Search

Hadronic atoms being Coulomb-bound systems in which the electron is substituted by a hadron like a negatively charged K meson are perfect probes for the study of strong interaction at lowest energies using x-ray spectroscopy. New large area x-ray detectors (silicon drift detectors, SDDs) were developed to provide excellent energy resolution as well as timing capability. For the first time large area SDDs were employed to measure the L-lines of kaonic helium at high precision thus succeeding in clarifying a puzzle persisting for 30 years since the 70's. An array of about 200 even more sophisticated SDDs (1 [cm.sup.2] SDDs with monolithically integrated FET) will be used to perform precision measurements (i.e., at the eV level) of kaonic hydrogen and kaonic deuterium at the DAFNE [PHI] factory of LNF/Italy. The new x-ray detectors and their performance for precision experiments in the accelerator environment are presented. Index Terms--kaonic atoms, silicon drift detectors, strong interaction studies, X-ray spectroscopy.

The performance of a silicon drift detector (SDD) with an integrated FET, delivered by the company PNSensor, Munich, Germany, was studied in gamma spectrometry at room temperature (23-25[degrees]C) with a La[Br.sub.3]:Ce crystal of 6 mm diameter and 6 mm height. The SDD characteristics were compared with those measured with a Photonis XP5212 photomultiplier, a Large Area Avalanche Photodiode (LAAPD) of Advanced Photonix, Inc., and a Hamamatsu S3590-18 Photodiode (PD). Energy resolution versus gamma ray energies and its components related to the photoelectron/electron-hole pair statistics and dark noise were measured and compared. At low energies, below 100 keV, the light readout by the photomultiplier gives the best results, while for high energies, above 300 keV, the light readout by the SDD delivers superior energy resolution. In particular, the best energy resolution of 2.7 % was determined for 662 keV gamma rays from a [sup.137]Cs source. Index Terms--Avalanche photodiodes, energy resolution, La[Br.sub.3] scintillator, photomultipliers, pin photodiodes, silicon drift detectors.

Abstract: At the DAΦNE electron-positron collider of Laboratori Nazionali di Frascati we study kaonic atoms, taking advantage of the low-energy kaons produced in the Φ-meson decay. The low-energy kaon-nucleon interaction [...]

In this paper, the authors propose a gamma-ray spectrometer based on a La[Br.sub.3] :Ce scintillator coupled to a silicon drift detector (SDD). The SDD is a photodetector characterized by a very low noise thanks to the low value of output capacitance independent from the active area. With respect to a PMT, the SDD offers a higher quantum efficiency which reduces the spread associated to the statistic of photoelectrons generation. Also with respect to an APD, the SDD offers a lower photoelectrons statistic contribution, which, in the APD, is worsened by the excess noise factor with respect to pure Poisson statistics. Moreover, the SDD has a stable behavior, less sensitive to temperature and bias drift. In the past years, good energy resolutions were measured using a SDD coupled to a CsI:TI crystal. However, the long shaping time, to be used with this scintillator to prevent ballistic deficit, was too far to exploit the best noise performances achievable with a SDD obtained at shaping times in the order of 1 [micro]s. On the contrary, this optimum shaping time is fully compatible with the short decay time of the La[Br.sub.3] :Ce crystal (about 25 ns). The results of the experimental characterization of the La[Br.sub.3] :Ce-SDD gamma-ray spectrometer are presented in this work and are compared with the performances achieved with the same crystal coupled to a PMT and to a CsI(TI) crystal coupled to the same SDD. The SDD has an active area of 30 [mm.sup.2]. Antireflective coatings have been implemented. Good energy resolutions were measured at room temperature, thanks to the low leakage current of the detector: 2.7% at the [sup.137]Cs 661.7 KeV line and 6.1% at the [sup.57]Co 122 KeV line. A resolution of 5.7% at 122 KeV line was measured at 0[degrees]C. Index Terms--Gamma-ray spectroscopy, La[Br.sub.3], silicon drift detectors.

