Search results for " Resolution"
showing 10 items of 1159 documents
SpecTrap: precision spectroscopy of highly charged ions—status and prospects
2013
We present the status of the SpecTrap experiment currently being commissioned in the framework of the HITRAP project at GSI, Darmstadt, Germany. SpecTrap is a cryogenic Penning trap experiment dedicated to high-accuracy laser spectroscopy of highly charged ions (HCI) near rest. Determination of fine structure and hyperfine structure splittings in HCI with an expected relative spectral resolution of 10−7 will offer the possibility to test quantum electrodynamics in strong fields with unprecedented accuracy. Recently, we have demonstrated trapping and laser Doppler cooling of singly charged magnesium ions in SpecTrap. We report on the status of the experimental apparatus, measurements and pre…
Photometric and Hα Observations of LSI+61°303
1994
The Be massive X-ray binary LSI+61°303 is a 26.5 days periodic radiosource (Taylor & Gregory, 1984), exhibiting radio outbursts maxima between phases 0.6-0.8. Evidence of a photometric period of similar value has also been reported (Paredes & Figueras, 1986; Mendelson & Mazeh, 1989). The previous spectroscopic radial velocity observations of Hutchings & Crampton (1981) are in agreement with the radio period, and give support to the presence of a companion. We present new optical and infrared photometric observations and high resolution Hα spectra of LSI+61°303.
High resolution study of the and “hot” bands and ro-vibrational re-analysis of the polyad of the 32SO2 molecule
2011
Abstract The weak “hot” absorption bands, ν 1 + 2 ν 2 − ν 2 and 2 ν 2 + ν 3 − ν 2 , were analysed with high resolution using the Fourier transform interferometer Bruker IFS-120 HR. In order to make possible an analysis of the ν 1 + 2 ν 2 − ν 2 and 2 ν 2 + ν 3 − ν 2 bands, as the first step, we re-analysed considerably the stronger “cold” bands, ν 1 + ν 2 and ν 2 + ν 3 , which are located in the same spectral regions. As the result of analysis we obtained about 2650 and 2050 transitions (1069 and 1001 upper state ro-vibrational energy values) with Jmax. = 78, Kamax. = 27 and Jmax. = 68, Kamax. = 24 for the bands ν 1 + ν 2 and ν 2 + ν 3 , respectively, that is considerably higher than in the …
Monte Carlo evaluation of a CZT 3D spectrometer suitable for a Hard X- and soft-γ rays polarimetry balloon borne experiment
2015
Today, the measurement of the polarization status of cosmic sources high-energy' emission, is recognized as a key observational parameter to understand the active production mechanism and its geometry. Therefore, a mandatory requirement for new instrumentations operating in this energ.-y range will be to provide high sensitivity for polarimetric measurements. In this framework, we have presented the concept of a small high-performance imaging spectrometer optimized for polarimetry between 100 and 600 keV suitable for a stratospheric balloon-borne payload and as a pathfinder for a future satellite mission. The detector with 3D spatial resolution is based on a CZT spectrometer in a highly seg…
Discriminating short-range from van der Waals forces using total force data in noncontact atomic force microscopy
2014
Noncontact atomic force microscopy (NC-AFM) features the measurement of forces with highest spatial resolution and sensitivity, resolving forces of the order of pico-Newtons with submolecular resolution. However, the measured total force is a mixture composed of various interactions. While some interactions such as electrostatic or magnetic forces can be excluded by a careful design of the experiment, the subtraction of van der Waals forces, which mainly originate from London dispersion interactions between the macroscopic tip shank and the bulk sample, remains a challenge. We present the determination of the inherently present van der Waals forces in total interaction force data from fitti…
Modeling the energy thermalization of X-ray photons in a microcalorimeter with superconducting absorber
2003
We present a modeling of the response of a microcalorimeter to the absorption of X-ray photons, based on the main microscopical processes responsible for the energy thermalization. In particular, we have modeled a microcalorimeter with superconducting tin absorber (350 micron x 350 micron x 7 micron) and neutron transmutation doped (NTD) germanium thermistor (75 micron x 50 micron x 150 micron). Such a detector, operated at 60 mK, is expected to achieve a spectral resolution as good as 1 eV FWHM in the soft X-ray energy range, based on the known sources of thermal and electronic noise. Nevertheless, the best spectral resolution measured in laboratory experimental tests is of about 5 eV FWHM…
Development of a High Precision Axial 3-D PET for Brain Imaging
2009
We describe a PET device based on a novel method to extract the coordinates of the interaction point of the 511keV γ rays from 100 mm long and thin LYSO (Lutetium Yttrium OxyorthoSilicate) scintillator bars, positioned axially in the tomograph. The coordinate along the hit crystal is measured by using a hodoscope of Wave Length Shifting (WLS) plastic strips mounted perpendicularly to each plane of scintillators. As photodetectors, new Geiger mode Avalanche PhotoDetectors (G-APDs) with integrated electronics are being used to detect both the hit crystal in a block (x and y coordinates) and the interaction point in the crystal (z coordinate) through the light escaping from the crystal and tra…
Next generation of the Albira small animal PET based on high density SiPM arrays
2015
A new design of the small animal PET Albira system which detectors are based on arrays of SiPMs and monolithic LYSO scintillator is presented here. The system is made out of 3 rings of 8 detectors each, resulting on an axial and transaxial FOVs of 148 and 80 mm, respectively. The scanner is thermally stabilized using air-cooling. Working temperatures around 22–25°C are reached with individual detector variations around 0.2°C minimizing dark count rates and gain drifts. One of the most significant improvements of the current system is the accurate photon impact determination within the crystal volume, specially its depth of interaction. This allows the calculation of the true line of respons…
The AX-PET Concept: New Developments And Tomographic Imaging
2011
The Axial PET (AX-PET) concept proposes a novel detection geometry for PET, based on layers of long scintillating crystals axially aligned with the bore axis. Arrays of wavelength shifting (WLS) strips are placed orthogonally and underneath the crystal layers; both crystals and strips are individually readout by G-APDs. The axial coordinate is obtained from the WLS signals by means of a Center-of-Gravity method combined with a cluster algorithm. This design allows spatial resolution and sensitivity to be decoupled and thus simultaneously optimized. In this work we present the latest results obtained with the 2-module AX-PET scanner prototype, which consists of 6 radial layers of 8 LYSO crys…
Performance evaluation of a very high resolution small animal PET imager using silicon scatter detectors
2007
A very high resolution positron emission tomography (PET) scanner for small animal imaging based on the idea of inserting a ring of high-granularity solid-state detectors into a conventional PET scanner is under investigation. A particularly interesting configuration of this concept, which takes the form of a degenerate Compton camera, is shown capable of providing sub-millimeter resolution with good sensitivity. We present a Compton PET system and estimate its performance using a proof-of-concept prototype. A prototype single-slice imaging instrument was constructed with two silicon detectors 1 mm thick, each having 512 1.4 mm x 1.4 mm pads arranged in a 32 x 16 array. The silicon detector…