Shielded Superconducting Linear Motor for Towed-Grid Studies of Quantum Turbulence
Shielded Superconducting Linear Motor for Towed-Grid Studies of Quantum Turbulence
复制标题
用于量子湍流牵引网格研究的屏蔽超导直线电机
DOI：
10.1063/1.2354670
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发表时间：
2005
影响因子：
2
通讯作者：
G. Ihas
中科院分区：
文献类型：
--
作者：
Shu;G. Labbé;G. Ihas
目前正在进行的低温量子湍流研究的目的是产生类似于经典流体中研究的湍流，以比较实验数据和理论。具体地说，在没有粘性的情况下，湍流通过什么路径衰减？均匀各向同性湍流（HIT）是最好的表征经典的情况。为了在量子流体中产生HIT，我们必须在20 mK的超流氦通道中拖曳网格。要求网格运动1 cm，速度几乎恒定，最高可达1 μS。为了避免液氦的焦耳和涡流加热，磁屏蔽超导直线电机已经建成。栅极连接到轻绝缘电枢杆的端部，电枢杆具有两个固定到其上的中空圆柱形铌罐，间隔约26 mm。棒的这一部分位于超导螺线管内，当用适当形状的电流脉冲驱动时，该超导螺线管产生磁场，该磁场使棒（和栅极）加速1 mm，使棒和栅极以恒定速度移动10 mm，然后使其减速1 mm。该电机是通过模拟来构建的，模拟证明了所需的设计和电流脉冲是相当合理的。仿真和控制程序是在LabView中编写的，带有嵌入式C编译器。使用模拟器，各种设计的螺线管（有和没有屏蔽）和电枢进行了研究。我们比较了模拟和实验结果。通过在LabView中编写脉冲发生程序，我们几乎可以应用产生所需运动所需的任何脉冲形状。这是必要的，因为电机电路的负载几乎是纯感性的（零电阻）。模拟，设计过程，和实验数据证明电机的功能将被提交。
The purpose of ongoing low-temperature quantum turbulence research is to produce turbulence similar to that studied in classical fluids to compare the experimental data and theories. Specifically, in the absence of viscosity, through what path does the turbulence decay? Homogeneous isotropic turbulence (HIT) is the best characterized classical situation. To produce HIT in a quantum fluid, we must tow a grid through a channel of superfluid helium at 20 mK. A grid motion of 1 cm at a nearly constant speed up to 1 μS is required. To avoid Joule and eddy current heating of the liquid helium, a magnetically shielded superconducting linear motor has been built. The grid is attached to the end of a light insulating armature rod which has two hollow cylindrical niobium cans fixed to it about 26 mm apart. This part of the rod is inside a superconducting solenoid which, when driven with the properly shaped current pulse, produces a magnetic field that accelerates the rod (and grid) in 1 mm, moves the rod and grid at constant speed for 10 mm, and then decelerates it in 1 mm. The motor was built guided by simulations that demonstrated the design and current pulses required are quite reasonable. The simulation and control program is written in LabView with an embedded C compiler. Using the simulator, various designs of solenoid (with and without shielding) and armature were investigated. We compare the simulation and the experimental results. By writing a pulse-generating program in LabView, we can apply virtually any pulse shape required to produce the desired motion. This is necessary because of the almost purely inductive (zero resistance) load of the motor circuit. The simulations, design process, and the experimental data demonstrating the functioning motor will be presented.