1 / 21

The Physics of Resistive Plate Chambers

The Physics of Resistive Plate Chambers. Werner Riegler , Christian Lippmann CERN. Trigger RPC. Multi Gap RPC. R. Santonico, R. Cardarelli. M.C.S. Williams et al. Timing RPC. P. Fonte, V. Peskov et al. 2mm gas gap 2mm Bakelite,   10 10  cm

xue
Download Presentation

The Physics of Resistive Plate Chambers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Physics of Resistive Plate Chambers Werner Riegler, Christian Lippmann CERN Werner Riegler, CERN

  2. Trigger RPC Multi Gap RPC R. Santonico, R. Cardarelli M.C.S. Williams et al. Timing RPC P. Fonte, V. Peskov et al. • 2mm gas gap • 2mm Bakelite, 1010 cm • C2F4H2/Isobutane/SF6 96.7/3/0.3 • HV: 10kV  E:  50kV/cm • 0.3mm gas gap • 3mm glass,  2x1012 cm • 2mm aluminum • C2F4H2/Isobutane/SF6 85/5/10 • HV: 3/6 kV  E:  100kV/cm • 0.25mm gas gaps (5+5) • 0.4mm glass, 1013 cm • PCB with cathodes, anodes • C2F4H2/Isobutane/SF6 90/5/5 • HV: 12.5kV  E:  100kV/cm Werner Riegler, CERN

  3. Over the last years we have published several articles on RPC detector physics: [1] Detector Physics and Simulation of Resistive Plate Chambers, NIMA 500 (2003) 144-162, W. Riegler, C. Lippmann, R. Veenhof [2] Space Charge Effects in Resistive Plate Chambers, CERN-EP/2003-026, submitted to NIM, C. Lippmann, W. Riegler [3] Induced Signals in Resistive Plate Chambers, NIMA 491 (2002) 258-271, W. Riegler [4] Signal Propagation, Termination and Crosstalk and Losses in Resistive Plate Chambers, NIMA 481 (2002) 130-143, W. Riegler, D. Burgarth [5] Detector Physics of Resistive Plate Chambers, Proceedings of IEEE NSS/MIC (2002),C. Lippmann, W. Riegler [6] Static Electric Fields in an Infinite Plane Condenser with One or Three Homogeneous Layers, NIMA489 (2002) 439-443,CERN-OPEN-2001-074, T. Heubrandtner, B. Schnizer, C. Lippmann, W. Riegler [7] Detector Physics of RPCs, Doctoral Thesis, C. Lippmann, May 2003 (CERN) Simulation studies by others: E. Cerron Zeballos et. al NIMA 381 (1996) 569-572 M. Abbrescia et al., NIMA 398 (1997) 173-179, NIMA 409 (1998) 1-5, Nucl. Phys. B 78 (1999) 459-464, NIMA 471 (2001) 55-59 P. Fonte, NIMA 456 (2000) 6-10, IEEE Trans. Nucl. Science Vol. 43 No. 3 (1996) A. Mangiarotti, A. Gobbi, NIMA 482 (2002) 192-215 G. Aielli Advanced Studies on RPCs (Doctoral thesis Dec. 2000) Werner Riegler, CERN

  4. Motivation for the Work For 0.3mm gas gap RPCs using pure Isobutane or a C2F4H2 gas mixture one finds  75% efficiency which requires about 100 primary clusters/cm and a Townsend coefficient of 1000/cm. A ‘popular’ value for Isobutane that is found in literature is 50 clusters/cm. Even in case the above values were real, the expected average avalanche charge would be 107 pC, while one measures 5 pC. Can a space charge effects provide such a large suppression factor ? Eds along the gas gap is constant: If there is a region in the avalanche where the electric field is low, there will also be a region where the field is high. Therefore one expects a ‘limited’ region for space charge suppression before the avalanche ‘explodes’. In order to solve the problems, speculations about ‘strange new effects’ where started. Werner Riegler, CERN

  5. [1] Simulation Input Avalanche mode operation opens the possibility of a detailed simulation. We assume that the gas is fully quenching. • RPC material: FLUKA • Primary ionization:HEED(Igor Smirnov) • Townsend, attachment coefficient: IMONTE (Steve Biagi) • Diffusion, drift velocity: MAGBOLTZ 2(Steve Biagi) • Avalanche fluctuations: Werner Legler (1960) • Space charge field: Analytic Solutions [6] • Frontend electronics + noise: Analytic Werner Riegler, CERN

  6. [1] Secondaries in RPCs: FLUKA electrons, photons hadron showers Probability that the Pion is accompanied by at least one charged particle is4.92% (H. Vincke, CERN). This should have only a small effect on the efficiency. Werner Riegler, CERN

