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

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

ILC-GDE Meeting Beijing Feb 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 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

ILC-GDE Meeting Beijing Feb 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 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

ILC-GDE Meeting Beijing Feb 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 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

ILC-GDE Meeting Beijing Feb 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 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

ILC-GDE Meeting Beijing Feb 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 Backup Slides

ILC-GDE Meeting Beijing Feb 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 (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 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 (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

ILC-GDE Meeting Beijing Feb 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 (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 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 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

ILC-GDE Meeting Beijing Feb TeV 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.