[en] In our previous experiment on CR-39 detectors, we found out that bulk etch rate of irradiated area is different from unirradiated area. Therefore, the traditional etching model should be revised. In this case, our modification which based on the theoretical studies printing out and the AFM observation was put forward and new etch rate : V'=V_t/V_irr, was defined. Then, modified track-diameter kinetics was used to clarify AFM analysis. In this research, the key parameters for 100 MeV Silicon ion include V_t=4.12 μm/h, V_irr=2.55 μm/h, V'=1.62, θ=61.03°. And the bulk etch rate V_b=1.58 μm/h. So the etch rate can be calculated whose value in V=2.61>V’. (authors)

[en] The observation of CR-39 Solid State Nuclear Track Detectors is an essential part of analysing its track structure and dosimetry. Proceeding from the theory of latent tracks' formation and growth in CR-39 detector, is discussed the effect factors of etched tracks, and studied the characteristics and contrast of two chosen track reading methods, which include the optic method and electronic microscope method. Based on this, the experiment was applied. The CR-39 detectors, which were irradiated by Si ions with energy of 100 MeV and different fluence, were etched in NaOH etchant (70℃, 6.2 N) for 6 hours and 5 minutes separately. The tracks enlarged and in nano-scale were observed under optic microscope and Atomic Force Microscope. Moreover, bulk etch was measured with partial masked and surface profiler, and the bulk etch rate V_b=1.53 μm/h was got. (authors)

[en] Formulas for detection efficiency and sensitivity of plate boron-lined ionization chamber were derived from its working principle, and their values for thermal neutrons were obtained. The saturated value of the detection efficiency for thermal neutrons of ionization chamber is 1.35% and the sensitivity is 9.65 x 10^-14 A·cm^-2·s^-1, which approximately coincides with the result of 8.43 x 10^-14 A·cm^-2·s^-1 given by a known formula. Contribution of α particles to the detection efficiency shows small difference with Li ions while that to the sensitivity is predominating. A suitable thickness of boron film, slowing fast neutron and using enriched boron can improve both detection efficiency and sensitivity of boron-lined ionization chamber. (authors)

[en] A boron-lined proportional counter (BLPC) with a count rate limit close to the multi-wire proportional counter was manufactured to measure the mixed field around reactors. After measurement with a standard Am-Be neutron source (activity: 100 mCi), the results show that the operating voltage of the BLPC is 800 V, the plateau length is 100 V and the slope is 13.2%/100 V. The width and rise time of the output pulse of the BLPC are 1.26 μS and 370 ns, respectively. When the BLPC works at a count rate of 1.0 × 10⁵ count/s, the pulse pile-up probability of the BLPC is 3.6%. A clear peak can be seen in the pulse height spectrum of the BLPC. and the performances illustrate that a BLPC working in pulse mode can serve as a source range detector of reactors. (authors)