B. Manil

A large area CCD X-ray detector for exotic atom spectroscopy

A large area, position and energy sensitive detector has been developed to study the characteristic X-radiation of exotic atoms in the few keV range. The detector, built up from an array of six high-resistivity CCDs, is used as the focal plane of a reflection-type crystal spectrometer. A large detection area is necessary because of the need to detect simultaneously two or more lines close in energy as well as broad structures like fluorescence X-rays from electronic atoms. The fine pixel structure provides accurate determination of the X-ray line position while the excellent background rejection capabilities of the CCD, using both energy and topographical discrimination, are essential in the high background environment of a particle accelerator.

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.

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.

FOCAL - precision x-ray spectroscopy for extreme fields in high-z ions

H.F. Beyer1, D. Banaś2, K.-H. Blumenhagen8, F. Bosch1, C. Brandau4, W. Chen1, Chr. Dimopoulou1, E. Forster3,8, T. Gasner1,8, A. Gumberidze4, S. Hagmann1,5, R. Hes1, P.-M. Hillenbrand1, P. Indelicato6, P. Jagodzinski2, T. Kampfer8, Chr. Kozhuharov1, M. Lestinsky1, D. Liesen1, Yu.A. Litvinov1, R. Loetzsch8, B. Manil7, R. Martin8, F. Nolden1, N. Petridis4,5, M.S. Sanjari1,4, K.S. Schulze8, M. Schwemlein1, A. Simionovici10, U. Spillmann1, M. Steck1, Th. Stohlker1,8, C.I. Szabo6, M. Trassinelli10, S. Trotsenko8, I. Uschmann3,8, G. Weber8, O. Wehrhan3,8, N. Winckler1, D. Winters1, N. Winters1, and E. Ziegler11 1GSI Helmholtzzentrum, Darmstadt, Germany; 2Institute of Physics, Swietokrzyska Academy, Kielce, Poland; 3Inst. fur Optik und Quantenelektronik, Friedrich-Schiller-Universitat, Jena, Germany; 4Extreme Matter Institute, EMMI, GSI Helmholtzzentrum, Darmstadt, Germany; 5Institut fur Kernphysik, Goethe-Universitat, Frankfurt am Main, Germany; 6Lab. Kastler Brossel, Universite P. et M. Curie, Paris, France; 7Laboratoire de Physique des Lasers (LPL) UMR 7538 CNRS Universite Paris 13, Villetaneuse, France; 8Helmholtz-Institut Jena, Jena, Germany; 9LGIT, Observatoire des Sciences de l’Univers de Grenoble, Grenoble, France; 10Institut des Nanosciences de Paris, Universite Pierre et Marie Curie-Paris 6 and CNRS-UMR 7588, Paris, France; 11ESRF, Grenoble, France Introduction and Motivation The extraordinarily strong electric field provided by the nucleus of a very heavy one-electron ion exposed to its inner electrons is the testing ground for bound-state quantum electrodynamics (QED) in a largely unexplored domain. Experimentally the QED contribution to the 1s binding energy is accessible via a direct measurement of the K-shell transitions with sufficient accuracy. The corresponding Lyman transitions in highZ ions lie in the hard x-ray region. Previously the x-ray energy has been measured with the aid of germanium xray detectors of limited resolution [1]. The present experiment marks the leap to wavelength-dispersive spectroscopy of substantially higher spectral resolving power simultaneously coping with the low x-ray intensity.

Lifetime Measurement of the Metastable 23 p 0 State in Helium-like 197au

The determination of atomic lifetimes offers the possibility to investigate various aspects of the atomic structure. In the case of helium-like 197Au with nuclear spin 3/2, due to hyperfine-quenching, one can determine the 23P0–23P1 fine-structure splitting from the lifetime measurement of the metastable 23P0 state. This lifetime has been measured at the GSI accelerator facility with the beam-foil time-of-flight technique and has taken advantage of particle-X-ray coincidences using a charge state spectrometer in conjuction with a newly developed CVD-diamond particle detector. A preliminary analysis has given a value of 22.45±0.66 ps for the lifetime of the 23P0 state in helium-like gold. This is in good agreement with theoretical predictions.

Spectroscopy of Ly-α Lines at Storage Rings by Crystal Spectrometry and Absorption Edge Technique

Crystal spectrometry and absorption edge technique have the capability to overcome the gap in accuracy between experiment and theory in the strong field domain of QED. New results are presented which indicate the capacity of these methods to measure the energies of X-rays emitted by highly charged heavy ions at modern storage rings with a precision sensitive to second order corrections to the Lambshift in H-like very heavy ions.

Precision Measurement of the Charged Pion Mass by High Resolution X-Ray Spectroscopy

A new experiment for a high-precision measurement of the pion mass at a 1 ppm level is presented. It combines an improved cyclotron trap that produces pionic and muonic atoms in a small volume with a doubly focusing crystal spectrometer to measure the corresponding exotic X-ray transitions with high accuracy and a novel type of CCD detector. The muonic X-rays lines serve as highly accurate calibration lines. The measurement has been accomplished recently. A detailed analysis of the data is on the way.