H. Krueger

Counting and integrating readout for direct conversion X-ray imaging concept, realization and first prototype measurements

A novel signal processing concept for X-ray imaging with directly converting pixelated semiconductor sensors is presented. The novelty of this approach compared to existing concepts is the combination of charge integration and single photon counting in every single pixel. Simultaneous operation of both signal processing chains extends the dynamic range beyond the limits of the individual schemes and allows determination of the mean photon energy. Medical applications such as X-ray computed tomography can benefit from this additional spectral information through improved contrast and the ability to determine the hardening of the tube spectrum due to attenuation by the scanned object. A prototype chip in 0.35-micrometer technology was successfully tested. The pixel electronics are designed using a low-noise differential current mode logic and provide configurable feedback modes, leakage current compensation and various test circuits. This paper will discuss measurement results of the prototype structures and give details on the circuit design

An integrated Shunt-LDO regulator for serial powered systems

In this paper, a new type of regulator is proposed for integration in ASICs used in serially powered systems. In the serial powering scheme, modules are placed in series and fed by a constant current source to reduce the IR drop on the cables which increases powering efficiency. At the module level the needed supply voltages are generated redundantly out of the current supply by several parallel operating ASICs with integrated regulation circuitry. A Shunt-LDO regulator has been developed to allow robust and redundant regulator operation and the generation of different supply voltages by parallel placed devices. The Shunt-LDO regulator scheme combines the capability of Low Drop-Out regulators to generate a constant supply voltage with the feature of shunt regulators to assure a constant current flow through the device. The Shunt-LDO regulator has been developed for application in the framework of next generation hybrid pixel detectors used in high energy physics experiments. This circuit has been prototyped in a 130nm CMOS technology, capable of generating voltages in a range of 1.2-1.5V with a minimum drop out voltage of 200mV. The maximum shunt current is 500mA with a load regulation factor corresponding to an output impedance of 30mΩ.

AGIPD, a high dynamic range fast detector for the European XFEL

AGIPD—(Adaptive Gain Integrating Pixel Detector) is a hybrid pixel X-ray detector developed by a collaboration between Deutsches Elektronen-Synchrotron (DESY), Paul-Scherrer-Institut (PSI), University of Hamburg and the University of Bonn. The detector is designed to comply with the requirements of the European XFEL. The radiation tolerant Application Specific Integrated Circuit (ASIC) is designed with the following highlights: high dynamic range, spanning from single photon sensitivity up to 104 12.5keV photons, achieved by the use of the dynamic gain switching technique using 3 possible gains of the charge sensitive preamplifier. In order to store the image data, the ASIC incorporates 352 analog memory cells per pixel, allowing also to store 3 voltage levels corresponding to the selected gain. It is operated in random-access mode at 4.5MHz frame rate. The data acquisition is done during the 99.4ms between the bunch trains. The AGIPD has a pixel area of 200× 200 μ m2 and a 500μ m thick silicon sensor is used. The architecture principles were proven in different experiments and the ASIC characterization was done with a series of development prototypes. The mechanical concept was developed in the close contact with the XFEL beamline scientists and is now being manufactured. A first single module system was successfully tested at APS.

Charge collection properties of a depleted monolithic active pixel sensor using a HV-SOI process

New pixel detector concepts, based on commercial high voltage and/or high resistivity CMOS processes, are being investigated as a possible candidate to the inner and outer layers of the ATLAS Inner Tracker in the HL-LHC upgrade. A depleted monolithic active pixel sensor on thick film SOI technology is being extensively investigated for that purpose. This particular technology provides a double well structure, which shields the thin gate oxide transistors from the Buried Oxide (BOX). In addition, the distance between transistors and BOX is one order of magnitude bigger than conventional SOI technologies, making the technology promising against its main limitations, as radiation hardness or back gate effects. Its radiation hardness to Total Ionizing Dose (TID) and the absence of back gate effect up to 700 Mrad has been measured and published [1]. The process allows the use of high voltages (up to 300V) which are used to partially deplete the substrate. The process allows fabrication in higher resistivity, therefore a fully depleted substrate could be achieved after thinning. This article shows the results on charge collection properties of the silicon bulk below the BOX by different techniques, in a laboratory with radioactive sources and by edge Transient Current Technique, for unirradiated and irradiated samples.

AGIPD, the electronics for a high speed X-ray imager at the Eu-XFEL

The AGIPD (Adaptive Gain Integrated Pixel Detector) X-ray imaging camera will be operated at the X-ray Free Electron Laser, Eu-XFEL, under construction in Hamburg, Germany. Key parameters are 1 mil ...

