arXiv subjects

A. -S. Müller

Publications and source records attributed to A. -S. Müller.

6 recordsLinked to original sources

arXiv2025

An electro-optical bunch profile monitor for FCC-ee

The Future Circular Lepton Collider (FCC-ee) presents challenges for a longitudinal bunch profile monitor due to its wide range of bunch lengths and charge densities across its four distinct operational modes. For commissioning, monitoring the top-up injection, and energy calibration, the FCC-ee requires non-destructive, single-shot measurements of the bunch length and profile. This contribution proposes an in-vacuum electro-optical (EO) longitudinal bunch profile monitor for single-shot measurements at high repetition rates, building on the successful EO monitor at the Karlsruhe Research Accelerator (KARA) at the Karlsruhe Institute of Technology. A novel single-pass conceptual design for the in-vacuum holder of the electro-optical crystal is presented, utilizing prisms instead of a mirror to guide the laser through the crystal, which additionally allows measurements of the long bunches foreseen for FCC-ee operation mode at the Z-pole energy. A first prototype has been constructed and tested at the in-air test stand of the CERN Linear Electron Accelerator for Research (CLEAR). Results from the prototype tests are presented, demonstrating the proof of principle for the single-pass prism-based EO monitor design for FCC-ee.

physics.acc-ph↗

arXiv2024

KIT Superconducting Undulator Development -- Story of a successful industrial collaboration & future prospects

Undulators are X-ray sources widely used in synchrotron storage rings and free-electron laser facilities. With the commercial availability of low-temperature superconductors, a new type of undulator was born, the superconducting undulator (SCU). In this context, the industrial cooperation between the Karlsruhe Institute of Technology and Bilfinger Nuclear and Energy Transition GmbH started more than 15 years ago. Since then, many projects have been successfully completed, leading to the production of the world's leading full-scale commercial SCUs based on conduction cooling. Starting with the SCU15, the first of its kind installed SCU providing light to a beamline, followed by the SCU20 installed and still in operation at the Karlsruhe Research Accelerator. The successful realisation of such SCUs has required the simultaneous development of appropriate measurement facilities such as CASPER I and CASPER II.

physics.acc-ph↗

arXiv2021

Developing a 50 MeV LPA-based Injector at ATHENA for a Compact Storage Ring

The laser-driven generation of relativistic electron beams in plasma and their acceleration to high energies with GV/m-gradients has been successfully demonstrated. Now, it is time to focus on the application of laser-plasma accelerated (LPA) beams. The "Accelerator Technology HElmholtz iNfrAstructure" (ATHENA) of the Helmholtz Association fosters innovative particle accelerators and high-power laser technology. As part of the ATHENAe pillar several different applications driven by LPAs are to be developed, such as a compact FEL, medical imaging and the first realization of LPA-beam injection into a storage ring. The latter endeavour is conducted in close collaboration between Deutsches Elektronen-Synchrotron (DESY), Karlsruhe Institute of Technology (KIT) and Helmholtz Institute Jena (HIJ). In the cSTART project at KIT, a compact storage ring optimized for short bunches and suitable to accept LPA-based electron bunches is in preparation. In this conference contribution we will introduce the 50 MeV LPA-based injector and give an overview about the project goals. The key parameters of the plasma injector will be presented. Finally, the current status of the project will be summarized.

physics.acc-ph↗

arXiv2012

Highly responsive Y-Ba-Cu-O thin film THz detectors with picosecond time resolution

High-temperature superconducting YBa2Cu3O7-d (YBCO) thin-film detectors with improved responsivities were developed for fast time-domain measurements in the THz frequency range. YBCO thin films of 30 nm thickness were patterned to micro- and nanobridges and embedded into planar log-spiral THz antennas. The YBCO thin-film detectors were characterized with continuous wave radiation at 0.65 THz. Responsivity values as high as 710 V/W were found for the YBCO nanobridges. Pulsed measurements in the THz frequency range were performed at the electron storage ring ANKA from the Karlsruhe Institute of Technology (KIT). Due to the high responsivities of the nanobridges no biasing was required for the detection of the coherent synchrotron radiation pulses achieving very good agreement between the measured pulse shapes and simulations.

cond-mat.supr-con↗

arXiv2012

Non-thermal response of YBCO thin films to picosecond THz pulses

The photoresponse of YBa2Cu3O7-d thin film microbridges with thicknesses between 15 and 50 nm was studied in the optical and terahertz frequency range. The voltage transients in response to short radiation pulses were recorded in real time with a resolution of a few tens of picoseconds. The bridges were excited by either femtosecond pulses at a wavelength of 0.8 μm or broadband (0.1 - 1.5 THz) picosecond pulses of coherent synchrotron radiation. The transients in response to optical radiation are qualitatively well explained in the framework of the two-temperature model with a fast component in the picosecond range and a bolometric nanosecond component whose decay time depends on the film thickness. The transients in the THz regime showed no bolometric component and had amplitudes up to three orders of magnitude larger than the two-temperature model predicts. Additionally THz-field dependent transients in the absence of DC bias were observed. We attribute the response in the THz regime to a rearrangement of vortices caused by high-frequency currents.

cond-mat.supr-con↗

arXiv2011

Spectrum and Charge Ratio of Vertical Cosmic Ray Muons up to Momenta of 2.5 TeV/c

The ALEPH detector at LEP has been used to measure the momentum spectrum and charge ratio of vertical cosmic ray muons underground. The sea-level cosmic ray muon spectrum for momenta up to 2.5 TeV/c has been obtained by correcting for the overburden of 320 meter water equivalent (mwe). The results are compared with Monte Carlo models for air shower development in the atmosphere. From the analysis of the spectrum the total flux and the spectral index of the cosmic ray primaries is inferred. The charge ratio suggests a dominantly light composition of cosmic ray primaries with energies up to 10^15 eV.

hep-ex↗