Effect of MDI Design on BDS Collimation Depth

1. Effect of MDI Design on BDS Collimation Depth Frank Jackson ASTeC Daresbury Laboratory Cockcroft Institute ILC-GDE Meeting Beijing Feb 2007

2. Contents • Collimation depth and method • RDR collimation depth (SiD MDI) • Other MDIs (GLD, GLC) • Other parameter sets ILC-GDE Meeting Beijing Feb 2007

3. Collimation Depth Philosophy • Halo synchrotron radiation (SR) from final doublet must pass cleanly through interaction region (IR) • Small apertures in the IR include vertex detector, masking, forward calorimetry, extraction quadrupoles • Halo size & divergence at final doublet entrance must be constrained to ‘collimation depth’ • Effective collimation depth (actual spoiler gaps) may need to be tighter to compensate for spoilerFD transport ILC-GDE Meeting Beijing Feb 2007

4. Collimation Depth Method • Possible to solve problem analytically • SR fan profile through detector depends on halo size in FD • Halo size in FD depends on collimation aperture • Constrain SR fan size to solve for collimation depth • Many SR emission points • No unique solution; solution ellipse in x, y IR Aperture SR fan profile y s Collimated beam halo x ILC-GDE Meeting Beijing Feb 2007

5. Implementing the Method • Analytical method implemented by O. Napoly (Saclay) for TESLA TDR (2001) • Calculates the solution ellipses from very many SR emission points through whole FD • Halo phase space at each emission point is reverse-traced (linear, on-energy optics) from IP. • Repeat analysis for each small IR aperture • Find global collimation depth vtx beamcal mask ILC-GDE Meeting Beijing Feb 2007

6. 2006c beamcal & low-Z mask RDR collimation depth • IR design assumes SID-like detector, L* = 3.51 • Collimation depth constraint comes from first extraction quad (R= 15mm) • Beamcal mask (r=12mm) comes close to SR fan • 11.9x , 70.7y spoiler full gaps 2.7mm (x) 1.3mm (y) 2006e ILC-GDE Meeting Beijing Feb 2007

7. MDI Impact on Collimation Depth • MDI depends on final detector concept • Effect of changing MDI on IR parameters • L* • Forward calorimetry geometry • Extraction line design • (possibly) final quad changes • Difficult to evaluate the effect of change in MDI on collimation depth • Complete MDI designs don’t exist for all the concepts ILC-GDE Meeting Beijing Feb 2007

8. MDI parameter space • Need complete MDI parameter set to calculate each collimation depth • Used detector outline docs to get information (red means guess) • Extraction quad QEX is the limiting aperture in all cases • But my QEX guesses are very uncertain for LDC and GLD • Results show expected - SR fan size at a fixed point from IP increases with L* (for fixed FD) ILC-GDE Meeting Beijing Feb 2007

9. Parameter Sets • Calculation has been done for nominal parameter set • Other parameter sets have smaller * larger IP angles  tighter collimation • ‘Low P’ & ‘high lumi’, * twice as small as nominal • Reduced collimation depth by factor 1/2 • ~ 8.5x , 50y ILC-GDE Meeting Beijing Feb 2007

10. QD QD Alternative Crossing Angles? • 2mrad remains alternative ‘small angle’ option • Lack of symmetry in problem, shared magnets for incoming/extracted beam • Force symmetry by using ‘virtual apertures’ that ensure SR clearance incoming beam axis detector axis 1.0mrad 2.0mrad outgoing beam axis ILC-GDE Meeting Beijing Feb 2007

11. Conclusion • Latest extraction line design now constrains collimation depth • Impossible to say which is the best detector concept for collimation, without complete MDI design (inc. extraction line) for each concept. • Greater L* will probably lead to tighter collimation • Philosophy has been for perfect clean SR passing through IR • More sophisticated analysis • Can we tolerate SR on the extraction quads and beamcal – and so relax collimation depths • The answer to those questions will be strongly affected by MDI design. ILC-GDE Meeting Beijing Feb 2007

12. Backup Slides ILC-GDE Meeting Beijing Feb 2007

13. SID Concept Geometry • L*=3.51 m • BeamCal inner radius 15mm (p28, last para) • BeamCal Beampipe inner radius 12 mm (Fig 80, p131) • BeamCal LowZ covering mask radius 12mm (for 20 mrad, p160) • BeamCal Z location 321-334 (Table 1, p13) • Vertex beampipe radius 12mm (fig 29, p 53) • Much of the beamcal geometry worked out for 20 mrad, hope it is same for 14 mrad ILC-GDE Meeting Beijing Feb 2007

14. GLD Concept Geometry • L* = 4.5 m (first para, p96) • BeamCal inner radius 20mm (Tab 2.13, p 97) • BeamCal Beampipe inner radius 15mm (Tab 3.1, p104) • BeamCal LowZ covering mask radius 20mm (Tab 2.13, p 97) • BeamCal Z location 430-450 (2nd para, p73) • Vertex beampipe radius 15mm (first para, p 96) • Much of the beamcal geometry worked out for 20 mrad, hope it is same for 14 mrad ILC-GDE Meeting Beijing Feb 2007

15. LDC concept • L* = 4.05 m (p98) • BeamCal inner radius 13mm (Tab 6, p 9) • BeamCal Beampipe inner radius ??? • BeamCal LowZ covering mask ???? • BeamCal Z location 355-375 (Tab 6, p 9) • Vertex inner radius (not beam pipe) 16mm (Table 1, p8) • Much of the beamcal geometry worked out for 20 mrad, hope it is same for 14 mrad ILC-GDE Meeting Beijing Feb 2007

16. GLD extraction geometry • Justification for my guess at extraction line params on slide 8. • Slide from Valencia meeting T. Tauchi ‘Background Study at GLD-IR’ • Has used 2006c deck designed for L*=3.51 • Changed QD0 position to L*=4.5, • But no changes to extraction quads position & aperture ILC-GDE Meeting Beijing Feb 2007

17. Off-Energy Halo? • DBLT routine uses linear, on-energy beam transport • Can cross check with BDSIM simulation • Off-energy, collimated halo (p = 1% Gaussian), at FD entrance, track and plot resulting SR fan • Plot below are for 2006c lattice SR profile at 1st Extraction Quad (r=18mm) p=1%, Gaussian On-energy, p=1% Gaussian ILC-GDE Meeting Beijing Feb 2007

18. 1TeV Parameters • IP angle = Sqrt(e/b) • From 500GeV to 1TeV, e2e, bx1.5bx, by0.75by • IP angle in y more than doubles • Collimation depth twice as tight in y. ILC-GDE Meeting Beijing Feb 2007