# Beam Commissioning Results from the CBETA Fractional Arc Test

## TL;DR

This paper reports the initial commissioning results of the CBETA fractional arc test, including beamline calibration, energy gain demonstration, and magnet measurements, advancing the development of energy recovery linacs.

## Contribution

It presents the first commissioning results of the CBETA fractional arc, including beamline setup, magnet testing, and measurement techniques, with detailed comparison to simulations.

## Key findings

- Successful recommissioning of the Cornell photo-injector.
- First full energy operation of the main linac with beam.
- Development of procedures for BPM offset and tune measurements.

## Abstract

This work describes first commissioning results from the Cornell Brookhaven Energy Recovery Test Accelerator Fractional Arc Test. These include the recommissioning of the Cornell photo-injector, the first full energy operation of the main linac with beam, as well as commissioning of the lowest energy matching beamline (splitter) and a partial section of the Fixed Field Alternating gradient (FFA) return loop featuring first production Halbach style permanent magnets. Achieving these tasks required characterization of the injection beam, calibration and phasing of the main linac cavities, demonstration of the required 36 MeV energy gain, and measurement of the splitter line horizontal dispersion and R56 at the nominal 42 MeV. In addition, a procedure for determining the BPM offsets, as well as the tune per cell in the FFA section via scanning the linac energy and inducing betatron oscillations around the periodic orbit in the fractional arc was developed and tested. A detailed comparison of these measurements to simulation is discussed.