the andrzej soltan institute for nuclear studies, cosmic ray laboratory, ul. uniwersytecka 5, 90-950...

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



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).



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.



Scintillator detectors:s1, s2, s5 - 0.5 m2

s3, s4, s6 - 1 m2

EAS Trigger:hits from s1, s2, s4 and s5



Muon hodoscope:

Geiger-Müller tubes,one unit has 5 GM tubs,unit area 0.135m2,24 +56 +24 = 104 unitsmuon threshold 0.5 GeV



Boron counter10B(n,alpha)7Liarea 120 cm2

Boron counter is connectedto 8bit, 10 MHz FADC, 32kB memory



Boron counter10B(n,alpha)7Liarea 120 cm2

typical distribution of signals from neutrons



Boron counter surrounded by water

Boron counterwithout moderator



MCNP code (Los Alamos) was used to simulate neutron diffusion, thermalisation and registration processes

LeadironGM areaconcretesoilwater



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



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.

the andrzej soltan institute for nuclear studies, cosmic ray laboratory, ul. uniwersytecka 5, 90-950...

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