Primary Collimator Update

1. Primary Collimator Update Juliette Mammei on behalf of the Primary Collimator Working Group Juliette Mammei Qweak Meeting, October ‘05

2. General Outline Brief Description of the current collimator Reasons for re-examining the primary collimator Procedure for optimizing the acceptance Overview of current primary collimator “Tests” of current primary collimator What next? Juliette Mammei Qweak Meeting, October ‘05

3. Description of Current Version Profile at the detector (new estimate of acceptable inelastic percentage is .08% instead of .02%) Global Picture Juliette Mammei Qweak Meeting, October ‘05

4. Issues with the recent attempts to optimize acceptance mistake in the error calculation no internal bremsstrahlung or energy loss before the vertex not using actual error on Qpweakto optimize acceptance limiting elements defined in simulation Juliette Mammei Qweak Meeting, October ‘05

5. Error Calculation program written by Mark Pitt uses the histogram of accepted theta values adds the errors in quadrature includes latest hadronic form factor results →hadronic form factor dilution factor, 1.4 → 1.64 include Dave’s factor of 1.03 on statistical error Juliette Mammei Qweak Meeting, October ‘05

6. Fixed Running Time, increasing errors hadronic form factor dilution factor in addition, there is another factor of 1.03 on the statistical error including additional effects in the simulation reduced our rates using a “figure of merit” of R<Q2>2 was a bit misleading → use actual error on Qpweak →increase the acceptance Juliette Mammei Qweak Meeting, October ‘05

7. Optimization Procedure use “stripped down” version of experiment use actual calculated error on Qpweak as the criteria Find largest acceptance through QTOR choose downstream vs. upstream collimator location → downstream detector shape, size, z location chosen → iteratively trimmed to “fit” acceptance on bar refine collimator cutout → fit unradiated profile on bar → choose an machine-able shape Juliette Mammei Qweak Meeting, October ‘05

8. QTOR support structure Juliette Mammei Qweak Meeting, October ‘05

9. Upstream v. Downstream Considering ... Up Down same "extreme" rays smaller error on Qpweak for downstream  mechanical tolerances looser for the downstream helicity-correlated beam motion/size tolerances looser for downstream the acceptance over the target is flatter for the downstream downstream collimator would be visible to survey: it wouldn’t get so activated that no one could ever survey it again  collimators with different acceptances could be changed out mini-torus upstream of the primary collimator appears not to be a problem ? ? Based on the above, we recommended adopting the downstream collimator, and it was accepted by the collaboration. Juliette Mammei Qweak Meeting, October ‘05

10. Choosing the detector Juliette Mammei Qweak Meeting, October ‘05

11. Refining the shape Largest acceptance through QTOR Largest acceptance through QTOR trimmed for reasonable sized bar trimmed for reasonable sized bar better GEANT definition better GEANT definition more reasonable cutout more reasonable cutout fit unradiated profile on chosen bar and use straight sides fit unradiated profile on chosen bar and use straight sides Juliette Mammei Qweak Meeting, October ‘05

12. Description of Current Version Cleanup collimators upstream and downstream of primary six-sided opening – approximately square at large theta and at an angle at smaller theta so far top and bottom point to upstream and downstream end of target, respectively, using “normal” angles sides not slanted at all in y designed for minitorus off error on Qpweak = 4.18% - including Dave Mack's factor of 1.03 on the statistical errorNote: The asymmetry is -.237 ppm, while the hadronic fraction is 30.2% and the axial fraction is 3.4% Juliette Mammei Qweak Meeting, October ‘05

