In the past E. Lorenz has collaborated on articles with K. Thiel and H. Iglseder. One of their most recent publications is Phenomenology and dynamic behavior of the dust component in the KOSI experiments. Which was published in journal Planetary and Space Science.

More information about E. Lorenz research including statistics on their citations can be found on their Copernicus Academic profile page.

E. Lorenz's Articles: (21)

Phenomenology and dynamic behavior of the dust component in the KOSI experiments

AbstractThe KOSI (Kometensimulation) project (1987–1993) was intended as a series of multi-discipline experiments to investigate porous ice-dust mixtures under space conditions in view of a better understanding of comets. The present paper gives a synoptic summary of results obtained in the simulation experiments that are related particularly to the phenomenology and dynamic behavior of the dust component. Sample preparation was achieved by spraying aqueous suspensions of mineral powders (olivine, montmorillonite) into liquid nitrogen, which implies contact to liquid water. After sublimation of the ice both montmorillonite and olivine containing residues show a size dependence in porosity and mass density that is typical for fractal-like particles. The montmorillonite containing dust residues after artificial insolation were found to form coherent “tactoids” of high electrical conductivity. The decrease of the dust emission activity of fresh ice-dust mixtures with increasing time of insolation is explained by the formation of a volatile-depleted dust mantle that quenches further activity. The surface temperature was found to be directly related to the thickness of the ice-free dust cover and to the elevation angle of the light source above the local horizon. The surface topography of the sample after irradiation indicates the occurrence of local mantle displacements (“dust avalanches”) on inclined surfaces due to gas drag induced lifting and slipping down of parts of the dust cover. The local dust removal and deposition leads to the formation of valleys and ridges parallel to the gradient of inclimation. Similar features are expected to occur on cometary nuclei. Test particles of defined size and density were used to simulate meteoroid impact events on a developed dust mantle during insolation. The mean local surface temperature was found to drop immediately after impact by 1–7 K, depending on the total cross-section of the particles. A simultaneous enhancement of the gas emission was observed, the increase of the local gas flux density being anticorrelated to the surface temperature. Particle acceleration due to the enhanced gas drag was found to vary from <10 to 17 m s−2 depending on the particle size. Implications for impact induced phenomena on comets are discussed.

INEO—Imaging of near-Earth objects☆

AbstractINEO is a program of four explorer flyby missions for imaging near-Earth objects by means of small spin stabilized spacecrafts. A low-cost approach is achieved by using existing hardware and available scientific instrumentation. For the first mission the payload consists of the flight space model of the Halley multicolour camera and three Munich dust counters. The imaging instrument will determine the physical properties of the target. The dust environment of the asteroid or comet will be investigated with the dust detectors. For the follow-on missions different cameras and spectrometers and a magnetometer are proposed. In this paper the outline of INEO is presented which will either be launched as an auxiliary passenger on large launch systems, like ARIANE IV, or as the main payload on medium sized launch vehicles, like TAURUS, M-3S-II or CZ-1D, without changing the configuration of the space probe. First results of mission analysis will be presented.

Photodiode readout for scintillating crystals of BGO and Nal(Tl)

AbstractWe present first results using a photodiode readout for BGO and Nal(Tl) crystals. The measurements indicate that photodiodes might replace photomultiplier tubes in electromagnetic calorimetry. Using commercial photodiodes, a noise equivalent r.m.s. error of 1–2 MeV has been observed. Limitations and possible future improvements are discussed.

A concept for a hadron calorimeter with photodiode readout

AbstractA concept for a hadron calorimeter will be described. The calorimeter is a scintillator sandwich type with WLS-bars and photodiode readout. Emphasis is put on compactness, high stability, easy fabrication, and safety.

II. CalorimetryFast readout of plastic and crystal scintillators by avalanche photodiodes

AbstractAvalanche photodiodes (APDs) of improved quality and a sensitive area up to cm2 area are becoming commercially available now. In certain applications they can replace photomultipliers for fast readout of scintillation detectors. Expected performances will be discussed and some test measurements presented. Examples of possible applications will be given.

