RPC SENSITIVITY TO LOW ENERGY NEUTRONS ANDGAMMA RAYS
EPS-HEP2001Budapest, , july 12-18, 2001EPS-HEP2001
Budapest, , july 12-18, 2001
SERGIO P. RATTISERGIO P. RATTIINFN and Dipartimento di Fisica Nucleare e Teorica – PAVIA
for the Pavia-Bari collaboration in CMS
SERGIO P. RATTISERGIO P. RATTIINFN and Dipartimento di Fisica Nucleare e Teorica – PAVIA
for the Pavia-Bari collaboration in CMS
RPC SENSITIVITY TO LOW ENERGY NEUTRONS ANDGAMMA RAYS
MotivationMotivation
Experimental setupExperimental setup
ResultsResults
Conclusions and Conclusions and outlookoutlook
OUTLINE OF THE TALKOUTLINE OF THE TALK
Experimental Experimental setupsetupExperimental Experimental setupsetup
BaF2 scintillators
2 single gap/common readout RPC’s2 single gap/common readout RPC’s
sourcesource1717CiCi 252 252Cf:Cf:a-3%a-3% spontaneous fission;spontaneous fission;b-b-97%97% decay decay (irrelevant, (irrelevant,absorbed by the source’absorbed by the source’container).container).
1717CiCi 252 252Cf:Cf:a-3%a-3% spontaneous fission;spontaneous fission;b-b-97%97% decay decay (irrelevant, (irrelevant,absorbed by the source’absorbed by the source’container).container).
1 gap oiled1 gap not oiled1 gap oiled1 gap not oiled
THE SOURCETHE SOURCETHE SOURCETHE SOURCE
3.8 n/fission3.8 n/fissionEEavav= 2.14 MeV= 2.14 MeV 10.310.3 prompt prompt
per fissionper fission
80% E<1MeV80% E<1MeV
NEUTRON AND NEUTRON AND SPECTRA OF THE SOURCE SPECTRA OF THE SOURCE
Sensitive area: 35 cm x 35 cmGas mixture (97 % C2H2F4 – 3% iC4H10)
Sensitive area: 35 cm x 35 cmGas mixture (97 % C2H2F4 – 3% iC4H10)
OUTPUT signals: LVDS to the counting electronics
(Low Voltage Differential Signals)
16 strips
RPCs Cross RPCs Cross SectionSection
Pickup strips
FOUR FOUR CONFIGURATIONSCONFIGURATIONS:FOUR FOUR CONFIGURATIONSCONFIGURATIONS:
A) No absorber between RPC and source
B) 6 cm Pb between RPC and source
C) 6 cm Pb and 4 cm PE
D) 6 cm Pb and 10 cm PE
Experimental method:Experimental method:
TriggerTrigger
Trigger AND
Chamber OR16
Trigger AND
Chamber OR16
RPCRPC
BaF2 scintillatorsBaF2 scintillators
SourceSource
= (Triggers x OR16)/Triggers
= efficiency to fission
= chamber acceptance
= (Triggers x OR16)/Triggers
= efficiency to fission
= chamber acceptance
Compare to simulation
results
Compare to simulation
results
Experimental dataExperimental data Experimental dataExperimental data
Effective Neutron Interaction length
Xeq
Xeq = XPb/Pb + XPE/PE
=interaction length
Effective Neutron Interaction length
Xeq
Xeq = XPb/Pb + XPE/PE
=interaction length
What we measure is
= (Triggers x OR16)/Triggers
= efficiency to fission
= chamber acceptance
What we measure is
= (Triggers x OR16)/Triggers
= efficiency to fission
= chamber acceptance
GAP oil
Xeq
Double Gap
Xe
q
GAP non oil
Xeq
Xeq
Experimental data vs simulation results
Experimental data vs simulation results
Data contain contribution from:
a) Prompt rays from source
b) Prompt neutrons from Source
c) Secondary rays from neutron interactions within the different absorbers
Data contain contribution from:
a) Prompt rays from source
b) Prompt neutrons from Source
c) Secondary rays from neutron interactions within the different absorbers
Simulation (with GEANT3.21) used to extract the relative contribution of each component a)
b) c)
Simulation (with GEANT3.21) used to extract the relative contribution of each component a)
b) c)
Xeq Xeq
-oil-oil
Gamma ray sensitivity (preliminary results)Gamma ray sensitivity (preliminary results)
Prompt rays Secondary rays
Neutron Sensitivity Results (preliminary)
Neutron Sensitivity Results (preliminary)
Sensitivity independent on oiling!
Xeq
-oil
CONCLUSIONSCONCLUSIONS
Poor measurements
of this parameter
Sensitivity (S)
less than 1%;
SSn;
Double gap doubles;
S independ
on surface treatment
(at least
at this
low energies
1 MeV)
Poor measurements
of this parameter
Sensitivity (S)
less than 1%;
SSn;
Double gap doubles;
S independ
on surface treatment
(at least
at this
low energies
1 MeV)
Summary of sensitivity results
Single Gap Sensitivity <Energy>(MeV)
Prompt 3,50E-03 0,84
" 7,50E-03 1,45
Secondary 6,50E-03 1,35
Neutron 3,00E-04 2,1
Double Gap Sensitivity <Energy>(MeV)
Prompt 6,00E-03 0,84
" 1,30E-02 1,45
Secondary 1,10E-02 1,35
Neutron 5,30E-04 2,1
