- D'Arcy, R;
- Wesch, S;
- Aschikhin, A;
- Bohlen, S;
- Behrens, C;
- Garland, MJ;
- Goldberg, L;
- Gonzalez, P;
- Knetsch, A;
- Libov, V;
- de la Ossa, A Martinez;
- Meisel, M;
- Mehrling, TJ;
- Niknejadi, P;
- Poder, K;
- Röckemann, J-H;
- Schaper, L;
- Schmidt, B;
- Schröder, S;
- Palmer, C;
- Schwinkendorf, J-P;
- Sheeran, B;
- Streeter, MJV;
- Tauscher, G;
- Wacker, V;
- Osterhoff, J
A tunable plasma-based energy dechirper has been developed at FLASHForward to remove the correlated energy spread of a 681 MeV electron bunch. Through the interaction of the bunch with wakefields excited in plasma the projected energy spread was reduced from a FWHM of 1.31% to 0.33% without reducing the stability of the incoming beam. The experimental results for variable plasma density are in good agreement with analytic predictions and three-dimensional simulations. The proof-of-principle dechirping strength of 1.8 GeV/mm/m significantly exceeds those demonstrated for competing state-of-the-art techniques and may be key to future plasma wakefield-based free-electron lasers and high energy physics facilities, where large intrinsic chirps need to be removed.