Punktfokussierende Heliostaten aus Hochleistungsbeton

aus dem Inhalt: „Die im Teilprojekt Mark/Schnell des SPP 1542 erbrachten Entwicklungen an Parabolrinnen (siehe S. 536 ff . des vorliegenden Buches) haben gezeigt, wie aussichtsreich die Verwendung von Feinkornbetonen für die Herstellung hochpräziser, formstabiler Bauteile ist [1], [2]. Die gewonnenen Erkenntnisse und die Nachfrage aus der Solartechnik ermutigen zur Übertragung auf verwandte Anwendungsgebiete, nämlich auf Heliostate [3] unter der Leitidee einer weitgehend industrialisierten Präzisionsfertigung. Wegen der extrem hohen Wiederholungszahl gleicher oder sehr ähnlicher Fertigteile sind Heliostate für den Betonfertigteilbau auch unter wirtschaftlichen Gesichtspunkten in nahezu idealer Weise geeignet....”from the content: „Recent developments on parabolic troughs (see p. 536 seq. of this book) in Mark/Schnell’s project of the SPP 1542 have shown that the use of finegrained concrete is a promising alternative for the manufacture of highly precise components with low deformations [1], [2]. Their findings and requests in solar technology have encouraged a transfer to related fields of application, namely to heliostats [3]. The guiding principle is broadly industrialized precision manufacturing. Due to an extremely high number of identical or utmost similar precast elements, heliostats seem to be ideally suited for precast concrete construction from an economic point of view....

Genotype–phenotype associations within the Li-Fraumeni spectrum: a report from the German Registry

Li-Fraumeni syndrome (LFS) is a cancer predisposition syndrome caused by pathogenic TP53 variants. The condition represents one of the most relevant genetic causes of cancer in children and adults due to its frequency and high cancer risk. The term Li-Fraumeni spectrum reflects the evolving phenotypic variability of the condition. Within this spectrum, patients who meet specific LFS criteria are diagnosed with LFS, while patients who do not meet these criteria are diagnosed with attenuated LFS. To explore genotype-phenotype correlations we analyzed 141 individuals from 94 families with pathogenic TP53 variants registered in the German Cancer Predisposition Syndrome Registry. Twenty-one (22%) families had attenuated LFS and 73 (78%) families met the criteria of LFS. NULL variants occurred in 32 (44%) families with LFS and in two (9.5%) families with attenuated LFS (P value < 0.01). Kato partially functional variants were present in 10 out of 53 (19%) families without childhood cancer except adrenocortical carcinoma (ACC) versus 0 out of 41 families with childhood cancer other than ACC alone (P value < 0.01). Our study suggests genotype-phenotype correlations encouraging further analyses

Optical testbed for the LISA phasemeter

The planned spaceborne gravitational wave detector LISA will allow the detection of gravitational waves at frequencies between 0.1 mHz and 1 Hz. A breadboard model for the metrology system aka the phasemeter was developed in the scope of an ESA technology development project by a collaboration between the Albert Einstein Institute, the Technical University of Denmark and the Danish industry partner Axcon Aps. It in particular provides the electronic readout of the main interferometer phases besides auxiliary functions. These include clock noise transfer, ADC pilot tone correction, inter-satellite ranging and data transfer. Besides in LISA, the phasemeter can also be applied in future satellite geodesy missions. Here we show the planning and advances in the implementation of an optical testbed for the full metrology chain. It is based on an ultra-stable hexagonal optical bench. This bench allows the generation of three unequal heterodyne beatnotes with a zero phase combination, thus providing the possibility to probe the phase readout for non-linearities in an optical three signal test. Additionally, the utilization of three independent phasemeters will allow the testing of the auxiliary functions. Once working, components can individually be replaced with flight-qualified hardware in this setup.DLR/50 OQ 1301Bundesministerium f¨ur Wirtschaft und Technologi

Picometer-Stable Hexagonal Optical Bench to Verify LISA Phase Extraction Linearity and Precision

The Laser Interferometer Space Antenna (LISA) and its metrology chain have to fulfill stringent performance requirements to enable the space-based detection of gravitational waves. This implies the necessity of performance verification methods. In particular, the extraction of the interferometric phase, implemented by a phasemeter, needs to be probed for linearity and phase noise contributions. This Letter reports on a hexagonal quasimonolithic optical bench implementing a three-signal test for this purpose. Its characterization as sufficiently stable down to picometer levels is presented as well as its usage for a benchmark phasemeter performance measurement under LISA conditions. These results make it a candidate for the core of a LISA metrology verification facility

Suppressing ghost beams: Backlink options for LISA

In this article we discuss possible design options for the optical phase reference system, the so called backlink, between two moving optical benches in a LISA satellite. The candidates are based on two approaches: Fiber backlinks, with additional features like mode cleaning cavities and Faraday isolators, and free beam backlinks with angle compensation techniques. We will indicate dedicated ghost beam mitigation strategies for the design options and we will point out critical aspects in case of an implementation in LISA. © Published under licence by IOP Publishing Ltd.DFG/SFB/1128Deutsches Zentrum für Luft- und Raumfahrt (DLR)Bundesministerium für Wirtschaft und Technologie/50 OQ 0601NASA/NNX15AC48

2⋅10−132\cdot 10^{-13} fractional laser frequency stability with a 7-cm unequal-arm Mach-Zehnder interferometer

To achieve sub-picometer sensitivities in the millihertz band, laser interferometric inertial sensors rely on some form of reduction of the laser frequency noise, typically by locking the laser to a stable frequency reference, such as the narrow-linewidth resonance of an ultra-stable optical cavity or an atomic or molecular transition. In this paper we report on a compact laser frequency stabilization technique based on an unequal-arm Mach-Zehnder interferometer that is sub-nanometer stable at $10\,\mu$Hz, sub-picometer at $0.5\,$mHz, and reaches a noise floor of $7\,\mathrm{fm}/\!\sqrt{\mathrm{Hz}}$ at 1 Hz. The interferometer is used in conjunction with a DC servo to stabilize the frequency of a laser down to a fractional instability below $4 \times 10^{-13}$ at averaging times from 0.1 to 100 seconds. The technique offers a wide operating range, does not rely on complex lock acquisition procedures, and can be readily integrated as part of the optical bench in future gravity missions.Comment: 9 pages, 7 figure

2×10-13 Fractional Laser-Frequency Stability with a 7-cm Unequal-Arm Mach-Zehnder Interferometer

To achieve subpicometer sensitivities in the millihertz band, laser interferometric inertial sensors rely on some form of reduction of the laser-frequency noise, typically by locking the laser to a stable frequency reference, such as the narrow-line-width resonance of an ultrastable optical cavity or an atomic or molecular transition. In this paper, we report on a compact laser-frequency stabilization technique based on an unequal-arm Mach-Zehnder interferometer that is subnanometer stable at 10μHz, subpicometer at 0.5 mHz, and reaches a noise floor of 7fm/Hz at 1 Hz. The interferometer is used in conjunction with a dc servo to stabilize the frequency of a laser down to a fractional instability below 4×10-13 at averaging times from 0.1 to 100 s. The technique offers a wide operating range, does not rely on complex lock-acquisition procedures, and can be readily integrated as part of the optical bench in future gravity missions