38 research outputs found
I-BEAT: New ultrasonic method for single bunch measurement of ion energy distribution
The shape of a wave carries all information about the spatial and temporal
structure of its source, given that the medium and its properties are known.
Most modern imaging methods seek to utilize this nature of waves originating
from Huygens' principle. We discuss the retrieval of the complete kinetic
energy distribution from the acoustic trace that is recorded when a short ion
bunch deposits its energy in water. This novel method, which we refer to as
Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a generalization of the
ionoacoustic approach. Featuring compactness, simple operation,
indestructibility and high dynamic ranges in energy and intensity, I-BEAT is a
promising approach to meet the needs of petawatt-class laser-based ion
accelerators. With its capability of completely monitoring a single, focused
proton bunch with prompt readout it, is expected to have particular impact for
experiments and applications using ultrashort ion bunches in high flux regimes.
We demonstrate its functionality using it with two laser-driven ion sources for
quantitative determination of the kinetic energy distribution of single,
focused proton bunches.Comment: Paper: 17 Pages, 3 figures Supplementary Material 16 pages, 7 figure
The proton radius puzzle
High-precision measurements of the proton radius from laser spectroscopy of
muonic hydrogen demonstrated up to six standard deviations smaller values than
obtained from electron-proton scattering and hydrogen spectroscopy. The status
of this discrepancy, which is known as the proton radius puzzle will be
discussed in this paper, complemented with the new insights obtained from
spectroscopy of muonic deuterium.Comment: Moriond 2017 conference, 8 pages, 4 figure
Improved X-ray detection and particle identification with avalanche photodiodes
Avalanche photodiodes are commonly used as detectors for low energy x-rays.
In this work we report on a fitting technique used to account for different
detector responses resulting from photo absorption in the various APD layers.
The use of this technique results in an improvement of the energy resolution at
8.2 keV by up to a factor of 2, and corrects the timing information by up to 25
ns to account for space dependent electron drift time. In addition, this
waveform analysis is used for particle identification, e.g. to distinguish
between x-rays and MeV electrons in our experiment.Comment: 6 pages, 6 figure
Colossal dielectric constants in transition-metal oxides
Many transition-metal oxides show very large ("colossal") magnitudes of the
dielectric constant and thus have immense potential for applications in modern
microelectronics and for the development of new capacitance-based
energy-storage devices. In the present work, we thoroughly discuss the
mechanisms that can lead to colossal values of the dielectric constant,
especially emphasising effects generated by external and internal interfaces,
including electronic phase separation. In addition, we provide a detailed
overview and discussion of the dielectric properties of CaCu3Ti4O12 and related
systems, which is today's most investigated material with colossal dielectric
constant. Also a variety of further transition-metal oxides with large
dielectric constants are treated in detail, among them the system La2-xSrxNiO4
where electronic phase separation may play a role in the generation of a
colossal dielectric constant.Comment: 31 pages, 18 figures, submitted to Eur. Phys. J. for publication in
the Special Topics volume "Cooperative Phenomena in Solids: Metal-Insulator
Transitions and Ordering of Microscopic Degrees of Freedom
I-BEAT: Ultrasonic method for online measurement of the energy distribution of a single ion bunch
The shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens' principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. This novel method, which we refer to as Ion-Bunch Energy Acoustic Tracing (I-BEAT), is a refinement of the ionoacoustic approach. With its capability of completely monitoring a single, focused proton bunch with prompt readout and high repetition rate, I-BEAT is a promising approach to meet future requirements of experiments and applications in the field of laser-based ion acceleration. We demonstrate its functionality at two laser-driven ion sources for quantitative online determination of the kinetic energy distribution in the focus of single proton bunches
Progress in hybrid plasma wakefield acceleration
Plasma wakefield accelerators can be driven either by intense laser pulses (LWFA) or by intense particle beams (PWFA). A third approach that combines the complementary advantages of both types of plasma wakefield accelerator has been established with increasing success over the last decade and is called hybrid LWFAâPWFA. Essentially, a compact LWFA is exploited to produce an energetic, high-current electron beam as a driver for a subsequent PWFA stage, which, in turn, is exploited for phase-constant, inherently laser-synchronized, quasi-static acceleration over extended acceleration lengths. The sum is greater than its parts: the approach not only provides a compact, cost-effective alternative to linac-driven PWFA for exploitation of PWFA and its advantages for acceleration and high-brightness beam generation, but extends the parameter range accessible for PWFA and, through the added benefit of co-location of inherently synchronized laser pulses, enables high-precision pump/probing, injection, seeding and unique experimental constellations, e.g., for beam coordination and collision experiments. We report on the accelerating progress of the approach achieved in a series of collaborative experiments and discuss future prospects and potential impact
Physics of High-Charge Electron Beams in Laser-Plasma Wakefields
Laser wakefield acceleration (LWFA) and its particle-driven counterpart, particle or plasma wakefield acceleration (PWFA), are commonly treated as separate, though related, branches of high-gradient plasma-based acceleration. However, novel proposed schemes are increasingly residing at the interface of both concepts where the understanding of their interplay becomes crucial. Here, we present a comprehensive study of this regime, which we may term laser-plasma wakefields. Using datasets of hundreds of shots, we demonstrate the influence of beam loading on the spectral shape of electron bunches. Similar results are obtained using both 100-TW-class and few-cycle lasers, highlighting the scale invariance of the involved physical processes. Furthermore, we probe the interplay of dual electron bunches in the same or in two subsequent plasma periods under the influence of beam loading. We show that, with decreasing laser intensity, beam loading transitions to a beam-dominated regime, where the first bunch acts as the main driver of the wakefield. This transition is evidenced experimentally by a varying acceleration of a low-energy witness beam with respect to the charge of a high-energy drive beam in a spatially separate gas target. Our results also present an important step in the development of LWFA using controlled injection in a shock front. The electron beams in this study reach record performance in terms of laser-to-beam energy transfer efficiency (up to 10%), spectral charge density (regularly exceeding 10ââpCâMeVâ1), and angular charge density (beyond 300ââpCâÎŒsrâ1 at 220 MeV). We provide an experimental scaling for the accelerated charge per terawatt (TW) of laser power, which approaches 2 nC at 300 TW. With the expanding availability of petawatt-class (PW) lasers, these beam parameters will become widely accessible. Thus, the physics of laser-plasma wakefields is expected to become increasingly relevant, as it provides new paths toward low-emittance beam generation for future plasma-based colliders or light sources