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In this paper we present a description of the new complex installation for the study of extensive air showers which was created at the Tien Shan mountain cosmic ray station, as well as the results of the test measurements made there in 2014-2016. At present, the system for registration of electromagnetic shower component consists of ∼100 detector points built on the basis of plastic scintillator plates with the sensitive area of 0.25m 2 and 1m 2 , spread equidistantly over ∼10 4 m 2 space. The dynamic range of scintillation amplitude measurements is currently about (3 − 7) · 10 4 , and there is a prospect of it being extended up to ∼10 6 . The direction of shower arrival is defined by signal delays from a number of the scintillators placed cross-wise at the periphery of the detector system. For the investigation of nuclear active shower components there was created a multi-tier 55m 2 ionization-neutron calorimeter with a sum absorber thickness of ∼1000g/cm 2 , typical spatial resolution of the order of 10cm, and dynamic range of ionization measurement channel about ∼10 5 . Also, the use of saturation-free neutron detectors is anticipated for registration of the high-and lowenergy hadron components in the region of shower core. A complex of underground detectors is designed for the study of muonic and penetrative nuclear-active components of the shower.The full stack of data acquisition, detector calibration, and shower parameters restoration procedures are now completed, and the newly obtained shower size spectrum and lateral distribution of shower particles occur in agreement with conventional data. Future studies in the field of 10 14 − 10 17 eV cosmic ray physics to be held at the new shower installation are discussed.

Purposeful investigation of radiation fluxes strongly delayed in relation to the main particles front of extensive air shower (EAS) was undertaken at the Tien Shan Mountain Cosmic Ray Station. It was found that the passage of the EAS can be accompanied by the delayed thermal neutrons and by the soft (30-50) keV gamma rays, mostly concentrated within a region of about (5-10) m around shower axis, where the integral radiation fluence can vary in the limits of (10 −4 − 1) cm −2 for neutrons, and of (0.1 − 1000) cm −2 for gamma rays. The dependence of signal multiplicity on the shower size N e has a power shape both for the neutron and gamma ray components, with a sharp increase of its power index around the value of N e ≈ 10 6 , which corresponds to the position of the 3 · 10 15 eV knee in the primary cosmic ray spectrum. Total duration of detectable radiation signal after the EAS passage can be of some tens of milliseconds in the case of neutron component, and up to a few whole seconds for gamma rays. The delayed accompaniment of low-energy radiation particles can be an effective probe to study the interaction of the hadronic component of EAS.

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