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EPS-HEP2001 Budapest , july 12-18, 2001. SERGIO P. RATTI INFN and Dipartimento di Fisica Nucleare e Teorica – PAVIA for the Pavia-Bari collaboration in CMS. RPC SENSITIVITY TO LOW ENERGY NEUTRONS AND GAMMA RAYS. RPC SENSITIVITY TO LOW ENERGY NEUTRONS AND GAMMA RAYS.
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EPS-HEP2001 Budapest, july 12-18, 2001 SERGIO P. RATTI INFN and Dipartimento di Fisica Nucleare e Teorica – PAVIA for the Pavia-Bari collaboration in CMS RPC SENSITIVITY TO LOW ENERGY NEUTRONS AND GAMMA RAYS RPC SENSITIVITY TO LOW ENERGY NEUTRONS AND GAMMA RAYS
OUTLINE OF THE TALK Motivation Experimental setup Results Conclusions and outlook
2 single gap/common readout RPC’s source Experimental setup 1 gap oiled 1 gap not oiled BaF2 scintillators 17 mCi 252Cf: a-3%spontaneous fission; b-97%a decay (irrelevant, absorbed by the source’ container).
THE SOURCE 3.8 n/fission Eav= 2.14 MeV 10.3prompt g per fission 80% E<1MeV NEUTRON AND g SPECTRA OF THE SOURCE
Pickup strips Sensitive area: 35 cm x 35 cm Gas mixture (97 % C2H2F4 – 3% iC4H10) OUTPUT signals: LVDS to the counting electronics (Low Voltage Differential Signals) 16 strips RPCs Cross Section
FOUR CONFIGURATIONS: • No absorber between RPC and source • B)6 cm Pb between RPC and source • 6 cm Pb and 4 cm PE • D)6 cm Pb and 10 cm PE
Source Experimental method: RPC Trigger AND Chamber OR16 Trigger BaF2 scintillators = (Triggers x OR16)/Triggers e= efficiency to fission = chamber acceptance Compare to simulation results
eh eh eh Double Gap GAP non oil GAP oil Xeq Xeq Xeq Experimental data What we measure is = (Triggers x OR16)/Triggers e= efficiency to fission = chamber acceptance Effective Neutron Interaction length Xeq Xeq = XPb/lPb + XPE/lPE l=interaction length
Xeq Experimental data vs simulation results • Data contain contribution from: • Prompt g rays from source • Prompt neutrons from Source • Secondary g rays from neutron interactions within the different absorbers Simulation (with GEANT3.21) used to extract the relative contribution of each component a) b) c)
Gamma ray sensitivity (preliminary results) -oil -oil Xeq Xeq Secondary g rays Prompt g rays
Neutron Sensitivity Results (preliminary) -oil Xeq Sensitivity independent on oiling!
CONCLUSIONS Poor measurements of this parameter Sensitivity (S) less than 1%; Sg10Sn; Double gap doubles; S independ on surface treatment (at least at this low energies 1 MeV) Summary of sensitivity results g g g g