Current Research Projects
(You can also view our recent publications here)
The E-167 Experiment at the Stanford Linear Accelerator Center (SLAC)
The goal of this experiment is to study plasma wakefield acceleration in the
context of a high energy accelerator. The plasma wave or wakefield is driven
by a single ultra-short (10-40 µm long), ultra-relativistic (28.5 GeV)
electron bunch. In this single bunch scheme, the plasma density is adjusted
so that, while the core electrons lose energy in driving the plasma wake,
the trailing electrons gain energy. For the bunch lengths of interest, the
plasma density is in the 1-3.5x1017 cm-3 range. The accelerating gradient
expected with a bunch with ≈1.8x1010 e- is in the 30-40 GV/m range. A unique
feature of this experiment is that the plasma is created through
field-ionization of a lithium vapor by the large space-charge field of the
high peak current (>10 kA) electron bunch. The electron bunch therefore
creates its own plasma and accelerating structure. Recent results have shown
energy gains in the 4 GeV range over a plasma length of about 10 cm,
demonstrating the excitation and sustainability of gradients in the 40 GV/m
range over a long distance (M. J. Hogan et al., Phys. Rev. Lett. 95, 054802,
2005).
The AE31 Experiment at the Brookhaven National Laboratory (BNL), Accelerator
Test Facility (ATF)
The goal of this experiment is to study plasma wakefields driven by a train
a electron bunches rather that one or two bunches. In the multi-bunch plasma
wakefield accelerator (MB-PWFA) scheme, a train of N bunches resonantly
drives a plasma wave or wake to a large amplitude. The energy of a trailing
bunch separated from the last bunch by half the distance between consecutive
drive bunches can then be multiplied by N. In these experiments the number
of drive bunches in the 45 MeV, 0.2-0.4 pC beam is larger than 100. The
train of bunches is created by modulation of the energy of a picosecond-long
electron bunch in an inverse free electron laser (IFEL) driven by a powerful
carbon dioxide (CO2) laser pulse with a wavelength of 10.2 µm. After a drift
distance of ≈2.5 m the electrons are bunched longitudinally with a spacing
equal to the laser wavelength (10.2 µm) and each bunch is ≈1 µm long. The
corresponding resonant plasma density is ≈1x1019 cm-3. The plasma is created
in an ablative capillary discharge. The expected accelerating gradient is in
the 7 GV/m range, much larger than the gradient previously measured with the
non-modulated electron bunch (35 MV/m, V. Yakimenko et al., Phys. Rev. Lett.
91, 014802 2003).
Past Research Projects
Refraction of a Particle Beam at a Plasma-Gas Interface
Laser acceleration in hollow channels