Showing papers by "Peter Fischer published in 2019"

Characterization of TOF-PET detectors for a second generation radiofrequency-penetrable PET insert for simultaneous PET/MRI

Abstract: Simultaneous PET/MRI combines two powerful and complementary modalities, providing multiparametric information to assess the anatomic as well as biochemical basis of disease. However, the high cost of the current commercial integrated PET/MRI systems limit the long-term potential, accessibility, and availability of PET/MRI. A portable PET insert provides a cost- effective alternative to achieve simultaneous PET/MRI for the sites that are already equipped with MR systems. Therefore, we are developing a radiofrequency (RF)-penetrable MR-compatible time-of-flight (TOF)-PET insert that can acquire simultaneous PET/MR data using the MR systems built-in body coil for RF transmission. In this study, we characterized performance of two detector modules in the MR bore under four different MRI conditions: B 0 only, echo planar imaging (EPI), gradient echo (GRE), and fast spin echo (FSE), each running for 15 minutes. The one-hour study results for coincidence timing resolution, energy resolution, coincidence count rate and ASIC chip temperature of two detector modules demonstrate the PET performance stability as well as the MR compatibility of the PET detectors under different MRI sequences. The global coincidence timing and energy resolution achieved was 264.21 ± 4.82 ps FWHM and 13.66 ± 0.08 % FWHM, respectively.

Charge Sensitive Amplifier With Offset-Compensated V-to-I Converter for the Mini-SDD-Based DSSC Detector

Abstract: In this article, we present the study and the experimental results of a charge sensitive amplifier (CSA) for the mini-silicon drift detector (SDD) pixel sensors of the DEPleted Field-Effect Transistor (DEPFET) sensor with signal compression (DSSC) detector for photon science applications at the European X-ray free electron laser (XFEL) GmbH in Hamburg area. The DSSC detector must be able to cope with an image frame rate up to 4.5 MHz and with a dynamic range up to 104 photons/pixel/pulse for a photon energy of 1 keV. These goals will be pursued with the adoption of the DEPFET detector strategy. For the first camera prototype, a simpler solution based on a mini-SDD array read out by a conventional CSA has been adopted. We present here the CSA solution with a very simple V-to-I converter stage, which allows the self-canceling of the offset current flowing between the CSA and the filter, without the need of an intermediate stage. The CSA is compatible with the same application-specified integrated circuit (ASIC) architecture and readout chain already designed for the DEPFET detector. We present two versions of the CSA: one with a linear response and another with a nonlinear output characteristic. The nonlinear version provides increased input dynamic range preserving single-photon sensitivity. The experimental measurements have demonstrated the functionality of the proposed self-canceling solution and good noise performance with an equivalent noise charge (ENC) of 65 e- rms at the 4.5-MHz frame rate and a linearity error lower than 0.25% of the complete channel. In addition, the functionality of the nonlinear version (signal compression version) of the CSA has been demonstrated, without penalty in noise performance in the linear region of the CSA response.

Qualification and Integration Aspects of the DSSC Mega-Pixel X-Ray Imager

Abstract: The focal-plane module is the key component of the DEPFET sensor with signal compression (DSSC) mega-pixel X-ray imager and handles the data of 128 $\times512$ pixels We report on assembly-related aspects, discuss the experimental investigation of bonding behavior of different adhesives, and present the metrology and electrical test results of the production The module consists of two silicon (Si) sensors with flip-chip connected CMOS integrated circuits, a Si-heat spreader, a low-temperature co-fired ceramics circuit board, and a molybdenum frame A low-modulus urethane-film adhesive fills the gaps between on-board components and frame It is also used between board and heat spreader, reduces the misfit strain, and minimizes the module warpage very efficiently The heat spreader reduces the on-board temperature gradient by about one order of magnitude The placement precision of the bare modules to each other and the frame is characterized by a standard deviation below 10 and 65 $\mu \text{m}$ , respectively The displacement due to the in-plane rotation and vertical tilting errors remains below 80 and 50 $\mu \text{m}$ , respectively The deflection of the sensor plane shows a mean value below 30 $\mu \text{m}$ with a standard deviation below 15 $\mu \text{m}$ Less than 4% of the application-specified integrated circuits (ASICs) exhibit a malfunction More than two-thirds of the sensors have a maximum leakage current below 1 $\mu \text{A}$