ILC-GDE Meeting Beijing Feb 2007 1

Effect of MDI Design on BDS Collimation Depth

Frank JacksonASTeC 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 spoilerFD 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 x

s Collimated beam halo

SR fan profile

IR Aperture

y

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

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

11.9x , 70.7y spoiler full gaps 2.7mm (x) 1.3mm (y)

2006e

2006c

beamcal & low-Z mask

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)

Concept L* Beamcal mask r, z (mm)

Beamcal r, z (mm)

QEX r, z (mm)

FD params

Collim depth x, y

SID 3.51 12, 331 15, 334 15, 656 “2006e” 11.9, 70.7

LDC 4.05 13, 355 13, 375 15, 656 “2006e” 10.5, 55.6

GLD 4.50 20, 430 20, 450 15, 656 “2006e” 9.5, 46.7

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

~ 8.5x , 50y

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

QD

2.0mrad 1.0mrad

incoming beam axis

outgoing beam axis

detector 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, e2e, bx1.5bx, by0.75by IP angle in y more than doubles Collimation depth twice as tight in y.