arXiv subjects

B. Hoffmann

Publications and source records attributed to B. Hoffmann.

7 recordsLinked to original sources

arXiv2010

Tube Width Fluctuations in F-Actin Solutions

We determine the statistics of the local tube width in F-actin solutions, beyond the usually reported mean value. Our experimental observations are explained by a segment fluid theory based on the binary collision approximation (BCA). In this systematic generalization of the standard mean-field approach effective polymer segments interact via a potential representing the topological constraints. The analytically predicted universal tube width distribution with a stretched tail is in good agreement with the data.

cond-mat.soft↗

arXiv2009

Direct observation of the tube model in F-actin solutions

Mutual uncrossability of polymers generates topological constraints on their conformations and dynamics, which are generally described using the tube model. We imaged confinement tubes for individual polymers within a F-actin solution by sampling over many successive micrographs of fluorescently labeled probe filaments. The resulting average tube width shows the predicted scaling behavior. Unexpectedly, we found an exponential distribution of tube curvatures which is attributed to transient entropic trapping in network void spaces.

cond-mat.soft↗

arXiv2003

CVcat: an interactive database on cataclysmic variables

CVcat is a database that contains published data on cataclysmic variables and related objects. Unlike in the existing online sources, the users are allowed to add data to the catalogue. The concept of an ``open catalogue'' approach is reviewed together with the experience from one year of public usage of CVcat. New concepts to be included in the upcoming AstroCat framework and the next CVcat implementation are presented. CVcat can be found at http://www.cvcat.org.

astro-ph↗

arXiv2000

The H1 Forward Proton Spectrometer at HERA

The forward proton spectrometer is part of the H1 detector at the HERA collider. Protons with energies above 500 GeV and polar angles below 1 mrad can be detected by this spectrometer. The main detector components are scintillating fiber detectors read out by position-sensitive photo-multipliers. These detectors are housed in so-called Roman Pots which allow them to be moved close to the circulating proton beam. Four Roman Pot stations are located at distances between 60 m and 90 m from the interaction point.

hep-ex↗

arXiv1998

Testrun results from prototype fiber detectors for high rate particle tracking

A fiber detector concept has been realized allowing to registrate particles within less than 100 nsec with a space point precision of about 0.1 mm at low occupancy. Three full size prototypes have been build by different producers and tested at a 3 GeV electron beam at DESY. After 3 m of light guides 8-10 photoelectrons were registrated by multichannel photomultipliers providing an efficiency of more than 99%. Using all available data a resolution of 0.086 mm was measured.

physics.ins-det↗

arXiv1998

Tests of a fiber detector concept for high rate particle tracking

A fiber detector concept is suggested allowing to registrate particles within less than 100 nsec with a space point precision of about 0.1 mm at low occuppancy. The fibers should be radiation hard for 1 Mrad/year. Corresponding prototypes have been build and tested at a 3 GeV electron beam at DESY. Preliminary results of these tests indicate that the design goal for the detector is reached.

physics.ins-det↗

arXiv1997

Development of scintillating fiber detector technology for high rate particle tracking

The performance of a scintillating fiber detector prototype for tracking under high rate conditions is investigated. A spatial resolution of about100 micron is aimed for the detector. Further demands are low occupancy and radiation hardness up to 1 Mrad/year. Fibers with different radii and different wavelengths of the scintillation light from different producers have been extensively tested concerning light output, attenuation length and radiation hardness, with and without coupling them to light guides of different length and diameter. In a testrun at a 3 GeV electron beam the space dependent efficiency and spatial resolution of fiber bundels were measured by means of two external reference detectors with a precision of 50 micron. The light output profile across fiber roads has been determined with the same accuracy. Different technologies were adopted for the construction of tracker modules consisting of 14 layers of 0.5 mm fibers and 0.7 mm pitch. A winding technology provides reliable results to produce later fiber modules of about 25 cm x 25 cm area. We conclude that on the basis of these results a fiber tracker for high rate conditions can be built.

hep-ex↗