21 research outputs found
Numerical Studies of Electron Acceleration Behind Self-Modulating Proton Beam in Plasma with a Density Gradient
Presently available high-energy proton beams in circular accelerators carry
enough momentum to accelerate high-intensity electron and positron beams to the
TeV energy scale over several hundred meters of the plasma with a density of
about 1e15 1/cm^3. However, the plasma wavelength at this density is 100-1000
times shorter than the typical longitudinal size of the high-energy proton
beam. Therefore the self-modulation instability (SMI) of a long (~10 cm) proton
beam in the plasma should be used to create the train of micro-bunches which
would then drive the plasma wake resonantly. Changing the plasma density
profile offers a simple way to control the development of the SMI and the
acceleration of particles during this process. We present simulations of the
possible use of a plasma density gradient as a way to control the acceleration
of the electron beam during the development of the SMI of a 400 GeV proton beam
in a 10 m long plasma. This work is done in the context of the AWAKE project
--- the proof-of-principle experiment on proton driven plasma wakefield
acceleration at CERN.Comment: 4 pages, 5 figures
Long-term evolution of broken wakefields in finite radius plasmas
A novel effect of fast heating and charging a finite-radius plasma is
discovered in the context of plasma wakefield acceleration. As the plasma wave
breaks, the most of its energy is transferred to plasma electrons which create
strong charge-separation electric field and azimuthal magnetic field around the
plasma. The slowly varying field structure is preserved for hundreds of
wakefield periods and contains (together with hot electrons) up to 80% of the
initial wakefield energy.Comment: 5 pages, 6 figure
Self-modulation instability of a long proton bunch in plasmas
An analytical model for the self-modulation instability of a long
relativistic proton bunch propagating in uniform plasmas is developed. The
self-modulated proton bunch resonantly excites a large amplitude plasma wave
(wake field), which can be used for acceleration of plasma electrons.
Analytical expressions for the linear growth rate and the number of
exponentiations are given. We use the full three-dimensional particle-in-cell
(PIC) simulations to study the beam self-modulation and the transition to the
nonlinear stage. It is shown that the self-modulation of the proton bunch
competes with the hosing instability which tends to destroy the plasma wave. A
method is proposed and studied through PIC simulations to circumvent this
problem which relies on the seeding of the self-modulation instability in the
bunch
Proton Beam Defocusing as a Result of Self-Modulation in Plasma
The AWAKE experiment will use a \SI{400}{GeV/c} proton beam with a
longitudinal bunch length of to create and sustain
GV/m plasma wakefields over 10 meters . A 12 cm long bunch can only drive
strong wakefields in a plasma with after the self-modulation instability (SMI)
developed and microbunches formed, spaced at the plasma wavelength. The fields
present during SMI focus and defocus the protons in the transverse plane
\cite{SMI}. We show that by inserting two imaging screens downstream the
plasma, we can measure the maximum defocusing angle of the defocused protons
for plasma densities above .
Measuring maximum defocusing angles around 1 mrad indirectly proves that SMI
developed successfully and that GV/m plasma wakefields were created. In this
paper we present numerical studies on how and when the wakefields defocus
protons in plasma, the expected measurement results of the two screen
diagnostics and the physics we can deduce from it.Comment: 3 pages, 2 figures, Conference Proceedings of NAPAC 201
High quality electron beam generation in a proton-driven hollow plasma wakefield accelerator
Simulations of proton-driven plasma wakefield accelerators have demonstrated
substantially higher accelerating gradients compared to conventional
accelerators and the viability of accelerating electrons to the energy frontier
in a single plasma stage. However, due to the strong intrinsic transverse
fields varying both radially and in time, the witness beam quality is still far
from suitable for practical application in future colliders. Here we
demonstrate efficient acceleration of electrons in proton-driven wakefields in
a hollow plasma channel. In this regime, the witness bunch is positioned in the
region with a strong accelerating field, free from plasma electrons and ions.
We show that the electron beam carrying the charge of about 10% of 1 TeV proton
driver charge can be accelerated to 0.6 TeV with preserved normalized emittance
in a single channel of 700 m. This high quality and high charge beam may pave
the way for the development of future plasma-based energy frontier colliders.Comment: 10 pages, 7 figure
AWAKE: On the path to particle physics applications
Proton-driven plasma wakefield acceleration allows the transfer of energy
from a proton bunch to a trailing bunch of particles, the `witness' particles,
via plasma electrons. The AWAKE experiment at CERN is pursuing a demonstration
of this scheme using bunches of protons from the CERN SPS. Assuming continued
success of the AWAKE program, high energy electron or muon beams will become
available, opening up an extensive array of future particle physics projects
from beam dump searches for new weakly interacting particles such as Dark
Photons, to fixed target physics programs, to energy frontier electron-proton,
electron-ion, electron-positron and muon colliders.
The time is right for the particle physics community to offer strong support
to the pursuit of this new technology as it will open up new avenues for high
energy particle physics
Proton Driven Plasma Wakefield Acceleration
Plasma wakefield acceleration, either laser driven or electron-bunch driven,
has been demonstrated to hold great potential. However, it is not obvious how
to scale these approaches to bring particles up to the TeV regime. In this
paper, we discuss the possibility of proton-bunch driven plasma wakefield
acceleration, and show that high energy electron beams could potentially be
produced in a single accelerating stage.Comment: 13 pages, 4 figure