1. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 DEPFET Geometry for SuperBelle Sensor Geometry Pixel Pitch Constant/variable pitch in z Bricking

2. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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) ?

3. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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

4. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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!)

5. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 Module layout LOI layout: 12 moduls @ 1.3cm 12 modules @ 1.6cm proposed layout: 8 moduls @ 1.3cm 12 modules @ 1.8cm Less inner module  less material, connectors, services => larger lever arm

6. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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 + 7.25cm9.76cm R max R min L-L- L+L+ 150deg 17deg

7. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 Loi layoutDEPFET layout Layer 1Layer 2Layer 1Layer 2 R min /cm1.31.61.31.8 N12 8 Width/cm (sensitive)0.851.001.15 Width/cm (geometrical)1.051.201.35 R max /cm1.411.721.451.95 L min /cm7.058.617.259.76 L real /cm7.18.67.39.8 Pitch x (  m) 48 53.5 Pitch z (  m) 71 71.3 Clock (MHz)12.58138.7 Time/line (ns)8012577115 Columns177208215 Lines1000121110241374 DCD channels (per module end) 708834860 Switcher channels (1/2)125151128172 DCDs (1/2)5666 Frame time/  s 10191020 Occupancy1.36%1.70%1.50%1.57% Data rate/Gbit/s (per module end) 1.22.11.62.2 X0X0 0.18%0.16%0.14% Small adjustments needed to match geometry and timing

8. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 N812 Width/cm (sensitive)1.15 Width/cm (geometrical)1.35 R max /cm1.451.95 L min /cm7.259.76 L real /cm7.39.8 Pitch x (  m) 53.5 Pitch z (  m) 71.371.3 (96) Clock (MHz)138.7 (13) Time/line (ns)77115 (77) Columns215 Lines10241374 (1024) DCD channels (per module end) 860 Switcher channels (1/2)128172 (128) DCDs (1/2)66 Frame time/  s 1020 (10) Occupancy1.50%1.6% (1.1%) Data rate/Gbit/s (per module end) 1.62.2 (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

9. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 Variable Pitch Z-range (mm) Pitch (  m) N pix (-25.1) – (-22.5)7038 (-22.5) - 060375 0 - 22.560375 22.5 - 27.57072 27.5 – 32.510050 32.5 - 4012560 40 – 47.115048 1018 Track projection larger for large z Pixel length ~ track projection Z-range (mm) Pitch (  m) N pix (-33.8) – (-27.5)10063 (-27.5) – 080344 0 - 27.580344 27.5 – 3510075 35 – 4512580 45 – 5515067 55 – 63.817550 1023 Layer 1Layer 2

10. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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?)

11. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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

12. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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)

13. H.-G. Moser Max-Planck-Institut fuer Physik DEPFET Meeting Heidelberg Sept. 10 2008 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