Search results for "Nuclear and High Energy Physic"
showing 10 items of 8253 documents
Polarization-Dependent Disappearance of a Resonance Signal -- Indication for Optical Pumping in a Storage Ring?
2021
We report on laser spectroscopic measurements on Li$^+$ ions in the experimental storage ring ESR at the GSI Helmholtz Centre for Heavy Ion Research. Driving the $2s\,^3\!{S}_1\;(F=\frac{3}{2}) \,\leftrightarrow\,2p\,^3\!P_2\;(F=\frac{5}{2}) \leftrightarrow 2s\,^3\!{S}_1\;(F=\frac{5}{2})$ $\Lambda$-transition in $^7$Li$^+$ with two superimposed laser beams it was found that the use of circularly polarized light leads to a disappearance of the resonance structure in the fluorescence signal. This can be explained by optical pumping into a dark state of polarized ions. We present a detailed theoretical analysis of this process that supports the interpretation of optical pumping and demonstrate…
Direct Measurement of Focusing Fields in Active Plasma Lenses
2018
Physical review accelerators and beams 21(12), 122801 (2018). doi:10.1103/PhysRevAccelBeams.21.122801
Simulations and measurements of beam loss patterns at the CERN Large Hadron Collider
2014
The CERN Large Hadron Collider (LHC) is designed to collide proton beams of unprecedented energy, in order to extend the frontiers of high-energy particle physics. During the first very successful running period in 2010-2013, the LHC was routinely storing protons at 3.5-4 TeV with a total beam energy of up to 146 MJ, and even higher stored energies are foreseen in the future. This puts extraordinary demands on the control of beam losses. An uncontrolled loss of even a tiny fraction of the beam could cause a superconducting magnet to undergo a transition into a normal-conducting state, or in the worst case cause material damage. Hence a multistage collimation system has been installed in ord…
International workshop on next generation gamma-ray source
2022
Journal of physics / G 49(1), 010502 (2022). doi:10.1088/1361-6471/ac2827
Highly efficient isotope separation and ion implantation of 163Ho for the ECHo project
2019
Abstract The effective electron neutrino mass measurement in the framework of the ECHo experiment requires radiochemically pure 163 Ho, which is ion implanted into detector absorbers. To meet the project specifications in efficiency and purity, the entire process chain of ionization, isotope separation , and implantation of 163Ho was optimized. A new two-step resonant laser ionization scheme was established at the 30 kV magnetic mass separator RISIKO. For ionization and separation, an average efficiency of 69 ( 5 ) stat(4)sys% was achieved using intra-cavity frequency doubled Ti:sapphire lasers. The implantation of undesired 166 m Ho, which is present in trace amounts in the initial 163Ho…
Characterization and Tuning of Ultra High Gradient Permanent Magnet Quadrupoles
2009
The application of quadrupole devices with high field gradients and small apertures requires precise control over higher order multipole field components. We present a new scheme for performance control and tuning, which allows the illumination of most of the quadrupole device aperture because of the reduction of higher order field components. Consequently, the size of the aperture can be minimized to match the beam size achieving field gradients of up to $500\text{ }\text{ }\mathrm{T}\text{ }{\mathrm{m}}^{\ensuremath{-}1}$ at good imaging quality. The characterization method based on a Hall probe measurement and a Fourier analysis was confirmed using the high quality electron beam at the M…
Developments towards in-gas-jet laser spectroscopy studies of actinium isotopes at LISOL
2015
To study exotic nuclides at the borders of stability with laser ionization and spectroscopy techniques, highest efficiencies in combination with a high spectral resolution are required. These usually opposing requirements are reconciled by applying the in-gas-laser ionization and spectroscopy (IGLIS) technique in the supersonic gas jet produced by a de Laval nozzle installed at the exit of the stopping gas cell. Carrying out laser ionization in the low-temperature and low density supersonic gas jet eliminates pressure broadening, which will significantly improve the spectral resolution. This article presents the required modifications at the Leuven Isotope Separator On-Line (LISOL) facility…
Quantification of Regional Intrapulmonary Oxygen Partial Pressure Evolution during Apnea by 3He MRI
1999
We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized (3)Helium ((3)He-->). Single-breath, single-bolus visualization of (3)He--> administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure p(O(2))(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of p(O(2)) with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional …
Final results of the searches for neutral Higgs bosons in e+e- collisions at sqrt(s) up to 209GeV
2002
The final results of the ALEPH search for the Standard Model Higgs boson at LEP, with data collected in the year 2000 at centre-of-mass energies up to 209 GeV, are presented. The changes with respect to the preceding publication are described and a complete study of systematic effects is reported. The findings of this final analysis confirm the preliminary results published in November 2000 shortly after the closing down of the LEP collider: a significant excess of events is observed, consistent with the production of a $115 \Gcs$ Standard Model Higgs boson. The final results of the searches for the neutral Higgs bosons of the MSSM are also reported, in terms of limits on $\mh$, $\mA$ and $…
Automatic calculation of massive two-loop self-energies with XLOOPS
1997
Abstract Within the program package XLOOPS it is possible to calculate self-energies up to the two-loop level for arbitrary massive particles. The program package — written in MAPLE (Char et al., Maple V Language Reference Manual (Springer, 1991); Char et al., Maple V Library Reference Manual (Springer, 1991)) — is designed to deal with the full tensor structure of the occurring integrals. This means that applications are not restricted to those cases where the reduction to scalars via equivalence theorem is allowed. The algorithms handle two-loop integrals analytically if this is possible. For those topologies where no analytic result for the general mass case is available, the diagrams ar…