74 research outputs found
Highly charged ion X-rays from Electron-Cyclotron Resonance Ion Sources
Radiation from the highly-charged ions contained in the plasma of
Electron-Cyclotron Resonance Ion Sources constitutes a very bright source of
X-rays. Because the ions have a relatively low kinetic energy ( eV)
transitions can be very narrow, containing only 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
High-pressure operation of a xenon-GPSC/MSGC hybrid detector for hard X-ray spectrometry
The performance of a high-pressure xenon gas proportional scintillation counter/microstrip gas chamber (GPSC/MSGC) hybrid detector has been investigated for filling pressures from 1 up to 10 bar, for 22-, 30- and 60-keV photons. GPSC/MSGC hybrid detectors are based on a xenon-GPSC instrumented with a CsI-coated microstrip plate photosensor placed directly within the xenon envelope, as a substitute for the photomultiplier tube. This design avoids the constraints due to the use of a quartz scintillation window for GPSC-photosensor coupling, which absorbs a significant amount of scintillation and is a drawback for applications where large detection areas and high filling pressures are needed. The lowest energy resolutions are achieved for 2 bar (5.5% and 3.4%, FWHM, for 22- and 60-keV photons, respectively). Increasing the pressure to the 5-6 bar range, competitive energy resolutions of 7% and 4.5% are still achieved for 22- and 60-keV photons, respectively. This detector could be a compelling alternative in applications where compactness, large detection area, insensitivity to strong magnetic fields, room temperature operation, large signal-to-noise ratio and good energy resolution are important requirements.http://www.sciencedirect.com/science/article/B6TJM-4M3B6DG-8/1/04ba8b77386c4c69025c7ca19342f79
Pionic Deuterium
The strong interaction shift and broadening in pionic deuterium have been
remeasured with high statistics by means of the (3p-1s) X-ray transition using
the cyclotron trap and a high-resolution crystal spectrometer. Preliminary
results are (-2325+/-31) meV (repulsive) for the shift and (1171+23/-49} meV
for the width, which yields precise values for the pion-deuteron scattering
length and the threshold parameter for pion production.Comment: Conf. Proc. Few Body 19 (FB19), August 31 - September 5, 2009, Bonn,
Germany 9 pages, 13 figure
Line shape of the muH(3p - 1s) hyperfine transitions
The (3p - 1s) X-ray transition to the muonic hydrogen ground state was
measured with a high resolution crystal spectrometer. A Doppler effect
broadening of the X-ray line was established which could be attributed to
different Coulomb de-excitation steps preceding the measured transition. 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 results allow a
decisive test of advanced cascade model calculations and establish a method to
extract fundamental strong-interaction parameters from pionic hydrogen
experiments.Comment: Submitted to Physical Review Letter
Precision determination of the dpi -> NN transition strength at threshold
An unusual but effective way to determine at threshold the dpi -> NN
transition strength is to exploit the hadronic ground-state broadening in
pionic deuterium, accessible by x-ray spectroscopy. The broadening is dominated
by the true absorption channel dpi- -> nn, which is related to s-wave pion
production pp -> dpi+ by charge symmetry and detailed balance. Using the exotic
atom circumvents the problem of Coulomb corrections to the cross section as
necessary in the production experiments. Our dedicated measurement finds
(1171+23/-49) meV for the broadening yielding (252+5/-11) \mub.Comment: 4 pages, 2 figures, 1 tabl
Line shape analysis of the K transition in muonic hydrogen
The K transition in muonic hydrogen was measured with a
high-resolution crystal spectrometer. The spectrum is shown to be sensitive to
the ground-state hyperfine splitting, the corresponding triplet-to-singlet
ratio, and the kinetic energy distribution in the state. The hyperfine
splitting and triplet-to-singlet ratio are found to be consistent with the
values expected from theoretical and experimental investigations and,
therefore, were fixed accordingly in order to reduce the uncertainties in the
further reconstruction of the kinetic energy distribution. The presence of
high-energetic components was established and quantified in both a
phenomenological, i.e. cascade-model-free fit, and in a direct deconvolution of
the Doppler broadening based on the Bayesian approach.Comment: 22 pages, 21 figure
THGEM-based detectors for sampling elements in DHCAL: laboratory and beam evaluation
We report on the results of an extensive R&D program aimed at the evaluation
of Thick-Gas Electron Multipliers (THGEM) as potential active elements for
Digital Hadron Calorimetry (DHCAL). Results are presented on efficiency, pad
multiplicity and discharge probability of a 10x10 cm2 prototype detector with 1
cm2 readout pads. The detector is comprised of single- or double-THGEM
multipliers coupled to the pad electrode either directly or via a resistive
anode. Investigations employing standard discrete electronics and the KPiX
readout system have been carried out both under laboratory conditions and with
muons and pions at the CERN RD51 test beam. For detectors having a
charge-induction gap, it has been shown that even a ~6 mm thick single-THGEM
detector reached detection efficiencies above 95%, with pad-hit multiplicity of
1.1-1.2 per event; discharge probabilities were of the order of 1e-6 - 1e-5
sparks/trigger, depending on the detector structure and gain. Preliminary beam
tests with a WELL hole-structure, closed by a resistive anode, yielded
discharge probabilities of <2e-6 for an efficiency of ~95%. Methods are
presented to reduce charge-spread and pad multiplicity with resistive anodes.
The new method showed good prospects for further evaluation of very thin
THGEM-based detectors as potential active elements for DHCAL, with competitive
performances, simplicity and robustness. Further developments are in course.Comment: 15 pages, 11 figures, MPGD2011 conference proceedin
The proton radius puzzle
High-precision measurements of the proton radius from laser spectroscopy of
muonic hydrogen demonstrated up to six standard deviations smaller values than
obtained from electron-proton scattering and hydrogen spectroscopy. The status
of this discrepancy, which is known as the proton radius puzzle will be
discussed in this paper, complemented with the new insights obtained from
spectroscopy of muonic deuterium.Comment: Moriond 2017 conference, 8 pages, 4 figure
Improved X-ray detection and particle identification with avalanche photodiodes
Avalanche photodiodes are commonly used as detectors for low energy x-rays.
In this work we report on a fitting technique used to account for different
detector responses resulting from photo absorption in the various APD layers.
The use of this technique results in an improvement of the energy resolution at
8.2 keV by up to a factor of 2, and corrects the timing information by up to 25
ns to account for space dependent electron drift time. In addition, this
waveform analysis is used for particle identification, e.g. to distinguish
between x-rays and MeV electrons in our experiment.Comment: 6 pages, 6 figure
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