TACTIC: A time projection ionization chamber for low energy nuclear astrophysics

我们提出了一种用于测量低能带电粒子反应的探测器的结构，它几乎覆盖了整个立体角。该探测器命名为TACTIC，将是一个圆柱形的时间投影电离室，电场方向为径向。中心区域将包含气体目标，取决于配置，该气体目标也可以是场区域中的检测气体。中心区域处于恒定电位，并且对检测不可见。离子，通常是从一些核反应中以非零方位角发射出来的，穿过离开中心区域的金属丝网格，然后在电场区域产生一个痕迹，即自由电子。电子被吸引向电场的阳极。然而，在它们的途中，电子会遇到GEM（气体电子倍增器）箔，将信号放大很大一部分。在阳极条上记录的信号将被数字化，随后在VME板条箱中进行处理。因此，腔室将记录完整的轨迹，包括方向、完整的能量测量以及每个阳极条的能量损失测量。此外，与射束RF的时间相关性也是可能的。一个BGO探测器阵列将围绕该室，并允许过滤掉伽马带电粒子反应。阳极条将在极性方向上分开，以允许更高的计数率以及多个颗粒的检测。到目前为止提出的反应包括测量8Li（alpha，n）11B反应，测量7 Be（p，p）7 Be弹性和非弹性反应，以及12 C +12 C实验，还有更多的后续实验。我们已经建立了一个测试设施，以观察信号放大的GEM以及测试室中的几种气体。所有这些测试都证明了TACTIC所基于的原理确实是合理的，并且该室的建造是可行的。此外，我们还进行了广泛的GEANT计算，确认了基本的设计配置。J-实验室已建造了一个类似的探测器BONUS，并已通过实验证明其工作。在此拨款中，我们要求提供所需人力和运营费用的资金。提交的一份单独的RTI赠款申请涉及硬件的采购。

We propose the construction of a detector for the measurement of low energy charged particle reactions covering nearly the full solid angle. The detector, named TACTIC, will be a cylindrical time projection ionization chamber with the electrical field in radial direction. The central region will contain the gas target which, depending on configuration, can also be the detection gas in the field region. The central region is at constant potential and is not visible to detection. Ions, typically emanating from some nuclear reaction with a non-zero azimuthal angle, pass through a grid of wires leaving the central region.They will then produce a trace in the field region, i.e. free electrons.The electrons are drawn towards the anode of the electric field. However, on their way the electrons will encounter a GEM (Gas Electron Multiplier) foil amplifying the signal by a large factor. Signals registered at the anode strip will be digitized and later processed in an VME crate. Therefore the chamber will register full traces which include directions, a full energy measurement, and for each anode strip an energy loss measurement.In addition, a time correlation with the beam RF is possible. An array of BGO detectors will surround the chamber and allow to filter out gamma charged particle reactions. The anode strip will be divided in polar direction to allow for higher counting rates as well as for the detection of multiple particles. The reactions so far proposed include a measurement of the 8Li(alpha,n)11B reaction, the measurement of the 7Be(p,p)7Be elastic and inelastic reaction, and a 12C+12C experiment, with more to follow. We have built a test facility to observe signal amplification by the GEM as well as to test several gases in the chamber. All those tests have proven that the principle on which TACTIC is based is indeed sound and the construction of the chamber feasible.In addition, we have performed extensive GEANT calculations confirming basic design configurations. A similar detector, BONUS, has been built at the J-Laboratory and has been experimentally demonstrated to work.In this grant we request the funding for the necessary manpower and operational expenses. A separate RTI grant request submitted deals with the acquisition of the hardware.