The performance of a small-cell drift chamber operated with two helium-based gas mixtures, He/C_3H_8(60/40) and ~He/CH_4(60/40), was studied using cosmic rays, respectively.

• 利用宇宙线分别研究了一个小单元漂移室在He/C3H8(60/40)和He/CH4(60/40)两种氦基混合气下的性能.