ilc-gde meeting beijing feb 20071 effect of mdi design on bds collimation depth frank jackson astec...
DESCRIPTION
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 transportTRANSCRIPT
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
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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.