Detector Developments at DESY

With the increased brilliance of state-of-the-art synchrotron radiation sources and the advent of free-electron lasers (FELs) enabling revolutionary science with EUV to X-ray photons comes an urgent need for suitable photon imaging detectors. Requirements include high frame rates, very large dynamic range, single-photon sensitivity with low probability of false positives and (multi)-megapixels. At DESY, one ongoing development project - in collaboration with RAL/STFC, Elettra Sincrotrone Trieste, Diamond, and Pohang Accelerator Laboratory - is the CMOS-based soft X-ray imager PERCIVAL. PERCIVAL is a monolithic active-pixel sensor back-thinned to access its primary energy range of 250 eV to 1 keV with target efficiencies above 90%. According to preliminary specifications, the roughly 10 cm × 10 cm, 3.5k × 3.7k monolithic sensor will operate at frame rates up to 120 Hz (commensurate with most FELs) and use multiple gains within 27 µm pixels to measure 1 to ∼100000 (500 eV) simultaneously arriving photons. DESY is also leading the development of the AGIPD, a high-speed detector based on hybrid pixel technology intended for use at the European XFEL. This system is being developed in collaboration with PSI, University of Hamburg, and University of Bonn. The AGIPD allows single-pulse imaging at 4.5 MHz frame rate into a 352-frame buffer, with a dynamic range allowing single-photon detection and detection of more than 10000 photons at 12.4 keV in the same image. Modules of 65k pixels each are configured to make up (multi)megapixel cameras. This review describes the AGIPD and the PERCIVAL concepts and systems, including some recent results and a summary of their current status. It also gives a short overview over other FEL-relevant developments where the Photon Science Detector Group at DESY is involved.

The adaptive gain integrating pixel detector

The adaptive gain integrating pixel detector (AGIPD) is a development of a collaboration between Deustsches Elektronen-Synchrotron (DESY), the Paul-Scherrer-Institute (PSI), the University of Hamburg and the University of Bonn. The detector is designed to cope with the demanding challenges of the European XFEL. Therefore it comes along with an adaptive gain stage allowing a high dynamic range, spanning from single photon sensitivity to 104 × 12.4 keV photons and 352 analogue memory cells per pixel. The aim of this report is to briefly explain the concepts of the AGIPD electronics and mechanics and then present recent experiments demonstrating the functionality of its key features.

Results of FE65-P2 Pixel Readout Test Chip for High Luminosity LHC Upgrades

A pixel readout test chip called FE65-P2 has been fabricated on 65 nm CMOS technology. FE65-P2 contains a matrix of 64 x 64 pixels on 50 micron by 50 micron pitch, designed to read out a bump bonded sensor. The goals of FE65-P2 are to demonstrate excellent analog performance isolated from digital activity well enough to achieve 500 electron stable threshold, be radiation hard to at least 500 Mrad, and prove the novel concept of isolated analog front ends embedded in a flat digital design, dubbed “analog islands in a digital sea”. Experience from FE65-P2 and hybrid assemblies will be applied to the design for a large format readout chip, called RD53A, to be produced in a wafer run in early 2017 by the RD53 collaboration. We review the case for 65 nm technology and report on threshold stability test results for the FE65-P2.

Front end ASIC for AGIPD, a high dynamic range fast detector for the European XFEL

The Adaptive Gain Integrating Pixel Detector (AGIPD) is a hybrid pixel X-ray detector for the European-XFEL. One of the detectors important parts is the radiation tolerant front end ASIC fulfilling the European-XFEL requirements: high dynamic range—from sensitivity to single 12.5keV-photons up to 104 photons. It is implemented using the dynamic gain switching technique with three possible gains of the charge sensitive preamplifier. Each pixel can store up to 352 images in memory operated in random-access mode at ≥4.5 MHz frame rate. An external vetoing may be applied to overwrite unwanted frames.

The AGIPD System for the European XFEL

The European XFEL will generate extremely brilliant pulses of X-rays organized in pulse trains consisting of 2700 pulses <100 fs long, with <1012 photons, and with a 220 ns spacing. The pulse trains are running at a 10Hz repetition rate. The detector to be used under these conditions will have to face several challenges: the dynamic range has to cover the detection of single photons and extend up to <104 photons/pixel/pulse in the same image, framing rates of 4.5 MHz (220 ns) are required in order to record one image per pulse, and as many images as possible have to be recorded during the pulse trains. Due to the high flux, the detector will have to withstand a dose up to 1GGy integrated over 3 years. To meet these challenges a consortium, consisting of Deutsches Elektronensynchrotron (DESY), Paul-Scherrer-Institut (PSI), University of Hamburg and University of Bonn, is developing the Adaptive Gain Integrating Pixel Detector (AGIPD). It is a hybrid-pixel detector, featuring a charge integrating amplifier with dynamic gain switching to cope with the extended dynamic range, and an analogue on-pixel memory for image storage at the required 4.5 MHz frame rate. The readout chip consists of 64×64 pixels of (200μm)2, 8×2 of these readout chips are bump-bonded to a monolithic silicon sensor to form the basic module with 512 × 128 pixels. 4 of these modules are stacked to form a quadrant of the 1k ×1k detector system. Each quadrant is independently moveable in order to adjust a central hole, needed for the direct beam to pass through. Special designs are employed for both the sensor and the readout chip to withstand the integrated dose for 3 years.