High-resolution Silicon Drift Detectors Research Articles

Measurement of the radiative L3-M vacancy transfer probabilities of some 4f elements and compounds using Indus-2 synchrotron radiation

The L X-ray intensity ratios (ILα/ILl, ILα/ILβ, ILα/ILγ) and the radiative L3-M vacancy transfer probabilities (ηL3-M) of some 4f elements such as Gd, Tb, Ho and compounds; Pr2O3, Pr2(CO3)3·8H2O, Nd2O3, Sm2O3, Sm2(CO3)3·2.85H2O, Sm2(SO4)3·8H2O, Gd2(CO3)3, Tb2O3, Dy2(SO4)3, Ho2O3 and HoF3 have been measured using Indus-2 synchrotron radiation. The elements and compounds are excited by synchrotron radiation and the emitted characteristic L X-ray photons are measured with high resolution silicon drift detector. The measured intensity ratios of compounds are not influenced by the chemical environment. However, the ηL3-M values of compound targets indicate the effect of crystal structure.

Combining CdTe and Si detectors for Energy‐Dispersive X‐Ray Fluorescence

Most energy‐dispersive X‐ray fluorescence (EDXRF) instruments use Si diodes as X‐ray detectors. These provide very high energy resolution, but their sensitivity falls off at energies of 10–20 keV. They are well suited for measuring the K lines of elements with Z < 40, but for heavier elements, one must use K lines at low efficiency or use L or M lines that often overlap other lines. Either is a challenge for accurate quantitative analysis. CdTe detectors offer much higher efficiency at high energy but poorer energy resolution compared with Si diodes.In many important EDXRF measurements, both high and low Z elements are present. In this paper, we will compare the precision and accuracy of systems using the following: (1) a high resolution Si detector, (2) a high efficiency CdTe detector, and (3) a composite system using both detectors. We will show that CdTe detectors generally offer better analytical results than even a high resolution silicon drift detectors for K lines greater than 20 or 25 keV, whereas the high resolution Si detectors are much better at lower energies. We will also show the advantages of a combined system, using both detectors. Although a combined system would be more expensive, the increased accuracy, precision, and throughput will often outweigh the small increase in cost and complexity. The systems will be compared for representative applications that include both high and low Z elements. Copyright © 2012 John Wiley & Sons, Ltd.

Kaonic3He and4He measurements in the SIDDHARTA experiment at the DAΦNE collider

The SIDDHARTA collaboration measured kaonic 3 He and 4 He 3d → 2p X-rays with gaseous targets at the DAΦNE e + e − collider. The 2p -state strong-interaction shifts and widths were precisely determined by using 144 high-resolution silicon drift detectors. The shift of K −4 He is in good agreement with theoretical calculations and consistent with the recent experimental result of KEK-PS E570. The shift of K −3 He is also determined for the first time. The newly determined widths are in agreement with optical model calculations.

Design consideration of a multipinhole collimator with septa for ultra high-resolution silicon drift detector modules

The aim of this study was to design a multipinhole (MP) collimator with lead vertical septa coupled to a high-resolution detector module containing silicon drift detectors (SDDs) with an intrinsic resolution approaching the sub-millimeter level. Monte Carlo simulations were performed to determine pinhole parameters such as pinhole diameter, focal length, and number of pinholes. Effects of parallax error and collimator penetration were investigated for the new MP collimator design. The MP detector module was evaluated using reconstructed images of resolution and mathematical cardiac torso (MCAT) phantoms. In addition, the reduced angular sampling effect was investigated over 180°. The images were reconstructed using dedicated maximum likelihood expectation maximization (MLEM) algorithm. An MP collimator with 81-pinhole was designed with a 2-mm-diameter pinhole and a focal length of 40mm . Planar sensitivity and resolution obtained using the devised MP collimator were 3.9cps/μCi and 6mm full-width at half-maximum (FWHM) at a 10cm distance. The parallax error and penetration ratio were significantly improved using the proposed MP collimation design. The simulation results demonstrated that the proposed MP detector provided enlarged imaging field of view (FOV) and improved the angular sampling effect in resolution and MCAT phantom studies. Moreover, the novel design enables tomography images by simultaneously obtaining eight projections with eight-detector modules located along the 180° orbit surrounding a patient, which allows designing of a stationary cardiac SPECT. In conclusion, the MP collimator with lead vertical septa was designed to have comparable system resolution and sensitivity to those of the low-energy high-resolution (LEHR) collimator per detector. The system sensitivity with an eight-detector configuration would be four times higher than that with a standard dual-detector cardiac SPECT.

