H. Fuhrmann

On the characterisation of a Bragg spectrometer with X-rays from an ECR source

Narrow X-ray lines from helium-like argon emitted from a dedicated ECR source have been used to determine the response function of a Bragg crystal spectrometer equipped with large area spherically bent silicon (111) or quartz (10¯ crystals. The measured spectra are compared with simulated ones created by a ray-tracing code based on the expected theoretical crystal’s rocking curve and the geometry of the experimental set-up.

Experimental investigation of muon-induced fusion in liquid deuterium

Abstract The aim of this work was the accurate determination of the absolute values of the formation rates of muonic molecules from both hyperfine states of the muonic atoms in liquid deuterium (23.8 K) by measuring the absolute yield and time distribution of 2.45 MeV neutrons from dd fusion. The resulting dμd formation rates are λ 1 2 = [5.00 ± 0.34 (stat.) ± 0.22 (syst.)] × 10 4 s −1 and λ 1 2 = [3.25 ± 0.23 (stat.) ± 0.23 (syst.)]× 10 6 s −1 , respectively. In addition, the hyperfine transition rate between the upper and the lower hyperfine state was determined to be λhf = [3.05 ± 0.04(stat.) ± 0.06(syst.)]×107s−1. All results are normalized to the density of liquid hydrogen.

Hadronic shift in pionic hydrogen

The hadronic shift in pionic hydrogen has been redetermined to be ε1s = 7.086 ± 0.007(stat) ± 0.006(sys) eV by X-ray spectroscopy of ground-state transitions applying various energy calibration schemes. The experiment was performed at the high-intensity low-energy pion beam of the Paul Scherrer Institut by using the cyclotron trap and an ultimate-resolution Bragg spectrometer with bent crystals.

Highly charged ions in exotic atoms research at PSI

During their de-excitation, exotic atoms formed in low pressure gases reach a state of high or even complete ionization. X-rays emitted from higher n-states of electron-free atoms have well defined energies with the error originating only from the error in the mass values of the constituent particles. They served as a basis for a new determination of the pion mass as well as for a high precision measurement of the pionic hydrogen ground state shift. The response function of the Bragg spectrometer has been determined with X-rays from completely ionized pionic carbon and with a dedicated electron cyclotron resonance ion trap (ECRIT). A further extension of the ECRIT method implemented in the experiment allows a direct calibration of exotic atom transitions as well as a precise determination of the energy of fluorescence lines.

Precision measurements in pionic hydrogen

Abstract The strong interaction in the pion nucleon system leads to a shift and a broadening of the 1s-ground state in pionic hydrogen. These two quantities are being measured in an experiment at the Paul Scherrer Institute with much improved precision and allow an experimental test of recent calculations in the framework of Chiral Perturbation Theory. The experimental techniques using high resolution crystal spectroscopy are described as well as recent results.

Highly charged ion X-rays from Electron–Cyclotron Resonance Ion Sources

Abstract Radiation from the highly charged ions contained in the plasma of Electron–Cyclotron Resonance Ion Sources (ECRISs) constitutes a very bright source of X-rays. Because the ions have a relatively low kinetic energy ( ≈ 1 eV ) transitions can be very narrow, containing only a small Doppler broadening. We describe preliminary accurate measurements of two and three-electron ions with Z = 16 – 18 . We show how these measurement can test sensitively many-body relativistic calculations or can be used as X-ray standards for precise measurements of X-ray transitions in exotic atoms.

The pionic hydrogen experiment at PSI

The measurement of the strong-interaction effects in pionic hydrogen gives access to fundamental properties of the pion–nucleon interaction. Methods developed within the framework of Heavy-Baryon Chiral Perturbation Theory allow calculations with an accuracy of a few per cent, which should be tested by experiment.Techniques advanced for recent experiments on the precision spectroscopy of X-rays from antiprotonic and pionic atoms will be used in a new series of measurements for pionic hydrogen. The aim is to achieve finally an accuracy of 0.2% for the hadronic shift ∈1s and most important of about 1% for the broadening Γ1s.An essential part of the experimental program is an improved understanding of the atomic cascade. At first, the value of ∈1s has to be proven not to be influenced by molecular formation. Secondly, a more accurate determination of Γ1s requires a detailed study of Coulomb deexcitation.

High-precision x-ray spectroscopy in few-electron ions

The experimental and spectrum analysis procedures that led to about 15 new, high-precision, relative x-ray line energy measurements are presented. The measured lines may be used as x-ray reference lines in the 2.4?3.1?keV range. Applications also include tests of the atomic theory, and in particular of quantum electrodynamics and of relativistic many-body theory calculations. The lines originate from 2- to 4-electron ions of sulfur (Z=16), chlorine (Z=17) and argon (Z=18). The precision reached for their energy ranges from a few parts per million (ppm) to about 50?ppm. This places the new measurements among the most precise performed in mid-Z highly charged ions (Z is the nuclear charge number). The elements of the experimental setup are described: the ion source (an electron cyclotron resonance ion trap), the spectrometer (a single, spherically bent crystal spectrometer), as well as the spectrum acquisition camera (low-noise, high-efficiency CCD). The spectrum analysis procedure, which is based on a full simulation of the spectrometer response function, is also presented.

Precision measurement of the (3p–1s) X-ray transition in muonic hydrogen

The (3p — 1s) X-ray transition to the muonic hydrogen ground state was measured with a highresolution crystal spectrometer. The assumption of a statistical population of the hyperfine levels of the muonic hydrogen ground state was directly confirmed by the experiment and measured values for the hyperfine splitting can be reported. The measurement supplements studies on line broadening effects induced by Coulomb de-excitation hindering the direct extraction of the pion-nucleon scattering lengths from pionic hydrogen and deuterium X-ray lines.

Chapter 11 Experiments on Highly Charged Heavy Ions in Conjunction with Exotic Atoms

We demonstrate how combining highly-charged ions and exotic atoms measurements can provide high-accuracy information on particle properties, like the pion mass, on interactions, like the pion-proton strong interaction at low energy, and bound-state QED in strong fields. The use of highly-charged ion X-rays emitted by the plasma inside a super-conducting ion source provides a very detailed characterization of the response function of the X-ray spectrometer used to study exotic atoms, allowing for very accurate measurements. Conversely the use of the same high-resolution and high transmission spectrometer provides very accurate measurements of X-ray lines of few-electron ions.