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The ”mature” target (2000-2005)

The ”mature” target (2000-2005). Hermes End of Data Taking - Hamburg, 01.07.07. P. Lenisa – Università di Ferrara and INFN. Data taking: longitudinal run. Deuterium 2000 The “wonder” target. No T dependence of a and P a No recombination No wall depolarization (SEC negligible).

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The ”mature” target (2000-2005)

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  1. The ”mature” target(2000-2005) Hermes End of Data Taking - Hamburg, 01.07.07 P. Lenisa – Università di Ferrara and INFN

  2. Data taking:longitudinal run

  3. Deuterium 2000The “wonder” target • No T dependence of a and Pa • No recombination • No wall depolarization (SEC negligible) • 8 months of perfect running • HERA (no beam dumps) • HERMES (no vacuum breaks) • TARGET (no hardware failures) IDEAL target → no drawbacks from use of storage cell

  4. The enemies of a bad cell:Sampling corrections Average value in the cell Measured in the polarimeter

  5. The enemies of a bad cell:Sampling corrections Average value in the cell Measured in the polarimeter No recombination and no depolarization  “The polarization we measure is exactly what the beam sees”

  6. The beauty secret: water Excellent initial performance Improved with aging thanks to D20 covering

  7. 2003 reanalysis of 1997 hydrogen data“Now we understand our target” 4 different data periods Use of limit for sampling corrections Use of measured value for molecular polarization (b=Pm/Pa)

  8. Summary of target performance.Longitudinal running.

  9. Data taking:transverse run

  10. Fourier analysis of e-bunch: • Resonance condition: Depolarization Transverse running: beam induced depolarization Longitudinal holding field

  11. Transverse running: beam induced depolarization Transverse holding field

  12. Transverse magnet Field intensity: 297 mT • DB along z: 0.05 mT • DB along y: 0.18 mT • DB along x: 0.7 mT (requested: DB 0.15 mT)

  13. Cell correction coils

  14. Hydrogen 2003/04The “hidden” beauty No recombination Minimal depolarization for an H target Target reached the FOM limit

  15. Summary of target performance Transverse running.

  16. The cherries on the (target) cake…

  17. Measurement of polarization of recombined molecules Recombination on cell walls Impact on target polarization No measurements existing on recombination on an insulating surface (like Drifilm) Delicate measurement of surface physics

  18. Measurement’s principle b=Pm/Pa Tcell set to 260 K (recombination increased)

  19. Pm=bPa=0.34±0.22 -> atoms on Drifilm surface are polarized (tr~ 14s) Results bHERMES = Pa/Pm= 0.68±0.09stat±0.06syst

  20. First measurement of the spin-exchange collision cross-section in the low temperature region • Spin-exchange collision: two body process in which two atoms exchange their spins (conserving total angular momentum) • Control of the cell temperature allows for variations of atomic gas temperature • HERMES target unique tool for precision measurement of atomic polarization

  21. Measurement’s principle I • Pz+injected (|1>, |4>) spin-exchange collision |4> → |2> (DPz) • Pz- injected (|2>, |3>) spin-exchange collisions |2> → |4> (DPz) ↓ spin exchange collisions cause nuclear depolarization of the sample (DPz) A measurement of DPz gives access to sSE

  22. Measurement’s principle II Decoupling of the two effects by intensity variation of the atomic beam DPz=DPse DPz=DPse • Two depolarization mechanisms active in the cell • Wall depolarization (density independent) • Spin-exchange (density dependent)

  23. Results HERMES data

  24. Numbers…

  25. Data Best existing world sample Only existing world sample

  26. The “innocent” victim Cells • 13 cells used • 9 months average last (1 min, 18 max) • 20 produced • 50 man-months

  27. Records 2004 5 broken dissociator tubes 1999 4 beam dumps (Total: 9 bad dumps)

  28. Papers 3 Collaboration papers 7 dedicated target papers (3 possible additional papers) 10 PhD thesis 7 diploma thesis

  29. Manpower (1996-2005) B. Braun, C. Baumgarten, I. Brunn, M. Capiluppi, V.Carassiti, G. Ciullo, G. Court, P. Dalpiaz, D. Fick, A. Golendukhin, E. Garutti, G. Graw, W. Haeberli, M. Henoch, R. Hertenberger, N. Koch, H. Kolster, H. Marukyan, R. Mussa, A. Nass, S. P. Pod’yachev, M. Raithel, D. Reggiani, K. Rith, C. Simani, E. Steffens, J. Stenger, J. Stewart, P. Tait, S. Tessarin, S.Wang, H. Ye, Y. Ye, T. Wise 22 senior physicists 10 PhD students 7 Diploma students (> 70 man years)

  30. Target awards

  31. The best piece of art 02.03.02 – TGA chamber opened after 8 years of operation

  32. The most original DESY aquarium 07.02.03 – ABS flooded (50 liters of water)

  33. The most insane (realized) suggestion 19.05.04 – 1680 minutes of uninterrupted TGA chopper wheel observation

  34. The biggest pig which entered East Hall 15.08.05 – Spin and pork seminar

  35. The biggest pig which entered East Hall (dead) 15.08.05 – Spin and pork seminar

  36. Beginning 1988: “We will install an polarized internal target in HERA (with a storage cell) and measure its polarization with 3% absolute error” The most courageous (crazy?) intuition

  37. R.I.P. Apr. 23rd 1996 Nov. 13th 2005 but up and running for PAX(since 21.05.07) P.S. The HERMES target is not dead…

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