Synchrotron-based high-pressure research in materials science Page: 94 of 204

                                
Laboratory Directed Research and Development Program Activities

Dong, X., and M. Borland, "An Optimization of a DC Injector
with Merger for the Energy Recovery Linac Upgrade to the
APS," Proceedings of the 2009 Particle Accelerator Conference,
Vancouver, May 4-8, 2009.
Sajaev, V., "Simulation of Linear Lattice Correction and Cou-
pling Correction of an Energy-Recovery Linac Designed for an
APS Upgrade," Proceedings of the 2009 Particle Accelerator
Conference, Vancouver, May 4-8, 2009.
Xiao, A., and M. Borland, "Intrabeam Scattering Effect Calcu-
lated for a Non-Gaussian Distributed Linac Beam," Proceed-
ings of the 2009 Particle Accelerator Conference, Vancouver,
May 4-8, 2009.
Development of the Emittance Exchange
Technique for Improved Accelerator
Facility Performance

FY 2009 Results and Accomplishment
Our first experiments have been carried out. The goal was to
determine if the Argonne Wakefield Accelerator (AWA) facil-
ity beamline could achieve the desired initial emittance, (E.,
Ej0) = (17, 3). The transverse emittance was measured with a
quadrupole scan while the longitudinal emittance was mea-
sured by a linac phase scan. The measured values were (19.5,
7.4) respectively, close to the expected values. A jitter analysis
study of our optimized exchange parameters (Figure 1), (E,
E) = (17, 3) - (6, 18), showed that in order to keep emittance
dilution under 20% we have to maintain the phase jitter of
the deflecting cavity within 1 degree. The stripline and associ-
ated radio frequency receiver board for the EEX diagnostics
are now nearly complete. Finally, based on the limited space
currently available, we developed a new plan that uses half of
the EEX beamline to directly measure the longitudinal phase
space; the associated simulations were also carried out.
1201

100

2008-141-R1

-- - - -

John G. Power, Wei Gai, and Kwang-Je Kim
Project Description
The objective of this research is to develop a novel accelera-
tor scheme for generating beams capable of meeting the most
demanding accelerator requirements for the next generation
of particle accelerators. The goal of this proof-of-principle
Emittance Exchange eXperiment (EEX) is to exchange the
initial (low) longitudinal emittance (Ez0) with an initial (high)
transverse horizontal emittance (E,) and also to incorporate
room for possible parametric studies (e.g., using an incoming
flat beam with tunable horizontal emittance).
Mission Relevance
The project relates to DOE's science mission. Next generation
accelerator applications will require charged particle beams
with an optimized phase space partition. For example, high-
gain free-electron lasers will potentially benefit from high
transverse quality at the expense of reduced longitudinal qual-
ity. Proper phase space partitioning of electrons may eliminate
the need for an electron damping ring for the International
Linear Collider. A megawatt-scale average-power free-electron
laser based on an energy-recovery linac would benefit from an
emittance exchange to significantly reduce the energy spread
before the beam dump.

80I ! 1
E   80-
J   60   I  p  p  p
40
20

3          4           5

7        8

Distance from cathode (m)
Figure 1. Evolution of horizontal (red) and longitudinal (green) trace space
emittances along the beamline are shown. The dashed black line and the
green and cyan rectangles, respectively, correspond to the locations of the
quadrupoles, dipoles, and the deflecting cavity. A clear exchange between the
transverse and longitudinal emittance is seen after the full exchanger.
Proposed Work for FY 2010
The half-EEX beamline (2 magnetic dipoles and 1 deflecting
cavity, as well as a table, 2 vacuum chambers, 3 quadrupoles,
and 3 YAG [yttrium aluminum garnet] screens) will be installed
and used to measure the longitudinal phase space, bunch
length, and half-EEX characterization. The calibration of these
measurements will be one of our most challenging tasks, and
we will verify the longitudinal charge distribution measure-
ment using another method. Finally, we will prepare for the
installation of the full EEX beamline when the AWA facility
tunnel expansion is completed.

70