In the Cockcroft and Walton experiment, accelerated protons collided with lithium nuclei - Leaving Cert Physics - Question d - 2017

The protons were accelerated using a Cockcroft-Walton generator, which utilizes a voltage multiplier circuit to generate high voltages. This high voltage creates an electric field that accelerates the protons towards the target.

Alpha-particles were detected using a zinc sulfide screen, which produces flashes of light when struck by alpha-particles. These flashes can then be observed and counted.

The nuclear equation for the reaction can be represented as:

$\text{Li}^6_3 + \text{p}^1_1 \rightarrow 2 \text{He}^4_2$

(where 1 proton interacts with the lithium nucleus to produce 2 alpha particles).

The mass of the lithium nucleus is approximately 1.165 \times 10^{-26} \text{ kg} and the loss in mass during the reaction is calculated as:

$\text{Loss in mass} = 3.09 \times 10^{-29} \text{ kg}$

Using the mass-energy equivalence $E = mc^2$, the energy released can be calculated as:

$E = 3.09 \times 10^{-29} \text{ kg} \times (3 \times 10^8 \text{ m/s})^2 \approx 17.35 \text{ MeV}.$

This experiment was historically significant as it verified the principle of energy-mass equivalence, $E = mc^2$, by demonstrating nuclear transmutation through artificially accelerated particles. Additionally, it marked a pivotal advancement in the development of particle accelerators, contributing to further research in nuclear physics and earning a Nobel Prize for its discoveries.