arXiv subjects

C. Tenzer

Publications and source records attributed to C. Tenzer.

At least 37 records · Page 2Linked to original sources

arXiv2016

Performance Verification of the FlashCam Prototype Camera for the Cherenkov Telescope Array

The Cherenkov Telescope Array (CTA) is a future gamma-ray observatory that is planned to significantly improve upon the sensitivity and precision of the current generation of Cherenkov telescopes. The observatory will consist of several dozens of telescopes with different sizes and equipped with different types of cameras. Of these, the FlashCam camera system is the first to implement a fully digital signal processing chain which allows for a traceable, configurable trigger scheme and flexible signal reconstruction. As of autumn 2016, a prototype FlashCam camera for the medium-sized telescopes of CTA nears completion. First results of the ongoing system tests demonstrate that the signal chain and the readout system surpass CTA requirements. The stability of the system is shown using long-term temperature cycling.

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arXiv2016

An Efficient Test Facility For The Cherenkov Telescope Array FlashCam Readout Electronics Production

The Cherenkov Telescope Array (CTA) is the planned next-generation instrument for ground-based gamma-ray astronomy, currently under preparation by a world-wide consortium. The FlashCam group is preparing a photomultiplier-based camera for the Medium Size Telescopes of CTA, with a fully digital Readout System (ROS). For the forthcoming mass production of a substantial number of cameras, efficient test routines for all components are currently under development. We report here on a test facility for the ROS components. A test setup and routines have been developed and an early version of that setup has successfully been used to test a significant fraction of the ROS for the FlashCam camera prototype in January 2016. The test setup with its components and interface, as well as first results, are presented here.

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arXiv2016

Actuator Development at IAAT for the Cherenkov Telescope Array Medium Size Telescopes

The Cherenkov Telescope Array (CTA) will be the future observatory for TeV gamma-ray astronomy. In order to increase the sensitivity and to extend the energy coverage beyond the capabilities of current facilities, its design concept features telescopes of three different size classes. Based on the experience from H.E.S.S. phase II, the Institute for Astronomy and Astrophysics Tübingen (IAAT) develops actuators for the mirror control system of the CTA Medium Size Telescopes (MSTs). The goals of this effort are durability, high precision, and mechanical stability under all environmental conditions. Up to now, several revisions were developed and the corresponding prototypes were extensively tested. In this contribution our latest design revision proposed for the CTA MSTs are presented.

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arXiv2015

FlashCam: a fully-digital camera for the medium-sized telescopes of the Cherenkov Telescope Array

The FlashCam group is currently preparing photomultiplier-tube based cameras proposed for the medium-sized telescopes (MST) of the Cherenkov Telescope Array (CTA). The cameras are designed around the FlashCam readout concept which is the first fully-digital readout system for Cherenkov cameras, based on commercial FADCs and FPGAs as key components for the front-end electronics modules and a high performance camera server as back-end. This contribution describes the progress of the full-scale FlashCam camera prototype currently under construction, as well as performance results also obtained with earlier demonstrator setups. Plans towards the production and implementation of FlashCams on site are also briefly presented.

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arXiv2015

Recent developments for the testing of Cherenkov Telescope Array mirrors and actuators in Tübingen

The Cherenkov Telescope Array (CTA) is the next generation Cherenkov telescope facility. It will consist of a large number of segmented-mirror telescopes of three different diameters, placed in two locations, one in the northern and one in the southern hemisphere, thus covering the whole sky. The total number of mirror tiles will be on the order of 10,000, corresponding to a reflective area of ~10^4 m^2. The Institute for Astronomy and Astrophysics in Tübingen (IAAT) is currently developing mirror control alignment mechanics, electronics, and software optimized for the medium sized telescopes. In addition, IAAT is participating in the CTA mirror prototype testing. In this paper we present the status of the current developments, the main results of recent tests, and plans for the production phase of the mirror control system. We also briefly present the Tübingen facility for mirror testing.

