P. Bastia

ICARUS ASIC: a 16 channel photodiode read out system

In the framework of the INTEGRAL satellite, the second medium size mission of the ESA Horizon 2000 plus plan, it is required that the gamma ray detector of IBIS, one of the main on board instruments, exhibits position sensitive capabilities. This detector will be realised in two different planes covering different energy ranges. Although constructed with different technologies (Solid State and Scintillator detectors), both layers will be assembled using arrays of independent detectors (pixels) whose size will determine the spatial resolution of the instrument. In this approach each pixel needs its individual electronic chain able to process the charge delivered via a low noise charge amp and a shaping stage. Each chain will be completed with a trigger discriminator and peak and hold stage that will maintain the signal amplitude information locally for successive read out. To fulfil the constraints of space and power available for the project, these electronic chains can only be realised using ASIC technology. In this work the ICARUS ASIC used to read-out the signals delivered by PhotoDiodes (PD) employed in the high energy plane of the IBIS instrument is described and the first performance evaluation reported.

EURECA - A European-Japanese micro-calorimeter array

The EURECA (EURopean-JapanEse Calorimeter Array) project aims to demonstrate the science performance and technological readiness of an imaging X-ray spectrometer based on a micro-calorimeter array for application in future X-ray astronomy missions, like Constellation-X and XEUS. The prototype instrument consists of a 5 × 5 pixel array of TES-based micro-calorimeters read out by by two SQUID-amplifier channels using frequency-domain-multiplexing (FDM). The SQUID-amplifiers are linearized by digital base-band feedback. The detector array is cooled in a cryogenfree cryostat consisting of a pulse tube cooler and a two stage ADR. A European-Japanese consortium designs, fabricates, and tests this prototype instrument. This paper describes the instrument concept, and shows the design and status of the various sub-units, like the TES detector array, LC-filters, SQUID-amplifiers, AC-bias sources, digital electronics, etc. Initial tests of the system at the PTB beam line of the BESSY synchrotron showed stable performance and an X-ray energy resolution of 1.58 eV at 250 eV and 2.5 eV @ 5.9 keV for the read-out of one TES-pixel only. Next step is deployment of FDM to read-out the full array. Full performance demonstration is expected mid 2009.

An integrated reset / pulse pile-up rejection circuit for pixel readout ASIC's

We present a compact and low power integrated circuit designed to control the reset and performs the pulse pile-up rejection in multi-channel spectroscopic-grade ASICs. The circuit has been implemented in 0.35 mum CMOS technology with an area of 60times80 mum2 and null static power consumption. These features makes this circuit suitable to be embedded into the front-end readout cells for spectroscopy/imaging X and gamma ray pixel detectors.

The x-ray microcalorimeter spectrometer onboard of IXO

One of the instruments on the International X-ray Observatory (IXO), under study with NASA, ESA and JAXA, is the X-ray Microcalorimeter Spectrometer (XMS). This instrument, which will provide high spectral resolution images, is based on X-ray micro-calorimeters with Transition Edge Sensor thermometers. The pixels have metallic X-ray absorbers and are read-out by multiplexed SQUID electronics. The requirements for this instrument are demanding. In the central array (40 x 40 pixels) an energy resolution of < 2.5 eV is required, whereas the energy resolution of the outer array is more relaxed (≈ 10 eV) but the detection elements have to be a factor 16 larger in order to keep the number of read-out channels acceptable for a cryogenic instrument. Due to the large collection area of the IXO optics, the XMS instrument must be capable of processing high counting rates, while maintaining the spectral resolution and a low deadtime. In addition, an anti-coincidence detector is required to suppress the particle-induced background. In this paper we will summarize the instrument status and performance. We will describe the results of design studies for the focal plane assembly and the cooling systems. Also the system and its required spacecraft resources will be given.

The x-ray microcalorimeter spectrometer onboard Athena

One of the instruments on the Advanced Telescope for High-Energy Astrophysics (Athena) which was one of the three missions under study as one of the L-class missions of ESA, is the X-ray Microcalorimeter Spectrometer (XMS). This instrument, which will provide high-spectral resolution images, is based on X-ray micro-calorimeters with Transition Edge Sensor (TES) and absorbers that consist of metal and semi-metal layers and a multiplexed SQUID readout. The array (32 x 32 pixels) provides an energy resolution of < 3 eV. Due to the large collection area of the Athena optics, the XMS instrument must be capable of processing high counting rates, while maintaining the spectral resolution and a low deadtime. In addition, an anti-coincidence detector is required to suppress the particle-induced background. Compared to the requirements for the same instrument on IXO, the performance requirements have been relaxed to fit into the much more restricted boundary conditions of Athena. In this paper we illustrate some of the science achievable with the instrument. We describe the results of design studies for the focal plane assembly and the cooling systems. Also, the system and its required spacecraft resources will be given.

