Design of Front End Electronics and a Full Scale 4k Pixel Readout ASIC for the DSSC X-ray Detector at the European XFEL

The goal of this thesis was to design a large scale readout ASIC for the 1-Mega pixel DEPFET Sensor with Signal Compression (DSSC) detector system which is being developed by an international collaboration for the European XFEL (EuXFEL). Requirements for the DSSC detector include single photon detection down to 0.5 keV combined with a large dynamic range of up to 10000 photons at frame rates of up to 4.5 MHz. The detector core concepts include full parallel readout, signal compression on the sensor or ASIC level, filtering, immediate digitization and local storage within the pixel. The DSSC is a hybrid pixel detector, each sensor pixel mates to a dedicated ASIC pixel, which includes the entire specified signal processing chain along with auxiliary circuits. One ASIC comprises 4096 pixels and a full periphery including biasing and digital control. This thesis presents the design of the ASIC, its components and integration are decribed in detail. Emphasis is put on the design of the analog front-end. The first full format ASIC (F1) has been fabricated within the scope of this thesis along with numerous test chips. Furthermore, the EuXFEL and the DSSC detector system are presented to create the context for the ASIC, which is the core topic of this thesis

Photon shot-noise limited transient absorption soft X-ray spectroscopy at the European XFEL

Femtosecond transient soft X-ray Absorption Spectroscopy (XAS) is a very promising technique that can be employed at X-ray Free Electron Lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here we present a dedicated setup for soft X-rays available at the Spectroscopy & Coherent Scattering (SCS) instrument at the European X-ray Free Electron Laser (EuXFEL). It consists of a beam-splitting off-axis zone plate (BOZ) used in transmission to create three copies of the incoming beam, which are used to measure the transmitted intensity through the excited and unexcited sample, as well as to monitor the incoming intensity. Since these three intensity signals are detected shot-by-shot and simultaneously, this setup allows normalized shot-by-shot analysis of the transmission. For photon detection, the DSSC imaging detector, which is capable of recording up to 800 images at 4.5 MHz frame rate during the FEL burst, is employed and allows approaching the photon shot-noise limit. We review the setup and its capabilities, as well as the online and offline analysis tools provided to users.Comment: 11 figure

Hydrochemical Characterization of Groundwaters’ Fluid Flow through the Upper Mesozoic Carbonate Geothermal Reservoirs in the Geneva Basin: An Evolution more than 15,000 Years Long

Groundwaters circulating in Upper Mesozoic carbonates are of great interest for geother‐ mal heat production and storage applications in the Geneva area. This study aims at providing new insights and proposing new interpretations about the mineral‐water reactions and the fluid‐flow paths mechanisms across the Geneva Basin (GB). Data from previous studies are combined and improved by new ones collected from cold and hot springs and geothermal exploration wells in 2018 and 2020 in the framework of the GEothermies program and HEATSTORE project. Major ions, trace elements, and the isotopes of Oxygen, Hydrogen, Sulfur, Strontium, and Carbo have been analysed and the results show that the sampled waters have a meteoric origin, the carbonate aqui‐ fers act as preferential host rocks for geothermal waters, and partial contribution from the Cenozoic sediments can be observed in some samples. The Jura Mountains and the Saleve Ridge are the main catchment areas and an evolution from a pure Ca‐HCO3 footprint for the cold springs, to a Na > Ca‐ HCO3 and a Na‐Cl composutions, is observed at the two geothermal wells. The residence time is in the order of a few years for the cold springs and reaches up to 15–20,000 years for the deep wells

