Suppressing drift chamber diffusion without magnetic field
Suppressing drift chamber diffusion without magnetic field
复制标题
无磁场抑制漂移室扩散
DOI：
10.1016/s0168-9002(99)00955-9
复制
发表时间：
2000
影响因子：
1.4
通讯作者：
M. Lehner
中科院分区：
文献类型：
--
作者：
C. Martoff;D. Snowden;T. Ohnuki;N. Spooner;M. Lehner
电离辐射漂移室探测器的空间分辨率受初级电子扩散的限制。通常沿漂移方向施加强磁场(Fancher et al., Nucl。Instr。和冰毒。A 161(1979) 383)，因为它抑制了横向扩散，提高了分辨率，但成本和复杂性大大增加。这里我们证明横向径迹扩散可以在没有任何磁场的情况下被强烈抑制。这是通过使用气体添加剂来实现的，该气体添加剂可逆地捕获初级电离电子，形成负离子。即使在很高的漂移场和较低的压力下（E/P=28.5 V / cm torr），离子也能随热能漂移，并且随着漂移场的增大，扩散减小。到达腔室的雪崩区后，负离子被有效地剥离，并获得普通的雪崩增益。利用该技术，在40 torr和零磁场条件下，在15 cm漂移路径上实现了小于200 μm的横向扩散。该方法可以在长漂移距离和零磁场条件下提供高空间分辨率。负离子漂移室在低压和天基或地下实验等情况下特别有用，这些情况下探测器的尺寸可扩展性很重要，并且成本、空间或功率限制无法使用磁场。
The spatial resolution in drift chamber detectors for ionizing radiation is limited by diffusion of the primary electrons. A strong magnetic field along the drift direction is often applied (Fancher et al., Nucl. Instr. and Meth. A 161 (1979) 383) because it suppresses the transverse diffusion, improving the resolution but at considerable increase in cost and complexity. Here we show that transverse track diffusion can be strongly suppressed without any magnetic field. This is achieved by using a gas additive which reversibly captures primary ionization electrons, forming negative ions. The ions drift with thermal energies even at very high drift fields and low pressures (E/P=28.5 V / cm torr), and the diffusion decreases with increasing drift field. Upon arrival at the avalanche region of the chamber the negative ions are efficiently stripped and ordinary avalanche gain is obtained. Using this technique, r.m.s. transverse diffusion less than 200 μm has been achieved over a 15 cm drift path at 40 torr with zero magnetic field. The method can provide high spatial resolution in detectors with long drift distances and zero magnetic field. Negative ion drift chambers would be particularly useful at low pressures and in situations such as space-based or underground experiments where detector size scaleability is important and cost, space, or power constraints preclude the use of a magnetic field.