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arXiv2015

Soft Proton Scattering Efficiency Measurements on X-Ray Mirror Shells

In-orbit experience has shown that soft protons are funneled more efficiently through focusing Wolter-type optics of X-ray observatories than simulations predicted. These protons can degrade the performance of solid-state X-ray detectors and contribute to the instrumental background. Since laboratory measurements of the scattering process are rare, an experiment for grazing angles has been set up at the accelerator facility of the University of Tübingen. Systematic measurements at incidence angles ranging from 0.3° to 1.2° with proton energies around 250 keV, 500 keV, and 1 MeV have been carried out. Parts of spare mirror shells of the eROSITA (extended ROentgen Survey with an Imaging Telescope Array) instrument have been used as scattering targets. This publication comprises a detailed description of the setup, the calibration and normalization methods, and the scattering efficiency and energy loss results. A comparison of the results with a theoretical scattering description and with simulations is included as well.

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arXiv2014

The Large Area Detector of LOFT: the Large Observatory for X-ray Timing

LOFT (Large Observatory for X-ray Timing) is one of the five candidates that were considered by ESA as an M3 mission (with launch in 2022-2024) and has been studied during an extensive assessment phase. It is specifically designed to perform fast X-ray timing and probe the status of the matter near black holes and neutron stars. Its pointed instrument is the Large Area Detector (LAD), a 10 m 2 -class instrument operating in the 2-30keV range, which holds the capability to revolutionise studies of variability from X-ray sources on the millisecond time scales. The LAD instrument has now completed the assessment phase but was not down-selected for launch. However, during the assessment, most of the trade-offs have been closed leading to a robust and well documented design that will be re- proposed in future ESA calls. In this talk, we will summarize the characteristics of the LAD design and give an overview of the expectations for the instrument capabilities.

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arXiv2014

Hyper-velocity impact test and simulation of a double-wall shield concept for the Wide Field Monitor aboard LOFT

The space mission LOFT (Large Observatory For X-ray Timing) was selected in 2011 by ESA as one of the candidates for the M3 launch opportunity. LOFT is equipped with two instruments, the Large Area Detector (LAD) and the Wide Field Monitor (WFM), based on Silicon Drift Detectors (SDDs). In orbit, they would be exposed to hyper-velocity impacts by environmental dust particles, which might alter the surface properties of the SDDs. In order to assess the risk posed by these events, we performed simulations in ESABASE2 and laboratory tests. Tests on SDD prototypes aimed at verifying to what extent the structural damages produced by impacts affect the SDD functionality have been performed at the Van de Graaff dust accelerator at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg. For the WFM, where we expect a rate of risky impacts notably higher than for the LAD, we designed, simulated and successfully tested at the plasma accelerator at the Technical University in Munich (TUM) a double-wall shielding configuration based on thin foils of Kapton and Polypropylene. In this paper we summarize all the assessment, focussing on the experimental test campaign at TUM.

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arXiv2014

The design of the wide field monitor for LOFT

LOFT (Large Observatory For x-ray Timing) is one of the ESA M3 missions selected within the Cosmic Vision program in 2011 to carry out an assessment phase study and compete for a launch opportunity in 2022-2024. The phase-A studies of all M3 missions were completed at the end of 2013. LOFT is designed to carry on-board two instruments with sensitivity in the 2-50 keV range: a 10 m 2 class Large Area Detector (LAD) with a <1° collimated FoV and a wide field monitor (WFM) making use of coded masks and providing an instantaneous coverage of more than 1/3 of the sky. The prime goal of the WFM will be to detect transient sources to be observed by the LAD. However, thanks to its unique combination of a wide field of view (FoV) and energy resolution (better than 500 eV), the WFM will be also an excellent monitoring instrument to study the long term variability of many classes of X-ray sources. The WFM consists of 10 independent and identical coded mask cameras arranged in 5 pairs to provide the desired sky coverage. We provide here an overview of the instrument design, configuration, and capabilities of the LOFT WFM. The compact and modular design of the WFM could easily make the instrument concept adaptable for other missions.

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arXiv2014

Optimisation of the design for the LOFT Large Area Detector Module

LOFT (Large Observatory for X-ray Timing) is an X-ray timing observatory that, with four other candidates, was considered by ESA as an M3 mission (with launch in 2022-2024) and has been studied during an extensive assessment phase. Its pointed instrument is the Large Area Detector (LAD), a 10 m 2 -class instrument operating in the 2-30 keV range, which is designed to perform X-ray timing of compact objects with unprecedented resolution down to millisecond time scales. Although LOFT was not downselected for launch, during the assessment most of the trade-offs have been closed, leading to a robust and well documented design that will be reproposed in future ESA calls. The building block of the LAD instrument is the Module, and in this paper we summarize the rationale for the module concept, the characteristics of the module and the trade-offs/optimisations which have led to the current design.

