Cerenkov Events Seen by The TALE Air Fluorescence Detector

The Telescope Array Low-Energy Extension (TALE) is a hybrid, Air Fluorescence Detector (FD) / Scintillator Array, designed to study cosmic ray initiated showers at energies above $\sim3\times10^{16}$ eV. Located in the western Utah desert, the TALE FD is comprised of 10 telescopes which cover the elevation range 31-58$^{\circ}$ in addition to 14 telescopes with elevation coverage of 3-31$^{\circ}$. As with all other FD's, a subset of the shower events recorded by TALE are ones for which the Cerenkov light produced by the shower particles dominates the total observed light signal. In fact, for the telescopes with higher elevation coverage, low energy Cerenkov events form the vast majority of triggered cosmic ray events. In the typical FD data analysis procedure, this subset of events is discarded and only events for which the majority of signal photons come from air fluorescence are kept. In this talk, I will report on a study to reconstruct the "Cerenkov Events" seen by the high elevation viewing telescopes of TALE. Monte Carlo studies and a first look at real events observed by TALE look very promising. Even as a monocular detector, the geometrical reconstruction method employed in this analysis allows for a pointing accuracy on the order of a degree. Preliminary Monte Carlo studies indicate that, the expected energy resolution is better than 25$$. It may be possible to extend the low energy reach of TALE to below $10^{16}$ eV. This would be the first time a detector designed specifically as an air fluorescence detector is used as an imaging Cerenkov detector.Comment: Presentation at the DPF 2013 Meeting of the American Physical Society Division of Particles and Fields, Santa Cruz, California, August 13-17, 2013. 5 pages, 2 figure

Beamforming Techniques for Large-N Aperture Arrays

Beamforming is central to the processing function of all phased arrays and becomes particularly challenging with a large number of antenna element (e.g. >100,000). The ability to beamform efficiently with reasonable power requirements is discussed in this paper. Whilst the most appropriate beamforming technology will change over time due to semiconductor and processing developments, we present a hierarchical structure which is technology agnostic and describe both Radio-Frequency (RF) and digital hierarchical beamforming approaches. We present implementations of both RF and digital beamforming systems on two antenna array demonstrators, namely the Electronic Multi Beam Radio Astronomy ConcEpt (EMBRACE) and the dualpolarisation all-digital array (2-PAD). This paper will compare and contrast both digital and analogue implementations without considering the deep system design of these arrays.Comment: 8 pages, Accepted IEEE Phased Array 201

Mapping our Universe in 3D with MITEoR

Mapping our universe in 3D by imaging the redshifted 21 cm line from neutral hydrogen has the potential to overtake the cosmic microwave background as our most powerful cosmological probe, because it can map a much larger volume of our Universe, shedding new light on the epoch of reionization, inflation, dark matter, dark energy, and neutrino masses. We report on MITEoR, a pathfinder low-frequency radio interferometer whose goal is to test technologies that greatly reduce the cost of such 3D mapping for a given sensitivity. MITEoR accomplishes this by using massive baseline redundancy both to enable automated precision calibration and to cut the correlator cost scaling from N^2 to NlogN, where N is the number of antennas. The success of MITEoR with its 64 dual-polarization elements bodes well for the more ambitious HERA project, which would incorporate many identical or similar technologies using an order of magnitude more antennas, each with dramatically larger collecting area.Comment: To be published in proceedings of 2013 IEEE International Symposium on Phased Array Systems & Technolog

A Trigger Interface Board to manage trigger and timing signals in CTA Large-Sized Telescope and Medium-Sized Telescope cameras

One of the main goals of the Cherenkov Telescope Array (CTA) observatory is to improve the $\gamma$-ray detection sensitivity by an order of magnitude, compared to the current ground-based observatories. Widening the energy coverage down to 20 GeV and up to 300 TeV is also an important goal. This goal will be possible by using Large-Sized Telescopes (LSTs) for the energy range of 20--200 GeV, Medium-Sized Telescopes (MSTs) for 100 GeV--10 TeV, and Small-Sized Telescopes (SSTs) for energies above 5 TeV. The LSTs, which focus on the lowest energies, are operated in a region dominated by background events originated from the night sky background. To reduce such background events as much as possible, the LST cameras are only read out if at least two of them have been triggered in a short-time coincidence window. Such trigger is implemented for each LST camera in a dedicated module called Trigger Interface Board (TIB). In addition, the TIB is also used in MSTs equipped with the NectarCAM camera system to manage the different trigger and timing signals between LSTs and MSTs, as well as to monitor the different counting rates and dead-time of the cameras. It also assigns a time stamp to each event, which is recorded along with the information provided by the CTA global timing distribution system, based on the White Rabbit protocol. Therefore, the event arrival time can be determined in a redundant way. In this contribution, the main features and the technical performance of the TIB are presented.Comment: All CTA contributions at arXiv:1709.03483. In Proceedings of the 35th International Cosmic Ray Conference (ICRC2017), Busan, Kore

Experimental investigation of inter-element isolation in a medical array transducer at various manufacturing stages

This work presents the experimental investigation of vibration maps of a linear array transducer with 192 piezoelements by means of a laser Doppler vibrometer at various manufacturing finishing steps in air and in water. Over the years, many researchers have investigated cross-coupling in fabricated prototypes but not in arrays at various manufacturing stages. Only the central element of the array was driven at its working frequency of 5 MHz. The experimental results showed that the contributions of cross-coupling depend on the elements of the acoustic stack: Lead Zirconate Titanate (PZT), kerf, filler, matching layer, and lens. The oscillation amplitudes spanned from (6 ± 38%) nm to (110 ± 40%) nm when the energized element was tested in air and from (6 ± 57%) nm to (80 ± 67%) nm when measurements were obtained under water. The best inter-element isolation of -22 dB was measured in air after cutting the kerfs, whereas the poorest isolation was -2 dB under water with an acoustic lens (complete acoustic stack). The vibration pattern in water showed a higher standard deviation on the displacement measurements than the one obtained in air, due to the influence of acousto-optic interactions. The amount increased to 30% in water, as estimated by a comparison with the measurements in air. This work describes a valuable method for manufacturers to investigate the correspondence between the manufacturing process and the quantitative evaluations of the resulting effects

Studies of the nature of the low-energy, gamma-like background for Cherenkov Telescope Array

The upcoming Cherenkov Telescope Array (CTA) project is expected to provide unprecedented sensitivity in the low-energy ( <~100 GeV) range for Cherenkov telescopes. In order to exploit fully the potential of the telescopes the standard analysis methods for gamma/hadron separation might need to be revised. We study the composition of the background by identifying events composed mostly of a single electromagnetic subcascade or double subcascade from a {\pi}0 (or another neutral meson) decay. We apply the standard simulation and analysis chain of CTA to evaluate the potential of the standard analysis to reject such events.Comment: All CTA contributions at arXiv:1709.03483. Proc. of the 35th International Cosmic Ray Conference, Busan, Kore