Amplification of Beam Acceleration in a Plasma by Plasma Instability Page: 1 of 13
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Amplification of Beam Acceleration in a
Plasma by Plasma Instability
V. A. Le ev
12000 Jefferson A Newport News, VA 23606, USA.
Abstract. Although achieving of high accelerating field in a plasma has been demonstrated
experimentally, a practical use of such a scheme for building a large accelerator is
questionable. A novel scheme of beam acceleration by a plasma wave is considered in this
article. The scheme is based on an initial excitation of a plasma wave by a probe beam with
comparatively modest intensity. This seed excitation is then amplified by plasma instability, so
that the test beam which follows the probe beam with a small delay will be accelerated by the
plasma wave with an amplitude significantly exceeding the initial amplitude of the wave.
Because of small interaction between the synchronization beam and the plasma, such a scheme
allows one to excite a plasma over large length and, consequently, to build a large accelerator.
Beam acceleration by plasma wave first suggested in reference (1) has created new
horizons in achieving high accelerating gradients in linear accelerators. In comparison
with a general linear accelerator based on an electromagnetic wave propagated in a
waveguide, it allows one to reach an order of magnitude higher accelerating gradient
of about 1 GeV/m. Achieving such high gradients has been recently demonstrated
experimentally by a few groups (2, 3), but many technical and scientific problems
have to be resolved before such an accelerator can be built.
Plasma acceleration has a serious advantage in comparison with classical
accelerators: it does not involve high electromagnetic fields on vacuum chamber walls
and therefore does not have a problem of high voltage breakup. In general, the plasma
accelerator is based on plasma excitation by an intense laser (1) or electron (4) pulse.
We will call this the probe bunch. Then, after a short delay, when the amplitude of the
plasma wave reaches the maximum, the accelerated bunch is injected. We will call that
the test bunch. While creating the initial plasma does not represent great difficulties,
both electron and plasma excitations have the common problem of creating a
sufficiently intense probe bunch. To resolve this problem one needs to reduce the
amount of energy pumped into the plasma, which requires a smaller electromagnetic
field volume and, consequently, smaller wavelength.
There is another basic reason pushing us to smaller wavelength. It is determined by
properties of the plasma oscillations. To make an estimate we consider the flat plasma
wave propagating with phase velocity equal to the light velocity, c, in a boundless
plasma. For simplicity we will use non-relativistic formulas. In this case from the
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Lebedev, Valeri. Amplification of Beam Acceleration in a Plasma by Plasma Instability, article, September 1, 1998; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc722442/m1/1/: accessed July 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.