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arXiv2014

The digital data processing concepts of the LOFT mission

The Large Observatory for X-ray Timing (LOFT) is one of the five mission candidates that were considered by ESA for an M3 mission (with a launch opportunity in 2022 - 2024). LOFT features two instruments: the Large Area Detector (LAD) and the Wide Field Monitor (WFM). The LAD is a 10 m 2 -class instrument with approximately 15 times the collecting area of the largest timing mission so far (RXTE) for the first time combined with CCD-class spectral resolution. The WFM will continuously monitor the sky and recognise changes in source states, detect transient and bursting phenomena and will allow the mission to respond to this. Observing the brightest X-ray sources with the effective area of the LAD leads to enormous data rates that need to be processed on several levels, filtered and compressed in real-time already on board. The WFM data processing on the other hand puts rather low constraints on the data rate but requires algorithms to find the photon interaction location on the detector and then to deconvolve the detector image in order to obtain the sky coordinates of observed transient sources. In the following, we want to give an overview of the data handling concepts that were developed during the study phase.

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arXiv2013

The Hot and Energetic Universe: The Wide Field Imager (WFI) for Athena+

The Wide Field Imager (WFI) is one of the two scientific instruments proposed for the Athena+ X-ray observatory. It will provide imaging in the 0.1-15 keV band over a wide field, simultaneously with spectrally and time-resolved photon counting. The instrument is designed to make optimal use of the grasp (collecting area times solid angle product) provided by the optical design of the Athena+ mirror system (Willingale et al. 2013), by combining a sensitive approx. 40' diameter field of view (baseline; 50' goal) DEPFET detector with a pixel size properly sampling the angular resolution of 5 arc sec on-axis (half energy width).This synthesis makes the WFI a very powerful survey instrument, significantly surpassing currently existing capabilities (Nandra et al. 2013; Aird et al. 2013). In addition, the WFI will provide unprecedented simultaneous high-time resolution and high count rate capabilities for the observation of bright sources with low pile-up and high efficiency. In this paper, we summarize the instrument design, the status of the technology development, and the baseline performance.

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arXiv2013

FlashCam: A fully digital camera for the Cherenkov Telescope Array

FlashCam is a Cherenkov camera development project centered around a fully digital trigger and readout scheme with smart, digital signal processing, and a "horizontal" architecture for the electromechanical implementation. The fully digital approach, based on commercial FADCs and FPGAs as key components, provides the option to easily implement different types of triggers as well as digitization and readout scenarios using identical hardware, by simply changing the firmware on the FPGAs. At the same time, a large dynamic range and high resolution of low-amplitude signals in a single readout channel per pixel is achieved using compression of high amplitude signals in the preamplifier and signal processing in the FPGA. The readout of the front-end modules into a camera server is Ethernet-based using standard Ethernet switches. In its current implementation, data transfer and backend processing rates of ~3.8 GBytes/sec have been achieved. Together with the dead-time-free front end event buffering on the FPGAs, this permits the cameras to operate at trigger rates of up to several tens of kHz. In the horizontal architecture of FlashCam, the photon detector plane (PDP), consisting of photon detectors, preamplifiers, high voltage-, control-, and monitoring systems, is a self-contained unit, which is interfaced through analogue signal transmission to the digital readout system. The horizontal integration of FlashCam is expected not only to be more cost efficient, it also allows PDPs with different types of photon detectors to be adapted to the FlashCam readout system. This paper describes the FlashCam concept, its verification process, and its implementation for a 12 m class CTA telescope with PMT-based PDP.

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arXiv2012

FlashCam: A fully digital camera for CTA telescopes

The future Cherenkov Telescope Array (CTA) will consist of several tens of telescopes of different mirror sizes. CTA will provide next generation sensitivity to very high energy photons from few tens of GeV to >100 TeV. Several focal plane instrumentation options are currently being evaluated inside the CTA consortium. In this paper, the current status of the FlashCam prototyping project is described. FlashCam is based on a fully digital camera readout concept and features a clean separation between photon detector plane and signal digitization/triggering electronics.

