FWHM Resolution Research Articles

A scintillator-based detector with sub-100-μm spatial resolution comprising a fibre-optic taper with wavelength-shifting fibre readout for time-of-flight neutron imaging

A scintillator-based neutron-counting imaging detector with a sub-100-μm spatial resolution was developed for energy-selective neutron imaging. The detector head of the detector comprised a thin ZnS/6LiF scintillator screen, a fibre-optic taper and crossed wavelength-shifting (WLS) fibre arrays. A high spatial resolution was achieved by constructing the scintillator with a thickness of 100μm and placing it in contact with the fibre-optic taper at a magnification ratio of 3.1:1. WLS fibres with a diameter of 100±5μm (mean±SD) were specially made, and their dye content was optimized for use in crossed WLS-fibre arrays. The developed detector had a pixel size of 34μm×34μm, and exhibited spatial FWHM resolutions of 80±7μm and 61±6μm in the x and y directions, respectively. A small prototype detector demonstrated the capability of neutron imaging using Bragg edges of a Cu/Fe sample when using the pulsed-neutron source in the Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex.

3D super-resolution imaging with blinking quantum dots.

Quantum dots are promising candidates for single molecule imaging due to their exceptional photophysical properties, including their intense brightness and resistance to photobleaching. They are also notorious for their blinking. Here we report a novel way to take advantage of quantum dot blinking to develop an imaging technique in three-dimensions with nanometric resolution. We first applied this method to simulated images of quantum dots and then to quantum dots immobilized on microspheres. We achieved imaging resolutions (fwhm) of 8-17 nm in the x-y plane and 58 nm (on coverslip) or 81 nm (deep in solution) in the z-direction, approximately 3-7 times better than what has been achieved previously with quantum dots. This approach was applied to resolve the 3D distribution of epidermal growth factor receptor (EGFR) molecules at, and inside of, the plasma membrane of resting basal breast cancer cells.

Eight-Channel TES Microcalorimeter System for Detector and Source Development

Nuclear forensics and environmental monitoring require rapid isotopic analysis of trace samples that contain multiple radioisotopes with closely spaced alpha particle energies. Conventional measurement of such a sample typically requires expensive and time-consuming radiochemical separations, measurement of multiple subsamples by silicon alpha spectrometry, and destructive analysis by mass spectrometry. The superior energy resolution of microcalorimeter detectors allows isotopic analysis with a single nonconsumptive alpha spectrometry measurement. In order to bring microcalorimeter alpha detector technology towards the goal of a practical analytical instrument, we have developed an eight-channel transition-edge sensor microcalorimeter system to enable rapid detector and source development. This system is now fully functional, and has enabled the identification of instabilities in our alpha detector response that resulted in degraded performance. A redesigned set of detectors has been fabricated and tested, and has shown significantly improved response. With the improved detectors, we have been able to consistently achieve energy resolution of less than 1 keV full width at half maximum at 5.3 MeV. We have prepared electroplated sources that contain 239-Pu and 240-Pu, demonstrated the ability to resolve their ~ 5.1 MeV alpha energy peaks with 0.74 keV FWHM resolution, and shown that the 240/239-Pu isotopic ratios obtained from our microcalorimeter spectra are in statistical agreement with mass spectrometry results.

Near-intrinsic energy resolution for 30–662 keV gamma rays in a high pressure xenon electroluminescent TPC

We present the design, data and results from the NEXT prototype for Double Beta and Dark Matter (NEXT-DBDM) detector, a high-pressure gaseous natural xenon electroluminescent time projection chamber (TPC) that was built at the Lawrence Berkeley National Laboratory. It is a prototype of the planned NEXT-100 136Xe neutrino-less double beta decay (0νββ) experiment with the main objectives of demonstrating near-intrinsic energy resolution at energies up to 662keV and of optimizing the NEXT-100 detector design and operating parameters. Energy resolutions of ∼1% FWHM for 662keV gamma rays were obtained at 10 and 15atm and ∼5% FWHM for 30keV fluorescence xenon X-rays. These results demonstrate that 0.5% FWHM resolutions for the 2459keV hypothetical neutrino-less double beta decay peak are realizable. This energy resolution is a factor 7–20 better than that of the current leading 0νββ experiments using liquid xenon and thus represents a significant advancement. We present also first results from a track imaging system consisting of 64 silicon photo-multipliers recently installed in NEXT–DBDM that, along with the excellent energy resolution, demonstrates the key functionalities required for the NEXT-100 0νββ search.

