We propose to use a higher-frequency rf bunch structure for the primary proton beam on target and precision timing to select different energy and flavor spectra from a wide-band neutrino beam, based ...on the relative arrival times of the neutrinos with respect to the rf bunch structure. This "stroboscopic" approach is complementary to techniques that select different neutrino energy spectra based on the angle with respect to the beam axis. A timing-based approach allows for the selection of varying energy spectra from the same on-axis detector, and applies equally to both the near and far detectors in an oscillation experiment. Energy and flavor discrimination of neutrinos produced by hadrons in-flight will require proton bunch lengths on the order of 100 ps and commensurate time resolution in the detector. Correlating neutrino events with the parent proton interaction is currently limited by the nanosecond-scale width of the proton bunches impinging on the target. We show that these limitations can be addressed by using a superconducting rf cavity to rebunch the present 53.1 MHz rf bunch structure with a factor of 10 higher rf frequency, thus attaining the required shorter bunch length.
We propose PET scanners using low atomic number media that undergo a persistent local change of state along the paths of the Compton recoil electrons. Measurement of the individual scattering ...locations and angles, deposited energies, and recoil electron directions allows using the kinematical constraints of the 2-body Compton scattering process to perform a statistical time-ordering of the scatterings, with a high probability of precisely identifying where the gamma first interacted in the detector. In these cases the Line-of-Response is measured with high resolution, determined by the underlying physics processes and not the detector segmentation. There are multiple such media that act through different mechanisms. As an example in which the change of state is quantum-mechanical through a change in molecular configuration, rather than thermodynamic, as in a bubble chamber, we present simulations of a two-state photoswitchable organic dye, a ‘Switchillator’, that is activated to a fluorescent-capable state by the ionization of the recoil electrons. The activated state is persistent, and can be optically excited multiple times to image individual activated molecules. Energy resolution is provided by counting the activated molecules. Location along the LOR is implemented by large-area time-of-flight MCP-PMT photodetectors with single photon time resolution in the tens of ps and sub-mm spatial resolution. Simulations indicate a large reduction of dose.
We present 81 paleomagnetic sites (Early Triassic to Early Cretaceous) from the central sector of the northern Calcareous Alps (NCA, Eastern Alps, Austria and Germany). Stepwise thermal ...demagnetization defines three magnetic directions mostly carried by low unblocking temperature and low‐coercivity minerals: J3, 350°; J2, 500°; J1, 575° and 680°. J3 and J2 show positive inclinations, whereas J1 (very seldom) is of dual polarity. The fold tests show that a J3 can be interpreted as a postfolding and posttilting remagnetization and J2 as a postfolding and pre(syn)tilting. J1 can be considered as primary because of the occurrence of two polarities and evidence presented by other authors in the area. All three components show a systematic and significant clockwise rotation after comparing with the expected European references. J2 or J1 are marked by higher rotation values than J3. J2 shows different inclinations depending on the structural position (north or southward dips). Considering the structural evolution and the observed inclinations, the first postfolding and pretilting remagnetization event (J2) could have taken place between Late Cretaceous and Eocene times but certainly before the thrusting of the NCA over the Rhenodanubian Flysch and northward tilting caused by the stacking of the lower Austroalpine nappes. The second postfolding and posttilting remagnetization (J3) would have been acquired after the final thrusting of the NCA over Penninic units. From then, the NCA behaved as a set of rigid blocks recording the main stage of vertical axis clockwise rotation (65° in average) associated with the continental collision. The variable degree of rotation in the different positions (from 40° to 134°) can be explained by individual vertical axis rotation in a block system trying to adjust to space problems. The constant declination differences between J2 and J3 (25° in average) would reflect the rotation related with the lateral differences of shortening during the oblique thrust of the Austroalpine units over the Penninic units.
The classical concept of the nappe structure of the central Northern Calcareous Alps (NCA) is in contradiction with modern stratigraphic, structural, metamorphic and geochronological data. We first ...perform a palinspastic restoration for the time before Miocene lateral tectonic extrusion, which shows good continuity of structures, facies and diagenetic/metamorphic zones. We present a new nappe concept, in which the Tirolic unit practically takes the whole area of the central NCA and is divided into three subunits (nappes): Lower and Upper Tirolic subunit, separated by the Upper Jurassic Trattberg Thrust, and the metamorphic Ultra-Tirolic unit. The Hallstatt (Iuvavic) nappe(s) formed the highest unit, but were completely destroyed by erosion after nappe stacking. Remnants of the Hallstatt nappes are only represented by components of up to 1 km in size in Middle/Upper Jurassic radiolaritic wildflysch sediments ("Hallstatt Mélange" belonging to the Tirolic unit). Destruction of the continental margin started in Middle to Upper Jurassic time and prograded from the oceanic side towards the shelf. The original substratum of the external nappes (Bavaric units) of the NCA was largely the Austroalpine crystalline basement, of the internal nappes (Tirolic units) the weakly metamorphosed Palaeozoic sequences (Greywacke Zone and equivalents). Eocene movements caused limited internal deformation in the Tirolic unit.PUBLICATION ABSTRACT
Advanced photoinjectors, which are critical to many next generation accelerators, open the door to new ways of material probing, both as injectors for free electron lasers and for ultra-fast electron ...diffraction. For these applications, the nonuniformity of the electric field near the cathode caused by surface roughness can be the dominant source of beam emittance. Therefore, improving the photocathode roughness while maintaining quantum efficiency is essential to the improvement of beam brightness. In this paper, we report the demonstration of a bi-alkali antimonide photocathode with an order of magnitude improved roughness by sputter deposition from a K2CsSb sputter target, using in situ and operando X-ray characterizations. We found that a surface roughness of 0.5 nm for a sputtered photocathode with a final thickness of 42 nm can be achieved while still yielding a quantum efficiency of 3.3% at 530 nm wavelength.
We report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have ...been measured. In the saturation regime, the peak energy approached 170 µJ for individual pulses, and the average energy per pulse reached 70 µJ. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20 mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples.
Performance of Large Area Picosecond Photo-Detectors (LAPPDTM) Lyashenko, A.V.; Adams, B.W.; Aviles, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2020, Letnik:
958, Številka:
C
Journal Article
Recenzirano
Odprti dostop
We report on performance results achieved for recently produced LAPPDs - largest commercially available planar geometry photodetectors based on microchannel plates. These results include electron ...gains of up to 107, low dark noise rates (∼100 Hz/cm2 at a gain of 6⋅106), single photoelectron (PE) timing resolution of ∼50 picoseconds RMS (electronics limited), and single photoelectron spatial resolution along and across strips of 3.2mm (electronics limited) and 0.8 mm RMS respectively and high (about 25% or higher in some units) QE uniform bi-alkali photocathodes. LAPPDs is a good candidate to be employed in neutrino experiments (e.g. ANNIE (Back et al., 2017) 1, WATCHMAN (Askins et al., 2015) 2, DUNE (Capozzi et al., 2018) 3), particle collider experiments (e.g. EIC (Accardi et al., 2016) 4), neutrinoless double-beta decay experiments (e.g. THEIA (Fischer et al., 2018) 5), medical and nuclear non-proliferation applications.
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