PSR J1023+0038 is the first millisecond pulsar discovered to pulsate in the visible band; such a detection took place when the pulsar was surrounded by an accretion disk and also showed X-ray ...pulsations. We report on the first high time resolution observational campaign of this transitional pulsar in the disk state, using simultaneous observations in the optical (Telescopio Nazionale Galileo, Nordic Optical Telescope, Telescopi Joan Oró), X-ray (XMM-Newton, NuSTAR, NICER), infrared (Gran Telescopio Canarias), and UV (Swift) bands. Optical and X-ray pulsations were detected simultaneously in the X-ray high-intensity mode in which the source spends ∼70% of the time, and both disappeared in the low mode, indicating a common underlying physical mechanism. In addition, optical and X-ray pulses were emitted within a few kilometers and had similar pulse shapes and distributions of the pulsed flux density compatible with a power-law relation F ∝ −0.7 connecting the optical and the 0.3-45 keV X-ray band. Optical pulses were also detected during flares with a pulsed flux reduced by one-third with respect to the high mode; the lack of a simultaneous detection of X-ray pulses is compatible with the lower photon statistics. We show that magnetically channeled accretion of plasma onto the surface of the neutron star cannot account for the optical pulsed luminosity (∼1031 erg s−1). On the other hand, magnetospheric rotation-powered pulsar emission would require an extremely efficient conversion of spin-down power into pulsed optical and X-ray emission. We then propose that optical and X-ray pulses are instead produced by synchrotron emission from the intrabinary shock that forms where a striped pulsar wind meets the accretion disk, within a few light cylinder radii away, ∼100 km, from the pulsar.
Radioguided surgery (RGS) is a medical practice which thanks to a radiopharmaceutical tracer and a probe allows the surgeon to identify tumor residuals up to a millimetric resolution in real-time. ...The employment of β− emitters, instead of γ or β+, reduces background from healthy tissues, administered activity to the patient, and medical exposure. In a previous work the possibility of using a CMOS Imager (Aptina MT9V011), initially designed for visible light imaging, to detect β− from 90Y or 90Sr sources has been established. Because of its possible application as counting probe in RGS, the performances of MT9V011 in clinical-like conditions were studied.11This work financed by Istituto Nazionale Fisica Nucleare, Italy, project CHIR2, and partially supported by Universitá degli Studi di Perugia, Italy , Fondo Ricerca di Base 2017, project SEISIPO.
Through horizontal scans on a collimated 90Sr source of different sizes (1, 3, 5, 7 mm), we have determined relationships between scan fit parameters and the source dimension, namely A quadratic correlation and a linear dependency of, respectively, signal integrated over scan interval, and maximum signal against source diameter, are determined. Horizontal scan measurements on a source, interposing collimators of different size, aim to determine relationships or correlations between scan fit parameters and source dimension. A quadratic correlation and a linear dependency of, respectively, signal integrated over scan interval, and maximum signal against source diameter are determined.
In order to get closer to clinical conditions, agar–agar phantoms containing 90Y with different dimensions and activities were prepared. A 90Y phantom is characterized by a central spot and a ring all around, for simulating both signal (tumor) and background (surrounding healthy tissue). The relationship found between scan maximum and 90Sr source diameter is then exploited to extract the concentration ratio between spot and external ring of the 90Y phantom. This observable, defined as the ratio between the tumor and the nearby healthy tissues uptake simulates the Tumor-to-Non-tumor Ratio (TNR). With the aim of evaluating the sensor’s ability to discriminate signal from background relying on the significance parameter, a further 90Y phantom, featuring a well-known and clinical-like activity will mimic the signal only condition. This result is used to extrapolate to different source sizes, after having estimated the background for various TNR. The obtained significance values suggest that the MT9V011 sensor is capable of distinguishing a signal from an estimated background, depending on the interplay among TNR, acquisition time and tumor diameter.
•A CMOS imager has been used as sensor for beta- emission from isotopes (90Y) of interest in Radioguided surgery.•Using a position scan a correlation between the source dimension and the shape of the response has been found.•The sensitivity of the sensor to tumor detection has been determined by studying the interplay among TNR, acquisition time and tumor diameter.