A monolithic X- and gamma-ray detector based on a silicon drift detector coupled to a CsI(Tl) scintillator is presented. The detector is operated both as a direct X-ray detector for photons interacting in silicon and as an indirect detector for photons interacting in the scintillator. As interactions in silicon and in CsI yield different amount of charge per unit energy deposited, discrimination of the place of interaction is necessary to obtain the correct energy. Discrimination of the interaction type is carried out by means of pulse shape discrimination performed with two parallel processing chains with different shaping times. In this paper an extensive characterization of the detector with temperature is presented. It is shown that cooling the detector at 10 [degrees]C allows to obtain a nearly 100% efficiency between 8 and 200 keV. Further cooling below 0 [degrees]C allows pulse shape discrimination with 100% accuracy throughout the detector's energy range. The detector has also been tested with X-rays at various energies by means of a tunable X-ray facility. These tests allowed an investigation of the light yield nonproportionality in CsI(Tl) at low energies, necessary for a proper energy calibration of the detector. Index Terms--Gamma-ray detectors, pulse shape discrimination, scintillation detectors, silicon drift detectors, X-ray detectors.

Monolithic arrays of Silicon Drift Detectors (SDDs) have been employed successfully in X-ray spectroscopy and [gamma]-ray imaging applications. Thanks to the low electronics noise achieved at short shaping time, the SDD is an ideal device for high-resolution and high-rate X-ray spectroscopy experiments at synchrotron sources. Moreover, small monolithic arrays of SDDs have also been used as photodetector of the scintillation light in a first prototype of Anger Camera for [gamma]-ray imaging characterized by an intrinsic resolution better than 0.3 mm. In this work we present a new large-area monolithic array of Silicon Drift Detectors. It consists of a single chip composed by 77 single hexagonal units, each one with a front-end JFET integrated in its center, arranged in a honeycomb configuration. Each SDD unit has an active area of 8.7 [mm.sup.2], for a total active area of the device of 6.7 [cm.sup.2]. The linear dimensions of the active area are approximately 29 x 26 [mm.sup.2]. It represents the largest monolithic array of SDDs with on-chip JFETs produced up to now for X-ray and [gamma]-ray detection. The results achieved in the experimental characterization of a first prototype of the detector array are presented. They include also the preliminary X-ray spectroscopy characterization of the SDD's units. The energy resolution measured at 6 keV with the single unit of the array is of 142 eV at -10 [degrees]C. Index Terms--Gamma-ray imaging, silicon drift detectors, X-ray spectroscopy.

DEPFET pixel detectors are unique devices in terms of energy and spatial resolution because very low noise operation can be obtained (ENC = [2.2e.sup.-] at room temperature) by implementing the amplifying transistor in the pixel cell itself. Full DEPFET pixel matrices have been built and operated for autoradiographical imaging with imaging resolutions of 4.3 [+ or -] 0.8 [micro]m at 22 keV. For applications in low energy X-ray astronomy the high energy resolution of DEPFET detectors is attractive. For partide physics, DEPFET pixels are interesting as low mass detectors with high spatial resolution. For a linear collider detector the readout must be very fast. New readout chips have been designed and produced for the development of a DEPFET module for a pixel detector at the proposed TESLA collider, containing 520 x 4000 pixels, with 50 MHz line rate and 25 kHz frame rate. The circuitry contains current memory cells and current hit scanners for fast pedestal subtraction and sparsified readout. The imaging performance of DEPFET devices as well as present achievements toward a DEPFET vertex detector for a linear collider are presented. Index Terms--DEPFET, medical imaging, pixel detector, silicon detector.

This paper describes an innovative X-ray fluorescence spectrometer designed to achieve high-energy resolution, position resolution, and detection rate in elemental mapping applications. The spectrometer is based on a ring-shaped monolithic array of silicon drift detectors (SDDs) with a hole cut in its center. A coaxial X-ray excitation beam is transported to the sample through this hole. In this way, the solid angle for the collection of the X-ray fluorescence is optimized. Moreover, the X-ray beam is collimated on the sample using capillary optics in order to obtain high photon density in a small excitation spot. Detector, optics, and generator are assembled in a compact vacuum tightened unit. The structure of the proposed spectrometer and the first experimental results of its characterization are presented. Index Terms--Elemental mapping, silicon drift detectors, X-ray optics, XRF, X-ray spectrometry.