A 64-by-64 pixel-ADC matrix

An 8-bit 5-MS/s Wilkinson-type analog-to-digital converter (ADC) cell has been designed for parallel in-pixel digitization in a 64-by-64 pixel readout ASIC. Due to its simplicity, low power consumption, and small area requirement this type of ADC is suitable for pixel-level implementations. 720-ps time stamps are generated globally by means of 8-bit Gray-code counters. They are distributed column-wise to the pixel blocks together with a conversion-start signal along 13-mm long transmission lines. The analog input voltage is sampled-and-held on a capacitor. A pixel-internal current source is used to generate a voltage ramp. The conversion into a digital word is done when the ramp voltage equals the reference voltage, and the corresponding time stamp is latched. The ASIC is fabricated in IBM's 130-nm CMOS technology. The pixel-wise gain trimming properties provide a homogeneous gain distribution. Full matrix measurements demonstrate the achievement of a signal-to-noise ratio of 70 dB when all 4096 ADCs are working simultaneously. 75 % of the pixels show DNL better than 0.4 LSB, and the INL remains within ± 0.5 LSB for 99% of the pixels. The area and power dissipation of the in-pixel ADC amounts to 100 × 120 μm2 and 150 μW at 1.2-V power supply, respectively

A 64k pixel CMOS-DEPFET module for the soft X-rays DSSC imager operating at MHz-frame rates

The 64k pixel DEPFET module is the key sensitive component of the DEPFET Sensor with Signal Compression (DSSC), a large area 2D hybrid detector for capturing and measuring soft X-rays at the European XFEL. The final 1-megapixel camera has to detect photons with energies between 250eV and 6keV , and must provide a peak frame rate of 4.5MHz to cope with the unique bunch structure of the European XFEL. This work summarizes the functionalities and properties of the first modules assembled with full-format CMOS-DEPFET arrays, featuring 512×128 hexagonally-shaped pixels with a side length of 136 μm. The pixel sensors utilize the DEPFET technology to realize an extremely low input capacitance for excellent energy resolution and, at the same time, an intrinsic capability of signal compression without any gain switching. Each pixel of the readout ASIC includes a DEPFET-bias current cancellation circuitry, a trapezoidal-shaping filter, a 9-bit ADC and a 800-word long digital memory. The trimming, calibration and final characterization were performed in a laboratory test-bench at DESY. All detector features are assessed at 18°C . An outstanding equivalent noise charge of 9.8 e−rms is achieved at 1.1-MHz frame rate and gain of 26.8 Analog-to-Digital Unit per keV (ADU/keV). At 4.5MHz and 3.1ADU/keV , a noise of 25.5 e−rms and a dynamic range of 26ke- are obtained. The highest dynamic range of 1.345Me- is reached at 2.25MHz and 1.6ADU/keV . These values can fulfill the specification of the DSSC projec

A 64k pixel CMOS-DEPFET module for the soft X-rays DSSC imager operating at MHz-frame rates

The 64k pixel DEPFET module is the key sensitive component of the DEPFET Sensor with Signal Compression (DSSC), a large area 2D hybrid detector for capturing and measuring soft X-rays at the European XFEL. The final 1-megapixel camera has to detect photons with energies between 250eV and 6keV, and must provide a peak frame rate of 4.5MHz to cope with the unique bunch structure of the European XFEL. This work summarizes the functionalities and properties of the first modules assembled with full-format CMOS-DEPFET arrays, featuring 512×128 hexagonally-shaped pixels with a side length of 136 μm. The pixel sensors utilize the DEPFET technology to realize an extremely low input capacitance for excellent energy resolution and, at the same time, an intrinsic capability of signal compression without any gain switching. Each pixel of the readout ASIC includes a DEPFET-bias current cancellation circuitry, a trapezoidal-shaping filter, a 9-bit ADC and a 800-word long digital memory. The trimming, calibration and final characterization were performed in a laboratory test-bench at DESY. All detector features are assessed at 18°C. An outstanding equivalent noise charge of 9.8 e⁻rms is achieved at 1.1-MHz frame rate and gain of 26.8 Analog-to-Digital Unit per keV (ADU/keV). At 4.5MHz and 3.1 ADU/keV, a noise of 25.5 e⁻rms and a dynamic range of 26 ke⁻ are obtained. The highest dynamic range of 1.345 Me⁻ is reached at 2.25 MHz and 1.6 ADU/keV. These values can fulfill the specification of the DSSC project

