Tamar Thesis CEBAF

The continuous electron beam accelerator facility (CEBAF) at Thomas Jefferson National Lab contains two anti-parallel 0.5 GeV linacs connected by five sets of recirculated arcs and a high quality 45 MeV electron beam injector with transverse emittence of less than [math]\pi[/math] mm-mrad and longitudinal emittence of less than [math]15 \pi[/math] keV-degrees. In oder to minimize the total accelerator circumference the accelerator structure was arranged in two separate linac segments. Each linac segment contains 25 crymodules, which itself are made of 8 superconducting radio-frequency cavities. Each crymodule is seperated by a vacuum equipment, beam diagnostics and quadrupole and dipole magnets. Quadrupole and dipole magnets are used for steering the beam. Electrons are accelerated by microwave fields generated in klystrons and propagated through wave guides to radio-frequency accelerating cavities.

Klystron is a powerful type of microwave amplifier in which a low energy microwave signal breaks a continuous electron beam into so called bunches. After that the beam passes through the resonant waveguide, where it induces a high energy microwave signal. The transmitted microwave radiation is transported to a superconducting radio-frequency(RF) cavity where it accelerates electrons.

The electromotive force(EMF) induced in the RF cavity is roughly parallel to the beam axis and decaying to zero radially at the walls. The EMF induces charge on the interior surfaces of the cavities such that the electrons moving through the cavity see a positive charge in front of them and accelerate towards that charge.

After the beam reaches the desired energy the three beams are separated at the switch yard and send to the A, B and C Halls with the separation between the bunches of 2.04 ns.

The CEBAF accelerator parameters

Quantity	Range

Notes

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Delta_D_over_D