1. Anti-did and B-field for ILD
Short summary of past activities
AntiDID info
From the point of view of the TPC, based on the experience with Aleph
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Ron Settles, MPI Munich

2. Some anti-did information
from earlier studies,
nicely summarized by Andrei Seryi
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Ron Settles, MPI Munich

3. Paris
Ron Settles, MPI Munich

4. Optimizing anti-DID for LDC
With optimal anti-DID, more than 60% of pairs are directed into the extraction aperture
SR effects are larger in LDC than in GLD.
One can use 30% weaker antiDID to reduce SR, but still >50% pairs will go to extraction aperture
L loss due to SR effects
Normal DID
DID OFF
Optimal anti-DID
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Ron Settles, MPI Munich

5. Andrei’s conclusion
Application of anti-DID was considered for SiD, GLD, LDC
The anti-DID field strength was optimized to maximize the number of pairs directed to extraction aperture
SiD: more than 60% of pairs are directed into extraction aperture
GLD: more than 50% pairs
LCD: more than 60% for 5% Lumi cost, ~50% for 2% Lumi cost
The anti-DID does increase SR effects for incoming beam, but effect is
negligible in SiD (less than 0.2% of Lumi)
very small in GLD (less than 1% of Lumi)
small in LDC (about 2%)
The modified DID field shape with flattened central region was used for GLD and LDC
→ the flattening at the center was dropped later
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Ron Settles, MPI Munich

6. Recommendation
Anything reasonable that can be done to reduce the backgrounds, should be done
Paris
Ron Settles, MPI Munich

7. Time Projection Chamber Issues
What about the B-field?
A brief history, reviewed at the ILD meeting in Paris 2010
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Ron Settles, MPI Munich

8. ILD MDI meeting, the SOLENOID… ILD @ Paris, 27 January 2010
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

9. Picture courtesy Henri Videau
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Ron Settles, MPI Munich

10. correction coils were originally foreseen, as in Aleph
B-field
correction coils were originally foreseen, as in Aleph
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Ron Settles, MPI Munich

11. B-field in Aleph
The ‘BIG’ question: “Do we need the corrector windings for ILD?” The history of this issue…
Henri Deports, Francois Kircher, and team corrected the solenoid for Aleph to Br/Bz dz ≤ ~ 2mm, based on two notes by John Rander.
The idea from John’s notes was that the B field had to be homogeneous to ~ 2mm for the above integral so that displacement of electron drift remains small.
John mentioned that “the events themselves may be used to measure [certain effects like] tilted E and B axes.” This was done later by Werner Wiedenmann, see
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

12. John didn‘t mention the B-field map, but Aleph did make a good one, which was important...
…by investing sufficient effort in measuring it, but several problems remained which we must avoid (read the note for details).
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

13. The proposal is documented in an LCNote
Then at ILC came the idea of the antiDID, for which the ~2mm would become ~20mm. What could we do?
The proposal is documented in an LCNote
...see below...
LC-DET at
ILC-NOTE at
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

14. Paris
Ron Settles, MPI Munich

15. The basic idea: any B-inhomogeniety can be corrected if the B-field is known exactly, i.e., mapped well enough. We just have to invest sufficient effort in measuring it…
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

16. The basic idea: any B-inhomogeniety can be corrected if the B-field is known exactly, i.e., mapped well enough. We just have to invest sufficient effort in measuring it…
e.g., √100² + 30² = 105²
e.g., √ 70² + 55² = 105²
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

17. The recipe: increase the number of measuring points if you need more accuracy…
And a.o.t. the Bphi component (which is zero in the main coil by design, but there are other sources) is more important than Br…
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

18. B-field
Items from the note --B-fields should be mapped for the various configurations forseen for the ILD running. --The maps should have an accuracy of about 1-2 G, as was achieved at Lep. --The number of points to be measured, the number of Hall probes and NMR probes, the accuracy of their positioning, the stability of the power supplies, etc should be estimated by simulation. --There are several other items in the note; above are the main ones.
Paris
Ron Settles, MPI Munich

19. Now for calculations of possible distortions by Olivier Delferriere...
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Ron Settles, MPI Munich

20. Where were we? The 20mm Werner and I thought about had become 35mm with the antiDID and 50mm without correctors is only a factor 1.5 larger, again the BIG question was: “Do we need the corrector windings?” At Paris, the decision was NO!¹·² ¹It doesn’t make sense to ‘correct’ the field if there is a gradient due to the antiDID anyway ²The 50mm divided by ωτ is ~5mm, which is significant and must be corrected
27/01/2010 and later
Ron Settles MPI-Munich ILD MDI at the Paris ILD meeting Jan and later

21. B-field
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Ron Settles, MPI Munich

22. The accuracy needed for the B-map will define the number of points to be measured in the drift volume
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Ron Settles, MPI Munich

23. The TPC places NO requirement on the homogeniety of the B-field
Conclusion
The TPC places NO requirement on the homogeniety of the B-field
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Ron Settles, MPI Munich

24. ADDITIONAL MATERIAL
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Ron Settles, MPI Munich

25. ...from Toshiaki Taucho‘s talk at the ILC detector meeting at KEK on 20160929...
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Ron Settles, MPI Munich

26. ...from Karsten Büsser‘s talk at the ILC@Desy Project meeting on 20161007...
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Ron Settles, MPI Munich