Development of Si-PM Based Imaging Systems for Molecular Imaging

Silicon photomultiplier (Si-PM) is a promising photodetector for PET for the use in magnetic resonance imaging (MRI) systems because it is insensitive to static magnetic fields. Si-PM is also a promising for high resolution PET systems due to its small channels and high gain.  We have developed several Si-PM based imaging systems for molecular imaging. First, we developed a high resolution Si-PM based PET system for small animals and tested its performance. The Si-PM PET system had 1.6mm FWHM resolution. Then we combined it into the MRI and simultaneous measurements were conducted. Although there were some interference between PET and MRI, images could be obtained with reasonable signal-to-noise ratio (S/N) on both modalities without any distortion. Finally we explored to improve the spatial resolution of the Si-PM PET system by reducing the scintillator size to be around 0.6mm pixels. We could resolve all pixels on the SiPM based detectors. We conclude the Si-PM is a promising photodetector for the development of imaging systems for

THE ALLEN TELESCOPE ARRAY Pi GHz SKY SURVEY. III. THE ELAIS-N1, COMA, AND LOCKMAN HOLE FIELDS

We present results from a total of 459 repeated 3.1 GHz radio continuum observations (of which 379 were used in a search for transient sources) of the ELAIS-N1, Coma, Lockman Hole, and NOAO Deep Wide Field Survey fields as part of the Pi GHz Sky Survey (PiGSS). The observations were taken approximately once per day between 2009 May and 2011 April. Each image covers 11.8 square degrees and has 100 arcsecond FWHM resolution. Deep images for each of the four fields have rms noise between 180 and 310 uJy and the corresponding catalogs contain ~200 sources in each field. Typically 40 - 50 of these sources are detected in each single-epoch image. This represents one of the shortest cadence, largest area, multi-epoch surveys undertaken at these frequencies. We compare the catalogs generated from the combined images to those from individual epochs, and from monthly averages, as well as to legacy surveys. We undertake a search for transients, with particular emphasis on excluding false positive sources. We find no confirmed transients, defined here as sources that can be shown to have varied by at least a factor 10. However, we find one source which brightened in a single-epoch image to at least six times the upper limit from the corresponding deep image. We also find a source associated with a z = 0.6 quasar which appears to have brightened by a factor of about three in one of our deep images, when compared to catalogs from legacy surveys. We place new upper limits on the number of transients brighter than 10 mJy: fewer than 0.08 transients / sq. deg. with characteristic timescales of months to years; fewer than 0.02 / sq. deg. with timescales of months; and fewer than 0.009 / sq. deg with timescales of days. We also plot upper limits as a function of flux density for transients on the same timescales.

RESOLVING THE RADIO SOURCE BACKGROUND: DEEPER UNDERSTANDING THROUGH CONFUSION

We used the Karl G. Jansky Very Large Array (VLA) to image one primary beam area at 3 GHz with 8 arcsec FWHM resolution and 1.0 microJy/beam rms noise near the pointing center. The P(D) distribution from the central 10 arcmin of this confusion-limited image constrains the count of discrete sources in the 1 < S(microJy/beam) < 10 range. At this level the brightness-weighted differential count S^2 n(S) is converging rapidly, as predicted by evolutionary models in which the faintest radio sources are star-forming galaxies; and ~96$% of the background originating in galaxies has been resolved into discrete sources. About 63% of the radio background is produced by AGNs, and the remaining 37% comes from star-forming galaxies that obey the far-infrared (FIR) / radio correlation and account for most of the FIR background at lambda = 160 microns. Our new data confirm that radio sources powered by AGNs and star formation evolve at about the same rate, a result consistent with AGN feedback and the rough correlation of black hole and bulge stellar masses. The confusion at centimeter wavelengths is low enough that neither the planned SKA nor its pathfinder ASKAP EMU survey should be confusion limited, and the ultimate source detection limit imposed by "natural" confusion is < 0.01 microJy at 1.4 GHz. If discrete sources dominate the bright extragalactic background reported by ARCADE2 at 3.3 GHz, they cannot be located in or near galaxies and most are < 0.03 microJy at 1.4 GHz.

AMoRE experiment: a search for neutrinoless double beta decay of 100Mo isotope with 40Ca100MoO4 cryogenic scintillation detector

AMoRE (Advanced Mo based Rare process Experiment) collaboration is going to use calcium molybdate crystals as cryogenic scintillation detector in a search for neutrinoless DBD of 100Mo isotope. Simultaneous detection of phonons and light will be used to reject internal background. A FWHM resolution of 0.2% in the phonon channel has been achieved with a 0.5 cm3 crystal. Several 40Ca100MoO4 crystals (≈ 0.5 kg) have been developed from enriched 100Mo and depleted 40Ca materials. The light yield of these crystals has been shown to be comparable with reference CaMoO4 scintillators for temperatures ranging down to 8 K. The content of dangerous radioisotopes in the crystals is under measurement. The projected sensitivity of the experiment for a 250 kg × years exposure is lim T1/2 ∼ 3 × 1026 years, which corresponds to the effective Majorana neutrino mass ⟨mv⟩ ∼ 0.02 – 0.06 eV.

