Verification of lifetime and mechanical load aspects for ITER diagnostic pressure gauges based on ZrC emitter.

Hot cathode ionization gauges will measure the neutral gas pressure in the vacuum vessel of ITER. Overall, 52 gauge heads based on the concept of the ASDEX pressure gauge but using novel ZrC emitters are located in the divertor, in equatorial ports and in pumping ducts. The initial lifetime tests of the novel gauge design have raised the concern that the pyrolytic graphite used to indirectly heat the ceramic ZrC emitter erodes too fast during operation. This effect might limit the lifetime of the gauges below the limits acceptable according to the inherent availability (ignoring operational delays) requirement of 99.8% for the diagnostic system over the lifetime of ITER. Long term operation tests have been performed using 0.1 mm thick W, Ir, and Mo foils as an interlayer between the pyrolytic graphite and the ZrC within a constant atmosphere of 20 Pa H2. The longest lifetime of 860 h has been achieved with the Ir foil. Subsequent vibration tests applying accelerations on a shaker with magnitudes typical for seismic and ITER disruption loads demonstrated that the emitter can survive such demanding loads even after far-progressed erosion of the pyrolytic graphite. Additional ON/OFF cycle tests demonstrated that the gauge is still fully operational. In combination with a revision and consolidation of the operational plan and the reliability, accessibility, maintainability, and inspectability (RAMI) analysis, ITER's inherent availability requirement for the diagnostic system could be demonstrated successfully.

Effects of neutral gas pressure on calibration parameters of resistive bolometer sensors in fusion devices.

Ambient pressure may influence the thermal path between the absorber and heat sink of resistive bolometers and thus impact the calibration parameters. This effect is investigated for metal resistive bolometer sensors as used in bolometer diagnostics on fusion experiments. Measurements in the test facility IBOVAC indicate that pressure has no effect up to 10-3 mbar. However, a significant change in the cooling time constant is observed for pressures above 10-2 mbar, a reduction up to a factor of three at 1 mbar. The measurements performed in N2 and He atmospheres and simulations in H2 indicate no difference between the results from different gas species up to 10-3 mbar and less than 10 % up to 0.1 mbar. A model based on the thermal conductivity of the surrounding gas combined with the geometry of the sensor holder successfully demonstrates that the additional cooling path through the gas, which may vary between the measurement and reference absorbers, can explain the measurement results. Applying the model to the geometry of a sensor holder designed for port-mounted bolometer cameras in ITER led to design modifications that should help reduce the impact of high environmental pressures on the bolometer measurements. Similarly, it can be assumed that applying the model to the geometries and sensors of operating bolometer diagnostics can help correct the measurements and improve the understanding of plasma radiation in the case of high pressures at the location of bolometer sensors.

Generic approach to assess the measuring performance of total-radiated power quantities by multi-channel resistive bolometer diagnostics on fusion experiments.

On present-day magnetic-confinement fusion experiments, the performance of multi-channel bolometer diagnostics has typically evolved over time through experience with earlier versions of the diagnostic and experimental results obtained. For future large-scale fusion experiments and reactors, it is necessary to be able to predict the performance as a function of design decisions and constraints. A methodology has been developed to predict the accuracy with which the volume-integrated total radiated power can be estimated from the measurements by a resistive bolometer diagnostic, considering, in particular, its line-of-sight geometry, étendues of individual lines of sight, bolometer-sensor characteristics, and the expected noise level that can be obtained with its electronics and signal chain. The methodology depends on a number of assumptions in order to arrive at analytical expressions but does not restrict the final implementation of data-processing of the diagnostic measurements. The methodology allows us to predict the performance in terms of accuracy, total-radiated power level, and frequency or time resolution and to optimize bolometer-sensor characteristics for a set of performance requirements. This is illustrated for the bolometer diagnostic that is being designed for the ITER experiment. The reasonableness, consequences, and limitations of the assumptions are discussed in detail.

[Speech comprehension and cognitive performance in acoustically difficult situations]. / Sprachverstehen und kognitive Leistungen in akustisch schwierigen Situationen.

Understanding speech strongly depends on sensory processes (bottom-up); however, especially in acoustically difficult situations, cognitive processes (top-down), such as attention and working memory also play a role. In older people both hearing and certain cognitive abilities typically decrease. This has consequences for everyday communication. In clinical practice it is relevant to improve the audibility of speech through appropriate rehabilitative measures and at the same time to reduce the cognitive burden during understanding speech. In this context, future audiometric methods will have to consider "listening effort" as an expression of cognitive load in addition to the improvement of speech intelligibility.

