Graduate Exam Abstract

Christopher Hall

Ph.D. Final
February 2, 2016, 3:00 pm - 5:00 pm
ERC A210
Study of Collective Beam Effects in the Jefferson Lab ERL FEL

Abstract: Collective beam effects such as coherent synchrotron radiation (CSR) and longitudinal space charge (LSC) can degrade the quality of high- energy electron beams used for free- electron lasers. The advent of energy recovery linac (ERL) based FELs brings exciting possibilities for very high average current FELs that can operate with greater efficiency. However, due to the structure of ERLs they may be even more susceptible to CSR. It is therefore necessary that these collective beam effects be well understood if future FEL designs are to be successful. The Jefferson Laboratory ERL driven IR FEL provides an ideal test-bed for looking how CSR impacts the electron beam. Due to its novel design we can easily test how CSR's impact on the beam varies as a function of compression within the machine. In this work we will look at measurements of both average energy loss and energy spectrum fragmentation as a function of bunch compression. These results are compared to 1D and 2D CSR models and, in general, good agreement is seen between simulation and measurement. Of particular interest is fragmentation of the energy spectrum that is observed due to CSR and LSC. We will also show how this fragmentation develops and how it can be mitigated through use of the sextupoles in the JLab FEL.

Adviser: Dr. Sandra Biedron
Co-Adviser: Dr. Stephen Milton
Non-ECE Member: Dr. William Fairbank
Member 3: Dr. Carmen Menoni
Addional Members: N/A

C.C. Hall, S.G. Biedron, H.P. Freund, S.V. Milton, “Start-to-end Simulation of Free-electron Lasers”,
Proceedings of IPAC 2015, Richmond, VA, USA

C.C. Hall, et al., “Measurement and simulation of the impact of coherent synchrotron radiation on the
Jefferson Laboratory energy recovery linac electron beam”, Phys. Rev. ST Accel. Beams 18, 030706

S. Biedron, et al., “Colorado State University (CSU) Accelerator and FEL Facility”, Proceedings of
IPAC 2014, Dresden, Germany

C.C. Hall, et al., “Study of CSR Effects in the Jefferson Laboratory FEL Driver”, Proceedings of FEL
2013, New York, NY, USA

Program of Study:
ECE 580A7
ECE 581A3
ECE 641
ECE 680A3
ECE 680A4
ECE 799
ENGR 697
GSTR 600