  7. [1] Primary Ionization: HEED Rieke et al., Phys. Rev. A 6 (1972) 1507 CERN-77-09 Rieke et al. CERN-77-09 C2F4H2 gas: 9. 5 clusters/mm for 7GeV Pion  105m between clusters C2F4H2 gas:  2.7 electrons/cluster, long tail Werner Riegler, CERN

  8. [1] Gas Gain, Attachment: IMONTE 2mm Trigger RPCs, 50 kV/cm: Effective Townsend Coefficient  10/mm 0.3mm Timing RPCs, 100 kV/cm: Effective Townsend Coefficient  110/mm Werner Riegler, CERN

  9. [1] Driftvelocity: Magboltz 2mm Trigger RPCs, 50 kV/cm:  130 m/ns C2F4H2 0.3mm Timing RPCs, 100 kV/cm:  210 m/ns Isobutane E. Gorini, 4th workshop in RPCs (1997) Werner Riegler, CERN

  10. [1] Avalanche Fluctuations W. Legler, 1960: Die Statistik der Elektronenlawinen in elektronegativen Gasen bei hohen Feldstärken und bei grosser Gasverstärkung Assumption: ionization probability independent of the last collision Avalanches started by a single electron: The very beginning of the avalanche decides on the final charge. Werner Riegler, CERN

  11. [1] Approximate Time Resolution We expect: •Time resolution depends only on effective Townsend coefficient and drift-velocity. • Dependence on threshold is weak. Trigger RPC: v  130 m/ns, - 10/mm, t  1ns Timing RPC: v  210 m/ns, - 110/mm, t  56ps Time resolution is in the correct range Werner Riegler, CERN

  12. [1] Approximate Efficiency 0.3mm Timing RPCs, 100 kV/cm: d=0.3mm,  0.105mm,   123/mm,   13/mm, Qt=20fC, Ew/Vw 1.48/mm    73% Efficiency is in the correct range Werner Riegler, CERN

  13. [1] Monte Carlo Results Monte Carlo Measurement, P. Fonte et al., NIMA 449 (2000) 295 Monte Carlo Measurement, P. Fonte, VIC 2001 Formula 0.3mm single gap RPC 4x 0.3mm quad gap RPC Efficiency and time resolution are reproduced quite nicely Werner Riegler, CERN

  14. [1] Expected Signal Charges • 2mm Trigger RPC 10kV • Simulated Measured • Qtot103 pC 40 pC • Qfast 102 pC 2 pC • 0.3mmTiming RPC 3kV • Simulated Measured • Qtot107 pC 5 pC • Qfast 105pC  0.5 pC Discrepancy for timing RPCs is formidable Werner Riegler, CERN

  15. [6] Space Charge Effects Electric field of a point charge in an RPC Werner Riegler, CERN

  16. [2] Space Charge Effects 0.3mm timing RPC, 3kV electrons, positive ions, negative ions,field Avalanche is simulated by dividing the development into time steps and calculating the field at every point within the avalanche at each step  Local field, Townsend coefficient, attachment coefficient, driftvelocity Werner Riegler, CERN

  17. [2] Space Charge Effects Simulation Measurement P. Fonte et al., Preprint LIP/00-04 The detailed simulation indeed reproduces the small charges of a few pC - compared to 107pC without space charge effect ! Werner Riegler, CERN

  18. [2] Space Charge Effects Electric field in a single electron avalanche, 0.3mm timing RPC, 2.8kV Super thesis page 133 Werner Riegler, CERN

  19. [3] Induced Signals Theorems about signals induced on electrodes connected with arbitrary networks and embedded in a medium with position and frequency dependent permittivity and conductivity. They allow analytic solutions of the influence of the RPC material on the RPC signals: E.g. Influence of carbon layer resistivity on the RPC signal T=electron drift time,   Rr0d R ... Carbon Layer Resistivtiy (/) r … Material Permittivity d… Gap Size Werner Riegler, CERN

  20. Crosstalk for Long Strips [4] RPC with long readout strips is an inhomogeneous multi-conductor transmission line. Signal on N-strips travels as an overlay of N different velocities (modal dispersion). Crosstalk depends on the distance of the impact point from the amplifiers. Signal termination is a complex issue  N(N+1)/2 resistors. All effects can be exactly calculated with elementary matrix transformations. Werner Riegler, CERN

  21. Conclusions • Over the last three years we have systematically studied many aspects of RPC detector physics. • In our opinion, no strange effects have to be assumed in order to explain time resolution, efficiency and charge spectra. • Space charge effects are very prominent in this detector. • RPC signals and crosstalk can be studied with the help of very general theorems about signal induction and signal propagation. • In order to reproduce streamers, photon effects have to be included … there is more to do ! Werner Riegler, CERN

More Related