Building a particle accelerator is not inherently illegal. Particle accelerators are complex scientific instruments used for research in various fields, including particle physics, materials science, and medical applications. Many countries around the world have built and operate particle accelerators for scientific purposes.
However, it's important to note that the construction and operation of a particle accelerator may be subject to regulations and oversight. The specific requirements and regulations can vary depending on the jurisdiction and the type and scale of the accelerator being built.
In many cases, the construction and operation of high-energy particle accelerators may require permits, licenses, and compliance with safety regulations. These regulations are in place to ensure the safety of the facility, the personnel involved, and the surrounding environment.
If you are interested in building a particle accelerator, it is advisable to consult with relevant authorities and experts in your jurisdiction to understand the legal and regulatory requirements that need to be met. They can provide guidance on the necessary permits, safety standards, and any other legal considerations that may apply in your specific situation.