CFBR—Ⅱ快中子脉冲堆泵浦^3He—Ar—Xe激光器谐振腔研制

CFBR-ⅡFAST-BURSTNUCLEAR REACTOR PUMPING￣3He-Ar-Xe LASER RESONATOR

报导了我国第一台堆泵浦￣３Ｈｅ－ＡＩ－Ｘｅ激光器谐振腔研究的要点及所采用的技术措施。堆泵浦激光器属于大型物理实验范畴，况且还缺少某些实验数据作为谐振腔设计依据，为此，从激光谐振腔的各个环节上加以研究和保证，即使实验中出现了预计中较差的情况，激光器仍能产生振荡。

AbstractIn this paper the design and related technical measures of the resonator for the first nuclearreactor pumped ￣3He-Ar-Xe laser in China are given.The optics resonator was a stable half-symmetry cavity of 0.9m length with a concave mirror M_1 of2m curvature radius and a flat mirror M_2.In order to lower the threshold condition,the reflectivity of theoutput mirror was changed from low to high,such as T_2 =0.3%,1.4%, 3% and so on. Atom Xehas many transmissions from 1.73μm to 3.5μm, but the dominant transmissions 1.73μmand2.03μm wavelength share a common upper level.Therefore,as the first order approximation thedominant wavelength is determined by the quenching of lower laser level. In our situation heliumbuffered gas preferential quenches the lower level of the 2.03μmtransmission,so both mirrors ofthe cavity have the high reflectivities of 1.73μm and the low reflectivities of 2.03μm. The ratio ofthe single trip losses of cavity of 2.03μm wavelength to 1.73μmwavelength was more than 20.Ifthe1.73μmlaser oscillation has established,the population of the upper level cannot increasecontinuely and the higher oscillation threshold of 2.03μm wavelength is not be able to reach,so2.03μmwavelength is suppressed effectively.The cavity alignment accruacy of 20”was achived by means of inner focusing collimator.Thevibriation near the laser was eliminated carefully. The first running of reactor pumped ￣3He-Ar-Xe laser was successful.The typical waveformsof the 1.73μmlaser output and the neutron signal are shown in Fig.5.The delay time fromneutron signal to laser signal was 110μs.The resonator method was used to identify the laser oscillation. If a piece of paper was in-serted in cavity to block up the optical way between full reflective mirror and activity medium,the feedback effect of resonator was stoped and the laser signal was extinguished.At thattime only a very small fluorescence signal was on,as shown in Fig.6.