System level design of the ITER bolometer port plug cameras.

The ITER bolometer diagnostic is planned to have 550 lines of sight (LOS) distributed all over the vessel. 240 channels are provided by cameras mounted in two upper ports and in one equatorial port. This paper describes the current status of the system level design of the port cameras and the solutions proposed on how to implement all required camera components while meeting a multitude of competing requirements. Sensor holders, support structures, and different apertures depending on the camera type (pinhole or collimator), cable connectors, ceramic track plates, and many mineral insulated cables have to be integrated within a restricted space envelope to guarantee functionality. The design of the internal electrical interfaces and the external mechanical mountings will be described as well. Using the example of an upper port camera with 60 LOS, the assembly of the camera components is explained and two currently discussed architecture options for the remote handling maintenance scheme in the hot cell are compared.

Speech audiometric assessment of informational masking.

BACKGROUND: In communication situations with multiple speakers, speech recognition is adversely affected by energetic masking (EM) and informational masking (IM). IM characterizes masking effects caused by irrelevant information from competing speakers. This work investigates an approach to assess IM based on the Oldenburg Sentence Test (OLSA). Furthermore, the influence of interaural time differences (ITD) and aging effects on IM are considered. MATERIALS AND METHODS: IM was measured by superimposing two sentences from the OLSA. The beginning of the target sentence was indicated by the keyword "Stefan". To segregate between target and masker sentences, ITDs from 50 to 400 µs were included. The participants were asked to selectively attend to the target sentence and repeat the spoken words. Potential factors associated with speech recognition results were assessed by an auditory measure of temporal fine structure and a neuropsychological profile. The study comprised 16 normal-hearing listeners between 18 and 77 years of age. RESULTS: Despite the clinically normal hearing participants, the analysis showed a significant relationship between speech recognition outcome and pure tone thresholds. All participants benefited from small ITDs between the target and masker sentence with regard to the unmasking of IM. The magnitude of unmasking could not be explained by any of the factors assessed in this study. Error analysis and the comparison with the literature reveal that the OLSA could be a useful tool to assess IM. Also in line with the current literature is the relationship between speech recognition outcome and pure tone thresholds, as well as the strong effect of ITDs on the release from IM. CONCLUSION: Speech audiometric assessment of IM is of high relevance with regard to everyday communication situations. Due to its structure, the OLSA seems to be a useful tool for determining IM.

[Speech audiometric assessment of informational masking. German version]. / Sprachaudiometrische Erfassung von "informational masking".

BACKGROUND: In communication situations with multiple speakers, speech recognition is adversely affected by energetic masking (EM) and informational masking (IM). IM characterizes masking effects caused by irrelevant information from competing speakers. This work investigates an approach to assess IM based on the Oldenburg Sentence Test (OLSa). Furthermore, the influence of interaural time differences (ITD) and aging effects on IM are considered. MATERIALS AND METHODS: IM was measured by superimposing two sentences from the OLSa. The beginning of the target sentence was indicated by the keyword "Stefan". To segregate between target and masker sentences, ITDs from 50 to 400 µs were included. The participants were asked to selectively attend to the target sentence and repeat back the spoken words. Potential factors associated with speech recognition results were assessed by an auditory measure of temporal fine structure and a neuropsychological profile. 16 normal-hearing listeners between 18 and 77 years of age participated in the study. RESULTS: Despite the clinically normal-hearing participants, the analysis showed a significant relationship between speech recognition outcome and pure-tone thresholds. All participants benefited from small ITDs between the target and masker sentence with regard to the unmasking of IM. The magnitude of unmasking could not be explained by any of the factors assessed in this study. Error analysis and the comparison to the literature reveal that the OLSa could be a useful tool to assess IM. Also in line with the current literature is the relationship between speech recognition outcome and pure-tone thresholds, as well as the strong effect of ITDs on the release from IM. CONCLUSION: Speech audiometric assessment of IM is of high relevance with regard to everyday communication situations. Due to its structure, the OLSa seems to be a useful tool for determining IM.

Speech audiometry, speech perception, and cognitive functions : English version.

Examination of cognitive functions in the framework of speech perception has recently gained increasing scientific and clinical interest. Especially against the background of age-related hearing impairment and cognitive decline, potential new perspectives in terms of a better individualization of auditory diagnosis and rehabilitation might arise. This review addresses the relationships between speech audiometry, speech perception, and cognitive functions. It presents models of speech perception, discusses associations of neuropsychological and audiometric outcomes, and shows examples of recent efforts undertaken in Germany to consider cognitive functions with speech audiometry.

