Optical suppression of tilt-to-length coupling in the LISA long-arm interferometer

The arm length and the isolation in space enable the Laser Interferometer Space Antenna (LISA) to probe for signals unattainable on the ground, opening a window to the subhertz gravitational-wave universe. The coupling of unavoidable angular spacecraft jitter into the longitudinal displacement measurement, an effect known as tilt-to-length (TTL) coupling, is critical for realizing the required sensitivity of picometer / √ Hz . An ultrastable interferometer test bed has been developed in order to investigate this issue and validate mitigation strategies in a setup representative of LISA and in this paper it is operated in the long-arm interferometer configuration. The test bed is fitted with a flat-top beam generator to simulate the beam received by a LISA spacecraft. We demonstrate a reduction of TTL coupling between this flat-top beam and a Gaussian reference beam via the introduction of two- and four-lens imaging systems. TTL coupling factors below ± 25 μ m / rad for beam tilts within ± 300 μ rad are obtained by careful optimization of the system. Moreover, we show that the additional TTL coupling due to lateral-alignment errors of elements of the imaging system can be compensated by introducing lateral shifts of the detector and vice versa. These findings help validate the suitability of this noise-reduction technique for the LISA long-arm interferometer

Reducing tilt-to-length coupling for the LISA test mass interferometer

Objects sensed by laser interferometers are usually not stable in position or orientation. This angular instability can lead to a coupling of angular tilt to apparent longitudinal displacement - tilt-to-length coupling (TTL). In LISA this is a potential noise source for both the test mass interferometer and the long-arm interferometer. We have experimentally investigated TTL coupling in a setup representative for the LISA test mass interferometer and used this system to characterise two different imaging systems (a two-lens design and a four-lens design) both designed to minimise TTL coupling. We show that both imaging systems meet the LISA requirement of ±25 μm rad-1 for interfering beams with relative angles of up to ±300 μrad. Furthermore, we found a dependency of the TTL coupling on beam properties such as the waist size and location, which we characterised both theoretically and experimentally. © 2018 IOP Publishing Ltd

Descrição anatômica da língua do mão-pelada (Procyon cancrivorus) Anatomical description of the crab-eating raccoon tongue - (Procyon cancrivorus)

O mão-pelada é um mamífero da família Procyonidae com poucas descrições anatômicas detalhadas a seu respeito. O objetivo deste trabalho foi descrever, anatomicamente, a língua do mão-pelada, proporcionando base para futuros estudos clínico-cirúrgicos, além de contribuir com a anatomia comparada de carnívoros. Foram utilizadas as línguas de dois exemplares de mãos-pelada, fixados em formaldeído a 10%. A língua do mão-pelada possui, em média, 9,5cm de comprimento, é alongada e apresenta um sulco mediano pouco evidente. Possui lissa, quatro pares de papilas valadas na raiz lingual e um par no corpo, várias papilas fungiformes e cônicas no corpo e raiz e papilas filiformes pouco desenvolvidas e presentes principalmente no ápice. Outros três pares de papilas, sugestivas de serem papilas valadas, foram observadas na região lateral da base lingual. A língua do mão-pelada possui algumas características anatômicas similares às do cão, como a presença da lissa e a disposição das papilas, com exceção das folhadas, as quais não foram observadas.<br>The crab-eating raccoon is a mammal of the Procyonidae family of rare anatomical descriptions about it. This paper aimed to anatomically describe the crab-eating raccoon's tongue, providing data on future clinical and surgical studies, besides contributing to the carnivores compared anatomy. Two tongues were used after formaldehyde fixation. Crab-eating raccoon's tongue is, in average, 9.5cm in length; it is elongated and with a less evident median sulcus. It presents lyssa, four pairs of vallate papillae in the root and one pair in the body, several fungiform and conical papillae in the body and root and less developed filiform papillae in the apex, mainly. Other three papillae pairs, taken as vallates, were observed in the lateral area of the tongue root. The crab-eating raccoon's tongue presents some anatomical aspects which are similar to the dog's, as the lyssa and the distribution of papilae, but foliates, which were not observed