Search for isotropic γ radiation in the cosmological window between 65 and 200 TeV

AbstractElectromagnetic energy injected into the universe above a few hundred TeV is expected to pile up as γ radiation in a relatively narrow energy interval below 100 TeV due to its interaction with the 2.7°K background radiation. We present an upper limit (90% C.L.) on the ratio of primary γ to charged cosmic rays in the energy interval 65–160 TeV (80–200 TeV) of 10.3 · 10−3 (7.8 · 10−3). Data from the HEGRA cosmic-ray detector complex consisting of a wide angle Čerenkov array (AIROBICC) measuring the lateral distribution of air Čerenkov light and a scintillator array, were used with a novel method to discriminate γ-ray and hadron induced air showers. If the presently unmeasured universal far infrared background radiation is not too intense, the result rules out a topological-defect origin of ultrahigh energy cosmic rays for masses of the X particle released by the defects equal to or larger than about 1016 GeV.

A partial-wave analysis of the pp system produced at low four-momentum transfer in the reaction π−p→ppn at 18 GeV

AbstractResults of an analysis of two high-statistic samples of pp events (10 700 events at plab = 18.8 GeV and 35 000 events at plab = 18.4 GeV) are presented. The data extend from threshold to 2.8 GeV invariant mass. The production proceeds dominantly via one-pion exchange with absorption corrections. The mass spectrum and decay angular distribution can be explained as a superposition of resonating partial waves with spin J = 2, 3, 4, 5,. Indications of a spin-6 state at 2.71 GeV are found.

The MAGIC telescope project for gamma ray astronomy in the 15 to 300 GeV energy range

In gamma ray astronomy the energy range between 15 and 300 GeV is up to now inaccessible for both satellite borne γ detectors and ground based air Cerenkov telescopes. It is expected that in this energy range the universe is highly transparent and sources such as active galactic nuclei at red shifts of up to ≈2.8 can be observed. The detection of gamma ray bursts would allow one to place a limit on their distance. A short description of a project to build a new, high sensitivity, 17 mØ, air Cerenkov telescope, dubbed the MAGIC telescope, and an overview of its physics potential will be given. The telescope is based upon a 17 mØ decommissioned solar concentrator.

Separation of gamma and hadron initiated air showers with energies between 20 and 500 TeV

AbstractThe discrimination between air showers initiated by γ rays and by hadrons is one of the fundamental problems in experimental cosmic-ray physics. The physics of this ‘γ/hadron separation’ is discussed in this paper. We restrict ourselves to the energy range from about 20 to 500 TeV, and take only the information contained in the lateral Čerenkov light distribution and the number of electrons at the detector level into consideration. An understanding of the differences between air showers generated by γ rays and those due to hadrons leads us to formulate suitable observables for the separation process. Angle integrating Čerenkov arrays (AICA) offer a promising new approach to ground-based γ-ray astronomy in the energy region from about 20 to 500 TeV. In order to establish this technique, an efficient suppression of the overwhelming hadronic background radiation is required. As an example for our general discussion, we present one method for γ/hadron separation in AICAs called ‘LES’. It is based on the simultaneous determination of the shower size and some characteristic parameters of the lateral distribution of the Čerenkov light. The potential inherent within this technique is demonstrated in quantitative detail for the existing ‘AIROBICC’ AICA. We also propose an objective measure of the intrinsic sensitivity of a detection scheme in ground-based γ-ray astronomy, the ‘reduced quality factor’. It is shown that AICAs may reach a sensitivity to γ-ray point sources in the high VHE range similar to that of the Čerenkov-telescope imaging technique in the low VHE region.

Methods to determine the angular resolution of the HEGRA extended air shower scintillator array

AbstractA precise knowledge of the angular resolution of scintillator arrays used to observe extended air showers (EAS) is of key importance in the search for VHE/UHE γ point sources. Four independent methods have been used to determine the mean resolution for which a value of 〈ΔΘ63〉 of 0.8°(1.0°) at a proton threshold of 50 (40) TeV has been found for the HEGRA EAS-array.

Development and validation of a new method for accelerated and economic wear testing of tool materials for deep drawing applications

Highlights•A new quick and economical method for the simulation of tool wear in deep drawing.•Modified wear test device, with transfer possibility to other wear test systems.•Representation of test limits by the juxtaposition of different tool materials.

Comparative characterization of two galectins excreted-secreted from intestine-dwelling parasitic versus free-living females of the soil-transmitted nematode Strongyloides

Highlights•7 galectin genes were identified in in soil-transmitted intestinal nematode Strongyloides ratti, 4 are excreted/secreted from the parasite.•These 4 galectin genes are differentially expressed in Strongyloides stages.•Sr-Gal-3 of intestine-dwellimg parasitic females binds β-galactoside glycans, while Sr-Gal-1 of free-living females did not bind to the glycans.•Sr-Gal-3 and at low degree Sr-Gal-1 induced type 2 cytokines IL-22 and TSLP in 3D co-cultures of intestinal epithelial cells with dendritic cells.•Sr-Gal-1 and Sr-Gal-3 can promote cell migration of intestinal cells compatible with influencing wound healing process.

