Laser-interferometric dilatometry

Highly dimensionally stable materials and structures are particularly needed in optical systems such as ultra precise optical clocks, as well as materials with excellent dimensional stability and light weight properties for space applications such as telescopes, optical benches, and optical resonators. Also, the dimensional stability of mounting technologies of materials with different properties is of high interest for such applications. Glass ceramics and composite materials can be tuned to reach a very low coefficient of thermal expansion (CTE) at different temperatures, enabling best stability in the operating temperature for certain applications. In order to determine the CTE of such highly stable materials, very accurate set-ups are needed. In this thesis, metrology set-ups to measure the CTE of a large variety of material samples are designed, realized and verified, measuring dimensionally stable glass ceramics. The set-ups are able to characterize tube shaped samples at a temperature range of 140 K to 333 K. Due to our unique mirror mount design all kind of materials can be characterized. The optical dilatometer set-ups are based on a heterodyne interferometer with a displacement sensitivity at the sub-nanometer level. This instrument is used to measure the expansion of a sample when applying controlled small amplitude temperature signals. A carbon fiber reinforced polymer (CFRP) sample was characterized where CTE levels of 10 -8 K -1 from 140 K to 250 K were measured and a detailed uncertainty analysis was performed. The verified metrology set-up for tube shaped samples was adapted for CTE measurements of larger structures. Therefore, a large thermal chamber was set up and a 0.5 m CFRP spacer with Zerodur endfittings as a representative joint technology demonstrator for the GRACE Follow-On space mission at 302 K was investigated

Optomechanical resonator-enhanced atom interferometry

Matter-wave interferometry and spectroscopy of optomechanical resonators offer complementary advantages. Interferometry with cold atoms is employed for accurate and long-term stable measurements, yet it is challenged by its dynamic range and cyclic acquisition. Spectroscopy of optomechanical resonators features continuous signals with large dynamic range, however it is generally subject to drifts. In this work, we combine the advantages of both devices. Measuring the motion of a mirror and matter waves interferometrically with respect to a joint reference allows us to operate an atomic gravimeter in a seismically noisy environment otherwise inhibiting readout of its phase. Our method is applicable to a variety of quantum sensors and shows large potential for improvements of both elements by quantum engineering. © 2020, The Author(s)

Laserinterferometrische Dilatometrie

Highly dimensionally stable materials and structures are particularly needed in optical systems such as ultra precise optical clocks, as well as materials with excellent dimensional stability and light weight properties for space applications such as telescopes, optical benches, and optical resonators. Also, the dimensional stability of mounting technologies of materials with different properties is of high interest for such applications. Glass ceramics and composite materials can be tuned to reach a very low coefficient of thermal expansion (CTE) at different temperatures, enabling best stability in the operating temperature for certain applications. In order to determine the CTE of such highly stable materials, very accurate set-ups are needed. In this thesis, metrology set-ups to measure the CTE of a large variety of material samples are designed, realized and verified, measuring dimensionally stable glass ceramics. The set-ups are able to characterize tube shaped samples at a temperature range of 140 K to 333 K. Due to our unique mirror mount design all kind of materials can be characterized. The optical dilatometer set-ups are based on a heterodyne interferometer with a displacement sensitivity at the sub-nanometer level. This instrument is used to measure the expansion of a sample when applying controlled small amplitude temperature signals. A carbon fiber reinforced polymer (CFRP) sample was characterized where CTE levels of 10 -8 K -1 from 140 K to 250 K were measured and a detailed uncertainty analysis was performed. The verified metrology set-up for tube shaped samples was adapted for CTE measurements of larger structures. Therefore, a large thermal chamber was set up and a 0.5 m CFRP spacer with Zerodur endfittings as a representative joint technology demonstrator for the GRACE Follow-On space mission at 302 K was investigated

DIMENSIONAL STABILITY INVESTIGATION OF LOW CTE MATERIALS AT TEMPERATURES FROM 140 K TO 250 K USING A HETERODYNE INTERFEROMETER

Light weight materials with excellent dimensional stability are increasingly needed in space based applications such as telescopes, optical benches, and optical resonators. Glass-ceramics and composite materials can be tuned to reach very low coe�cient of thermal expansion (CTE) at certain temperatures, including room temperature and cryogenics, where a growing number of instruments in scienfic and earth observation space missions are operated. Very accurate setups are needed to determine the CTE of such materials. With our laser-interferometric dilatometer setup we are able to measure CTEs of a large variety of materials in the temperature range of 140 K to 250 K. Special mirror mounts with a thermally compensating design enable measurements of the expansion of cylindrical tube-shaped samples using a heterodyne interferometer with demonstrated noise levels in the order of 10 pm/pHz. The temperature variation of the sample is obtained by a two stage controlled heating/cooling setup where a pulse tube cooler and electric heaters apply small amplitude temperature signals to cool/heat the sample radiatively in order to reach a homogeneous temperature over the whole sample. A carbon �ber reinforced polymer (CFRP) sample was selected to run CTE measurements, achieving results in the 10^8 K^1 range including all known uncertainties. The limitations of our setup have been identi�ed and the largest uncertainty contribution has been determined to be tilt-to-length coupling of the sample due to temperature variations. Several improvements are currently underway to minimize our uncertainty budget. New results with the enhanced setup will be presente

