Abstract
Longitudinal properties of electron bunches (energy spread and bunch length) and their manipulation are of importance in free electron lasers (FELs), where magnetic bunch length compression is a common feature of beam transport. Recirculating accelerators and energy recovery linac accelerators (ERLs) have been used as FEL drivers for several decades and control of longitudinal beam transport is particularly important in their magnet lattices. We report on measurements of longitudinal transport properties in an ERL-FEL, the ALICE (Accelerators and Lasers in Combined Experiments) accelerator at Daresbury Laboratory. ALICE is an energy recovery research accelerator that drives an infrared free electron laser. By measuring the time of arrival of electron bunches, the canonical longitudinal transport quantities were measured in the beam transport and bunch compression sections of the lattice. ALICE includes a four-dipole bunch compression chicane providing fixed longitudinal transport, and triple bend achromat arcs including sextupole magnets where the first and second order longitudinal transport can be adjusted. The longitudinal transport properties in these lattice sections were measured and compared with the theoretical model of the lattice. A reasonable level of agreement has been found. The effect of sextupoles in second order, as well as first order, longitudinal correction is considered, with the measurements indicating the level of alignment of the beam to the center of the sextupole.
Highlights
The ALICE facility is an energy recovery accelerator which drives an infrared free electron laser (IR-free electron lasers (FELs))
The beam is passed through the infrared free electron laser (IR-FEL) undulator and a nonisochronous decompressing arc to return the beam to the linac for energy recovery; the first arc is mechanically translatable to enable net path length variation
There are other comparable energy recovery linac accelerators (ERLs) machines of interest for which longitudinal dynamics are important. They include the ERL IR-FEL developed by the Japan Atomic Energy Agency (JAEA) [5] based on triple bend achromat (TBA) arcs
Summary
Longitudinal properties of electron bunches (energy spread and bunch length) and their manipulation are of importance in free electron lasers (FELs), where magnetic bunch length compression is a common feature of beam transport. Recirculating accelerators and energy recovery linac accelerators (ERLs) have been used as FEL drivers for several decades and control of longitudinal beam transport is important in their magnet lattices. We report on measurements of longitudinal transport properties in an ERL-FEL, the ALICE (Accelerators and Lasers in Combined Experiments) accelerator at Daresbury Laboratory. By measuring the time of arrival of electron bunches, the canonical longitudinal transport quantities were measured in the beam transport and bunch compression sections of the lattice. The effect of sextupoles in second order, as well as first order, longitudinal correction is considered, with the measurements indicating the level of alignment of the beam to the center of the sextupole
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