1. 1 4 Oct 05 Optimization of anti-DID for SiD, GLD and LDC A.Seryi October 4, 2005

2. 2 4 Oct 05 Motivation and Procedure For 14mrad x-ing, the SR effects are reduced => can optimize DID for outgoing beam (anti-DID) Optimize field strength of anti-DID in order to direct maximum number of pairs into extraction hole –for that, tracking of Guinea-pig pairs was included into the process For detectors with TPC, use DID with new field shape, with reduced field in the center Refs: Modification of DID for detectors with TPC & Anti-DID to improve background: http://www-project.slac.stanford.edu/lc/bdir/Meetings/beamdelivery/2005-09-27/index.htm http://www-project.slac.stanford.edu/lc/bdir/Meetings/beamdelivery/2005-09-27/index.htm

3. 3 4 Oct 05 Use 2005 field maps for SiD and GLD and older TESLA field for LDC Use 14mrad total crossing angle, L*=3.51m for SiD detector and L*=4.51m for GLD and LDC Use same FD structure, with FD quads and sextupoles rematched SiD field and FD with L*=3.5m GLD field and FD with L*=4.5m LDC field and FD with L*=4.5m

4. 4 4 Oct 05 Optimizing anti-DID for SiD With optimal anti-DID, more than 60% of pairs are directed into the extraction aperture Optimal anti-DIDDID OFFNormal DID

5. 5 4 Oct 05 SiD & anti-DID High energy pairs follow initial beam trajectory, and go to extraction aperture Low energy pairs follow the field line, and also go to extraction aperture Use Guinea-pig pairs for nominal ILC parameters

6. 6 4 Oct 05 Normal DID & SiD With normal DID, which is optimized for incoming beam, the high energy pairs go to extraction aperture, but low energy pairs directed away from extraction aperture

7. 7 4 Oct 05 SiD, L*=3.5m, 14mrad IP Y,  mIP Y’,  rad  SR, nm Lum, % anti-DID with 0.0205 T0-1020.3299.8 Incoming beam in SiD with anti-DID Anti-DID increase SR effects for incoming beam, but for 14mrad the impact is negligible (~ 0.2% on Lumi) QD0

8. 8 4 Oct 05 Optimal anti-DID for SiD Note that strength of anti-DID is smaller than nominal DID For 14mrad: –The optimal anti-DID max field is 0.0205 T –The nominal DID max field is 0.036 T Thus, normal DID is 1.75 times stronger than anti-DID for SiD

9. 9 4 Oct 05 Optimizing anti-DID for GLD With optimal anti-DID, more than 50% of pairs are directed into the extraction aperture Optimal anti-DID DID OFF Normal DID

10. 10 4 Oct 05 Normal DID Optimal anti-DID GLD

11. 11 4 Oct 05 GLD, L*=4.5m, 14mrad IP Y,  mIP Y’,  rad  SR, nm Lum, % anti-DID0-960.65> 99 Incoming beam in GLD with anti-DID Anti-DID does increase SR effects for incoming beam, but for 14mrad the impact is minor (less than 1% on Lumi) QD0

12. 12 4 Oct 05 Optimal anti-DID for GLD Field in the central region is flattened with two DID coils (short and long) whose currents are properly adjusted In comparison with air coil calculated field (see Sep 27 notes), this field takes into account an approximate effect of detector iron

13. 13 4 Oct 05 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 Optimal anti-DIDDID OFFNormal DID L loss due to SR effects

14. 14 4 Oct 05 Optimal anti-DIDNormal DID LDC

15. 15 4 Oct 05 LDC, L*=4.5m, 14mrad IP Y,  mIP Y’,  rad  SR, nm Lum, %Pairs to extr. hole, % anti-DID at 0.0235 T0-1221.019849 anti-DID at 0.0354 T0-1381.679562 Incoming beam in LDC with anti-DID SR is larger in LDC. Can use reduced anti-DID strength to minimize impact on Lumi. QD0 Pictures for anti-DID at 0.0235 T

16. 16 4 Oct 05 Optimal anti-DID for LDC Field in the central region is flattened with two DID coils (short and long) which current are properly adjusted Shown the field for the optimal case for pairs. May want to work ~30% below the optimum to reduce SR

17. 17 4 Oct 05 Discussion The vertical IP angle uncompensated – polarization measurements are more demanding. May use vertical correctors in downstream polarimeter to match the IP angle Reduction of vertical angle to 0-50urad is certainly possible in SiD, where SR effects are smallest and in GLD and LDC it will be more difficult and need more studies.

18. 18 4 Oct 05 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