K. Hansen

Deutsches Elektronen-Synchrotron, Hamburg, Hamburg, Germany

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Publications (35)20.3 Total impact

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    ABSTRACT: The DSSC (DEPFET Sensor with Signal Compression) consortium develops a IMPixel 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 229 × 204 μm2 pitch with a nonlinear characteristic to achieve a high dynamic range. The sensors will be bump bonded to readout ASICs of 64 × 64 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 8 × 8 pixels with the full functionality have been produced and characterized electronically and with DEPFET sensors. The architecture and the design of the 8 × 8 ASIC, measured results and an outlook to the large 64 × 64 pixel chip will be presented.
    Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE; 01/2012
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    ABSTRACT: The DSSC (DEPFET Sensor with Signal Compression) is a new instrument with non-linear compression of the input signal in the sensor and with parallel signal processing (filtering, linear amplification, and digitization) for all pixels. The DSSC will serve as 2d imaging detector at the European X-ray Free Electron Laser (XFEL.EU) currently under construction in Hamburg, Germany. The DSSC design goal is to achieve at the same time single photon detection and high dynamic range of about 104 photons, both for photon energies down to 0.5 keY and read-out speeds up to 4.5 MHz. Realization of this goal requires an accurate calibration of the non-linear system response (NLSR) over the full dynamic range of the detector. We present our strategy for calibrating the NLSR, for each of the 1024 × 1024 DSSC pixels, in the laboratory. The feasibility of our calibration strategy is demonstrated experimentally by calibrating the NLSR of a DSSC prototype set-up consisting of a prototype DEPFET sensor with non-linear signal compression connected to a prototype read-out ASIC.
    Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC), 2012 IEEE; 01/2012
  • K. Hansen · C. Reckleben · I. Diehl · M. Bach · P. Kalavakuru
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    ABSTRACT: A pixel-level 8-bit 5-MS/s digitizer for the DSSC X-ray imager utilizing the method of Wilkinson is presented. The timing information is generated column-wise by means of an 8-bit Gray-code counter. The 625-ps time stamps are distributed to the column pixels through 13-mm long shielded coplanar waveguides. Pixel-internal blocks comprise a sample-and-hold stage with current source for ramp generation, a temperature-compensated and supply voltage-stabilized reference circuitry, a comparator, a bank of eight receivers with latches for the time stamps, and control logic. These pixel-internal and global devices in 130-nm CMOS technology occupy 0.015 and 0.012 mm2, respectively. The power consumption amounts to at 1.2-V supply voltage. Taking the 0.8-V dynamic range into account, the simulated rms-noise voltage of about corresponds to a signal-to-noise ratio above 70 dB. The differential and integral nonlinearity is expected to remain below 0.4 LSB and 1 LSB, respectively. All results promise the compliance with underlying requirements.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 02/2011; 629(1-629):269-276. DOI:10.1016/j.nima.2010.11.104 · 1.32 Impact Factor
  • C. Reckleben · K. Hansen · P. Kalavakuru · I. Diehl
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    ABSTRACT: A single-slope 8-bit 5-MS/s Wilkinson-type analog-to-digital converter for the DSSC mega-pixel X-ray imager was designed. Due to its simplicity, low power consumption, and small area requirement this type of ADC is suitable for pixel-level implementations. 625-ps time stamps are generated globally by means of an 8-bit Gray-code counter. 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 final readout chip will be a 64-by-64 pixel matrix. The chip prototype comprises an 8-by-8 ADC matrix representing a single 64-pixel column of the final matrix. It is fabricated in the IBM 8M1P 130-nm CMOS technology. Linearity, noise, and temperature- dependent effects are evaluated. Measurements demonstrate the achievement of a signal-to-noise ratio of 67 dB, a mean DNL of less than 0.3 LSB, and an INL below 0.5 LSB for the 5-MHz sampling rate. The area and power dissipation of the ADC's pixel circuitry amounts to 0.0139 mm2 and 634 µW, respectively. The global blocks require an area of 0.0143 mm2, and consume a mean power of 3.07 mW.
