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Analytical Theory of Rate Effects in Timing RPCs: D. González-Díaz et al. Study (2004)

This study explores the rate effects on timing resolution in RPCs, focusing on fluctuation and drop in field, with data from HADES at GSI in 2003. Analyzing detector behavior at varying HV levels provides insights for efficiency and voltage trends.

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Analytical Theory of Rate Effects in Timing RPCs: D. González-Díaz et al. Study (2004)

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  1. First attempt of an analytical theory of rate effects in timming RPCs D. González-Díaz, A. Mangiarotti and P. Fonte

  2. [A. Mangiarotti, P. Fonte, A. Gobbi NIM A 533(2004)16] Ineff [%] στ(n0’) [1/s units] n0’ Primary statistics Multiplication process

  3. στ(n0’) [1/s units] rmsE /E Intrinsic time resolution Fluctuations in the field Drop in the field [ A. Blanco et al. NIM A 535 (2004) 272 ]

  4. DATA SET H. Alvarez-Pol et al, NIM A 533(2004)79 and 535(2004)277 • Date: April-2003. • Place: HADES, GSI • Physical conditions: Ionizing particles from CC collisions at 1 GeV A. • Detector: • 0.3 mm 4-gap RPC (Al-Glass-Al-Glass-Al) • Mixture: Freon/Iso-butan/SF6 (98.5/0.5/1) • HV: 3.1-3.4 kV/gap • Rates: 0.1-1.5 kHz/cm2

  5. OBSERVABLES NEEDED: Mainly the total charge and the rms of the total charge. They are directly related to the fluctuations of the field: Fluctuations in the field and to the drop in the field: Drop in the field As the gas mixture was slightly different from the standard one, it will help that S=α Vdcan also be obtained independently from data.

  6. HV = 3.1 kV/gap HV = 3.2 kV/gap HV = 3.3 kV/gap HV = 3.4 kV/gap OBSERVABLES AVAILABLE:

  7. How to go from the available to the needed?: [ the usual problem!! ] Accurate description of the efficiency trend with HV for this kind of detector Time delay Linear increase with voltage [A. Blanco et al. IEEE Trans. Nucl. Sci. 48(2001)1249 and C. Lippmann (Thesis)] Field in the gap Ohmic drop in the glass [G.Aielli, NIMA 456(2000)82] Behavior in strong space-charge regime [P.Fonte, V.Peskov, NIMA 477(2002)17 G. Carboni et al. , NIMA 498(2003)135]

  8. OBSERVABLES AVAILABLE->OBSERVABLES NEEDED [result]

  9. HV = 3.1 kV/gap HV = 3.2 kV/gap HV = 3.3 kV/gap HV = 3.4 kV/gap FITTED NOT FITTED! Data [re-scaled ‘prompt charge’]

  10. HV = 3.2 kV/gap HV = 3.3 kV/gap CONCLUSIONS: - A first (indirect) confirmation of the validity of the proposed model for describing rate effects on the time resolution of an RPC is shown. - Better comparison requires: * Direct measurement of the total charge as a function of the rate together with its rms. * At least a factor 4 larger files. [The expected improvement of sigma with voltage is 5ps/100V-> Hard to see!]. * Independent MC cross-check.

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