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abstract:
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A gaussian underdense plasma lens with peak density 5 x 1012 cm−3 and a full
width half maximum (FWHM) length of 2.2 cm has been used to focus a relativistic
electron beam. This plasma lens is equivalent in strength to a quadrupole magnet
with a 150 T/m field gradient. The lens focused a 15 MeV, 16 nC electron beam
with initial dimensions σx,y
≈ 650 μm and σz ≈ 6.5 mm onto an optical transition
radiation (OTR) screen
∼2 cm downstream of the lens. The average transverse
area of the plasma focused electron beam was typically demagnified by a factor
of 23. The evolution of the beam envelope in the area near the beam waist was
measured for both round beams and asymmetric beams with x:y aspect ratios as
large as 1:5. The light from the OTR screen in the round beam case was also
imaged into a streak camera in order to directly measure the correlation between
z and σ within the beam.
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