In this work, the preliminary results obtained with a high position resolution gamma-ray imaging detector are presented. The detector consists of a single CsI(TI) scintillator crystal optically coupled to a monolithic array of 19 silicon drift detectors (SDDs) used as photodetectors. In this array, having a total sensitive area of about 1 [cm.sup.2], each SDD has a front-end JFET directly integrated on the detector chip, close to the collecting anode. This architecture reduces the electronic noise of each single photodetector to a value small enough to obtain a submillimeter position resolution at 122 keV gamma-ray energy. The present detector module represents the development of a previous prototype based on a very limited numbers of SDDs. Index Terms--Gamma-ray imaging, scintillators, silicon drift detectors.

X-ray sensitive CCDs with outstanding properties have been developed and produced at the MPI Halbleiterlabor. They contribute to the focal plane instrumentation of two space missions: the European XMM and the German ABR, IXAS satellites. These CCDs, presented here, use exclusively ph-junctions on ultra-pure, high-ohmic silicon for all active components, in particular for the transfer electrodes and the on-chip readout circuitry. Full depletion of the detector chip, a homogeneous and thin entrance window and large pixel sizes can be realized by this technological concept. This concept results in low noise performance, spectroscopic energy resolution, high detection efficiency, radiation hardness and fast readout. With these properties the so-called pn-CCDs ideally match the requirements of the satellites, which are given by the specifics of their X-ray imaging optics as well as the intensity, energy range and dynamic behavior of the objects to be observed.

Byline: C. von Zanthier (1), H. Brauninger (2), K. Dennerl (2), R. Hartmann (2), G. Hartner (2), H. Hippmann (2), A. Kaltenberger (2), E. Kastelic (2), W. Kink (2), N. Krause (2), N. Meidinger (2), G. Metzner (2), E. Pfeffermann (2), M. Popp (2), C. Reppin (2), J. Riedl (2), D. Stotter (2), L. Struder (2), J. Trumper (2), W. Weber (2), D. Carathanassis (3), S. Engelhard (3), Th. Gebhart (3), D. Hauff (3), G. Lutz (3), R. H. Richter (3), H. Seitz (3), P. Solc (3), E. Biehler (4), H. Bottcher (3,4), E. Kendziorra (4,5), J. Kramer (4,5), B. Pfluger (4,5), R. Staubert (4,5), P. Holl (5), J. Kemmer (3), P. Lechner (5), B. Maier (5), H. Soltau (5), R. Stotter (5), E. Bihler (5) Abstract: This paper describes the performance of the Fully Depleted pn-junction CCD (pn-CCD) system, developed for ESA's XMM-satellite mission for soft x-ray imaging and spectroscopy in the single photon counting mode in the 100 eV to 10 keV photon range. The 58 mm x 60 mm large pn-CCD array, designed and fabricated at the Semiconductor Lab (Halbleiterlabor) of the Max-Planck-Institut, uses pn-junctions for registers and as backside structure. This concept naturally enables full depletion of the detector volume independent of the silicon wafer's resistivity and thickness, and as such make it an efficient detector for the x-ray region and the infrared. For high detection efficiency in the soft x-ray region and UV, an ultrathin pn-CCD backside deadlayer has been realized. Each pn-CCD-channel is equipped with its own on-chip JFET amplifier which, in combination with the CAMEX-amplifier and multiplexing chip, facilitates parallel readout and fast data rate: the cooled pn-CCD system can be read out at a data rate up to 3 MHz with an electronic noise floor of ENC &lt 5 e-. Author Affiliation: (1) KETEK GmbH, Am Isarbach 30, D - 85764, Oberschlei[beta]heim, Germany (2) Max-Planck -, Institut fur extraterrestische Physik, Gie[beta]enbachstr., D-85740, Garching, Germany (3) Max-Planck -Institut fur Physik, Fohringer Ring 6, D - 80805, Munchen, Germany (4) Institut fur Astronomie und, Astrophysik der Universitat Tubingen, Waldhauser Str. 64, D - 72076, Tubingen, Germany (5) Institut fur Astronomie und, Astrophysik der Universitat Tubingen, Waldhauser Stra[beta] 64, D - 72076, Tubingen, Germany Article History: Registration Date: 05/10/2004

A proposal for an international standard, 'To Determine the Thermal Performance of Uncovered Collectors,' is presented. Test particulars as the measurement of the longwave radiation and the characterization of the wind field determining the convective losses of the absorber surface are discussed, both for indoor and outdoor conditions. The model includes testing under unsteady conditions. A comparison with alternate test approaches is performed. Experimental results are presented.