Direct measurement of Nuclear Fusion Cross Section at Stars.

Ecm = 0.3MeV的^<12>C+^4He-&gt;^<16>O+γ反应截面在恒星核合成中起着至关重要的作用，国际上对该反应截面的测量已经进行了40多年，但由于实验难度大，至今还没有进行过测量。我们在九州大学串联实验室进行了15年的^<12>C+^4He-&gt;^<16>O+γ反应截面测量准备工作。在我们的方法中，我们<16>从Ecm = 2.4 - 0.7MeV的逆运动学12 C +4 He&gt; 16 O +γ反应中探测到了^ O，并将截面外推到0.3MeV。这只是达到目的的一种方法，但有很多困难。2004年，我们首次成功地探测到了Ecm = 2.4 MeV的<16>^<12>C+^4He-&gt;^<16>O+γ反应中的^ O，但未能获得截面的绝对值。为了达到这一目标，我们需要a）大于5 μA的C束流，B）25 Torr x 3cm的He无窗靶，c）低于10^的背景（BG）水平<-19>，d）脉冲束流，e）稳定的靶。 ...更多信息 e）2-6 MHz的RF电源，f）反冲质量分离器的优化狭缝系统，和g）外推方法。我们已经启动了光束。BG水平现在为10 μ V<-17>，剩余BG将低于Ecm = 1.2 MeV。2007年，在a）、B）和e）-g）方面取得了进展。我们成功地制备了25 Torr x 3cm的He无窗靶。无窗靶比过去厚5倍。2007年，我们通过测量2.4MeV的^<12>C+^4He-&gt;^<16>O+γ截面进行了系统校验，发现了反冲质量分离器中次级束晕在固定狭缝处散射产生的新BG。由于这个问题，1.5 MeV的实验被推迟到2008年。德国鲁尔大学<12><16>在Ecm = 5.0-1.9 MeV处测量了^ C+^4He&gt;^ O+y截面。由于本研究项目的前期准备工作，我们将能够在<12><16>2008-2011年进行Ecm= 1.5-0.7 MeV的^ C+^4He-&gt;^ O+y实验，并达到预期目标。少

Cross section of ^<12>C+^4He->^<16>O+γ reaction at Ecm = 0.3 MeV plays a crucial role in nuclear synthesis in stars, and measurements of the cross section have been attempted for about 40 years in the world However, the cross section has not measured yet since the experiment is extremely difficult. We have prepared the measurement of ^<12>C+^4He->^<16>O+γ reaction cross section at Kyushu University tandem laboratory for 15 years. In our method, we detect ^<16>O from inverse kinematics 12C+4He >16O+γ reaction at Ecm = 2.4 -0.7 MeV, and extrapolate the cross section down to 0.3 MeV. This is only one method to arrive the goal, but there are many difficulties. In 2004, we first succeeded in detecting ^<16>O from ^<12>C+^4He->^<16>O+γ reaction at Ecm = 2.4 MeV, although absolute value of the cross section could not be obtained.To arrive the goal, we need a)C beam intensity of more than 5 μA, b)He windowless target of 25 Torr x 3cm, c)background(BG)level below 10^<-19>, d)pulsed beam, e)stab … More le RF power supply of 2-6 MHz, f)optimized slit system of a recoil mass separator, and g)extrapolation method. Already we have pulsed the beam. BG level is now 10^<-17>, and remaining BG is to be found below Ecm = 1.2 MeV. In 2007, progress was made in a), b), and e)-g). We succeeded in preparing a He windowless target of 25 Torr x 3cm. The windowless target is 5 times thicker than those in the past. For a) and e)-g), we made concrete plan and 60-80% have been finished in 2007.In 2007, we made system check by measuring ^<12>C+^4He->^<16>O+γ cross section at 2.4 MeV, and found new BG produced by scattering of secondary beam halo at fixed slit in the recoil mass separator. By this trouble, experiment at 1.5 MeV was postponed to 2008. At Ruhr University, Germany, ^<12>C+^4He>^<16>O+y cross section has been measured at Ecm = 5.0-1.9 MeV. Owing to the preparation made in this research project, grant-in-aid, we will be able to make the ^<12>C+^4He->^<16>O+y experiment at Ecm= 1.5-0.7 MeV in 2008-2011, and arrive at the goal. Less