arXiv subjects

D. F. J. Nijhof

Publications and source records attributed to D. F. J. Nijhof.

5 recordsLinked to original sources

arXiv2025

First x-rays from a compact and tunable LINAC-based Compton scattering source

In this paper, we present the first measurements of x-rays produced with a compact, narrowband, and tunable inverse Compton scattering-based x-ray source, developed at Eindhoven University of Technology. A flux of $1.2 \cdot 10^3$ photons per shot was measured, in agreement with simulations. Using a high-resolution spectral camera, we show that the photon energy can be tuned continuously from 5.8~keV to 10.7~keV with a bandwidth of 4\%. The measured x-ray pulse length was in the picosecond range. Additionally, we show that the source allows full control over the x-ray polarization control. By optimizing experimental parameters, implementing improvements to the setup and further conditioning of the accelerator structure, a brilliance of $10^{12}$ photons/(s $\times$ mrad$^2$ $\times$ mm${^{2}}$ $\times$ 0.1\% BW) can be achieved, with photon energies up to 40 keV. Because the complete electron beamline fits on a single optical table, it is suitable as an in-house x-ray source for university laboratories, industrial production lines, museums, and hospitals.

physics.acc-ph↗

arXiv2023

RF acceleration of ultracold electron bunches

The ultrafast and ultracold electron source, based on laser cooling and trapping of an atomic gas and its subsequent near-threshold photoionization, is capable of generating electron bunches with a high transverse brightness at energies of roughly 10 keV. This paper investigates the possibility of increasing the range of applications of this source by accelerating the bunch using radio-frequency electromagnetic fields. Bunch energies of $\sim35$ keV are measured by analyzing the diffraction patterns generated from a mono-crystalline gold sample. Further analysis points to a largely preserved normalized transverse emittance during acceleration.

physics.acc-ph↗

arXiv2023

Design and optimization of a 100 keV DC/RF ultracold electron source

An ultracold electron source based on near-threshold photoionization of a laser-cooled and trapped atomic gas is presented in this work. Initial DC acceleration to $\sim$10 keV and subsequent acceleration of the created bunches to 100 keV by RF fields makes the design suitable to serve as injector for accelerator-based light sources, single-shot ultrafast protein crystallography, applications in dielectric laser acceleration schemes, and potentially as an injector for free electron lasers operating in the quantum regime. This paper presents the design and properties of the developed DC/RF structure. It is shown that operation at a repetition frequency of 1 kHz is achievable and detailed particle tracking simulations are presented showing the possibility of achieving a brightness that can exceed conventional RF photosources.

physics.acc-ph↗

arXiv2019

From ultracold electrons to coherent soft X-rays

Electromagnetic radiation in the soft x-ray spectral range ($1-100~\rm{nm}$ wavelengths or $0.01-1~\rm{keV}$ photon energies) is rapidly gaining importance in both fundamental research and industrial applications. At present the degree of coherence and the average photon flux required by advanced applications is only available at large-scale synchrotron facilities and Free Electron Lasers (FELs), severely limiting the range of applications. We propose a fully coherent soft x-ray source, based on Inverse Compton Scattering (ICS) of electron bunches created by photoionization of a laser-cooled and trapped atomic gas. By combining spatial modulation of the photoionization process with radiofrequency bunch compression techniques, micro-bunching at soft x-ray wavelengths and thus coherent amplification can be realised, resulting in a soft x-ray table-top Compton light source.

physics.acc-ph↗

arXiv2017

Measurements of the energy distribution of an ultracold rubidium ion beam

The energy distribution of an ultracold rubidium ion beam, which is intended to be used as the source for a focused ion beam instrument, is measured with a retarding field analyzer. The ions are created from a laser-cooled and compressed atomic beam by two-step photoionization in which the ionization laser power is enhanced in a build-up cavity. Particle tracing simulations are performed to ensure the analyzer is able to resolve the distribution. The lowest achieved full width 50% energy spread is $\left(0.205\pm0.006\right)$ eV. The energy spread originates from the variation in the ionization position of the ions which are created inside an extraction electric field. This extraction field is essential to limit disorder-induced heating which can decrease the ion beam brightness. The ionization position distribution is limited by a tightly focused excitation laser beam. Energy distributions are measured for various ionization and excitation laser intensities and compared with calculations based on numerical solutions of the optical Bloch equations including ionization. A good agreement is found between measurements and calculations.

physics.atom-ph↗