The AX-PET demonstrator—Design, construction and characterization Beltrame, P.; Bolle, E.; Braem, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2011, Letnik:
654, Številka:
1
Journal Article
Recenzirano
Axial PET is a novel geometrical concept for Positron Emission Tomography (PET), based on layers of long scintillating crystals axially aligned with the bore axis. The axial coordinate is obtained ...from arrays of wavelength shifting (WLS) plastic strips placed orthogonally to the crystals. This article describes the design, construction and performance evaluation of a demonstrator set-up which consists of two identical detector modules, used in coincidence. Each module comprises 48 LYSO crystals of 100
mm length and 156 WLS strips. Crystals and strips are readout by Geiger-mode Avalanche Photo Diodes (G-APDs). The signals from the two modules are processed by fully analog front-end electronics and recorded in coincidence by a VME-based data acquisition system. Measurements with point-like
22Na sources, with the modules used both individually and in coincidence mode, allowed for a complete performance evaluation up to the focal plane reconstruction of point sources. The results obtained are in good agreement with expectations and proved the set-up to be ready for the next evaluation phase with PET phantoms filled with radiotracers.
A New Fast Silicon Photomultiplier Photometer MEDDI, F; AMBROSINO, F; NESCI, R ...
Publications of the Astronomical Society of the Pacific,
05/2012, Letnik:
124, Številka:
915
Journal Article
Recenzirano
The realization of low-cost instruments with high technical performance is a goal that deserves some efforts in an epoch of fast technological developments; indeed, such instruments can be easily ...reproduced and therefore allow new research programs to be opened in several observatories. We realized a fast optical photometer based on the SiPM technology, using commercially available modules. Using low-cost components, we have developed a custom electronic chain to extract the signal produced by a commercial MPPC module produced by Hamamatsu Photonics, in order to obtain submillisecond sampling of the light curve of astronomical sources (typically, pulsars). In the early 2011 February, we observed the Crab pulsar with the Cassini telescope with our prototype photometer, deriving its period and power spectrum and the shape of its light curve, in very good agreement with the results obtained in the past with other instruments.
Missing-mass spectroscopy with the
3
H(
e
,
e′K
+
) reaction was carried out at Jefferson Lab’s (JLab) Hall A in Oct–Nov, 2018. The differential cross section for the
3
H(
γ
∗
,
K
+
)Λ
nn
was deduced ...at
ω
=
Ee
−
E
e′
= 2.102 GeV and at the forward
K
+
-scattering angle (0
°
≤ θ
γ
∗
K
≤ 5
°
) in the laboratory frame. Given typical predicted energies and decay widths, which are (
B
Λ
, Γ) = (−0.25, 0.8) and (−0.55, 4.7) MeV, the cross sections were found to be 11.2 ± 4.8(stat.)
+4.1
−2.1
(sys.) and 18.1 ± 6.8(stat.)
+4.2
−2.9
(sys.) nb/sr, respectively. The obtained result would impose a constraint for interaction models particularly between Λ and neutron by comparing to theoretical calculations.
Production status of the JLAB Hall-A GEM and Si μstrip Tracker Basile, E.; Bellini, V.; Capogni, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Letnik:
718
Journal Article
Recenzirano
We developed and tested a new charged particle tracking system, able to operate in high luminosity experiments, which will be installed at Jefferson Laboratory HallA (VA, USA) for optimally exploit ...the new 12GeV energy electron beam available at the end of 2013. The tracker is made of six GEM (Gas Electron Multiplier) large chambers and two 10×20cm2 planes of SIlicon microstrip Detectors (SIDs). Each GEM chamber is composed by three 40×50cm2 GEM modules, with two-dimensional strip readout, with expected spatial resolution of about 70μm. The same dedicated acquisition system will be used for both detectors (GEM & SID) for a grand total of more than 50,000 channels. The readout electronics is divided into two parts: the front-end cards (based on the existing APV25 chip), hosted on the detectors periphery and the digitizer, a multi purpose VME-64x/VXS board located far from the high radiation environment. The very same electronics has been adopted by the Olympus experiment (DESY, Hamburg, D) to read out the six GEM chambers of its luminosity monitor. The developed detectors and electronics are now ready for the production, which will last for the next 2 years.
Prostate cancer is the most common disease in men and the second leading cause of cancer death. Generic large instruments for diagnosis have sensitivity, spatial resolution, and contrast inferior ...with respect to dedicated prostate imagers. Multimodality imaging can play a significant role merging anatomical and functional details coming from simultaneous PET and MRI. The TOPEM project has the goal of designing, building, and testing an endorectal PET-TOF MRI probe. The performance is dominated by the detector close to the source. Results from simulation show spatial resolution of ∼1.5mm for source distances up to 80mm. The efficiency is significantly improved with respect to the external PET. Mini-detectors have been built and tested. We obtained, for the first time, to our best knowledge, timing resolution of <400ps and at the same time Depth Of Interaction (DOI) resolution of 1mm or less.
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