    01/2011; DOI:10.1109/NSSMIC.2011.6153987
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    ABSTRACT: The DSSC (DEPFET Sensor with Signal Compression) is a new instrument with non-linear compression of the input signal in the sensor and with parallel signal processing (filtering, linear amplification, and digitization) for all pixels. The design goal is to achieve at the same time single photon detection and high dynamic range, both for photon energies down to 0.5 keV and read-out speeds up to 4.5 MHz. Realization of this goal requires an accurate calibration of the non-linear system gain (NLSG), i.e. of the non-linear dependence of the digital DSSC output signal on the input signal charge generated by incident photons, over the full dynamic range of the detector. We present an overview of our basic strategy for calibrating the NLSG. The feasibility of our calibration strategy is demonstrated using our system simulation package, which is briefly described. Finally, we demonstrate the DSSC capabilities by simulating the measurement of a T4 virus diffraction image as recorded at the Linac Coherent Light Source.
    01/2011; DOI:10.1109/NSSMIC.2011.6153648
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    ABSTRACT: The DSSC collaboration is developing an instrument for the detection of synchrotron X-rays (E >; 0.5 keV) at XFEL. The hexagonal pixels of a DEPFET based sensor with integrated signal compression will be read out by bump-bonded pixel readout ASICs. Each ASIC will have 64 × 64 pixel channels of 236 × 204 μm<sup>2</sup> area, each one containing a low-noise (<; 50 e<sup>-</sup>) amplification of the DEPFET signal, an 8 bit single-slope ADC and a digital memory, as well as other blocks for test injection, gain switching and trimming. Data is acquired during the XFEL burst at a rate of up to 4.5 MHz. The signal is first processed by a trapezoidal shaping filter, digitized immediately and then stored to the in-pixel memory of >; 512 events capacity. The accumulated digital data is transferred off chip during the 100 ms long burst gaps on a single serial link while the analogue sections are shut down to bring the average power dissipation to <; 100 mW per ASIC. The chip architecture is described and results obtained from first test chips are presented.
    Nuclear Science Symposium Conference Record (NSS/MIC), 2010 IEEE; 12/2010
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    ABSTRACT: The new DSSC (DEPFET sensor with signal compression) detector system is being developed in order to fulfil the requirements of the future XFEL in Hamburg. The instrument will be able to record X-ray images with a maximum frame rate of 5 MHz and to achieve a high dynamic range. The system is based on a silicon pixel sensor with a new designed non-linear-DEPFET as a central amplifier structure. The detector chip is bump-bonded to mixed signal readout ASICs that provide full parallel readout and temporary data storage. The signals coming from the detector are processed by an analog filter, immediately digitized by 8-ENOB ADCs and locally stored in a custom designed memory. The ASICs are designed in 130 nm CMOS technology. During the time gap of 99 ms of the XFEL machine, the digital data are sent off the focal plane to a DAQ electronics that acts as an interface to the back-end of the whole instrument. The pixel sensor has been designed so as to combine high energy resolution at low signal charge with high dynamic range. This has been motivated by the desire to be able to be sensitive to single low energy photons and, at the same time, to measure at other positions of the detector signals corresponding to up to 104 photons of 1 keV. In order to fit this dynamic range into a reasonable output signal swing, achieving at the same time single photon resolution, a strongly non-linear characteristic is required. The new proposed DEPFET provides the required dynamic range compression at the sensor level, considerably facilitating the task of the electronics. At the same time the DEPFET charge handling capacitance is enormously increased with respect to standard DEPFETs. The sensor matrix will comprise 1024×1024 pixels of hexagonal shape with a side-length of . The simultaneous implementation of the 5 MHz frame rate, of the single low-energy photon resolution and of the high dynamic range goes beyond all the existing instruments and requires the development of new concepts and technologies.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 12/2010; 624(2-624):509-519. DOI:10.1016/j.nima.2010.02.254 · 1.32 Impact Factor