A fast, large dynamic range analog signal transfer system based on optical fibers

AbstractFor the project of the 17 m diameter MAGIC Telescope for GeV/TeV γ-astronomy an analog signal transfer system, based on optical fibers, has been developed. The system has a bandwidth of 250 MHz (-3 db) and is linear over 66 db and with some compression up to 80 db.

A new readout of large area smart photomultipliers by Geiger-mode APDs

AbstractFuture neutrino detectors require large, transparent detection volumes (water, ice, scintillator) and in turn a large number of large photomultipliers. We present a possible photon detector design based on the light amplification concept, e.g., a large, nearly spherical vacuum photon detector where the photoelectrons are accelerated onto a small scintillator. As secondary readout element Geiger-mode Avalanche photodiodes are used. Advantages and drawbacks of this readout will be discussed. Some results from initial studies will be presented.

Some studies for a development of a small animal PET based on LYSO crystals and Geiger mode-APDs

AbstractThe use of Geiger mode avalanche photodiodes (G-APD)/micro-cell APDs (MAPD) opens new simplifications in Positron Emission Tomography (PET) designs. We report on some test studies for a small animal PET based on LYSO crystals and G-APDs/MAPDs for readout. Emphasis is put on time and energy resolution.

First detection of Cherenkov light from cosmic-particle-induced air showers by Geiger-mode avalanche photodiodes

AbstractWe report on first tests of Geiger-mode APDs (G-APD) to detect Cherenkov light from cosmic particle induced air showers. The motivation for this study stems from the requirement to improve the sensitivity of large imaging atmospheric Cherenkov telescopes (IACT) by replacing the photomultipliers (PMT) by high detection efficiency G-APDs. Three tests have been carried out, confirming sufficiently high light sensitivity of blue-sensitive G-APDs as future replacement of PMTs in IACTs.

First detection of air shower Cherenkov light by Geigermode-Avalanche Photodiodes

AbstractGeigermode-Avalanche Photodiodes (G-APD) are novel solid state photon detectors with high photon detection efficiency (PDE). They are promising light sensors for very high energy (VHE) ground-based gamma-ray astronomy. We report about first tests to detect Cherenkov photons from cosmic ray air showers. Advantages and limitations of this new light sensor will be discussed.

Very high QE HPDs with a GaAsP photocathode for the MAGIC telescope project

AbstractHybrid photon detectors are one of the few low light level sensors that can provide an excellent single and multiple photoelectron amplitude resolution. The recently developed hybrid photon detectors for the Major Atmospheric Gamma-Imaging Cherenkov (MAGIC) telescope project with an 18-mm-diameter GaAsP photocathode (the Hamamatsu R9792U-40) have a peak quantum efficiency of more than 50% and a pulse width of ∼2.3ns. In addition, the afterpulsing rate of these tubes is ∼300 times lower compared to that of conventional photomultiplier tubes. Photocathode aging measurements showed lifetimes of more than 10 years under standard operating conditions of Cherenkov Telescopes. The temperature dependence of the avalanche gain can be reduced to the same level of a photomultiplier by a simple compensation circuit. Here we report on the recent progress with the above-mentioned hybrid photon detectors.

An evaluation of the new compact hybrid photodiodes R7110U-07/40 from Hamamatsu in high-speed light detection mode

AbstractThe main parameters of hybrid photodiodes (HPD) are constantly improving. In the new 20 mm ∅ HPDs from Hamamatsu an avalanche diode (AD) serves as anode. Due to high gain of the used ADs the HPDs show a total gain of 6−8×104 at nominal HV. This allows one to use HPDs with very fast low-noise voltage amplifiers and to detect fast pulses (down to the single photoelectron level) with very good amplitude resolution. Of special interest are HPDs of the type R7110U-40 with GaAsP photocathode which provide a quantum efficiency of ∼40% in maximum at ∼500 nm. Results on the evaluation of the above-mentioned HPDs and their comparison with HPDs from INTEVAC will be presented.

Invited talkVery high energy gamma ray astronomy

AbstractThe techniques, the status and prospects of very high energy (VHE) gamma ray astronomy with ground based telescopes will be reviewed

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