恒星的能量产生
核聚变是我们的太阳从原子核中产生能量的方法。核聚变是一种通过结合原子核来释放能量的方法。 “融合”这个词应该给你一个暗示，事情正在融合或融合在一起。不要将核聚变与核裂变混淆，核裂变是将原子核分解成微小的碎片。核电站就在地球上使用核裂变。另一方面，太阳采用核聚变。
四个氢核结合形成一个较轻的氦核的反应是人类理解的最关键的核聚变反应。单个质子存在于氢核中，而两个质子和两个中子存在于氦核中。当我们的太阳将它们融合在一起时，氦核的质量小于四个氢核。这种质量损失转化为能量。
这个反应可以用上面给出的简单方程来概括。你可以看到四个氢质子如何在那里结合形成氦和能量。不幸的是，这过于简单化了。事实要复杂得多，我们今天将讨论其中的一部分。我相信我只是无意中听到了一声抱怨。
什么是核聚变？
A process in which two very light nuclei (A≤8) combine to form a nucleus with a larger mass number along with the simultaneous release of a large amount of energy is called nuclear fusion.
例如：
- 当两个氘1 H 2原子核融合在一起时，会形成以下产物：
1 H 2 + 1 H 2 ⇢ 2 He 3 + 0 n 1 +Q
- 当四个氢（1H1）核融合在一起时，形成以下产物：
4 1 H 1 ⇢ 2 He 4 + 2 + 1 e 0 + 2v + Q
恒星的能量产生
据计算，太阳以每秒约 10 26 J 的速率辐射能量。太阳以这种速度辐射了数百万年。太阳的能量来源不可能是化学反应，因为化学反应释放的能量不可能持续那么久。还发现氢和氦构成了太阳质量的约 90%，而其他元素则占 10%。由于太阳中存在的重元素数量很少，所以太阳的能量来源不可能是核裂变。
聚变反应是太阳和恒星的能量来源，其内部温度约为 10 7 -10 8K 。太阳中基本的能量产生过程是氢核的聚变，许多其他恒星也是如此。
Hans Bethe in 1939 suggested that the source of Stellar energy is thermonuclear reactions. He proposed that the thermonuclear reactions taking place in the sun and other stars follow two different series of processes.
质子-质子循环
It is a thermonuclear reaction in which the direct collisions of protons result in the formation of heavy nuclei.
在质子-质子循环中，四个氢核 ( 1 H 1 ) 融合成氦核 ( 2 He 4 ) 发生在以下步骤中：
1 H 1 + 1 H 1 ⇢ 1 H 2 + 1 e 0 + v + 0.42MeV
1 H 2 + 1 H 1 ⇢ 2 He 3 + γ + 5.49 MeV
2 He 3 + 2 He 3 ⇢ 2 He 4 + 2 1 H 1 +12.86 Mev
上述组合给出
4 1 H 1 ⇢ 2 He 4 +2 1 e 0 +2v +2γ + 24.68MeV
因此，质子循环序列的净效应是四个质子（ 1 H 1 ）结合形成一个氦核（ 2 He 4 ）加上两个正电子（ 1 e 0 ，即β + ）两个伽马射线（γ）和两个释放约 25 MeV 能量的中微子。在约10 7 K 的温度下，质子-质子循环占主导地位。
碳氮循环
It is a thermo nuclear reaction in which carbon nuclei absorbs a succession of protons until they emit alpha particles to become carbon nuclei once more to repeat the cycle indefinitely.
Carbon -Nitrogen cycle starts that have hotter interiors carbon cycle predominates. The net result of this cycle again is the formation of a Helium nucleus, two positrons, two γ rays and two neutrinos from 4 protons with the evaluation of 24 .68 MeV.
核反应顺序如下：
6 C 12 + 1 H 1 ⇢ 7 N 13 + Q 1 (MeV)
7 N 13 ⇢ 6 C 13 + 1 e 0 +v
6 C 13 + 1 H 1 ⇢ 7 N 14 + Q 2 (MeV)
7 N 14 + 1 H 1 ⇢ 8 O 15 +Q 3 (MeV)
8 O 15 ⇢ 7 N 15 + 1 e 0 + v
7 N 15 + 1 H 1 ⇢ 6 C 12 + 2 He 4
本周期释放的总能量 = 24.68MeV
上述组合给出：
4 1 H 1 ⇢ 2 He 4 + 2 1 e 0 + 2v +2γ +24.68MeV
最初的6 C 12充当该过程的一种催化剂，因为它在其结束时重新出现。上述热核反应发生在太阳和其他恒星中，因此它们是太阳系中的能量来源。
因此，聚变释放的能量大于裂变释放的能量。
示例问题
问题1：所有的聚变反应都是放能的吗？
回答：
Fusion reactions between sufficiently light nuclei are exoergic because the B.E/A increases. If the nuclei are too massive, however, B.E/A decreases is the fusion is endoergic. (I.e.,it takes in energy rather than releasing it).
问题2：为什么在陆地上难以实现核聚变？
回答：
- The extremely high temperature required to initiate nuclear fusion cannot be easily realised .
- The nuclei which fuse together in nuclear fusion are at very high temperatures and they cannot be contained as no container remains in solid state at this temperature.
问题3：聚变反应比裂变反应更有能量。评论。
回答：
Since energy released by the fusion reaction is greater than the energy released by the fission reaction, therefore fusion reaction is more energetic than a fission reaction.
问题 4：引发核聚变反应需要非常高的温度。解释为什么？
回答：
When two nuclei fuse together, the process is called a nuclear fusion. Two nuclei being positively charged repel each other as they come closer to each other. To overcome this force of repulsion for fusing together, these two nuclei should have large kinetic energy. This large kinetic energy can be attained at a very high temperature.
Nuclear fusion can be carried out at extremely high temperature(∼107). Since this much temperature cannot be generated in any furnace, so nuclear fusion cannot be initiated. Moreover, if this amount of temperature is generated by atomic explosion, then it is difficult to contain the material used in fusion. Due to these difficulties, nuclear fusion cannot be carried out easily.
问题5：为什么实验室里不可能进行核聚变？
回答：
Because of very high temperature (∼107) needed for nuclear fusion cannot be attained by any known method in the laboratory.