The Andrzej Soltan Institute for Nuclear Studies, Cosmic Ray Laboratory, ul. Uniwersytecka 5, 90-950 Lodz, P.O.Box 447, Poland [email protected]
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
K. Jedrzejczak, J. Karczmarczyk, M. Kasztelan, J. Swarzynski, J. Szabelski, T. Wibig
S. A. Petrochenkov, A. PolanskiJoint Institute for Nuclear Research, Dubna, Russia
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Thien-Shan group (Chubenko et al.) reported excess of signals in neutron monitors correlated with EAS registration:
●EAS size above the knee,●EAS core near to the neutron monitor (~20 m),●Excess lasts up to 3-5 milliseconds after EAS front
Following Chubenko's suggestions, we confirm existence of similar effect in the EAS array in Lodz (sea level).
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Neutrons would be producedin interactions of EAS hadrons with leadat the time of EAS trigger.
These neutrons to be registeredin He or boron proportional counters have to
●diffuse to a counter vicinity,●be thermalized (from MeV to 10-3 eV range) (in moderator takes 20 - 50 microsec),●diffuse to the counter (up to a few milliseconds).
This might be a method to register hadrons in EAS.
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Scintillator detectors:s1, s2, s5 - 0.5 m2
s3, s4, s6 - 1 m2
EAS Trigger:hits from s1, s2, s4 and s5
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Muon hodoscope:
Geiger-Müller tubes,one unit has 5 GM tubs,unit area 0.135m2,24 +56 +24 = 104 unitsmuon threshold 0.5 GeV
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Boron counter10B(n,alpha)7Liarea 120 cm2
Boron counter is connectedto 8bit, 10 MHz FADC, 32kB memory
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Boron counter10B(n,alpha)7Liarea 120 cm2
typical distribution of signals from neutrons
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Boron counter surrounded by water
Boron counterwithout moderator
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
MCNP code (Los Alamos) was used to simulate neutron diffusion, thermalisation and registration processes
LeadironGM areaconcretesoilwater
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
Boron counter surrounded by water
Neutron signal time distribution (relative to EAS trigger)
Boron counter without water on the top of lead block
Simulated neutronsstart at EAS timewith MeV energy
Pylos, September 2004
REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS
CONCLUSIONS
1.Delayed signals are probably due to neutron registrations.
2.Registrations of time distribution are consistent with assumption that all "delayed" neutrons start in lead block at the time of EAS trigger
We plan to add more detectors (He counters) to study spacial distribution of neutrons.