The scientific payload of the Ultraviolet Transient Astronomy Satellite (ULTRASAT)

The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is a space-borne near UV telescope with an unprecedented large field of view (200 sq. deg.). The mission, led by the Weizmann Institute of Science and the Israel Space Agency in collaboration with DESY (Helmholtz association, Germany) and NASA (USA), is fully funded and expected to be launched to a geostationary transfer orbit in Q2/3 of 2025. With a grasp 300 times larger than GALEX, the most sensitive UV satellite to date, ULTRASAT will revolutionize our understanding of the hot transient universe, as well as of flaring galactic sources. We describe the mission payload, the optical design and the choice of materials allowing us to achieve a point spread function of ~10arcsec across the FoV, and the detector assembly. We detail the mitigation techniques implemented to suppress out-of-band flux and reduce stray light, detector properties including measured quantum efficiency of scout (prototype) detectors, and expected performance (limiting magnitude) for various objects.Comment: Presented in the SPIE Astronomical Telescopes + Instrumentation 202

It is about time: Design and test of a per-pixel high-resolution TDC

Modern detectors have to provide an ever increasing precision, that goes from the order of nanosecond in the large high energy physics experiments at CERN to picoseconds for other precision experiments. Moreover, they have to be capable of handling increasing particle rates both on the detection side and on the data readout speed. This thesis is focused on time measurements in gaseous pixel detectors and it is structured as follows. In chapter 1 a brief history of pixel detectors is presented, focusing mainly on the features of their readout systems. In the second part of the chapter, the focus is on the modern detectors at the Large Hadron Collider and their planned upgrades. Chapter 2 presents the operation principle of gaseous detectors with the basic mechanism behind ion-electron couples production and transport mechanism. GridPix detectors are also introduced describing some basic properties. Chapters 3 and 4 contain the main results of this thesis, illustrating the design and testing of two prototype chips featuring high-resolution Time to Digital Converter (TDC). The results on the TDC are complemented with results on other circuitry which has been designed and tested in view of a full size chip. Finally, chapter 5 presents the analysis of data from a beam test using a telescope that contains three GridPix detectors. Their limitations are studied and are used as a justification for the design of Timepix3, a full size chip which features some circuits developed in the prototypes

GOSSIPO-4: an array of high resolution TDCs with a PLL control

GOSSIPO-4 is a prototype chip featuring an array of high resolution Time to Digital Converters with a PLL control that has been taped out the 9th of August 2011. This prototype is the successor of GOSSIPO-3 test chip and the precursor of the 65k pixel chip TimePix3. The prototype is being developed to test a set of new features that will be used in TimePix3, including a 8 pixel structure sharing one fast oscillator with a new topology, a PLL to provide the control voltage to the oscillators, a custom fast counter and a new small-area cell library

Gossipo-3: A prototype of a Front-End Pixel Chip for Read-Out of Micro-Pattern GasDetectors

In a joint effort of Nikhef (Amsterdam) and the University of Bonn, the Gossipo-3 integrated circuit (IC) has been developed. This circuit is a prototype of a chip dedicated for read-out of various types of position sensitive Micro-Pattern Gas detectors (MPGD). The Gossipo-3 is defined as a set of building blocks to be used in a future highly granulated (60 μm) chip. The pixel circuit can operate in two modes. In Time mode every readout pixel measures the hit arrival time and the charge deposit. For this purpose it has been equipped with a high resolution TDC (1.7 ns) covering dynamic range up to 102 μs. Charge collected by the pixel will be measured using Time-over-Threshold method in the range from 400 e- to 28000 e- with accuracy of 200 e- (standard deviation). In Counting mode every pixel operates as a 24-bit counter, counting the number of incoming hits. The circuit is also optimized to operate at low power consumption (100 mW/cm2) that is required to avoid the need for massive power transport and cooling systems inside the construction of the detector

GOSSIPO-3: measurements on the prototype of a read-out pixel chip for Micro-Pattern Gaseous Detectors

GOSSIPO-3 is a demonstrator of a front-end chip designed in IBM 130 nm CMOS in collaboration between Nikhef (Amsterdam) and the Physics Department of the University of Bonn for the read-out of Micro-Pattern Gas Detectors. The prototype features charge sensitive amplifiers, discriminators, a high resolution Time to Digital Converter (TDC), two different Low Drop Out (LDO) voltage regulators for supply voltage control of the Time to Digital Converter, biasing circuits and control logic on a 2 × 1 mm2 die. The chip can be operated in a time measuring mode or an event counting mode. Following the prototype announcement at the TWEPP 2009, measurement data on gain, noise performance, channel to channel ToT spread and LDO load step responses is now available. The measurement results confirm the high gain and low noise (ENC = 25 e−) predicted by simulations. Stable and reproducible time bin sizes of the TDC are also confirmed

Development and Applications of the Timepix3 Readout Chip

A new pixel readout chip called Timepix3 is being developed that can be used in a wide range of applications varying from X-rays imaging to particle track reconstruction. The Timepix3 will be suitable for readout of both semiconductor detectors and gas-filled detectors. Depending on the application requirements user can choose one out of three data acquisition modes available in the Timepix3. In the most advanced mode both arrival time information and charge deposit information will be delivered for each hit together with the coordinates of the active pixel. The chosen architecture allows for continuous and trigger-free readout of sparsely distributed data with the rate up to 20Mhits•cm-2 •sec-1. For imaging applications and for calibrations the possibility exists of operating in frame-based (non-continuous) data readout mode. The Timepix3 chip is planned for production in the beginning of 2012

GridPix detectors: production and beam test results

The innovative GridPix detector is a Time Projection Chamber (TPC) that is read out with a Timepix-1 pixel chip. By using wafer post-processing techniques an aluminium grid is placed on top of the chip. When operated, the electric field between the grid and the chip is sufficient to create electron induced avalanches which are detected by the pixels. The time-to-digital converter (TDC) records the drift time enabling the reconstruction of high precision 3D track segments. Recently GridPixes were produced on full wafer scale, to meet the demand for more reliable and cheaper devices in large quantities. In a recent beam test the contribution of both diffusion and time walk to the spatial and angular resolutions of a GridPix detector with a 1.2 mm drift gap are studied in detail. In addition long term tests show that in a significant fraction of the chips the protection layer successfully quenches discharges, preventing harm to the chip