Neural-a detector for neutron reactions

长寿命的放射性同位素^26 Al是30年前在宇宙中发现的，它的星系分布遵循第I星族恒星之一，即大质量短寿命恒星。这样的恒星通常会以核心坍缩超新星的形式结束。^26 Al的主要产生是在大质量星星核心坍缩后的氖爆炸燃烧中。在这种情况下，^26 Al是通过捕获次级质子或（p，n）反应产生的。由于自由中子也存在，这就导致了主要的破坏性反应，即^26 Al（n，p）^26 Mg和^26 Al（n，alpha）^23 Na，它们控制了速率。这种破坏的最关键的中子能量范围是从150-200 keV，不幸的是，没有测量存在。我们计划利用TRIUMF-ISAC产生强放射性^26 Al束的独特能力，在薄碳箔中制造注入^26 Al靶。这样的目标具有独特的性质，即（i）目标中不存在主要的交叉污染，以及（ii）与改进的背景抑制相结合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受到背景问题的阻碍，无法覆盖中子能量范围。除了这种新的目标方法，我们还计划开发一种新的探测器。这个探测器（被称为神经）将包括一个时间投影室沿着与硅探测器周围的时间投影室。除了获得阻止本领信息外，还可以探测到反冲的^23 Na和^26 Mg粒子。这将进一步限制背景，原则上甚至允许确定中子能量。洛斯阿拉莫斯的LANSCE设施的中子能量通常由飞行时间条件给出，并在给定时间内显示出一定的扩散。所提出的实验方法已经取得了很高的分数与兰斯PAC。2009年12月，洛斯阿拉莫斯计划对该探测器进行测试。为此，我们正在组装一个探测器，该探测器由从TRIUMF-ISAC的其他实验设施中获得的部件组成。然而，由于缺少硅，探测器不能覆盖最大立体角。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.