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The HERMES polarized target

The HERMES polarized target. Paolo Lenisa – Universita’ and INFN – Sez. Ferrara, Italy. Principle of operation Target polarization Performance Discussion. The target in the HERMES experiment. Atomic Beam Source NIM A 505, (2003) 633. Principle of operation.

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The HERMES polarized target

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  1. The HERMES polarized target Paolo Lenisa – Universita’ and INFN – Sez. Ferrara, Italy • Principle of operation • Target polarization • Performance • Discussion

  2. The target in the HERMES experiment

  3. Atomic Beam Source NIM A 505, (2003) 633 Principle of operation Y. Ye :“Direct measurement of Intrabeam Scattering in Atomic Beam Sources”

  4. Atomic Beam Source NIM A 505, (2003) 633 Principle of operation Pz+ = |1> + |4> Pz- = |2> + |3>

  5. Atomic Beam Source NIM A 505, (2003) 633 Storage cell NIM A 496, (2003) 277 Diagnostics: • Target Gas Analyzer NIM A 508, (2003) 265 • Breit-Rabi Polarimeter NIM A 482, (2002) 606 Principle of operation

  6. Target operation Longitudinal Polarization (B=335 mT) • 1996 - 1997 Hydrogen • 1999 - 2000 Deuterium TransversePolarization (B=297 mT) • 2002 - … Hydrogen

  7. The storage cell Material:75 mm Al with Drifilm coating Size: length: 400mm, elliptical cross section (21 mm x 8.9 mm) Working temperature: 100 K ( variable 35 K – 300 K)

  8. The storage cell • Advantages: • No diluition • Rapid inversion of polarization • Increase in density respect free jet (~100) (Supposed) drawbacks

  9. Resonance condition: Depolarization Beam induced depolarization Hera e-beam time structure: • 220 bunches • Spacing: Dt = 96 ns • Width: st = 37.7 ps Fourier analysis of e-bunch:

  10. DB magnet 0.15 mT Resonance conditions p transitions (BST  BRF)long.&trans. s transitions (BST  BRF)trans. only DB s2-4 = 0.37 mT

  11. Transverse hydrogen running: holding field B = 297 mT DB  0.15 mT

  12. s resonance measurements Spin flip measurement • e-beam current: > 20 mA • Injection: state |4> • Target field: scanned around working point (297 mT) • Detection: states |1> and |2> A peak in the signal indicates a resonance D. Reggiani: “Beam Induced Depolarization in the HERMES polarized target”

  13. Eur. Phys. J. D 29 (2004) 21 Target polarization • PT = total target polarization • a0 =atomic fractionin absence of recombination • ar=atomic fractionsurviving recombination • Pa= polarization of atoms • Pm = polarization of recombined molecules • Relation to measured quantities: • Sampling corrections • ar=caarTGA • Pa= cPPaBRP

  14. Target performance Longitudinal Polarization (B=335 mT) • 1996-1997 Hydrogen 1999-2000 Deuterium Pt = 0.845 ± 0.028

  15. Target performance Longitudinal Polarization (B=335 mT) • 1996-1997 Hydrogen • 1999-2000 Deuterium Pt = 0.845 ± 0.028

  16. Target performance Transverse Polarization (B=297 mT) • 2002 - … Hydrogen PT = 0.795  0.033

  17. HERMES Coll.: submitted Summary of target performance since 1997

  18. Conclusions • The HERMES H/D polarized target is stably and reliably running since 1996. • High-polarization (P>80 %) • The systematics is fully under control (DP = 3%) • It expresses the work of: • 10 PhD thesis • 7 Diploma thesis • 17 senior scientists • It will be decommissoned in sommer 2005 (?) but this is not the end of the story… The target is ready for new challenges: F. Rathmann : “Spin-physics at GSI”

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