Intrinsic spatial resolution evaluation of the X’tal cube PET detector based on a 3D crystal block segmented by laser processing

The X'tal cube is a depth-of-interaction (DOI)-PET detector which is aimed at obtaining isotropic resolution by effective readout of scintillation photons from the six sides of a crystal block. The X'tal cube is composed of the 3D crystal block with isotropic resolution and arrays of multi-pixel photon counters (MPPCs). In this study, to fabricate the 3D crystal block efficiently and precisely, we applied a sub-surface laser engraving (SSLE) technique to a monolithic crystal block instead of gluing segmented small crystals. The SSLE technique provided micro-crack walls which carve a groove into a monolithic scintillator block. Using the fabricated X'tal cube, we evaluated its intrinsic spatial resolution to show a proof of concept of isotropic resolution. The 3D grids of 2 mm pitch were fabricated into an 18 × 18 × 18 mm(3) monolithic lutetium yttrium orthosilicate (LYSO) crystal by the SSLE technique. 4 × 4 MPPCs were optically coupled to each surface of the crystal block. The X'tal cube was uniformly irradiated by (22)Na gamma rays, and all of the 3D grids on the 3D position histogram were separated clearly by an Anger-type calculation from the 96-channel MPPC signals. Response functions of the X'tal cube were measured by scanning with a (22)Na point source. The gamma-ray beam with a 1.0 mm slit was scanned in 0.25 mm steps by positioning of the X'tal cube at vertical and 45° incident angles. The average FWHM resolution at both incident angles was 2.1 mm. Therefore, we confirmed the isotropic spatial resolution performance of the X'tal cube.

SPHERES, Jülich's high-flux neutron backscattering spectrometer at FRM II

SPHERES is a third-generation neutron backscattering spectrometer, located at the 20 MW German neutron source FRM II and operated by the Jülich Centre for Neutron Science. It offers an energy resolution (fwhm) better than 0.65 μeV, a dynamic range of ± 31 μeV, and a signal-to-noise ratio of up to 1750:1.

Abstract 1267: Characterization of carcinoembryonic antigen (CEA) microheterogeneity: a case study considering N-linked glycoforms

Abstract Colorectal cancer (CRC) is the second leading cause of cancer related deaths in the United States. A critical component of CRC care is post-surgical monitoring for cancer recurrence. Carcinogenicembryonic antigen (CEA) is a tumor marker for the clinical management of CRC which has the specific utility of monitoring post-operative disease recurrence. After surgery to remove cancerous tissue, the level of CEA in blood can be periodically monitored using an immunoassay. If the levels begin to rise above 6.0 ng/mL there is a high correlation with recurrence of the cancer. CEA, like many tumor markers is a glycoprotein and there is a significant body of work showing protein glycosylation is greatly affected by diseases such as cancer. We are investigating the CEA protein microheterogeneity in effort to improve its performance as a CRC biomarker. This poster presentation outlines our methods for glycoprotein characterization and includes qualitative and quantitative CEA glycoform data. CEA immuno-purified from cancerous liver was purchased from AbCam and processed without further purification. The purified protein was processed by SDS-PAGE on a 4-12% Bis-Tris NuPage gel (Invitrogen) in the MOPS buffer system. A second instance of the purified protein was deglycosylated with PNGaseF (New England Biolabs) and processed using the same SDS-PAGE conditions. The windows corresponding to the modified and unmodified proteins were excised and processed by in-gel digestion using a robot (ProGest, DigiLab) and Promega sequencing grade trypsin. The digested sample was analyzed by nano LC/MS/MS with a Waters NanoAcquity HPLC system interfaced to a ThermoFisher Orbitrap Velos Pro. Peptides were loaded on a trapping column and eluted over a 75µm analytical column at 350nL/min; both columns were packed with Jupiter Proteo resin (Phenomenex). The mass spectrometer was operated in data-dependent mode, with MS performed in the Orbitrap at 60,000 FWHM resolution and MS/MS performed in the dual linear ion traps. The fifteen most abundant ions were selected for MS/MS. Data were processed using bioinformatics tools and manually to identify and validate N-glycosylation sites and associated N-linked glycans. Glycoform quantitation was performed using High Resolution Accurate Mass (HRAM) and when necessary glycosites were confirmed using MS3 analysis. This presentation summarizes a workflow for the identification and quantification of protein glycoforms and shows the combination of immuno-purification, a targeted multiple enzyme approach and high resolution accurate mass data enables the accurate identification of N-glycosites and their glycoforms. The data from these experiments highlight the complexity of CEA glycoforms, for example a single N-linked glycosite on the peptide LQLSNGNR has over 30 associated glycoforms of varying abundance. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1267. doi:1538-7445.AM2012-1267