Position sensitive x- and gamma-ray scintillator detector for new space telescopes

The instruments on board the latest gamma observatories (INTEGRAL, SWIFT, AGILE, GLAST) combines technologies based on solid state and on scintillator detector, the first one being favorite when a low energy threshold and a good energy resolution is required, the latter being more convenient for large volume when worse performance are still acceptable. With the developments achieved both with the new scintillator material and even more with new low-noise light readout devices the differences between the two techniques are narrowing and for some application the cheaper scintillator detector can compete with solid state devices. Starting from the techniques used in INTEGRAL-IBIS and AGILE a new generation position sensitive X and gamma ray detector based on scintillator with Silicon Drift Chamber readout has been developed and tested. The ASIC read-out electronics make it suitable for replication in a large scale when a great number of pixel is needed. The performance of the detector as well as its applications in new generation space telescopes are presented and discussed.

Development of a TES based Cryo-Anticoincidence for a large array of microcalorimeters

The employment of large arrays of microcalorimeters in space missions (IXO, EDGE/XENIA)[1][2][3], requires the presence of an anticoincidence detector to remove the background due to the particles, with a rejection efficiency at least equal to Suzaku (98%) [1]. A new concept of anticoincidence is under development to match the very tight thermal requirements and to simplify the design of the electronic chain. The idea is to produce a Cryo‐AntiCoincidence (Cryo‐AC) based on a silicon absorber and read by a TES (Transition‐Edge Sensor). This configuration would ensure very good performances in terms of efficiency, time response and signal to noise ratio. We present the results of estimations, simulations and preliminary measurement.

Array of X and gamma ray scintillator detector for space gamma ray telescope application

The instruments on board the latest gamma observatories (INTEGRAL, AGILE, GLAST) combines technologies based either on solid state or on scintillator detector, the first one being favorite when a low energy threshold and a good energy resolution is required, the latter being more convenient for large volume when worse performance are still acceptable. With the development of new scintillator materials and even more with new low-noise ligth readout devices the differences between the two techniques are narrowing and for some application the cheaper scintillator detector can compete with solid state devices. Furthermore both these detector concepts can be combined in a single compact device by means of the Pulse Shape Discrimination (PSD) technique that allows to discriminate direct interactions in silicon from scintillation events. Combined in arrays they can be the base for position senstive planes to be combined with coded mask in imaging instruments or the component of new generation Compton based telescopes. For this purpose two prototype systems have been designed and realized, both based on a 20 channels Silicon Drift Detectors (SDD) monolithic array coupled to individual 1 cm thick CsI(Tl) scintillator crystals. In the first system the detector readout is implemented with ASICs tailored specifically to the SDD readout, while in the second system the PSD readout of the array is implemented. The performance of these kind of detectors tested in the various prototypes as well as their applications in new generation space telescopes are discussed.

The TES-based cryogenic anticoincidence detector for IXO: first results from large area prototypes

The technique which combines high resolution spectroscopy with imaging capability is a powerful tool to extract fundamental information in X-ray Astrophysics and Cosmology. TES (Transition Edge Sensors)-based microcalorimeters match at best the requirements for doing fine spectroscopy and imaging of both bright (high count rate) and faint (poor signal-to-noise ratio) sources. For this reason they are considered among the most promising detectors for the next high energy space missions and are being developed for use on the focal plane of the IXO (International X-ray Observatory) mission. In order to achieve the required signal-to-noise ratio for faint or diffuse sources it is necessary to reduce the particle-induced background by almost two orders of magnitude. This reduction can only be achieved by adopting an active anticoincidence technique. In this paper, we will present a novel anticoincidence detector based on a TES sensor developed for the IXO mission. The pulse duration and the large area of the IXO TESarray (XMS X-ray Microcalorimeter Spectrometer) require a proper design of the anticoincidence detector. It has to cover the full XMS area, yet delivering a fast response. We have therefore chosen to develop it in a four-pixel design. Experimental results from the large-area pixel prototypes will be discussed, also including design considerations.

A 32 × 32-Channels Chip for X-Ray Pixel Detector Read-Out

In this paper we present a spectrometer realized by bump-bonding a 300-μm-pitch, 32 × 32-pixel silicon X-ray detector chip to a 0.35-μm CMOS, 3-cm2 read-out chip. The selftriggered, mixed analog-digital read-out chip, with 1,024 channels, digitizes the X-ray photon energy with 10 bits of resolution, provides the coordinates of the triggered pixels and achieves 34 e- rms of input referred noise, ±3.3 LSB of INL and ±0.2 LSB of DNL, while consuming 555 mW from a 3.3-V supply. Preliminary experimental results on the complete spectrometer are reported.