1. The Andrzej Soltan Institute for Nuclear Studies, Cosmic Ray Laboratory, ul. Uniwersytecka 5, 90-950 Lodz, P.O.Box 447, Poland kj@zpk.u.lodz.pl 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. Polanski Joint Institute for Nuclear Research, Dubna, Russia

2. 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).

3. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS Neutrons would be produced in interactions of EAS hadrons with lead at the time of EAS trigger. These neutrons to be registered in 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.

4. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS

5. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS

6. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS Scintillator detectors: s1, s2, s5 - 0.5 m 2 s3, s4, s6 - 1 m 2 EAS Trigger: hits from s1, s2, s4 and s5

7. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS Muon hodoscope: Geiger-Müller tubes, one unit has 5 GM tubs, unit area 0.135m 2, 24 +56 +24 = 104 units muon threshold 0.5 GeV

8. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS

9. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS Boron counter 10 B(n,alpha) 7 Li area 120 cm 2 Boron counter is connected to 8bit, 10 MHz FADC, 32kB memory

10. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS Boron counter 10 B(n,alpha) 7 Li area 120 cm 2 typical distribution of signals from neutrons

11. Pylos, September 2004 REGISTRATION OF NEUTRONS WITHIN 2 MILLISEC AFTER EAS Boron counter surrounded by water Boron counter without moderator

12. 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 Lead iron GM area concrete soil water

13. 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 neutrons start at EAS time with MeV energy

14. 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.