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arXiv2012

Accelerator experiments with soft protons and hyper-velocity dust particles: application to ongoing projects of future X-ray missions

We report on our activities, currently in progress, aimed at performing accelerator experiments with soft protons and hyper-velocity dust particles. They include tests of different types of X-ray detectors and related components (such as filters) and measurements of scattering of soft protons and hyper-velocity dust particles off X-ray mirror shells. These activities have been identified as a goal in the context of a number of ongoing space projects in order to assess the risk posed by environmental radiation and dust and qualify the adopted instrumentation with respect to possible damage or performance degradation. In this paper we focus on tests for the Silicon Drift Detectors (SDDs) used aboard the LOFT space mission. We use the Van de Graaff accelerators at the University of Tübingen and at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg, for soft proton and hyper-velocity dust tests respectively. We present the experimental set-up adopted to perform the tests, status of the activities and some very preliminary results achieved at present time.

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arXiv2012

The on-board data handling concept for the LOFT Large Area Detector

The Large Observatory for X-ray Timing (LOFT) is one of the four candidate ESA M3 missions considered for launch in the time-frame of 2022. It is specifically designed to perform fast X-ray timing and probe the status of the matter near black holes and neutron stars. The LOFT scientific payload consists of a Large Area Detector and a Wide Field Monitor. The LAD is a 10 m^2-class pointed instrument with high spectral (200 eV @ 6 keV) and timing (< 10 μs) resolution over the 2-80 keV range. It is designed to observe persistent and transient X-ray sources with a very large dynamic range from a few mCrab up to an intensity of 15 Crab. An unprecedented large throughput (~280.000 cts/s from the Crab) is achieved with a segmented detector, making pile-up and dead-time, often worrying or limiting focused experiments, secondary issues. We present the on-board data handling concept that follows the highly segmented and hierarchical structure of the instrument from the front-end electronics to the on-board software. The system features customizable observation modes ranging from event-by-event data for sources below 0.5 Crab to individually adjustable time resolved spectra for the brighter sources. On-board lossless data compression will be applied before transmitting the data to ground.

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arXiv2012

A Large Area Detector proposed for the Large Observatory for X-ray Timing (LOFT)

The Large Observatory for X-ray Timing (LOFT) is one of the four candidate ESA M3 missions considered for launch in the 2022 time-frame. It is specifically designed to perform fast X-ray timing and probe the status of the matter near black holes and neutron stars. The LOFT scientific payload is composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a 10 m2-class pointed instrument with 20 times the collecting area of the best past timing missions (such as RXTE) over the 2-30 keV range, which holds the capability to revolutionize studies of X-ray variability down to the millisecond time scales. Its ground-breaking characteristic is a low mass per unit surface, enabling an effective area of ~10 m^2 (@10 keV) at a reasonable weight. The development of such large but light experiment, with low mass and power per unit area, is now made possible by the recent advancements in the field of large-area silicon detectors - able to time tag an X-ray photon with an accuracy <10 μs and an energy resolution of ~260 eV at 6 keV - and capillary-plate X-ray collimators. In this paper, we will summarize the characteristics of the LAD instrument and give an overview of its capabilities.

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arXiv2012

The LOFT Wide Field Monitor

LOFT (Large Observatory For x-ray Timing) is one of the four missions selected in 2011 for assessment study for the ESA M3 mission in the Cosmic Vision program, expected to be launched in 2024. The LOFT mission will carry two instruments with their prime sensitivity in the 2-30 keV range: a 10 m^2 class large area detector (LAD) with a <1° collimated field of view and a wide field monitor (WFM) instrument based on the coded mask principle, providing coverage of more than 1/3 of the sky. The LAD will provide an effective area ~20 times larger than any previous mission and will by timing studies be able to address fundamental questions about strong gravity in the vicinity of black holes and the equation of state of nuclear matter in neutron stars. The prime goal of the WFM will be to detect transient sources to be observed by the LAD. However, with its wide field of view and good energy resolution of <300 eV, the WFM will be an excellent monitoring instrument to study long term variability of many classes of X-ray sources. The sensitivity of the WFM will be 2.1 mCrab in a one day observation, and 270 mCrab in 3s in observations of in the crowded field of the Galactic Center. The high duty cycle of the instrument will make it an ideal detector of fast transient phenomena, like X-ray bursters, soft gamma repeaters, terrestrial gamma flashes, and not least provide unique capabilities in the study of gamma ray bursts. A dedicated burst alert system will enable the distribution to the community of ~100 gamma ray burst positions per year with a ~1 arcmin location accuracy within 30 s of the burst. This paper provides an overview of the design, configuration, and capabilities of the LOFT WFM instrument.

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