First operation of a DSSC hybrid 2D Soft X-ray imager with 4.5 MHz frame rate

The DSSC (DEPFET Sensor with Signal Compression) collaboration develops a hybrid pixelated X-Ray photon detector with 4.5 MHz frame rate and immediate amplitude digitization for experiments at the European XFEL. We present the first full format 14.9Ã\u9714 mm2F1 pixel readout ASIC for the DSSC detector. The readout architecture is specially adapted to the burst structure of the XFEL (bursts of 2880 pulses spaced by down to 220 ns at a rate of 10 Hz) by in-pixel digitization and digital hit data storage and data transfer during the burst gaps. The readout ASIC contains 64Ã\u9764 pixels of 229Ã\u97204 μm2size and includes per pixel two low noise front-end versions for DEPFET and silicon drift detectors (SDD), a single-slope 8-bit ADC and local memory. Measurements using the F1 ASIC and a matching mini-SDD sensor matrix are shown

The DSSC Pixel Readout ASIC with Amplitude Digitization and Local Storage for DEPFET Sensor Matrices at the European XFEL

The DSSC (DEPFET Sensor with Signal Compression) consortium develops a 1MPixel detector for low energy X-rays at the European XFEL. The XFEL will produce 10 bursts per second, each containing 2880 X-ray pulses with a repetition rate of 4.5 MHz. X-ray photons of 0.5 − 6 keV are absorbed in hexagonal DEPFET pixels of 229x204 um^2 pitch with a nonlinear characteristic to achieve a high dynamic range. The sensors will be bump bonded to readout ASICs of 64x64 pixels. Each pixel contains a filter with trapezoidal weighting function, a single slope ADC of 8-9 Bit resolution and a digital memory to store 640 events. A veto mechanism allows to discard uninteresting events. The digital hit data is read out serially during the ≈ 100 ms long burst gaps. Prototype matrix chips of 8x8 pixels with the full functionality have been produced and characterized electronically and with DEPFET sensors. The architecture and the design of the 8x8 ASIC, measured results and an outlook to the large 64x64 pixel chip will be presented

The interplay of local electron correlations and ultrafast spin dynamics in fcc Ni

The complex electronic structure of metallic ferromagnets is determined by a balance between exchange interaction, electron hopping leading to band formation, and local Coulomb repulsion. By combining high energy and temporal resolution in femtosecond time-resolved X-ray absorption spectroscopy with ab initio time-dependent density functional theory we analyze the electronic structure in fcc Ni on the time scale of these interactions in a pump-probe experiment. We distinguish transient broadening and energy shifts in the absorption spectra, which we demonstrate to be captured by electron repopulation respectively correlation-induced modifications of the electronic structure, requiring to take the local Coulomb interaction into account.ISSN:2166-383

Photon-shot-noise-limited transient absorption soft X-ray spectroscopy at the European XFEL

Femtosecond transient soft X-ray absorption spectroscopy (XAS) is a very promising technique that can be employed at X-ray free-electron lasers (FELs) to investigate out-of-equilibrium dynamics for material and energy research. Here, a dedicated setup for soft X-rays available at the Spectroscopy and Coherent Scattering (SCS) instrument at the European X-ray Free-Electron Laser (European XFEL) is presented. It consists of a beam-splitting off-axis zone plate (BOZ) used in transmission to create three copies of the incoming beam, which are used to measure the transmitted intensity through the excited and unexcited sample, as well as to monitor the incoming intensity. Since these three intensity signals are detected shot by shot and simultaneously, this setup allows normalized shot-by-shot analysis of the transmission. For photon detection, an imaging detector capable of recording up to 800 images at 4.5 MHz frame rate during the FEL burst is employed, and allows a photon-shot-noise-limited sensitivity to be approached. The setup and its capabilities are reviewed as well as the online and offline analysis tools provided to users.ISSN:0909-0495ISSN:1600-577