Using a LaBr3:Ce scintillator for positron annihilation lifetime spectroscopy

A LaBr3:Ce scintillator has a high light output (∼60000 p.e/MeV) and a short decay constant (<25 ns), which makes it good for time spectrometry. Compared with a BaF2 scintillator, it can bear a much higher count rate, and can be coupled to photomultipliers without using a quartz window. In this work, a positron annihilation lifetime spectrometer (PALS) consisting of two bulks of φ25 mm×25 mm LaBr3:Ce scintillator coupled to two XP20D0 photomultipliers, respectively, was built. A time resolution of FWHM=206 ps was measured for the PALS with a 60Co source at the energy window for 22Na. With this spectrometer, a reasonable lifetime value τ = 221±4 ps in a pure Si sample is obtained, which means that the utilization of LaBr3:Ce as the detector for a PALS is feasible.

Improvement of Performance of Cardiac SPECT Camera Using Curved Detectors With Pinholes.

SPECT is primarily used in the clinic for cardiac myocardial perfusion imaging. However, for SPECT, sensitivity is impaired due to the need for collimation. System resolution FWHM is poor as well (~ 1 cm). In this work the resolution of a curved detector was theoretically derived. The advantage of a curved detector over a flat detector with pinhole collimation was demonstrated for cardiac applications using theoretical derivations as well as a ray-tracing voxel-based forward projector. For the flat detector using parameters close to what was expected for the new multi-pinhole GE Discovery system, it is shown that using a paraboloid detector one may obtain a better system resolution (about 29% better on the average), keeping same pinhole opening. Alternately, sensitivity gains of as much as 2.25 may be obtained, for similar resolutions as a flat detector by just using a different pinhole with higher hole-diameter.

Determination of 239Pu/240Pu isotopic ratio by high-resolution alpha-particle spectrometry using the ADAM program

A novel analysis program to unfold alpha-particle energy spectra was introduced, demonstrated and validated using radiochemically processed test sources, which contained different amounts of 239Pu and 240Pu. A high-resolution alpha spectrometer was used for data acquisition. The software known as ADAM unfolds the spectra using nuclide-specific decay data as a constraint. The peaks can have different shapes and the software can also cope with the coincidences between alpha particles and electrons/photons. In the present paper, the 239Pu/240Pu activity ratios from alpha spectrometry agreed, within the stated uncertainties, with the reference values. Number of counts in the 239,240Pu peak group must be larger than 100 to obtain reliable values when using semiconductor detector of energy resolution FWHM=10.6keV.

Imaging X-ray detector front-end with high dynamic range: IDeF-X HD

Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250keV or more. The ASIC has been realized in AMS 0.35μm CMOS process.The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800μW per channel. With the in-channel variable gain stage the nominal 250keV dynamic range of the ASIC can be extended up to 1MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7μs peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1keV at 60keV and 4.3keV at 662keV with detection threshold below 4keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5°C.

SPEAR — ToF neutron reflectometer at the Los Alamos Neutron Science Center

This article discusses the Surface ProfilE Analysis Reflectometer (SPEAR), a vertical scattering geometry time-of-flight reflectometer, at the Los Alamos National Laboratory Lujan Neutron Scattering Center. SPEAR occupies flight path 9 and receives spallation neutrons from a polychromatic, pulsed (20Hz) source that pass through a liquid-hydrogen moderator at 20K coupled with a Be filter to shift their energy spectrum. The spallation neutrons are generated by bombarding a tungsten target with 800MeV protons obtained from an accelerator. The process produces an integrated neutron flux of ∼ 3.4×106 cm−2 s−1 at a proton current of 100μA. SPEAR employs choppers and frame overlap mirrors to obtain a neutron wavelength range of 4.5–16 A. SPEAR uses a single 200mm long 3He linear position-sensitive detector with ∼ 2 mm FWHM resolution for simultaneous studies of both specular and off-specular scattering. SPEAR’s moderated neutrons are collimated into a beam which impinges from above upon a level sample with an average angle of 0.9° to the horizontal, to facilitate air-liquid interface studies. In the vertical direction, the beam converges at the sample position. The neutrons can be further collimated to the desired divergence by finely slitting the beam using a set of two 10B4C slit packages. The instrument is ideally suited to study organic and inorganic thin films with total thicknesses between 5 and 3000 A in a variety of environments. Specifically designed sample chambers available at the instrument provide the opportunity to study biological systems at the solid-liquid interface. SPEAR’s unique experimental capabilities are demonstrated by specific examples in this article. Finally, an outlook for SPEAR and perspectives on future instrumentation are discussed.

