure of Merit involving P2, f2, and Beam Intensity. Special requirements like Thermal Conductance, Target Set-Up, and Experiment specifications must be considered. The development of target materials and possible experiments are outlined from the "gold diggers" era to systematic investigations. The description further delves into necessities for fruitful material research activities, equipment requirements, and man-power involvement in the Bonn research efforts.

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Future Perspectives of the Bonn Polarized Target: A Legacy of Excellence

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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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