Neural-a detector for neutron reactions

长寿命的放射性同位素^26Al是30年前在宇宙中发现的，它的银河系分布遵循第一类恒星之一，即大质量、短寿命恒星。这类恒星通常会以核心坍塌超新星的形式结束。^26Al的主要产生发生在大质量恒星核坍塌后的爆炸霓虹灯燃烧过程中。在这种情况下，^26Al是通过捕获次级质子或(p，n)反应产生的。由于也存在自由中子，这导致了主要的破坏性反应，即主导速率的^26Al(n，p)^26 mg和^26Al(n，α)^23Na。造成这种破坏的最关键的中子能量范围是150-200keV，不幸的是，目前还没有测量结果。我们计划利用TRIUMF-ISAC在产生强放射性^26Al束方面的独特能力，在薄碳箔中制造植入^26Al靶。这样的目标具有独特的性质：(I)在目标中不存在主要的交叉污染，以及(Ii)结合改进的背景抑制的更好的运动学重建是可行的。事实上，以前的测量在很大程度上是由于覆盖中子能量范围的背景问题而无法进行的。除了这种新颖的靶标方法，我们还计划开发一种新的探测器。这种探测器(称为神经探测器)将由一个时间投影室和围绕时间投影室的硅探测器组成。除了获得拦截力信息外，还将有可能检测到反冲^23Na和^26 mg粒子。这将对背景施加进一步的限制，原则上甚至允许确定中子能量。位于洛斯阿拉莫斯的LANSCE设施的中子能量通常是由飞行时间条件给出的，并在给定的时间内显示出一定的扩散。所提出的实验方法在Lansce PAC中获得了很高的分数。2009年12月，洛斯阿拉莫斯计划对该探测器进行一次测试。为了做到这一点，我们正在组装一个探测器，由从TRIUMF-ISAC的其他实验设施获得的部件组成。然而，由于缺乏硅，探测器无法覆盖最大立体角。因此，我们要求提供资金，以建立一个新的、改进的检测系统。

The long-lived, radioisotope, ^26Al, was discovered in the cosmos 30 years ago and its galactic distribution follows one of population I stars, i.e. massive, short-lived stars. Such stars typically end up in core collapse supernovae. The main production of ^26Al happens in the explosive neon burning following the core collapse of the massive star. In this scenario ^26Al is produced by capture of secondary protons or the (p,n) reaction. Since free neutrons are also present, this leads to the main destructive reactions, namely ^26Al(n,p) ^26Mg and ^26Al(n,alpha) ^23Na, which dominate the rate. The most critical neutron energy range for this destruction is from 150-200 keV and unfortunately, no measurements exist. We plan to use the unique capability of TRIUMF-ISAC in producing an intense radioactive ^26Al beam to fabricate an implanted ^26Al target in a thin carbon foil. Such a target has the unique property that (i), there are no major cross contaminations present in the target and (ii) a better kinematic reconstruction combined with an improved background suppression is feasible. Indeed, previous measurements were prevented largely by background problems to cover the neutron energy range. Besides this novel target approach, we also plan to develop a new kind of detector. This detector (dubbed Neural) will consist of a time projection chamber along with silicon detectors surrounding the time projection chamber. Besides obtaining stopping power information, it will also be possible to detect the recoil ^23Na and ^26Mg particles. This will put further constrains on the background and, in principle, even allow a determination of the neutron energy. The neutron energy at the LANSCE facility in Los Alamos is typically given by time of flight conditions and shows some spread for a given time. The proposed experimental approach has achieved high marks with the Lansce PAC. In December of 2009 a run at Los Alamos is scheduled to test this detector. To do this, we are assembling a detector consisting of parts obtained from other experimental facilities at TRIUMF-ISAC. However, the detector does not cover the maximum solid angle due to lack of silicon. Therefore, we request funding to construct a new, improved detection system.