note_09_accelerators

note_09_accelerators - Introduction to Elementary Particle...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
Introduction to Elementary Particle Physics. Note 09 Page 1 of 14 PARTICLE ACCELERATORS Prehistory: α -particles cosmic rays Early ideas: Cockcroft-Walton Van de Graaff Linear accelerator Cyclotrons Synchrotrons: Proton synchrotrons with weak focusing Proton synchrotrons with strong focusing Secondary beams from proton accelerators Electron accelerators Colliders
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Introduction to Elementary Particle Physics. Note 09 Page 2 of 14 Prehistory: α -particles as the first projectiles. There are three types of radioactive decays of nuclei: α , β , γ . The classification is based on the charge of emitted particles, which can be positive ( α -particles), negative ( β -particles), and neutral ( γ -particles). A typical energy released in nuclear decays is of the order of 1 MeV, a few MeV at most. In β -decay, a neutron decays to proton, electron, and anti-neutrino. As a result, the original element (Z,A) becomes (Z+1,A), while electron and neutrino are emitted (neutrino escapes undetected). A newly formed nucleus (eg as a result of a β -decay) is not necessarily at its ground energy state, i.e. it may be excited. There are two typical ways how such excitation can be released: via emitting a high energy photon ( γ -ray) or by shedding a nucleus of helium (two protons and two neutrons form a very strongly bound system and therefore get emitted in such a combination). 1900s Rutherford figured out that α -particles were He nuclei. 1910 Rutherford and Madsen were the first to use α -particles to bombard atoms with the goal to gain insights in the atom structure from α -particle scattering patterns. They did detect the presence of a nucleus . 1910s Rutherford and Madsen kicked out protons from various elements by bombarding them with α -particles. 1930s Bothe and Becker, Joliot-Curie family, Chadwick knocked out neutrons by bombarding Be nuclei with α - particles: α +Be 9 Æ C 13 + n. Chadwick convincingly showed that the emerging particles were neutrons .
Background image of page 2
Introduction to Elementary Particle Physics. Note 09 Page 3 of 14 Prehistory: Cosmic Rays 1900s Physicists were looking for radioactivity using electroscopes and electrometers, devices that allowed sensing the level of ionization. They started seeing that there was some radiation present even when all radioactive sources were removed far away from the apparatus. 1910 Father Theodore Wulf climbed up at the top of the Eiffel tower and saw a somewhat increased level of radiation. He speculated that the radiation might have an extraterrestrial origin and suggested doing similar measurements at higher altitudes. 1911-12 Victor Hess made 10 balloon ascends reaching altitudes of 5000 m and indeed observed the level of radiation increasing by a factor of 3-5 in comparison to the sea level. In 1936, he received the Nobel Prize “for his discovery of cosmic radiation” Important note: the “cosmic rays” we see at the sea level are not really cosmic. The primary cosmic rays, when the hit upper layers of the atmosphere, produce showers of particles some of which reach the sea level. The highest energy primary cosmic rays that we have seen so far
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 14

note_09_accelerators - Introduction to Elementary Particle...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online