Hardware, Firmware and Software Architecture of the DAQ for High-Resolution Position-Sensing Silicon Drift Detectors With Multiple-Pulse Processing Capability

The aim of the present work is the development of the hardware, firmware and software architecture of a data acquisition (DAQ) system suitable for the readout of high-speed high-resolution silicon drift detectors and of controlled-drift detectors for spectroscopic imaging of X-rays. The novelty of the developed DAQ system is to be sensitive to multiple pulses present in the sampled waveform without loss in measurement resolution with respect to a single pulse algorithm. This feature is particularly important at high event rates as it would improve the detected rate and also avoid errors in the pulse measurements. A multi-maximum search algorithm has been developed and implemented in order to demonstrate the feasibility of this approach. The focus of the paper is on the description of the general architecture and on the full test of the DAQ chain in experimental conditions. The resolution of the measured amplitude and time-of-arrival has been evaluated in the case of two pulses per waveform, including the case of partially overlapping events. In the case of Poissonian occurrence of pulses we compared the main performance parameters of the developed multiple-pulse DAQ (case of n = 2 pulses) with respect to a single-pulse DAQ which confirmed the expected increase of the event throughput in good agreement with the theoretical expectations and showed no degradation of the measurement resolution.

High-speed low-noise 8 channel BiCMOS preamplifier for silicon drift detector readout

We present the design and the experimental characterization of a novel 8 channel monolithic front-end preamplifier in 0.8 μm BiCMOS technology developed for the readout of high resolution silicon drift detectors having an integrated JFET source-follower stage. The preamplifier chip includes the low-noise current generator required to bias the on-detector JFET. The preamplifier tests showed fast rise-time constant (3 ns), linearity error better than 0.1% and crosstalk between channels less than 0.14% at 100 ns shaping time. The preamplifier has been successfully tested both at room temperature and at low temperature down to −40 °C. The Equivalent Noise Charge contribution of the preamplifier chip at 250 ns shaping time is 3.8 electrons rms at room temperature and 2.8 electrons rms at −40 °C.

Si drift detector in comparison to Si(Li) detector for total reflection X-ray fluorescence analysis applications

TXRF is routinely used and suited to inspect Si wafer surfaces for possible impurities of metallic elements at the level of pg and below. Lightweight, compact sized, high-resolution Silicon drift detectors (FWHM=148 eV at 5.9 keV) electically cooled and with high throughput are ideally as the new spectrometer and for clean room application. A KETEK 5 mm 2 Si drift detector was compared with a NORAN 80 mm 2 SiLi in a previously commercially available ATOMIKA 8010 wafer analyzer. Results are presented and show that almost the same detection limits for both detector types were achieved analyzing a droplet sample containing 1 ng Ni on a Si wafer. Also, the performance to detect low Z elements like Na, excited with monochromatic Cr Kα radiation in a vacuum chamber was tested and detection limits of 600 pg obtained.

High Resolution Silicon Drift Detector Array Designed for XAFS Spectroscopy

We have analysed the performances of an array of 6 silicon drift detectors with on chip integrated JFET's for XAFS spectroscopy. The key advantage of these detectors is that they combine a very good energy resolution together with high counting rates: at 150 K the energy resolution was 139 eV FWHM at 5.89 keV with a 5 μs gaussian shaping time constant whereas it was still 152 eV FWHM for 0.5 μs time constant. Macrocyclic complexes of Ce (III) were used as test samples. We also explored whether or not the energy discrimination between the Lα, Lβ fluorescence lines could allow us to get rid the unwanted L n edge signature that is spoiling the L III edge EXAFS oscillations.