328
J. Seeman et al.
in a spectral range of 90–240 microns. The ERL had recently (2015) been upgraded
to 42 MeV, based on four-pass energy recovery to drive a short wave FELs in a
spectral range of 8–15 microns [142].
7.8.2 S-DALINAC
The S-DALINAC energy-recovery linac is a superconducting electron accelerator
operated at Technical University Darmstadt since 1991. The ERL was recently
upgraded (2015–2016) and as of 2019 it is capable of operating as a one-pass, or
two-pass ERL with maximum energies of approximately 34 or 68 MeV, respectively
[143]. The ERL provides beam for Compton scattering of laser beams on intense
electron beams to generate quasi-monochromatic, energy-tunable, fully polarized
gamma-ray beams for photonuclear reactions [144]. The most recent upgrade [145]
started in 2017, and would enable an increase of the maximum achievable energy
close to its design value of 130 MeV. A newly-added beamline features a path-length
adjustment system capable of changing the phase of the beam by a full RF cycle.
7.8.3 MESA
MESA is a recirculating superconducting accelerator under construction at Johannes
Gutenberg-Universität Mainz. The facility [146] uses a superconducting accelerating system based on the TESLA operation frequency of 1.3 GHz. The 2-pass
recirculating linac has been configured to operate in two different modes: the
external beam (EB) mode, where a 150 μA polarized electron beam at 155 MeV
is dumped after being used at the experiment, and in energy-recovery mode (ERL)
with an unpolarized beam of 1 mA at 105 MeV [147]. At an upcoming later
construction stage, MESA’s maximum achievable beam current (in the ERL-mode)
will be upgraded to 10 mA (unpolarized).
7.8.4 Compact ERL
The compact ERL (cERL) at KEK is a test accelerator to develop ERL technologies
for high average beam current operation with high-quality beam performance [148].
The cERL consists of a photoinjector, a main linac for energy recovery, a recirculation loop, and a beam dump. To achieve energy-recovery operation with high
average beam current, collimator tuning to reduce unwanted beam loss has been
very important. After fine beam tuning and collimator tuning, stable CW operation
with 0.9 mA average beam current was achieved. Upgrade efforts are under way
to increase CW beam current to 10 mA through improved instrumentation. The
J. Seeman et al.
in a spectral range of 90–240 microns. The ERL had recently (2015) been upgraded
to 42 MeV, based on four-pass energy recovery to drive a short wave FELs in a
spectral range of 8–15 microns [142].
7.8.2 S-DALINAC
The S-DALINAC energy-recovery linac is a superconducting electron accelerator
operated at Technical University Darmstadt since 1991. The ERL was recently
upgraded (2015–2016) and as of 2019 it is capable of operating as a one-pass, or
two-pass ERL with maximum energies of approximately 34 or 68 MeV, respectively
[143]. The ERL provides beam for Compton scattering of laser beams on intense
electron beams to generate quasi-monochromatic, energy-tunable, fully polarized
gamma-ray beams for photonuclear reactions [144]. The most recent upgrade [145]
started in 2017, and would enable an increase of the maximum achievable energy
close to its design value of 130 MeV. A newly-added beamline features a path-length
adjustment system capable of changing the phase of the beam by a full RF cycle.
7.8.3 MESA
MESA is a recirculating superconducting accelerator under construction at Johannes
Gutenberg-Universität Mainz. The facility [146] uses a superconducting accelerating system based on the TESLA operation frequency of 1.3 GHz. The 2-pass
recirculating linac has been configured to operate in two different modes: the
external beam (EB) mode, where a 150 μA polarized electron beam at 155 MeV
is dumped after being used at the experiment, and in energy-recovery mode (ERL)
with an unpolarized beam of 1 mA at 105 MeV [147]. At an upcoming later
construction stage, MESA’s maximum achievable beam current (in the ERL-mode)
will be upgraded to 10 mA (unpolarized).
7.8.4 Compact ERL
The compact ERL (cERL) at KEK is a test accelerator to develop ERL technologies
for high average beam current operation with high-quality beam performance [148].
The cERL consists of a photoinjector, a main linac for energy recovery, a recirculation loop, and a beam dump. To achieve energy-recovery operation with high
average beam current, collimator tuning to reduce unwanted beam loss has been
very important. After fine beam tuning and collimator tuning, stable CW operation
with 0.9 mA average beam current was achieved. Upgrade efforts are under way
to increase CW beam current to 10 mA through improved instrumentation. The