Laser-interferometric dilatometry from 100 K to 325 K

To enable high precision optical measurements highly dimensionally stable materials are needed. Dimensional stability is an important material property describing the dependency of geometrical dimensions of an optical setup due to temperature fluctuations. Optical setups are often built with components made of glass-ceramics or composite materials which exhibit low coefficients of thermal expansion (CTE). These materials have to be characterized over the full operating temperature range to accurately predict the response of the optical system and the impact on its measurement performance. Our laser dilatometer setup is designed to characterize these low expansion materials in a temperature range from 100 K to 325 K, using a heterodyne laser interferometer to measure the dimensional changes of a sample due to well-controlled temperature variations. In this talk, we present the current status of our test facility, and recent improvements to decrease the uncertainty budget to levels of 10 ppb/K over the temperature range from 100 K to 325 K

First Middle East Aircraft Parabolic Flights for ISU Participant Experiments

Aircraft parabolic flights are widely used throughout the world to create microgravity environment for scientific and technology research, experiment rehearsal for space missions, and for astronaut training before space flights. As part of the Space Studies Program 2016 of the International Space University summer session at the Technion - Israel Institute of Technology, Haifa, Israel, a series of aircraft parabolic flights were organized with a glider in support of departmental activities on ‘Artificial and Micro-gravity’ within the Space Sciences Department. Five flights were organized with manoeuvres including several parabolas with 5 to 6 s of weightlessness, bank turns with acceleration up to 2 g and disorientation inducing manoeuvres. Four demonstration experiments and two experiments proposed by SSP16 participants were performed during the flights by on board operators. This paper reports on the microgravity experiments conducted during these parabolic flights, the first conducted in the Middle East for science and pedagogical experiments

Dilatometer Setup to Characterize Dimensionally Stable Materials by the Coefficient of Thermal Expansion at a Temperature Range from 100 K to 325 K

Space missions with the aim of high precision optical measurements are often limited by the dimensional stability of the instrument which can be exposed to high temperature fluctuations, due to the environment of the space probe. To minimize the change of the geometric dimension due to temperature changes, highly dimensionally stable materials are needed at the specific environmental temperatures. Materials like glass ceramics offer a minimal coefficient of thermal expansion (CTE) but they are also very heavy. Composite materials like CFRP or SiC offer also a very low CTE but with a lower weight and are more and more used for such applications. To characterize such low expansion materials we use a laser dilatometer with a heterodyne interferometer to measure length variations of the sample caused by an applied temperature variation. Using a cryocooler in combination with a heating system, we are able to determine CTEs at the 10 ppb/K level within a temperature range from 100 K to 325 K. In this talk, we present improvements of our setup and recent sample measurements

Laser-dilatometer calibration using a single-crystal silicon sample

Marginal changes in geometrical dimensions due to temperature changes affect the performance of optical instruments. Highly dimensionally stable materials can minimize these effects since they offer low coefficients of thermal expansion (CTE). Our dilatometer, based on heterodyne interferometry, is able to determine the CTE in range. Here, we present the improved interferometer performance using angular measurements via differential wavefront sensing to correct for tilt-to-length coupling. The setup was tested by measuring the CTE of a single-crystal silicon at 285 K. Results are in good agreement with the reported values and show a bias of less than 1%

Dilatometer setup for low coefficient of thermal expansion materials measurements in the 140 K-250 K temperature range

Space applications demand light weight materials with excellent dimensional stability for telescopes, optical benches, optical resonators, etc. Glass-ceramics and composite materials can be tuned to reach very low coefficient of thermal expansion (CTE) at different temperatures. In order to determine such CTEs, very accurate setups are needed. Here we present a dilatometer that is able to measure the CTE of a large variety of materials in the temperature range of 140 K to 250 K. The dilatometer is based on a heterodyne interferometer with nanometer noise levels to measure the expansion of a sample when applying small amplitude controlled temperature signals. In this article, the CTE of a carbon fiber reinforced polymer sample has been determined with an accuracy in the 10−8 K−1 range