TO LOW ENERGY NEUTRONS AND TO LOW ENERGY NEUTRONS AND 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

Experimental setup 2 single gap/common readout RPC’s 1 gap oiled 1 gap not oiled BaF2 scintillators source 17 mCi 252Cf: a-3% spontaneous fission; b-97% a decay (irrelevant, absorbed by the source’ container).

THE SOURCE NEUTRON AND g SPECTRA OF THE SOURCE 3.8 n/fission Eav= 2.14 MeV 10.3 prompt g per fission 80% E<1MeV NEUTRON AND g SPECTRA OF THE SOURCE

OUTPUT signals: LVDS to the counting electronics 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 Pickup 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

Compare to simulation results Experimental method: RPC Trigger AND Chamber OR16 Source Trigger BaF2 scintillators  = (Triggers x OR16)/Triggers e= efficiency to fission = chamber acceptance Compare to simulation results

Effective Neutron Interaction length Xeq Experimental data GAP oil Xeq Double Gap GAP non oil eh 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

Experimental data vs simulation results Xeq 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) Xeq -oil Secondary g rays Prompt g rays

Neutron Sensitivity Results (preliminary) Xeq -oil Sensitivity independent on oiling!

Summary of sensitivity results CONCLUSIONS Summary of sensitivity results Poor measurements of this parameter Sensitivity (S) less than 1%; Sg10Sn; Double gap doubles; S independ on surface treatment (at least at this low energies 1 MeV) g g g g