1. ILC-GDE Meeting Beijing Feb 20071 Effect of MDI Design on BDS Collimation Depth Frank Jackson ASTeC Daresbury Laboratory Cockcroft Institute

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

3. 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

4. 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 x s Collimated beam halo SR fan profile IR Aperture y

5. 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

6. ILC-GDE Meeting Beijing Feb 2007 6 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 2006c beamcal & low-Z mask

7. 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

8. 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) ConceptL*Beamcal mask r, z (mm) Beamcal r, z (mm) QEX r, z (mm) FD params Collim depth x, y SID3.5112, 33115, 33415, 656“2006e”11.9, 70.7 LDC4.0513, 35513, 37515, 656“2006e”10.5, 55.6 GLD4.5020, 43020, 45015, 656“2006e”9.5, 46.7

9. 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

10. ILC-GDE Meeting Beijing Feb 2007 10 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 QD 2.0mrad 1.0mrad incoming beam axis outgoing beam axis detector axis

11. 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.

12. ILC-GDE Meeting Beijing Feb 2007 12 Backup Slides

13. 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

14. 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 (2 nd 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

15. 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

16. 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

17. 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 1 st Extraction Quad (r=18mm)  p=1%, Gaussian On-energy,  p=1% Gaussian

18. 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.