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Cross-talk in strip RPCs

Cross-talk in strip RPCs. D. Gonzalez-Diaz, A. Berezutskiy and M. Ciobanu with the collaboration of N. Majumdar, S. Mukhopadhyay, S. Bhattacharya (thanks to A. Blanco for providing us with HADES cells) 10-03-2009. Index. 1. Single strip parameters and the RPC as a current generator.

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Cross-talk in strip RPCs

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  1. Cross-talk in strip RPCs D. Gonzalez-Diaz, A. Berezutskiy and M. Ciobanu with the collaboration of N. Majumdar, S. Mukhopadhyay, S. Bhattacharya (thanks to A. Blanco for providing us with HADES cells) 10-03-2009

  2. Index • 1. Single strip parameters and the RPC as a current generator. • 2. The induction profile. • 3. The Boundary Element Method (BEM). • 4. Propagation. • 5. Conclusions.

  3. 1. Single strip parameters and the RPC as a current generator.

  4. The RPC as a current generator. Signal shape. P. Fonte et al., IEEE, Trans. Nucl. Sci. 49, 3(2002)881. P. Fonte, private communication Diego Gonzalez Diaz, PhD. Thesis, Santiago de Compostela(2006), 2006 JINST TH 003

  5. The RPC as a current generator. Amplitude distribution.

  6. The RPC as a current generator. Correcting for propagation.

  7. Transmission in HADES cells

  8. Single-strip characterization measured with reflectometer

  9. 2. The induction profile.

  10. What is the weighting field? picture from C. Lippmann's PhD fast convergent analytical formula known since T. Heubrandtner et al. NIM A 489(2002)439

  11. A relevant example. The FOPI multi-strip design. Multi-strip-MRPC (MMRPC) Glass: ε=7.5, strip width = 1.64 mm, strip gap = 0.9 mm, strip length = 900 mm copper (20 μm) 1.1 mm 0.22 mm 0.5 mm 1.1 mm

  12. gap 1

  13. gap 2

  14. gap 3

  15. gap 4

  16. Input: charge distributions FOPI prototype 1st HADES prototype very different, indeed!

  17. Charge distributions fromMC (random variables: X, Q)

  18. Charge efficiency and weighting field for different widths

  19. Charge efficiency and weighting field for different widths

  20. Charge efficiency and weighting field for different widths

  21. cluster size dependence

  22. rms of cluster size distribution

  23. cluster size dependence with strip width > factor 2 ! typical CBM value

  24. Existing data on cross-talk/charge sharing A. Blanco et al. NIM A 485(2002)328

  25. Comparison with present code

  26. 3. Boundary Element Method (BEM).

  27. 12 gaps CBM version 1 (strip region) strip width = 22 mm, gap to next strip = 3 mm, length = 220 mm glass (εr=7.5, h=0.5 mm)‏ gas (εr=1, h=0.2 mm)‏ graphite (εr=12, h=0.02 mm) PCB (εr=5, h=0.86 mm) Cu strip (h=0.018 mm) (placed in the middle of the PCB)

  28. 12 gaps CBM version 2 (strip region) strip width = 22 mm, gap to next strip = 3 mm, length = 220 mm guard strips (1 mm) glass (εr=7.5, h=0.5 mm)‏ gas (εr=1, h=0.2 mm)‏ graphite (εr=12, h=0.02 mm) PCB (εr=5, h=0.86 mm) Cu strip (h=0.018 mm) (placed in the middle of the PCB)

  29. 12 gaps CBM version 3 (strip region) strip width = 22 mm, gap to next strip = 3 mm, length = 220 mm guard walls (1 mm) glass (εr=7.5, h=0.5 mm)‏ gas (εr=1, h=0.2 mm)‏ graphite (εr=12, h=0.02 mm) PCB (εr=5, h=0.86 mm) Cu strip (h=0.018 mm) (placed in the middle of the PCB)

  30. Preliminary calculations based on BEM. The neBEM solver.

  31. 4. Propagation.

  32. Measurements of cross-talk with RPC mockup

  33. Comparison with (APLAC) calculation signal trise~1ns

  34. Conclusions We are progressing in the direction of having a reasonable electromagnetic simulator for RPC design ! 1. Generate events with the RPC signal shape and amplitude distribution starting from measured values. On the way. 2. Calculate the fraction of signal induced to each strip. On the way. 3. Calculate cross-talk in the propagation for the given strips, treating them as current generators. On the way. 4. Compare with RPC oscillograms and/or digitized beam data. On the way. 5. Introduce this knowledge in CBM-root in order to do a meaningful design. To be done.

  35. Appendix

  36. Cross-talk from cell with shielding vias(to 1st and 2nd neighbour!)

  37. simulation of the S coefficient scattering matrix coefficient to neighbouring anode (equivalently: fraction of signal transmitted)

  38. Comparison with data from spectrum analyzer preliminary!

  39. simulation of a realistic structure RPC structure: strip width = 2.2 cm, gap to next strip = 0.3 cm 16 gaps, 0.16 mm gap 0.3 mm glass 0.86 mm PCB propagation ofexponential signal with 200 ps rise-time in anode and cathode simultaneously (differential mode)

  40. Transmission properties (with vias)

  41. Transmission properties (with vias)

  42. Transmission properties (with vias)

  43. Transmission properties (with vias)

  44. Transmission properties (with vias)

  45. Transmission properties (with vias)

  46. Transmission properties (with vias)

  47. Transmission properties (with vias)

  48. Transmission properties vias no vias

  49. Transmission properties vias no vias

  50. Transmission properties vias no vias

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