Exploitation of the Timing Capabilities of Metallic Magnetic Calorimeters for a Coincidence Measurement Scheme

In this report, we compare two filter algorithms for extracting timing information using novel metallic magnetic calorimeter detectors, applied to the precision X-ray spectroscopy of highly charged ions in a storage ring. Accurate timing information is crucial when exploiting coincidence conditions for background suppression to obtain clean spectra. For X-rays emitted by charge-changing interactions between ions and a target, this is a well-established technique when relying on conventional semiconductor detectors that offer a good temporal resolution. However, until recently, such a coincidence scheme had never been realized with metallic magnetic calorimeters, which typically feature much longer signal rise times. In this report, we present optimized timing filter algorithms for this type of detector. Their application to experimental data recently obtained at the electron cooler of CRYRING@ESR at GSI, Darmstadt is discussed

Towards an Intrinsic Doppler Correction for X-ray Spectroscopy of Stored Ions at CRYRING@ESR

We report on a new experimental approach for the Doppler correction of X-rays emitted by heavy ions, using novel metallic magnetic calorimeter detectors which uniquely combine a high spectral resolution with a broad bandwidth acceptance. The measurement was carried out at the electron cooler of CRYRING@ESR at GSI, Darmstadt, Germany. The X-ray emission associated with the radiative recombination of cooler electrons and stored hydrogen-like uranium ions was investigated using two novel microcalorimeter detectors positioned under 0∘ and 180∘ with respect to the ion beam axis. This new experimental setup allowed the investigation of the region of the N, M → L transitions in helium-like uranium with a spectral resolution unmatched by previous studies using conventional semiconductor X-ray detectors. When assuming that the rest-frame energy of at least a few of the recorded transitions is well-known from theory or experiments, a precise measurement of the Doppler shifted line positions in the laboratory system can be used to determine the ion beam velocity using only spectral information. The spectral resolution achievable with microcalorimeter detectors should, for the first time, allow intrinsic Doppler correction to be performed for the precision X-ray spectroscopy of stored heavy ions. A comparison with data from a previous experiment at the ESR electron cooler, as well as the conventional method of conducting Doppler correction using electron cooler parameters, will be discussed

A scintillator‐based particle detector for CRYRING@ESR

With the unprecedented range of ion species and energies offered by the newly commissioned CRYRING facility, the availability of single ion detectors is of significant importance as part of standard instrumentation as well as for novel experiments. A detector system was constructed on the basis of the YAP:Ce crystal scintillator, which is at once radiation‐hard, fast, and affordable. Results of a characterization experiment confirmed the feasibility of the setup for incident ion rates on the order of MHz and found a critical fluence of some $10^{13} cm^{-2}$ upon which the crystal is rendered locally blind to further ion irradiation. The device was first used in CRYRING commissioning runs in August and November 2018. Future efforts will complete the integration of the detector into the GSI control and data acquisition system MBS

Angle-differential cross sections for Rayleigh scattering of highly linearly polarized hard x rays on Au atoms

We perform a study on Rayleigh scattering of highly linearly polarized hard x rays on a thin Au foil target. Inthe study the angular distribution of the scattered radiation is analyzed in a relativistic regime both within and outof the plane of polarization of the incident beam. Within this experiment we scatter a synchrotron beam with aphoton energy of 175 keV on a high-Z target foil, namely, gold. Our findings correlate well with state-of-the-artcalculations of the scattering process performed in the framework of quantum electrodynamics and may haveconsiderable impact on future experiments regarding a polarization-resolved analysis of Delbrück scattering.Furthermore, we show that the angular distribution of Rayleigh scattering can be used for a highly sensitivedetermination of the degree and orientation of the linear polarization of the incident hard-x-ray beam, if we relyon the theoretical framework

Angle-differential cross sections for Rayleigh scattering of highly linearly polarized hard x rays on Au atoms

We perform a study on Rayleigh scattering of highly linearly polarized hard x rays on a thin Au foil target. Inthe study the angular distribution of the scattered radiation is analyzed in a relativistic regime both within and outof the plane of polarization of the incident beam. Within this experiment we scatter a synchrotron beam with aphoton energy of 175 keV on a high-Z target foil, namely, gold. Our findings correlate well with state-of-the-artcalculations of the scattering process performed in the framework of quantum electrodynamics and may haveconsiderable impact on future experiments regarding a polarization-resolved analysis of Delbrück scattering.Furthermore, we show that the angular distribution of Rayleigh scattering can be used for a highly sensitivedetermination of the degree and orientation of the linear polarization of the incident hard-x-ray beam, if we relyon the theoretical framework

Comparison of two low-noise CEP stabilization methods for an environmentally stable Yb:fiber oscillator

We demonstrate a low-noise carrier-envelope-offset frequency stabilized all-PM Yb:fiber oscillator. Two different stabilization methods lead to sub 200 mrad integrated fo phase noise (10 Hz to 1 MHz), suitable for comb spectroscopy applications

Comparison of two low-noise CEO frequency stabilization methods for an all-PM Yb:fiber NALM oscillator

We present a comparison of two low-noise carrier-envelope offset (CEO) frequency stabilization methods studied using an ytterbium (Yb) fiber laser oscillator based on a nonlinear amplifying loop mirror. We first investigate the phase locking performance achieved with cross-gain modulation (XGM) via injection of an auxiliary low-power continuous-wave (CW) laser into the fiber gain medium. Amplification of the injected CW laser light cross-modulates the gain of the oscillator, resulting in an intra-cavity power modulation, thus providing control of the CEO frequency. The XGM method is then compared with the conventional pump-current modulation scheme. Both stabilization methods provide similar locking performances with sub-200-mrad of integrated residual carrier-envelope-phase (CEP) noise (10 Hz to 1 MHz), suitable for high-resolution comb spectroscopy applications

Exploitation of the Timing Capabilities of Metallic Magnetic Calorimeters for a Coincidence Measurement Scheme

In this report, we compare two filter algorithms for extracting timing information using novel metallic magnetic calorimeter detectors, applied to the precision X-ray spectroscopy of highly charged ions in a storage ring. Accurate timing information is crucial when exploiting coincidence conditions for background suppression to obtain clean spectra. For X-rays emitted by charge-changing interactions between ions and a target, this is a well-established technique when relying on conventional semiconductor detectors that offer a good temporal resolution. However, until recently, such a coincidence scheme had never been realized with metallic magnetic calorimeters, which typically feature much longer signal rise times. In this report, we present optimized timing filter algorithms for this type of detector. Their application to experimental data recently obtained at the electron cooler of CRYRING@ESR at GSI, Darmstadt is discussed