Akoestische holografie

Akoestische holografie is een geluidmeettechniek waarbij een ruimtelijk geluidveld wordt vastgelegd door geluiddruk op een vlak te meten. Deze techniek maakt gebruik van de uit de optiek bekende Rayleigh integraal die beschrijft hoe het geluidveld in een denkbeeldige ruimte beschreven kan worden met een geluiddrukverdeling op de wanden van die ruimte. Geluidbronnen mogen zich daarbij overigens alleen buiten de ruimte bevinden, niet erin. Kenmerkend voor een hologram is dat niet alleen de geluiddruk, maar ook en vooral de fase van de geluidgolven bepaald wordt. Juist die fase geeft informatie over de richting waarin golven zich voortplanten en dat is weer onontbeerlijk voor transformaties naar een ruimtelijk geluidveld. Deze fase kan bij een stationair geluidveld gemeten worden ten opzichte van een punt in het hologram of een opnemer op de bron. Akoestische holografie wordt commercieel vooral gebruikt in de auto-industrie voor het vastieggen van de geluiduitstraling van met name motoren. Verder wordt holografie toe gepast in onderzoeksachtige toepassingen waarbij getracht wordt meer inzicht te krijgen in het akoestisch gedrag van allerlei, vooral plaatachtige constructies

The development of a cryogenic optical delay line for DARWIN

TNO, in cooperation with Micromega-Dynamics, SRON, Dutch Space and CSL, has designed a compact breadboard cryogenic delay line for use in future space interferometry missions. The work is performed under ESA contract in preparation for the DARWIN mission. The breadboard (BB) delay line is representative of a future flight mechanism, with all materials and processes used being flight representative. In order to enable single stage OPD actuation, the delay line needs to have: • low moving mass; • low friction variations (e.g. stick/slip, bearing noise, power and signal wire torques); • low hysteresis; • linear behaviour. An extensive trade off study has been performed to select the best concept for the DARWIN ODL [2]. TNO applies a minimum-number-of-stages philosophy to all delay lines it develops. A smaller number of actuation stages simplifies the OPD control algorithm The selected concept has a single stage voice coil actuator for Optical Path Difference (OPD) control, driving a two mirror cat’s eye. Five magnetic bearings constrain 5 degrees of freedom (the OPD controller constrains the other degree of freedom) and provide frictionless and wear free operation with zero-hysteresis

Measuring TGV source strength with Syntacan

A 10 m high, vertical, synthetic acoustic antenna (Syntacan) has been used to measure the acoustic source strength and the vertical source distribution of a French TGV, as a function of the speed of the train, the frequency of the sound and the coach type (passenger coach, power car). The results are intended as input for calculation schemes and reduced scale models that are used to predict sound exposure levels of high speed passenger trains in built-up areas

PACT: the actuator to support the primary mirror of the ELT

The European Southern Observatory (ESO) has started technology development for their next generation optical telescope. Due to its ultra large collecting area, The European Extremely Large Telescope (E-ELT) will require a paradigm shift in telescope design to keep the overall program cost at an acceptable level. The E-ELT will feature a 42 meter segmented primary mirror and will make extensive use of active and adaptive optics. Each primary mirror segment will be supported by three actuators that control piston and tilt. TNO has developed a low cost nanopositioning actuator (PACT) for the primary mirror segments. The actuators will be tested by IAC and ESO, with support from TNO, under operational conditions in a Wind Evaluation Breadboard (WEB) at the Roque de Los Muchachos observatory in La Palma

Delft Testbed Interferometer: a homothetic mapping test setup

The Delft Testbed Interferometer (DTI) will be presented. The basics of homothetic mapping will be explained together with the method of fulfilling the requirements as chosen in the DTI setup. The optical layout incorporates a novel tracking concept enabling the use of homothetic mapping in real telescope systems for observations on the sky. The requirements for homothetic mapping and the choices made in the DTI setup will be discussed. Finally the planned experiments will be discussed

Magnetic bearing optical delay line

TNO TPD, in close cooperation with Micromega-Dynamics and Dutch Space, has developed an advanced Optical Delay Line (ODL) for use in PRIMA, GENIE and other ground based interferometers. The delay line design is modular and flexible, which makes scaling for other applications a relatively easy task. The developed technology can also be applied in future cryogenic space interferometers, such as DARWIN, and TPF-I. The ODL has a single linear motor actuator for Optical Path Difference (OPD) control, driving a two-mirror cat's eye with SiC mirrors and CFRP structure. Magnetic bearings provide frictionless and wear free operation with zero-hysteresis. The delay line has been assembled and is currently being subjected to a comprehensive test program

High-speed AFM for 1x node metrology and inspection: does it damage the features?

This paper aims at unraveling the mystery of damage in high speed AFMs for 1X node and below. With the device dimensions moving towards the 1X node and below, the semiconductor industry is rapidly approaching the point where existing metrology, inspection and review tools face huge challenges in terms of resolution, the ability to resolve 3D, and throughput. In this paper, we critically asses the important issue of damage in high speed AFM for metrology and inspection of semiconductor wafers. The issues of damage in four major scanning modes (contact mode, tapping mode, non-contact mode, and peak force tapping mode) are described to show which modes are suitable for which applications and which conditions are damaging. The effects of all important scanning parameters on resulting damage are taken into account for materials such as silicon, photoresists and low K materials. Finally, we recommend appropriate scanning parameters and conditions for several use cases (FinFET, patterned photoresist, HAR structures) that avoid exceeding a critical contact stress such that sample damage is minimized. In conclusion, we show using our theoretical analysis that selecting parameters that exceed the target contact stress, indeed leads to significant damage. This method provides AFM users for metrology with a better understanding of contact stresses and enables selection of AFM cantilevers and experimental parameters that prevent sample damage

Advanced optical delay line demonstrator

TNO TPD, in cooperation with Micromega-Dynamics and Dutch Space, has designed an advanced Optical Delay Line (ODL) for use in future ground based and space interferometry missions. The work is performed under NIVR contract in preparation for GENIE and DARWIN. Using the ESO PRIMA DDL requirements as a baseline, the delay line can be used for PRIMA and GENIE without any modifications. The delay line design is modular and flexible, which makes scaling for other applications a relatively easy task. The ODL has a single linear motor actuator for Optical Path Difference (OPD) control, driving a two-mirror cat's eye with SiC mirrors and CFRP structure. Magnetic bearings provide frictionless and wear free operation with zero-hysteresis. The delay line is currently being assembled and will be subjected to a comprehensive test program in the second half of 2004