[Speech audiometry, speech perception and cognitive functions. German version]. / Sprachaudiometrie, Sprachwahrnehmung und kognitive Funktionen.

Examination of cognitive functions in the framework of speech perception has recently gained increasing scientific and clinical interest. Especially against the background of age-related hearing impairment and cognitive decline potential new perspectives in terms of better individualisation of auditory diagnosis and rehabilitation might arise. This review addresses the relationships of speech audiometry, speech perception and cognitive functions. It presents models of speech perception, discusses associations of neuropsychological with audiometric outcomes and shows recent efforts to consider cognitive functions with speech audiometry.

Acoustic effects of a superior semicircular canal dehiscence: a temporal bone study.

A dehiscence of the superior semicircular canal is said to be responsible for a number of specific and unspecific ear symptoms and possible a conductive hearing loss of up to 40 dB. As in vivo a dehiscence would not be opened against air, but is naturally patched with dura and the brain, it was our aim to investigate the effects of an superior semicircular canal dehiscence on the air conduction hearing in fresh human temporal bones with different boundary conditions. At ten fresh human temporal bones, we investigated the transmission of sound energy through the middle and inner ear using a round window microphone and laser Doppler vibrometer for perilymph motions inside the dehiscence. After baseline measurements, the superior semicircular canal was opened. We investigated the change of the transfer function when the canal is opened against air (pressure equivalent water column), against a water column and when it is patched with a layer of dura. Opening the superior semicircular canal resulted in a loss of sound transmission of maximal 10-15 dB only in frequencies below 1 kHz. When covering the dehiscence with a water column, the conductive hearing component was reduced to 6-8 dB. Placing a dura patch on top of the dehiscence resulted in a normalization of the transfer function. If our experiments are consistent with the conditions in vivo, then superior semicircular canal dehiscence does not lead to an extensive and clinically considerable conductive air conduction component.

Broad-band efficiency calibration of ITER bolometer prototypes using Pt absorbers on SiN membranes.

The energy resolved efficiency of two bolometer detector prototypes for ITER with 4 channels each and absorber thicknesses of 4.5 µm and 12.5 µm, respectively, has been calibrated in a broad spectral range from 1.46 eV up to 25 keV. The calibration in the energy range above 3 eV was performed against previously calibrated silicon photodiodes using monochromatized synchrotron radiation provided by five different beamlines of Physikalische Technische Bundesanstalt at the electron storage rings BESSY II and Metrology Light Source in Berlin. For the measurements in the visible range, a setup was realised using monochromatized halogen lamp radiation and a calibrated laser power meter as reference. The measurements clearly demonstrate that the efficiency of the bolometer prototype detectors in the range from 50 eV up to ≈6 keV is close to unity; at a photon energy of 20 keV the bolometer with the thick absorber detects 80% of the photons, the one with the thin absorber about 50%. This indicates that the detectors will be well capable of measuring the plasma radiation expected from the standard ITER scenario. However, a minimum absorber thickness will be required for the high temperatures in the central plasma. At 11.56 keV, the sharp Pt-L3 absorption edge allowed to cross-check the absorber thickness by fitting the measured efficiency to the theoretically expected absorption of X-rays in a homogeneous Pt-layer. Furthermore, below 50 eV the efficiency first follows the losses due to reflectance expected for Pt, but below 10 eV it is reduced further by a factor of 2 for the thick absorber and a factor of 4 for the thin absorber. Most probably, the different histories in production, storage, and operation led to varying surface conditions and additional loss channels.

[Examination of signals for tinnitus sound therapy. Effects of signal dynamics on sound acceptance and tinnitus masking]. / Untersuchungen von Rauschsignalen für die akustische Tinnitustherapie. Auswirkung von Dynamik auf Akzeptanz und Verdeckungswirkung.

BACKGROUND: In terms of sound acceptance and tinnitus-masking efficacy, tinnitus sound therapy appears to be more effective using dynamic natural sounds than static noise signals. The aim of this study was to systematically determine the effects of physical dynamics parameters on tinnitus masking and sound acceptance. MATERIALS AND METHODS: Based on a dynamic model, noise signals with different dynamic properties were synthesized and used to investigate minimal masking levels (MMLs) and spontaneous sound acceptance in six tinnitus patients. RESULTS: High signal dynamics resulted in high MMLs and low sound acceptance. In some instances, low signal dynamics gave rise to slightly lower MMLs than white noise. Despite unfavourable MMLs, natural dynamic sounds were better accepted than synthesized sounds with comparable dynamics. CONCLUSIONS: The higher spontaneous acceptance of natural sounds as compared to white noise appears not to be due solely to physical sound properties, but rather to result primarily from psychological factors. It may be possible to improve sound acceptance in tinnitus sound therapy by using signals with low amounts of dynamics and implementing the use of natural sounds.

