During the period of 1956- 1960, under the leadership of Dai Chuanceng, Zhang Huanqiao participated in the establishment of the first neutron crystal spectrometer and the first neutron diffractometer in China, which created conditions for the experimental study of slow neutron spectroscopy and nuclear reactor solid physics. In the spring of 1958, they simply transformed an X-ray diffractometer (made in Switzerland in 1933) that was idle by the former Academia Sinica into a high-resolution neutron crystal spectrometer, which was used until the mid-1980s. It is on this spectrometer that the phenomenon of neutron diffraction enhancement in piezoelectric oscillating single crystals was discovered. In the assembly process of another neutron crystal spectrometer built in cooperation with Changchun Institute of Optics and Mechanics, Zhang Huanqiao proposed a method of partially compensating the thickness of steel strip with metal foil, which solved the problem that it was difficult to guarantee the linkage accuracy index of 1: 2 crystal stage and counter support arm after many repairs, and the linkage accuracy reached 1.5× 10-6. For the best international level at that time (neutron crystal built by BNL Columbia University in July, 65438), the uniformity test of the first atomic bomb in China and the discovery of neutron diffraction enhancement of α-lithium iodate in the external field were all completed on this equipment.

During the period of 1960- 196 1, in the heavy water reactor of the Institute of Atomic Energy, under the auspices of Yang Zhen, the phenomenon of neutron diffraction enhancement of piezoelectric oscillating single crystals was discovered experimentally. Zhang Huanqiao wrote the article Explanation of Neutron Diffraction Enhancement in Piezoelectric Oscillating Single Crystal, pointing out that the piezoelectric vibration of the crystal produces strain, which makes the lattice change dynamically and increases the effective thickness of the crystal for neutron diffraction. The change of crystal plane spacing △d/d produces two effects: ① the energy of diffracted neutron beam is broadened; (2) The secondary extinction of neutrons in the crystal is weakened during oscillation. Both of them can lead to diffraction neutron enhancement. Based on the experimental data of diffraction neutron enhancement ratio changing with incident neutron energy at a fixed oscillation power, the △d/d value of the crystal is basically the same in the whole neutron energy region, indicating that the most likely reason for enhancement is the weakening of neutron secondary extinction. Therefore, he put forward an experimental verification scheme, and made two measurements on the neutron diffractometer: ① replacing the monochromator of the diffractometer with a piezoelectric crystal, moving the monochromator to the sample table, and analyzing the energy of diffracted neutrons with piezoelectric time, so as to determine the enhancement caused by the energy broadening of diffracted neutrons caused by △d/d; ② Put the piezoelectric crystal on the sample table of the diffractometer, and observe the enhancement of neutron diffraction in the piezoelectric oscillation time under the incidence of monochromatic light beam, so as to determine the effect caused by the attenuation of neutron secondary extinction. From the second measurement, it is observed that the diffraction neutron enhancement degree is the same under the incidence of monochromatic neutron beam, which indicates that the secondary extinction is the reason for the diffraction enhancement of single crystal neutron in response to piezoelectric oscillation. This achievement won the third prize of National Natural Science Award 1982 together with the neutron diffraction enhancement of α lithium iodate discovered by Yang Zhen et al. (5) 5) The correlation between the instantaneous neutron number distribution and the instantaneous neutron average and the kinetic energy of long-range alpha particles in the 252cf trisection. The experimental results of instantaneous neutron number distribution of 252Cf triple fission are given in the literature for the first time. It is observed that the instantaneous neutron number distribution of the third fission is similar to that of the second fission, but the average instantaneous neutron number of the third fission is 3.03 0.02, which is obviously smaller than that of the second fission (3.743 0.018), which means that the average total excitation energy of the fragments associated with the fission of 252Cf long-range α particles is about 6MeV lower than that of the second fission. It can be inferred from the similarity of the instantaneous neutron number distribution of the two kinds of fission that the fluctuations of the two kinds of fission around the average state at the time of fracture are very similar.

The average instantaneous neutron of 252Cf trisection is negatively correlated with the kinetic energy of long-range α particles. The results show that the number of neutrons emitted by debris is related to the initial deformation of debris at the moment of nuclear rupture. The change of instantaneous neutron average with the kinetic energy of long-range alpha particles mainly reflects the relationship between the deformation degree of nuclear third-time debris and the final kinetic energy of long-range alpha particles, which is discussed qualitatively in two extreme cases.