The HERMES polarized target

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The HERMES polarized target
Paolo Lenisa Universita and INFN Sez.
Ferrara, Italy

• Principle of operation
• Target polarization
• Performance
• Discussion

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The target in the HERMES experiment
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(No Transcript)
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Principle of operation
Y. Ye Direct measurement of Intrabeam Scatterin
g in Atomic Beam Sources
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Principle of operation
Pz 1gt 4gt Pz- 2gt 3gt
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Principle of operation
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Target operation

• Longitudinal Polarization (B335 mT)
• 1996 - 1997 Hydrogen
• 1999 - 2000 Deuterium

• Transverse Polarization (B297 mT)
• 2002 - Hydrogen

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The storage cell

• Material75 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)

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The storage cell

• Advantages
• No diluition
• Rapid inversion of polarization
• Increase in density respect free jet (100)

• (Supposed) drawbacks

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Beam induced depolarization

• Hera e-beam time structure
• 220 bunches
• Spacing Dt 96 ns
• Width st 37.7 ps

Fourier analysis of e-bunch
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Resonance conditions
p transitions (BST ? BRF) long. trans. s
transitions (BST ?? BRF) trans. only
DB s2-4 0.37 mT
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Transverse hydrogen running holding field
B 297 mT DB ? 0.15 mT
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s resonance measurements

• Spin flip measurement
• e-beam current gt 20 mA
• Injection state 4gt
• Target field scanned around working point (297
  mT)
• Detection states 1gt and 2gt
• A peak in the signal indicates a resonance

D. Reggiani Beam Induced Depolarization in the
HERMES polarized target
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Target polarization

• PT total target polarization
• a0 atomic fraction in absence of recombination
• ar atomic fraction surviving recombination
• Pa polarization of atoms
• Pm polarization of recombined molecules

• Relation to measured quantities
• Sampling corrections
• ar ca arTGA
• Pa cP PaBRP

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Target performance

• Longitudinal Polarization (B335 mT)
• 1996-1997 Hydrogen

1999-2000 Deuterium
Pt 0.845 0.028
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Target performance

• Longitudinal Polarization (B335 mT)
• 1996-1997 Hydrogen
• 1999-2000 Deuterium

Pt 0.845 0.028
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Target performance

• Transverse Polarization (B297 mT)
• 2002 - Hydrogen

PT 0.795 ? 0.033
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Summary of target performance since 1997
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Conclusions

• The HERMES H/D polarized target is stably and
  reliably running since 1996.
• High-polarization (Pgt80 )
• 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