Cognitive resources related to speech recognition with a competing talker in young and older listeners.

Speech recognition in a multi-talker situation poses high demands on attentional and other central resources. This study examines the relationship between age, cognition and speech recognition in tasks that require selective or divided attention in a multi-talker setting. Two groups of normal-hearing adults (one younger and one older group) were asked to repeat utterances from either one or two concurrent speakers. Cognitive abilities were then inspected by neuropsychological tests. Speech recognition scores approached its ceiling and did not significantly differ between age groups for tasks that demanded selective attention. However, when divided attention was required, performance in older listeners was reduced as compared to the younger group. When selective attention was required, speech recognition was strongly related to working memory skills, as determined by a regression model. In comparison, speech recognition for tests requiring divided attention could be more strongly determined by neuropsychological probes of fluid intelligence. The findings of this study indicate that - apart from hearing impairment - cognitive aspects account for the typical difficulties of older listeners in a multi-speaker setting. Our results are discussed in the context of evidence showing that frontal lobe functions in terms of working memory and fluid intelligence generally decline with age.

Reliability issues for a bolometer detector for ITER at high operating temperatures.

The first detector prototypes for the ITER bolometer diagnostic featuring a 12.5 µm thick Pt-absorber have been realized and characterized in laboratory tests. The results show linear dependencies of the calibration parameters and are in line with measurements of prototypes with thinner absorbers. However, thermal cycling tests up to 450 °C of the prototypes with thick absorbers demonstrated that their reliability at these elevated operating temperatures is not yet sufficient. Profilometer measurements showed a deflection of the membrane hinting to stresses due to the deposition processes of the absorber. Finite element analysis (FEA) managed to reproduce the deflection and identified the highest stresses in the membrane in the region around the corners of the absorber. FEA was further used to identify changes in the geometry of the absorber with a positive impact on the intrinsic stresses of the membrane. However, further improvements are still necessary.

[Examination of speech perception and cognitive functioning in the elderly]. / Untersuchungen zum Sprachverstehen und zu kognitiven Fähigkeiten im Alter.

BACKGROUND: Elderly persons frequently complain about problems with speech understanding especially in complex acoustic situations. Besides hearing impairment the decline of cognitive functions might explain these problems. METHODS: In 12 normal hearing young subjects and 14 elderly listeners with extraordinarily good hearing speech perception was measured in a broad range of different acoustic situations. Cognitive functioning was evaluated with different neuropsychological tests. RESULTS: Despite comparable pure tone thresholds the elderly listeners revealed worse speech discrimination than the young subjects in almost all test situations. Largest differences were found in situations with fluctuating maskers and competing talkers. Most of the speech perception results revealed significant correlations with the outcome from a neuropsychological test addressing declarative verbal memory. CONCLUSIONS: In complex listening situations elderly persons reveal worse speech understanding than younger subjects. Differences in speech perception can partly be attributed to cognitive abilities. In particular, working memory seems to be an important factor.

Optimization of a bolometer detector for ITER based on Pt absorber on SiN membrane.

Any plasma diagnostic in ITER must be able to operate at temperatures in excess of 200 °C and neutron loads corresponding to 0.1 dpa over its lifetime. To achieve this aim for the bolometer diagnostic, a miniaturized metal resistor bolometer detector based on Pt absorbers galvanically deposited on SiN membranes is being developed. The first two generations of detectors featured up to 4.5 µm thick absorbers. Results from laboratory tests are presented characterizing the dependence of their calibration constants under thermal loads up to 450 °C. Several detectors have been tested in ASDEX Upgrade providing reliable data but also pointing out the need for further optimization. A laser trimming procedure has been implemented to reduce the mismatch in meander resistances below 1% for one detector and the thermal drifts from this mismatch.

[Development of a German version of the Functioning After Pediatric Cochlear Implantation (FAPCI) questionnaire]. / Entwicklung einer deutschsprachigen Version des Fragebogens Functioning After Pediatric Cochlear Implantation (FAPCI).

