Experiments on the Transmutation of Elements by Protons
Experiments on the Transmutation of Elements by Protons
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质子对元素的嬗变实验
DOI：
10.1098/rspa.1933.0117
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发表时间：
1933
期刊：
影响因子：
--
通讯作者：
L. Rutherford
中科院分区：
文献类型：
--
作者：
M. Oliphant;L. Rutherford
在考克罗夫特和沃尔顿关于快速质子轰击元素转变的先驱实验中，人们发现，在相对较小的加速电压下——大约10万伏特——某些元素可以观察到容易测量的衰变效应。他们的实验装置是专门为使用高得多的电压而设计的。来自放电管的质子流在到达目标之前要经过很长的真空路径，并扩散到相当大的区域。通常采用1微安量级的质子电流。为了在更低的电压下研究这些转化效应，我们建造了一个特殊的放电管，它可以给我们一个更强、更集中的质子流，大约100微安，使用不超过25万伏特的加速电压。利用磁场分析了氢气放电产生的带电粒子流的组成，从而分别确定了氢离子和氢离子对放电的影响。质子流落在大约1平方英尺的靶上。厘米的面积和粒子进入检测室的立体角大大增加。通过这些方法，人们发现在任何电压下都可以获得至少1000倍于科克罗夫特和沃尔顿原始装置的分解粒子数。可用于计数的粒子数量的大量增加，使得在低电压下以极薄薄膜的形式检查锂和硼等活性元素的分解成为可能。此外，获得强烈但狭窄的粒子流并不困难，以便更详细地分析所排出粒子的范围和速度。
In the pioneer experiments of Cockcroft and Walton on the transformation of elements by bombardment with swift protons, it was found that easily measurable disintegration effects could be observed in certain elements for comparatively small accelerating voltages—of the order of 100,000 volts. Their experimental arrangement was specially devised for the use of much higher voltages. The proton stream from the discharge tube passed through a long evacuated path before reaching the target, and spread over a considerable area. Proton currents of the order of 1 microampere were usually employed. In order to study these transformation effects at still lower voltages we constructed a special discharge tube which would give us a more intense and concentrated stream of protons, of the order of 100 microamperes, using an accelerating voltage not greater than 250,000 volts. The stream of charged particles generated by the discharge through hydrogen was analysed into its components by means of a magnetic field, so that the effects due to the particles H+ and H2+ could be separately determined. The stream of protons fell on a target of about 1 sq. cm. in area and the solid angle over which particles passed into the detecting chamber was much increased. In these ways it was found possible to obtain for examination at least 1000 times the number of disintegration particles at any voltage as in the original apparatus of Cockcroft and Walton. This large increase in the number of particles available for counting made it possible to examine the disintegration of such active elements as lithium and boron at low voltages and in the form of very thin films. In addition, it was not difficult to obtain intense but narrow streams of particles in order to analyse with more detail the disintegration as regards both range and velocity of the expelled particles.