H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept DEPFET Geometry for SuperBelle Sensor Geometry Pixel Pitch Constant/variable pitch in z Bricking

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Requirements »Radius: 1.3 cm inner layer (if 1cm bream pipe radius) 1.6 cm (LOI), 1.8 cm (proposed) 2 nd layer »Acceptance: 17 o -150 o »Overlap in r-phi for alignment (how much?) »Frame readout time < 10  s »Four-fold parallel readout in both directions »Efficient use of DCD channels (N x 144/4 channels in r-phi) »Efficient use of switcher channels (N x 4 x 16) ?

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept LOI Design for Upgrade (cm) Two thin pixel layer Slanted layer to keep acceptance, optimize incident angle and save detector size 6 sensor layers to make low momentum tracking 2 pixel layers at 1.3cm and 1.6 cm (optimize?) 4 layers with double sided Si-strip detectors

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Pixel Layers 1.6 cm 1.3 cm 7.1 cm 8.4 cm LOI layout: L1 R=1.3 cm 0.8 x 7.1 cm 2 L2 R=1.6 cm 1.0 x 8.4 cm 2 Very small detector (only 24 modules)! Module size and layer spacing subject to optimisation Wider Sensors -> less modules needed -> less material (1.1 width cm at L1: only 8 modules needed!)

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Module layout LOI layout: cm cm proposed layout: 8 1.3cm cm Less inner module  less material, connectors, services => larger lever arm

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Geometry R min R max Off w bal layer12 R min 1.3cm1.8cm R max 1.45cm1.95cm w1.15cm bal0.2cm off0.5cm0.4cm L-L- 2.51cm3.38cm L+L+ 4.74cm6.38cm L - + L cm9.76cm R max R min L-L- L+L+ 150deg 17deg

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Loi layoutDEPFET layout Layer 1Layer 2Layer 1Layer 2 R min /cm N12 8 Width/cm (sensitive) Width/cm (geometrical) R max /cm L min /cm L real /cm Pitch x (  m) Pitch z (  m) Clock (MHz) Time/line (ns) Columns Lines DCD channels (per module end) Switcher channels (1/2) DCDs (1/2)5666 Frame time/  s Occupancy1.36%1.70%1.50%1.57% Data rate/Gbit/s (per module end) X0X0 0.18%0.16%0.14% Small adjustments needed to match geometry and timing

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept N812 Width/cm (sensitive)1.15 Width/cm (geometrical)1.35 R max /cm L min /cm L real /cm Pitch x (  m) 53.5 Pitch z (  m) (96) Clock (MHz)138.7 (13) Time/line (ns)77115 (77) Columns215 Lines (1024) DCD channels (per module end) 860 Switcher channels (1/2) (128) DCDs (1/2)66 Frame time/  s 1020 (10) Occupancy1.50%1.6% (1.1%) Data rate/Gbit/s (per module end) (1.1) X0X0 0.15% »Basically ok for the inner layer »Would like 50  m pitch in r-phi, needs more DCD channels »Readout time of outer layer exceeds 10  s (occupancy still ok because of 1/R 2, but not nice in terms of system aspects) »Larger pixel size in z (96  m) fixes the problem (resolution)? 2 nd layer

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Variable Pitch Z-range (mm) Pitch (  m) N pix (-25.1) – (-22.5)7038 (-22.5) – – Track projection larger for large z Pixel length ~ track projection Z-range (mm) Pitch (  m) N pix (-33.8) – (-27.5)10063 (-27.5) – – – – – Layer 1Layer 2

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Variable Pitch Smaller pitch in large part of the sensor Track projection matched to pitch => good charge sharing => smaller clusters (number of pixels) => can do “fine tuning” to get nicer numbers (1024!) Sensor not symmetric (reflects 17 – 150 deg acceptance) (should the boost of the B been taken into account (0.2 mm) ? Readout lines have different length in +/- (more capacitance compared to symmetric break in +) Still: break not at z=0! (equal number of pixels in both readout directions) Anyway: think more to find optimal solution: - different regions? - continuous variation - min/max pitch (homogenious charge collection?)

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Bricking DCD z r-phi Improves r-phi resolution by ~1/2 (even for binary readout) Number of neighbour pixels: 8 -> 6: less touching p clusters) However: r-phi resolution not that critical

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Bricking Physics information is in z! Especially important for B s : oscillation period ~ 50  m (of course, improvements in r-phi are still welcome…..) Improvements due to bricking not that evident in z (should help COG reconstruction)  Need MC studies  Need realistic charge sharing (simulation of electric fields)

H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept Summary Pixel pitch in r-phi:53.5  m Option: fixed pitch in z: 71.3  m (96  m in L2?) Option: variable pitch:60  m-150  m (L1) 80  m-175  m (L2) Prototyping should sample this parameter range Some prototypes with bricked pixels Longest readout lines: 55mm (variable pitch, L2)! Need MC studies comparing different options Backup solution in case beam pipe radius will stay at 1.3 cm needed