X-ray spectra following radiative recombination of free electrons with bare uranium ions (U92+) were measured at the electron cooler of the ESR storage ring. The most intense lines observed in the ...spectra can be attributed to the characteristic Lyman ground-state transitions and to the recombination of free electrons into the K shell of the ions. Our experiment was carried out by utilizing the deceleration technique which leads to a considerable reduction of the uncertainties associated with Doppler corrections. This, in combination with the 0 degree observation geometry, allowed us to determine the ground-state Lamb shift in hydrogenlike uranium (U91+) from the observed x-ray lines with an accuracy of 1%. The present result is about 3 times more precise than the most accurate value available up to now and provides the most stringent test of bound-state quantum electrodynamics for one-electron systems in the strong-field regime.
Stochastic cooling experiments for CSRe at IMP Zhu, G.Y.; Wu, J.X.; Caspers, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2019, Letnik:
932
Journal Article
Recenzirano
A novel type of perforated travelling wave pick-up/kicker structure was developed for CSRe stochastic cooling which was originally proposed by F. Caspers at CERN. The simulated and measured results ...of shunt impedance of the slotted travelling wave pickup electrode are in reasonable agreement. In December 2015 stochastic cooling of heavy ions was successfully applied for the first time at the CSRe storage ring of IMP in Lanzhou, China. During four days of commissioning, transverse and longitudinal cooling could be observed. Both the time-of-flight and the notch filter methods were used for longitudinal cooling. The measured cooling rates are presented.
A fast and sensitive resonant Schottky pick-up for heavy ion storage rings Nolden, F.; Hülsmann, P.; Litvinov, Yu.A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2011, Letnik:
659, Številka:
1
Journal Article
Recenzirano
A resonant pick-up for the detection of heavy ion Schottky noise was built into the ESR storage ring at GSI. A similar device will be installed at the cooler storage ring CSRe at IMP. Its purpose is ...a significant enhancement of the signal to noise ratio of Schottky spectra. A particular application of the new system is the measurement of circulating single ions. The resonator is based on a pillbox design. It is operated at air pressure, and is electromagnetically coupled to the vacuum tube of the storage ring via a cylinder-shaped ceramic gap. The resonant frequency can be changed by inserting plunger pistons. The resonator can easily be decoupled from the storage ring, if high beam impedances become a problem. The article describes the construction, electromagnetic properties of the pick-up as well as first experiments with heavy ion beams.
For radiative electron capture into the K shell of bare uranium ions, a study of the polarization properties has been performed. For this purpose a position sensitive germanium detector has been used ...as an efficient Compton polarimeter. This enabled us to measure the degree of linear polarization by analyzing Compton scattering inside the detector and to determine the orientation of the polarization plane. Depending on the observation angle and the beam energy used, the radiation is found to be linearly polarized by up to 80%. In all cases studied, the plane of polarization coincides with the collision plane. The results will be discussed in the context of rigorous relativistic calculations, showing that relativistic effects tend to lead to a depolarization of the radiation emitted.
Laser cooling is a powerful technique to reduce the longitudinal momentum spread of stored relativistic ion beams. Based on successful experiments at the experimental storage ring at GSI in ...Darmstadt, of which we show some important results in this paper, we present our plans for laser cooling of relativistic ion beams in the future heavy-ion synchrotron SIS100 at the Facility for Antiproton and Ion Research in Darmstadt.
Accurate spectroscopy of highly-charged high-Z ions in a storage ring is demonstrated to be feasible by the use of specially adapted crystal optics. The method has been applied for the measurement of ...the 1s Lamb shift in hydrogen-like gold (Au+78) in a storage ring through spectroscopy of the Lyman x-rays. This measurement represents the first result obtained for a high-Z element using high-resolution wavelength-dispersive spectroscopy in the hard x-ray regime, paving the way for sensitivity to higher-order QED effects.
Electron cooling experiments at the ESR Steck, M.; Beller, P.; Beckert, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2004, Letnik:
532, Številka:
1-2
Journal Article
Recenzirano
The properties of electron cooled beams of highly charged ions have been studied at the ESR. New experiments using a beam scraper to determine the transverse beam size provide the beam parameters in ...the intrabeam scattering dominated intensity regime, but also at very low intensity when the ion beam enters into an ultra-cold state. Extremely low values of longitudinal and transverse beam temperature on the order of meV were achieved for less than 1000 stored ions. An experiment with bunched ultra-cold beam showed a limit of the line density which agrees with the one observed for coasting beams. Cooling of decelerated ions at a minimum energy of 3MeV/u has been demonstrated recently.
Performance of the resonant Schottky pickup at CSRe Wu, J.X.; Zang, Y.D.; Nolden, F. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
12/2013, Letnik:
317
Journal Article
Recenzirano
Odprti dostop
•The single particle sensitivity of the new resonant pickup installed on CSRe was successfully confirmed.•This device will be used for nuclear mass and lifetime measurement, as well as other ...uses.•For the R/Q measurement, the perturbation measurement and the beam measurement have good agreements.
For a bunched beam, the signals on pickups are coherent, providing a signal power proportional to the square of the number of particles. For a coasting beam the individual particle signals have a random phase; therefore, the overall signal is proportional to the particle number N. As a consequence, Schottky signals are often relatively weak and have to compete with many noise sources. For a small number of particles, the S/N is always a problem. To achieve a high signal-to-noise ratio and better temporal resolution, which could yield important physical information about fast processes, a resonant pickup was developed at GSI (Nolden et al., 2011 1), and a similar device is now installed in the CSRe 2 at IMP. This device will be used for nuclear mass and lifetime measurement, as well as other uses. The final goal of the pickup is to detect single particles. In Dec 2012, we performed an experiment with a 112Sn50+ beam with an energy of 253MeV/u, and the single particle sensitivity of the pickup was successfully confirmed. This paper presents hardware measurements of the pickup as well as beam measurements.
The utilization of the resonant atomic electron-ion collision process of dielectronic recombination (DR) as a tool to probe nuclear properties via isotope shifts and hyperfine effects is discussed. ...Based on DR, this resonance reaction spectroscopy at electron coolers of heavy-ion storage rings denotes a versatile approach to access nuclear parameters such as charge radius, spin, magnetic moment or lifetimes of long-lived excited nuclear states (isomers). The high sensitivity of DR allows for experiments with artificially synthesized rare isotopes and isomers. Recent experimental progress in the preparation of such exotic species at the ESR storage ring in Darmstadt is presented. The DR technique is exemplified for the case of 234Pa88+ (Z = 91).
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