STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
STUDIES OF ENERGY RECOVERY LINACS AT ... - CASA
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implementation of energy recovery has been most active.<br />
The first demonstration of energy recovery occurred at Chalk River Nuclear<br />
Laboratories in 1977 using a two-pass reflexotron [6]. In a reflexotron the beam<br />
passes through an accelerating structure and is returned through the structure in<br />
the opposite direction by a 180 ◦ reflecting magnet. By changing the distance of the<br />
reflecting magnet from the accelerating structure, the phase of the beam relative<br />
to the accelerating field can be made to generate either energy doubling or energy<br />
deceleration and recovery. Using this method, output energies between 5 MeV (with<br />
energy recovery) and 25 MeV (with energy doubling) were achieved.<br />
In 1985 a 400 MeV electron beam was energy recovered to 23 MeV at the MIT-<br />
Bates Linac as part of an experiment to operate the recirculation system under a<br />
variety of conditions [7]. A unique three pass beam operation scenario was also<br />
demonstrated by producing a re-injection phase of 90 ◦ relative to the accelerating<br />
field with the recirculator. In this way, the second pass beam traveled through<br />
the linac without feeling any acceleration. A third pass beam was re-injected into<br />
the linac with a 180 ◦ phase difference relative to the accelerating field and energy<br />
recovered. Beam transmission was poor on the third pass however, due to the large<br />
energy spread acquired.<br />
In 1986, Stanford University’s Superconducting Accelerator (SCA) energy re-<br />
covered 150 µA of average beam current from 55 MeV to 5 MeV [8]. This experiment<br />
was significant in that it marked the first time energy recovery had been demon-<br />
strated in a superconducting RF environment.<br />
At about the same time, the free electron laser at Los Alamos National Labora-<br />
tory demonstrated energy recovery in a unique configuration where the decelerated<br />
beam deposited energy in a different cavity from which it was accelerated [9]. This<br />
scheme represents a departure from the previous examples of “same-cell” energy<br />
recovery. Using this setup, they successfully energy recovered 21 MeV to 5 MeV.<br />
11