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The NA48 Collaboration. CERN, Cambridge, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Vienna. NA48/2 KABES detector: a short overview. Massimiliano Fiorini (Università degli Studi di Ferrara). On behalf of:
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The NA48 Collaboration CERN, Cambridge, Chicago, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Northwestern, Perugia, Pisa, Saclay, Siegen, Torino, Vienna NA48/2 KABES detector: a short overview Massimiliano Fiorini (Università degli Studi di Ferrara) On behalf of: M. Boyer, C. Cheshkov, J.B. Cheze, X. Coppolani, A. Delbart, J. Derré, S. Herlant, P. Le-Bourlout, P. Legou, O. Maillard, I. Mandjavidze, C. Mazur, E. Mazzucato, F. Nizery, F. Orsini, B. Peyaud, M. Riallot, B. Vallage. CEA DSM/DapniaSaclay S. Basilev, Y. Potrebenikov, I. Slepnev, V. Slepnev. JINR/Dubna K RARE DECAY WORKSHOP - Frascati - 27 May 2005
NA48 KABES principle: TPC + micromegas Tdrift2 Micromegas Gap 50 μm Micromegas Gap 50 μm Tdrift1 TOTAL X/X0 ~1.3x10-3 Operated @ Edrift = 0.83 kV/cm vDRIFT = 8 cm/μs Tdrift1 + Tdrift2 = 750 ns 48 strips with 0.8 mm pitch Very low discharge probability
Tleading Ttrailing K2 K1 Threshold K5 K6 K3 K4 KABES main features Reference:B. Peyaud et al. NIM A 535 (2004) 247-252 Gas mixture Ne(79%)+C2H6(11%)+CF4(10%) Time window (extraction)0.5 s Number of TDC channels 6x48=288 Central strips rate ~ 2 MHz Limits of TDC readout Maximum particle flux 40Mp/s Maximum hit rate /strip8Mhit/s TOT =Ttrailing-Tleading <TOT> = 35 ns Low occupancy @20 MHz <Strip multiplicity> = 1.5
Time resolution: ~0.6 ns Using TOT to correct time slewing blank (T0)KABES- (T0)DCHSpectrometer(ns) Efficiency ~ 100% Momentum resolution ~ 0.9% Wrong K± tagging ~ 4% Space resolution [from drift time measurement]~70μm Performance in NA48/2
time units (2×1.04 ns) TEST of 25 μm mesh detector + FADC readout • 8 bit FADC 960 MHz (2 interleaved 480 MHz) only 18 channels at 480 MHz sampling frequency • new mesh gap <pulse width> reduced to ~ 20 ns • beam momentum 75 GeV/c (only K+) • beam intensity scan up to ~16x nominal intensity • better double pulse resolution with FADC • extract time information from fit • reconstruction of tracks even in high rate beam
Conclusions • high rate and high-resolution TPC operating with 50 μm micromegas amplification gap @20 MHz • further improvement of occupancy with 25 μm amplification gap is expected • all mesh currents are linear at high beam rate (up to 16xI0) KABES does NOT saturate • LATEST RESULT: use of a faster preamplifier reduces the pulse width of a factor of 2 • Further Investigations: different gas mixture, use of double amplification gap