U. Trunk

Combinatorial Synthesis of Peptide Arrays onto a Microchip

Arrays promise to advance biology through parallel screening for binding partners. We show the combinatorial in situ synthesis of 40,000 peptide spots per square centimeter on a microchip. Our variant Merrifield synthesis immobilizes activated amino acids as monomers within particles, which are successively attracted by electric fields generated on each pixel electrode of the chip. With all different amino acids addressed, particles are melted at once to initiate coupling. Repetitive coupling cycles should allow for the translation of whole proteomes into arrays of overlapping peptides that could be used for proteome research and antibody profiling.

Performance of the HERA-B vertex detector system

Abstract The Vertex Detector System (VDS) of the HERA-B experiment is a forward microvertex detector integrated into the HERA proton storage ring at DESY. Double-sided silicon microstrip detectors mounted in Roman pots are operated at typically 1 cm distance from the beam in a LHC-like high radiation environment. This paper presents results from the commissioning of the VDS that show its performance to meet the specifications.

AGIPD, a high dynamic range fast detector for the European XFEL

AGIPD—(Adaptive Gain Integrating Pixel Detector) is a hybrid pixel X-ray detector developed by a collaboration between Deutsches Elektronen-Synchrotron (DESY), Paul-Scherrer-Institut (PSI), University of Hamburg and the University of Bonn. The detector is designed to comply with the requirements of the European XFEL. The radiation tolerant Application Specific Integrated Circuit (ASIC) is designed with the following highlights: high dynamic range, spanning from single photon sensitivity up to 104 12.5keV photons, achieved by the use of the dynamic gain switching technique using 3 possible gains of the charge sensitive preamplifier. In order to store the image data, the ASIC incorporates 352 analog memory cells per pixel, allowing also to store 3 voltage levels corresponding to the selected gain. It is operated in random-access mode at 4.5MHz frame rate. The data acquisition is done during the 99.4ms between the bunch trains. The AGIPD has a pixel area of 200× 200 μ m2 and a 500μ m thick silicon sensor is used. The architecture principles were proven in different experiments and the ASIC characterization was done with a series of development prototypes. The mechanical concept was developed in the close contact with the XFEL beamline scientists and is now being manufactured. A first single module system was successfully tested at APS.

First experience and results from the HERA-B vertex detector system

The HERA-B collaboration is building a detector to realize the ambitious goal of observing CP violation in decays of neutral B-mesons. A central element of the apparatus is the silicon vertex detector used to selectively trigger on these decays in a high charged particle multiplicity background environment and to reconstruct secondary vertices from such decays with high precision. The vertex detector, the supporting infrastructure and first results using prototype detectors are described. Results include imaging of the proton interaction region on the HERA-B target, hit distributions in the detector planes, and alignment of the detectors with each other and the target. ( 1998 Elsevier Science B.V. All rights reserved.

A low noise high dynamic range analog front-end ASIC for the AGIPD XFEL detector

In this paper we present a low noise high dynamic range analog front-end ASIC designed for the Adaptive Gain Integrating Pixel Detector (AGIPD) being developed for the European X-ray Free Electron Laser (XFEL) facility. The ASIC has 64 × 64 pixels with a pixel size of 200 × 200 μm2, and is bump bonded to a silicon sensor for X-ray imaging. Each pixel includes an adaptive gain charge integrating amplifier (AGCIA) and 352 analog storage cells. The gain of the AGCIA dynamically adapts to the number of photons arriving at the sensor in order to achieve a single photon resolution and a dynamic range of more than 104 12 keV photons. The XFEL bunch trains consist of up to 2700 bunches separated by 220 ns (600 us in total) followed by an idle time of 99.4 ms. The AGCIA operates in a 220 ns repeating cycle by storing images and the gain information into the pixel memory during the pulse train. The stored images are read out during the breaks of the bunch trains. Several prototypes are designed and fabricated in IBM 130 nm CMOS technology. The measurements showed an input equivalent noise charge (ENC) lower than 300 e- and a dynamic range of 7000 photons.

Performance tests of an AGIPD 0.4 assembly at the beamline P10 of PETRA III

The Adaptive Gain Integrating Pixel Detector (AGIPD) is a novel detector system, currently under development by a collaboration of DESY, the Paul Scherrer Institute in Switzerland, the University of Hamburg and the University of Bonn, and is primarily designed for use at the European XFEL. To verify key features of this detector, an AGIPD 0.4 test chip assembly was tested at the P10 beamline of the PETRA III synchrotron at DESY. The test chip successfully imaged both the direct synchrotron beam and single 7.05 keV photons at the same time, demonstrating the large dynamic range required for XFEL experiments. X-ray scattering measurements from a test sample agree with standard measurements and show the chips capability of observing dynamics at the microsecond time scale.

Status of the HERA-B vertex detector

Abstract The HERA-B experiment is a forward magnetic spectrometer with good particle identification for hadrons and leptons designed to study violation of CP symmetry in the neutral B meson system. The silicon vertex detector operates in a high-rate environment similar to the ones expected at LHC. In this paper we report on our R&D on strip detector design, frontend ASICs, mechanical and thermal engineering, low-mass RF shielding of the HERA proton beam and on the status of our reconstruction software. First experiences with last years installation are discussed.

Noncontact charge measurement of moving microparticles contacting dielectric surfaces

In this study examples for a noncontact procedure that allow the description of instant electric charging of moving microparticles that contact dielectric surfaces, for instance, of a flow hose are presented. The described principle is based on the measurement of induced currents in grounded metal wire probes, as moving particles pass close to the probe. The feasibility of the approach was tested with laser printer toner particles of a given size for different basic particle flow and charging conditions. An analytic description for the induced currents was developed and compared to observed effects in order to interpret the results qualitatively. The implementation of the presented procedure can be applied to transparent and nontransparent particle containers and flow lines of complex geometry which can be composed from the presented basic flow stream configurations.

The HERA-B vertex detector system

Abstract The HERA-B experiment is being built to measure CP violation in the B-system using internal targets at the HERA proton storage ring at DESY. This paper presents an overview of its vertex detector which – apart from an additional superlayer – is realized by a system of 20 Roman pots containing seven superlayers of double-sided silicon microstrip detectors that are operated at 10 mm distance from the proton beam in a high-radiation environment.

The Cosmic Ray Tracking (CRT) detector system

Abstract The Cosmic Ray Tracking (CRT) project represents a study on the use of tracking detectors of the time projection chamber type to detect secondary cosmic ray particles in extensive air showers. In reconstructing the arrival direction of the primary cosmic ray particles, the CRT detectors take advantage of the angular correlation of secondary particles with the cosmic rays leading to these air showers. In this paper, the detector hardware including the custom-designed electronics system is described in detail. A CRT detector module provides an active area of 2.5 m 2 and allows to measure track directions with a precision of 0.4°. It consists of two circular drift chambers of 1.8 m diameter with six sense wires each, and a 10cm thick iron plate between the two chambers. Each detector has a local electronics box with a readout, trigger, and monitoring system. The detectors can distinguish penetrating muons from other types of charged secondaries. A large detector array could be used to search for γ -ray point sources at energies above several TeV and for studies of the cosmic-ray composition. Ten detectors are in operation at the site of the HEGRA air shower array.