  • K. Hansen · M. Randall · S. Schleitzer · C. Gutt
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    ABSTRACT: A system-level model of a low-noise high-speed mega-pixel camera with gain compression for X-ray photon correlation spectroscopy experiments at the European XFEL is presented. The model comprises the full signal chain from the sensor element via amplifier/filter and digitizer to the memory. The influence of gain- and offset errors as well as noise on the experiment-relevant image fidelity and intensity correlation function is discussed and compensation techniques are developed. A case study demonstrates the achievable efficiency of the chosen system parameters.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 02/2010; 613(2-613):323-333. DOI:10.1016/j.nima.2009.11.056 · 1.32 Impact Factor
  • K. Hansen · C. Reckleben · I. Diehl · H. Klär
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    ABSTRACT: A new Si-drift detector module for fast X-ray spectroscopy experiments was developed and realized. The Peltier-cooled module comprises a sensor with 7×7-mm2 active area, an integrated circuit for amplification, shaping and detection, storage, and derandomized readout of signal pulses in parallel, and amplifiers for line driving. The compactness and hexagonal shape of the module with a wrench size of 16 mm allow very short distances to the specimen and multi-module arrangements. The power dissipation is 186 mW. At a shaper peaking time of 190 ns and an integration time of 450 ns an electronic rms noise of ∼11 electrons was achieved. When operated at , FWHM line widths around 260 and 460 eV (Cu-Kα) were obtained at low rates and at sum-count rates of 1.7 MHz, respectively. The peak shift is below 1% for a broad range of count rates. At 1.7-MHz sum-count rate the throughput loss amounts to 30%.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 05/2008; 589(2-589):250-258. DOI:10.1016/j.nima.2008.02.010 · 1.32 Impact Factor
  • K. Hansen · C. Reckleben · I. Diehl · E. Welter
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    ABSTRACT: Ten detector modules based on monolithic 7-cell Si-drift detectors with integrated junction field effect transistors (JFETs) are currently under production. The modules’ hexagonal shape with a wrench size of 16 mm allows very small distances to the samples and a compact multi-module arrangement. The sensors have active areas of and a thickness of . A proper spectroscopy operation of all modules was obtained by five common supply voltages and a 6th voltage which must be individually adopted. Detector capacitances varied from 83 to 145 fF, where statistical spreading caused by device mismatch amounts to 0.4%. On-chip scattering of the JFET's transconductance and source potential in a source-follower configuration are around 1%. Their spreading caused by process variations and device mismatch remain below 8%. Typical spectral resolution and non-linearity is about 300 eV and below 1% between 4.5 and 18 keV, respectively. After irradiation with a total dose of the resolution decreases by ∼40%. By shielding the cell borders and JFETs from direct irradiation with usage of a Zr mask, a spectral peak-to-valley ratio of ∼1000 was achieved.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2008; 585(1-2-585):76-82. DOI:10.1016/j.nima.2007.11.007 · 1.32 Impact Factor
  • C. Reckleben · K Hansen · I. Diehl · H. Klar · E. Welter
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    ABSTRACT: A compact detector module based on Si-drift detectors with integrated junction-field effect transistors has been developed. It has been set up for X-ray absorption spectroscopy and X-ray standing-wave technique, and is usable in vacuum environment. The modules' hexagonal shape with a wrench size of 16 mm allows small distances to the samples and a compact multi-module arrangement. The monolithic 7-cell sensor has an active area of ~50 mm<sup>2</sup> and a thickness of 450 mum. It provides a spectral resolution of some hundred eV in the soft X-ray regime at room temperature. A fully differential 7-channel BiCMOS readout chip has been developed to process the detector signals at a power dissipation of 15 mW per channel. First spectral measurements with energies up to 43 keV have been performed with the prototype module. A rate-dependent energy-peak shift remains below 3% at integral photon- count rates of more than 6 Mcts/s. The deviation from the linear regression is within plusmn2% in the energy range between 6 and 20 keV. The on-chip gain variations are below 3.4%.