13. Coordinates of Corners of openings Upstream face Downstream face x y z x y z 16.34 3.83 -583.41 16.34 -3.83 -583.41 13.06 3.83 -583.41 13.06 -3.83 -583.41 5.00 1.47 -583.41 5.00 -1.47 -583.41 57.00 10.01 -360.719 57.00 -10.01 -360.719 40.04 10.08 -360.719 40.04 -10.08 -360.719 31.40 6.51 -360.719 31.40 -6.51 -360.719 79.00 17.22 -271.859 79.00 -17.22 -271.859 48.63 17.22 -271.859 48.63 -17.22 -271.859 38.00 13.46 -271.859 38.00 -13.46 -271.859 19.30 3.83 -568.17 19.30 -3.83 -568.17 13.06 3.83 -568.17 13.06 -3.83 -568.17 6.20 1.82 -568.17 6.20 -1.82 -568.17 62.00 10.03 -339.059 62.00 -10.03 -339.059 40.04 10.08 -339.059 40.04 -10.08 -339.059 33.10 7.21 -339.059 33.10 -7.21 -339.059 82.00 17.22 -256.619 82.00 -17.22 -256.619 48.63 17.22 -256.619 48.63 -17.22 -256.619 39.50 13.98 -256.619 39.50 -13.98 -256.619 downstream primary upstream cleanup cleanup Current Version Juliette Mammei Qweak Meeting, October ‘05

14. Profile at the focal plane Rate : 875 MHz <Q2> : .0258 GeV2 Error on Qpweak : 4.18 Inelastic %: .04% Juliette Mammei Qweak Meeting, October ‘05

15. Tests of the Collimator using air instead of helium variation of QTOR current variation of beam energy adjust BFIL to fit “minitorus on” profile on detector Jim Birchall sensitivity studies Juliette Mammei Qweak Meeting, October ‘05

16. Air instead of helium? air helium Juliette Mammei Qweak Meeting, October ‘05

17. Variation of QTOR current BFIL = 99% BFIL = 100% BFIL = 101% Juliette Mammei Qweak Meeting, October ‘05

18. Variation of beam energy Ebeam = 1065 MeV Ebeam = 1115 MeV Ebeam = 1215 MeV Juliette Mammei Qweak Meeting, October ‘05

19. Summary of Rates for Tests Version ep Rate <Q2> Error (MHz) (GeV2) on Qpweak “final” version, with BFIL = 1.00 875 .0258 4.18 same as row 1, BFIL =.99 889 .0257 4.17 same as row 1, BFIL =1.01 850 .0259 4.21 same as row 1, beam energy = 1065 MeV 998 .0218 4.01 same as row 1, beam energy = 1115 MeV 922 .0238 4.11 same as row 1, beam energy = 1215 MeV 793 .0276 4.33 same as row 1, air instead of helium 804 .0258 4.29 Juliette Mammei Qweak Meeting, October ‘05

20. Adjust QTOR current to fit “minitorus on” profile on bar Rate : 756 MHz <Q2> : .0274 GeV2 Error on Qpweak : 4.25 Inelastic %: .03% Juliette Mammei Qweak Meeting, October ‘05

21. Jim Birchall sensitivity studies See his talk later today... but basically, everything’s okay Juliette Mammei Qweak Meeting, October ‘05

22. TO DO List: “slant” in x and y of the openings background studies downstream cleanup collimator choice of material/thicknesses for three collimators beamline/shielding detector shielding wall minitorus on/off during production running dose on QTOR and minitorus support structures “slant” in x and y of the openings background studies downstream cleanup collimator choice of material/thicknesses for three collimators beamline/shielding detector shielding wall minitorus on/off during production running dose on QTOR and minitorus support structures Juliette Mammei Qweak Meeting, October ‘05

23. Conclusions z location of collimator chosen general cutout of acceptance is defined background studies are under way detector size/shape were chosen Technical report ... COMING SOON! http://www.phys.vt.edu/~jmammei/for_dave.html http://www.phys.vt.edu/~jmammei/coll_opt.html http://www.phys.vt.edu/~jmammei/track_group.html Juliette Mammei Qweak Meeting, October ‘05

24. Unradiated profile fits on bar Richard Jones’ internal bremsstrahlung and energy loss before vertex code switched off target, windows and global volume defined as vacuum gives a “clean” profile at the focal plane Juliette Mammei Qweak Meeting, October ‘05

25. Definition of angles extreme angles are black normal angles are red Juliette Mammei Qweak Meeting, October ‘05

26. “FOM vs. angular increments” Juliette Mammei Qweak Meeting, October ‘05