Digital Signal Processing Techniques to Improve Time Resolution in Positron Emission Tomography

Coincidence time resolution is one of the most important issues in PET detectors. Improving this resolution is required to increase the noise equivalent count rate (NECR) that reduces the noise in the reconstructed images. The aim of this work is to evaluate the behavior and time resolution of different proposed time pick-off algorithms in order to select the best configuration for our PET system. The experimental setup used for this research is composed by two monolithic LSO crystals+PSPMT detectors and an FPGA based PET data acquisition system (DAQ). The acquired signals are sampled using a 12-bit 70 MHz analog to digital converter (ADC) per channel. The setup has no centralized electronics for trigger and event time extraction. Consequently, events for each detector head are processed independently and all the signals are acquired in the same way. Time resolution in this kind of systems can be improved by means of digital processing techniques and using different shapings for the last dynode signals. Four digital algorithms extracting time information from the acquired pulses have been evaluated: (1) Amplitude bipolar digital constant fraction discriminator (BCFD), (2) charge BCFD, (3) interpolated amplitude BCFD and (4) interpolated charge BCFD. Two different architectures for the interpolation algorithm have been used (one-sample and two-sample interpolation), which allow us to work with two different FPGA internal sampling frequencies: 140 MHz and 210 MHz. The results show the importance of selecting the right algorithm and parameters. Time coincidence resolution in our hardware system can be improved by up to 6.9 ns FWHM depending on the chosen digital algorithm programmed on the FPGA. The measurements with our setup reveal that charge based algorithms are less sensitive to signal noise and generate better results than amplitude algorithms. The best configuration achieves a FWHM resolution close to 1.8 ns.

THE HUBBLE SPACE TELESCOPE WIDE FIELD CAMERA 3 EARLY RELEASE SCIENCE DATA: PANCHROMATIC FAINT OBJECT COUNTS FOR 0.2-2 μm WAVELENGTH

We describe the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Early Release Science (ERS) observations in the Great Observatories Origins Deep Survey (GOODS) South field. The new WFC3 ERS data provide calibrated, drizzled mosaics in the UV filters F225W, F275W, and F336W, as well as in the near-IR filters F098M (Ys), F125W (J), and F160W (H) with 1-2 HST orbits per filter. Together with the existing HST Advanced Camera for Surveys (ACS) GOODS-South mosaics in the BViz filters, these panchromatic 10-band ERS data cover 40-50 square arcmin at 0.2-1.7 {\mu}m in wavelength at 0.07-0.15" FWHM resolution and 0.090" Multidrizzled pixels to depths of AB\simeq 26.0-27.0 mag (5-{\sigma}) for point sources, and AB\simeq 25.5-26.5 mag for compact galaxies. In this paper, we describe: a) the scientific rationale, and the data taking plus reduction procedures of the panchromatic 10-band ERS mosaics; b) the procedure of generating object catalogs across the 10 different ERS filters, and the specific star-galaxy separation techniques used; and c) the reliability and completeness of the object catalogs from the WFC3 ERS mosaics. The excellent 0.07-0.15" FWHM resolution of HST/WFC3 and ACS makes star- galaxy separation straightforward over a factor of 10 in wavelength to AB\simeq 25-26 mag from the UV to the near-IR, respectively.

Dynamics Induced by the Central Supermassive Black Holes in Galaxies

Dynamics Induced by the Central Supermassive Black Holes in Galaxies

A compact positron annihilation lifetime spectrometer

Using LYSO scintillator coupled on HAMAMATSU R9800 (a fast photomultiplier) to form the small size γ-ray detectors, a compact lifetime spectrometer has been built for the positron annihilation experiments. The system time resolution FWHM=193 ps and the coincidence counting rate ∼8 cps/μCi were achieved. A lifetime value of 219±1 ps of positron annihilation in well annealed Si was tested, which is in agreement with the typical values published in the previous lectures.