    Nuclear Science Symposium Conference Record, 2007. NSS '07. IEEE; 01/2007
  • K. Hansen · C. Reckleben
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    ABSTRACT: We report on the temperature and count-rate dependent noise behavior of an Si-drift detector system using an on-sensor integrated JFET in a source-follower configuration. The readout chain of a 0.8-μm BiCMOS chip consists of a fully differential low-noise postamplifier, current-mode shaper with gated integrator, and analog storage cell. Six channels are processed in parallel using a 6 : 1 multiplexer buffered by a 100-Ω line driver. The readout chain's power dissipation is ∼15 mW/channel. The indexes for parallel, serial, and 1/f noise of the time-variant signal processor are calculated using weighting functions. For a detector capacitance of ∼140 fF and low count rates, the chip's and total electronics' input-referred equivalent noise charge is about 20 and 23 rms electrons, respectively. Due to an almost quadratical increase of the noise indexes with increasing count rate, the signal current deteriorates so that the spectral resolution of a Cu-K<sub>α</sub>-emission line at 20°C decreases from ∼300 eV (full-width at half-maximum) at low count rates to ∼850 eV at 600 kilocounts per second. The investigation of the temperature-dependent leakage current for different detectors leads to current densities between 1.5 pA/mm<sup>2</sup> and 3 pA/mm<sup>2</sup> at 20°C. The simulated and experimental data verify the theoretical results for a wide range of count rates and sensor temperatures.
    IEEE Transactions on Nuclear Science 01/2005; DOI:10.1109/TNS.2004.839369 · 1.46 Impact Factor
  • K. Hansen · C. Reckleben
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    ABSTRACT: We report on the spectral peak-shift behavior of a Si-drift detector with integrated JFET operated in a source follower configuration. The experimental results are based on the measurements of the JFET's source voltage in the time domain and the analysis of the corresponding multiline X-ray fluorescence spectra. The transient measurements confirm a slew-rate limited decay of the source voltage pulses, which is attributed to the I-V characteristic of the JFET's gate-to-channel junction. We found that the slew rate depends linearly on the product of the center of energy and the count rate. Transient analysis of SDD/JFET circuit model and a new BiCMOS readout chip show a baseline shift, which is directly proportional to the slew rate and responsible for the peak shift. Considering the offset and gain of the subsequent spectroscopy system, the simulated peak positions agreed very closely with the results obtained from the measurements.
    IEEE Transactions on Nuclear Science 07/2004; DOI:10.1109/TNS.2004.829374 · 1.46 Impact Factor
  • K Hansen
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    ABSTRACT: In this paper, the static thermal behavior of a 61-cell silicon drift detector module is investigated. The influence of thermal conductivity of the case material on the heat flux inside the module is discussed by 3-D simulations. The use of graphite allows an operation with spatial inhomogenities of ⩽1°C in the case parts and leads to a sufficient low sensor temperature level. Experiments with a single-stage thermoelectric cooler and heat sink mounted on top of the module confirm that the temperature of the sensor and electronics as well as the case temperature depend linearly on their power dissipation. A set of equations considering the thermal coupling between sensor and electronics fully describe the dependence of their operating temperatures on sensor and electronics power dissipation, cooling power, and ambient temperature under forced convection. The simulated curves show a very good quantitative agreement with the measured characteristics. At a power dissipation level of , an ambient temperature of 22°C and air velocity of the sensor can be operated down to 13°C and 9°C with a cooling power of 2.8 and , respectively. Without cooling fan and cooling power the sensor temperature remains below 35°C.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2004; 517(1-3):254-263. DOI:10.1016/j.nima.2003.09.067 · 1.32 Impact Factor
  • K. Hansen · C. Reckleben
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    ABSTRACT: We report on the transient behavior of the charge-to-voltage conversion of a silicon drift detector with an integrated JFET in a source follower configuration, suitable for X-ray spectroscopy and imaging applications. The experimental results are based on the measurements of the JFET's source voltage in the time domain. The dependence on count rate up to 600 kcts/s and on photon energy up to 15.7 keV are presented at operating temperatures around 20°C. The charge collecting capacitance shunting the gate of the JFET is discharged by a continuous reset current, which is attributed to the I-V characteristic of the JFET's gate-to-channel junction. Its influence on the signal amplitude is discussed with respect to the voltage dependence of the charge-collecting capacitance. A set of analytical equations and an equivalent circuit fully describes the dependence of the mean source voltage, of the discharging current, and of the signal amplitude as a function of count rate and photon energy. The simulated responses show a good quantitative agreement with the measured characteristics.
