High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan.
Phys Rev Lett. 2012 Mar 30;108(13):134801. doi: 10.1103/PhysRevLett.108.134801.
For the production of high-density ultracold neutrons (UCNs), we placed 0.8 K superfluid helium in a cold neutron moderator. We resolved previous heat-load problems in the spallation neutron source that were particularly serious below 1 K. With a proton-beam power of 400 MeV×1 μA, a UCN production rate of 4 UCN cm(-3) s(-1) at the maximum UCN energy of E(c)=210 neV and a storage lifetime of 81 s were obtained. A cryogenic test showed that the production rate can be increased by a factor of 10 with the same storage lifetime by increasing the proton-beam power as well as (3)He pumping speed.
为了生产高密度的超冷中子（UCN），我们将 0.8 K 超流氦放入冷中子减速剂中。我们解决了散裂中子源中在 1 K 以下特别严重的热负荷问题。在 400 MeV×1 μA 的质子束功率下，在最大 UCN 能量 E(c)=210 neV 下获得了 4 UCN cm(-3) s(-1)的 UCN 产生率和 81 s 的存储寿命。低温测试表明，通过增加质子束功率和（3）He 抽速，在相同的存储寿命下，产生率可以提高 10 倍。