BACKGROUND: The Functioning After Pediatric Cochlear Implantation (FAPCI) instrument was recently developed to determine the communicative performance of 2-5-year-old prelingually deafened, cochlear-implanted children. Because of its high reliability and validity, as well as possible additional information compared with existing questionnaires, the 23-item parent-proxy questionnaire was translated from U.S. English to German prior to validation. MATERIAL AND METHODS: Initially, the German inventory was qualitatively developed by experts in audiology and speech pathology in collaboration with a professional American translator. Based on a sample of parents' responses, the outcome was quantitatively validated using psychometric methods (Cronbach's alpha, principal components analysis). Finally, the nomological validity was verified by correlating the overall FAPCI value with an external criterion (i.e., hearing age). RESULTS: For almost all age groups, Cronbach's alpha exceeded the minimum value of the original study (0.86). Principal components analysis revealed a two-factor solution (speech perception/production). The fitting of a nonparametric regression line to the data points showed that the total FAPCI score was positively associated with the time of implant use. CONCLUSION: The results show concordance between the German and the English versions of the FAPCI. The two instruments agree in reliability as well as in validity. The suitability of the German version in the clinical and therapeutic routine needs to be confirmed in further investigations.

[Examining informational masking in cochlear implant users]. / Untersuchungen zum "Informational Masking" bei Kochleaimplantat-Nutzern.

BACKGROUND: Informational masking (IM) refers to the problem of understanding target speech in the simultaneous presence of a masking speech signal. The adverse effects are attributable to the additional information provided by the competing talker. Cochlear implant (CI) recipients are not able to understand speech satisfactorily in situations such as these. The aim of the present study is to examine the extent to which CI recipients are able to use differences between the speakers with respect to level (target-to-masker ratio, TMR) and fundamental frequency (f0) in order to improve speech intelligibility. SUBJECTS AND METHODS: Target (TS) and masker sentences (MS) were selected from the Oldenburg Sentence Test (OlSa) and were modified and superimposed. The TS were explicitly labelled using a keyword. The MS were changed with respect to TMR and f0. The TS intelligibility of different modifications was measured in six post-lingually deafened CI recipients and six normal listeners (NL). RESULTS: The NL revealed speech understanding close to 100% even for small differences in f0 of 40 Hz or level differences of 5 dB. In CI recipients, a significant change in intelligibility could only be demonstrated with increased TMR, but not with differences in f0. CONCLUSIONS: In CI recipients, IM cannot be reduced by means of differences in f0 between the competing talkers, but only by level differences. This might be explained by the restricted spectral resolution and the insufficient transmission of f0 in CIs. Adverse effects in NL can predominantly be attributed to IM, while additional masking effects take place in CI recipients.

The ITER bolometer diagnostic: status and plans.

A consortium consisting of four EURATOM Associations has been set up to develop the project plan for the full development of the ITER bolometer diagnostic and to continue urgent R&D activities. An overview of the current status is given, including detector development, line-of-sight optimization, performance analysis as well as the design of the diagnostic components and their integration in ITER. This is complemented by the presentation of plans for future activities required to successfully implement the bolometer diagnostic, ranging from the detector development over diagnostic design and prototype testing to RH tools for calibration.

[Conception and realisation of a prosody test battery]. / Konzeption und Realisierung einer Prosodie-Testbatterie.

BACKGROUND: Prosody reflects rhythmic and melodic aspects in speech and is one of the quality measures that shows--apart from pure speech understanding--a rising interest in the assessment of technical hearing aids, especially of cochlear implants. At present, there is no adequate test battery for the German speaking population. The test battery presented in this study aims to fill this gap. METHODS: The test battery consists of four different modules addressing different prosodic cues, namely duration, question vs statement, sentence stress, and speaker gender. One part of the test battery aims at reflecting everyday situations and was realized with six different speakers representing various pitch frequencies and speak rates. Another goal of the tests is to detect very small differences in prosody perception. Therefore, natural utterances were artificially modified by changing the underlying acoustic parameters (e.g. duration, fundamental frequency). Measurements were performed with 12 normal listeners in order to investigate the properties of the tests. RESULTS: As expected, the normal listeners revealed discrimination rates of close to 100% in that part of the test battery using natural utterances. For the part with the modified stimuli, all four modules revealed very steep discrimination functions indicating that the normal listeners were able to use very small changes in the acoustic parameters as cues for prosody perception. Moreover, the slope of the discrimination function revealed very low variability. CONCLUSIONS: Together with preliminary data from cochlear implant recipients who clearly showed different psychometric functions, the test battery seems suitable for a comprehensive evaluation of prosody perception. This facilitates future examinations of speech processing beyond the pure understanding of speech.