Walter Scott, Jr. College of Engineering

Graduate Exam Abstract

Christopher Hall
Ph.D. Final
Feb 02, 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