First results of the plasma wakefield acceleration experiment at PITZ

Abstract

a b s t r a c tThe self-modulation instability of long particle beams was proposed as a new mechanism to produce driver beams for proton driven plasma wakefield acceleration (PWFA). The PWFA experiment at the Photo Injector Test facility at DESY, Zeuthen site (PITZ) was launched to experimentally demonstrate and study the selfmodulation of long electron beams in plasma. Key aspects for the experiment are the very flexible photocathode laser system, a plasma cell and well-developed beam diagnostics. In this contribution we report about the plasma cell design, preparatory experiments and the results of the first PWFA experiment at PITZ.

Emittance Preservation in an Aberration-Free Active Plasma Lens

“…The capillary was filled with 1-100 mbar of gas through internal gas inlets, connected to an external flow regulator and a buffer volume. The gas escaping into the surrounding chamber was pumped out by a large turbo pump, which together with a 3 µm polymer (Mylar) window [22] preserved the ultrahigh vacuum in the upstream accelerator line. Holed copper electrodes on the up-and downstream side of the capillary were connected to a compact Marx bank [23], providing short 20 kV discharge pulses with a tunable 410-450 A peak current after 80 ns and a duration of 145 ns full width at half maximum (FWHM) [see Fig.…”

Proton-Beam-Driven Plasma Acceleration

“…At the Photo Injector Test facility at DESY Zeuthen (PITZ), complementary experiments are underway to demonstrate self-modulation of an electron beam [49]. In 2015 a first set of experiments was conducted utilizing a novel cross-shaped lithium heat pipe oven and an ArF excimer laser for plasma generation.…”

Observation of the Self-Modulation Instability via Time-Resolved Measurements

“…The heat pipe oven technology, capable of generating plasma with a density of 10 14 -10 15 cm −3 for beam driven plasma acceleration experiments [24] was utilized. For our purposes we developed and built a heat pipe oven that couples a pulsed UV laser through side windows to ionize lithium vapor [25]. This design allows flexible generation of the plasma channel by generating arbitrary transverse laser intensity profiles.…”

“…The electron beam was strongly focused into the plasma to maximize the amplitude of the induced plasma wakefield, and hence, the self-modulation depth. A combination of a focusing solenoid, positioned at the electron gun and four quadrupole magnets in front of the plasma cell focused the beam to a transverse rms size of ∼100 μm [25] at the entrance of the plasma. The plasma cell was operated with a heater temperature of 700°C and an argon buffer gas pressure of 1.4 mbar.…”

“…The ionization laser delivered pulses with an energy of up to 150 mJ to the plasma cell. This photoionization method leads to incomplete ionization of the lithium vapor, so that the plasma density is about 1 order of magnitude lower than the vapor density [20,25]. The plasma densities given below were deduced from the measured plasma wavelength.…”