    IEEE Transactions on Nuclear Science 11/2003; DOI:10.1109/TNS.2003.818268 · 1.46 Impact Factor
  • K. Hansen · M. Reinecke · H. Klar · M. Benca
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    ABSTRACT: A data acquisition system is presented for X-ray spectroscopic and imaging applications. It has the capability to process the signals of up to 120 silicon drift detector channels in parallel. The signal processing comprises a 12-bit digitization at 1 MSps per detector channel, an optical readout at 2.488 Gbit/s, and an online histogramming with a counting depth of 32 bits per energy class and channel. The user gains full system control and VMEbus-based data access by an additional bidirectional optical link and a commercial VME controller, respectively. The system's performance tests show that the integral nonlinearity and the rms noise do not exceed ±0.4 LSB and 0.58 LSB, respectively. The mean rms noise over all channels amounts to 0.55 LSB. The modular system's setup assures an upgradability to 1860 detector channels in steps of 120
    IEEE Transactions on Nuclear Science 05/2002; DOI:10.1109/TNS.2002.1003669 · 1.46 Impact Factor
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    ABSTRACT: Spatially resolved spectroscopic measurements with a 10 and 20μm pencil beam have been performed on a monolithic 7-element Silicon-Drift-Detector (SDD). Detailed studies are shown of the modification of the spectroscopic response at pixel edges and pixel centre. The results give quantitative insight into the local SDD performance. A simple model predicts global properties (e.g. peak-to-background ratio) of larger SDD arrays, like the 61-element detector currently under development.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 07/2001; 467:1163-1166. DOI:10.1016/S0168-9002(01)00586-1 · 1.32 Impact Factor
  • M. Reinecke · K. Hansen
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    ABSTRACT: We report on the performance of an optimized parallel channel coder for high-speed optical transmission systems. The coding properties are discussed by an evaluation of the signal statistics of the coded pulse train in the time and frequency domain. The discussion is mainly based on the results for the power spectral density (PSD) and the autocorrelation function (AKF). The theoretical investigations have been verified measurements with a developed 2.488 Gbit/s optical transmission system. Reliability studies have shown a system's bit error rate below 10<sup>-13</sup>
    Information Technology: Coding and Computing, 2001. Proceedings. International Conference on; 05/2001
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    ABSTRACT: Test measurements on the silicon pixel detector for the beam trajectory monitor at the free-electron laser of the TESLA test facility are presented. To determine the electronic noise of the detector and the read-out electronics and to calibrate the signal amplitude of different pixels, the 6 keV photons of the manganese Kα/Kβ line are used. Two different methods determine the spatial accuracy of the detector: in one setup a laser beam is focused to a straight line and moves across the pixel structure. In the other, the detector is scanned using a low-intensity electron beam of an electron microscope. Both methods show that the symmetry axis of the detector defines a straight line within . The sensitivity of the detector to low-energy X-rays is measured using a vacuum ultraviolet beam at the synchrotron light source HASYLAB. Additionally, the electron microscope is used to study the radiation hardness of the detector.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2000; DOI:10.1016/S0168-9002(00)00898-6 · 1.32 Impact Factor
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    ABSTRACT: In order to achieve the high brightness promised by the single-pass Free Electron Laser (FEL) at the TESLA Test Facility (TTF) at DESY, the electron beam position must be controlled better than 10 μm over a distance of 15 m. The design of a monitor system with this accuracy is described. The silicon pixel detector, which is critical to this monitor, must have a position resolution of m and an excellent sensitivity for soft X-rays above 150 eV. The silicon pixel detector and its readout electronics are also described.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/2000; 439(2-3-439):601-605. DOI:10.1016/S0168-9002(99)00911-0 · 1.32 Impact Factor