Background rates of x-ray transition-edge sensor micro-calorimeters under a frequency domain multiplexing readout for solar axion-like particles' detection.

We report on the x-ray background rate measured with transition-edge sensors (TES) micro-calorimeters under frequency-domain multiplexing (FDM) readout as a possible technology for future experiments aiming at a direct detection of axion-like particles. Future axion helioscopes will make use of large magnets to convert axions into photons in the keV range and x-ray detectors to observe them. To achieve this, a detector array with high spectral performance and extremely low background is necessary. TES are single-photon, non-dispersive, high-resolution micro-calorimeters and represent a possible candidate for this application. We have been developing x-ray TES micro-calorimeters and an FDM readout technology in the framework of the space-borne x-ray astronomical observatories. We show that the current generation of our detectors is already a promising technology for a possible axion search experiment, having measured an x-ray background rate of 2.2(2) × 10-4 cm-2 s-1 keV-1 with a cryogenic demonstrator not optimized for this specific application. We then make a prospect to further improve the background rate down to the required value (<10-7 cm-2 s-1 keV-1) for an axion-search experiment, identifying no fundamental limits to reach such a level.

Voltage Fluctuations in ac Biased Superconducting Transition-Edge Sensors.

We present a detailed analysis of the fundamental noise sources in superconducting transition-edge sensors (TESs), ac voltage biased at MHz frequencies and treated as superconducting weak links. We have studied the noise in the resistive transition as a function of bath temperature of several detectors with different normal resistances and geometries. We show that the "excess" noise, typically observed in the TES electrical bandwidth, can be explained by the equilibrium Johnson noise of the quasiparticles generated within the weak link. The fluctuations at the Josephson frequency and higher harmonics contribute significantly to the measured voltage noise at the detector bandwidth through the nonlinear response of the weak link with a sinusoidal current-phase relation.

Frequency shift algorithm: Application to a frequency-domain multiplexing readout of x-ray transition-edge sensor microcalorimeters.

In the frequency-domain multiplexing (FDM) scheme, transition-edge sensors (TESs) are individually coupled to superconducting LC filters and AC biased at MHz frequencies through a common readout line. To make efficient use of the available readout bandwidth and to minimize the effect of non-linearities, the LC resonators are usually designed to be on a regular grid. The lithographic processes, however, pose a limit on the accuracy of the effective filter resonance frequencies. Off-resonance bias carriers could be used to suppress the impact of intermodulation distortions, which, nonetheless, would significantly affect the effective bias circuit and the detector spectral performance. In this paper, we present a frequency shift algorithm (FSA) to allow off-resonance readout of TESs, while preserving the on-resonance bias circuit and spectral performance, demonstrating its application to the FDM readout of an x-ray TES microcalorimeter array. We discuss the benefits in terms of mitigation of the impact of intermodulation distortions at the cost of increased bias voltage and the scalability of the algorithm to multi-pixel FDM readout. We show that with FSA, in the multi-pixel and frequencies shifted on-grid, the line noises due to intermodulation distortion are placed away from the sensitive region in the TES response and the x-ray performance is consistent with the single-pixel, on-resonance level.

Performance and uniformity of a kilo-pixel array of Ti/Au transition-edge sensor microcalorimeters.

Uniform large transition-edge sensor (TES) arrays are fundamental for the next generation of x-ray space observatories. These arrays are required to achieve an energy resolution ΔE < 3 eV full width at half maximum (FWHM) in the soft x-ray energy range. We are currently developing x-ray microcalorimeter arrays for use in the future laboratory and space-based x-ray astrophysics experiments and ground-based spectrometers. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with 140 × 30 µm2 Ti/Au TESs with the Au x-ray absorber. We report on extensive measurements on 60 pixels in order to show the uniformity of our large TES array. The averaged critical temperature is Tc = 89.5 ± 0.5 mK, and the variation across the array (∼1 cm) is less than 1.5 mK. We found a large region of detector's bias points between 20% and 40% of the normal-state resistance where the energy resolution is constantly lower than 3 eV. In particular, results show a summed x-ray spectral resolution ΔEFWHM = 2.50 ± 0.04 eV at a photon energy of 5.9 keV, measured in a single-pixel mode using a frequency domain multiplexing readout system developed at SRON/VTT at bias frequencies ranging from 1 MHz to 5 MHz. Moreover, we compare the logarithmic resistance sensitivity with respect to temperature and current (α and ß, respectively) and their correlation with the detector's noise parameter M, showing a homogeneous behavior for all the measured pixels in the array.

A six-degree-of-freedom micro-vibration acoustic isolator for low-temperature radiation detectors based on superconducting transition-edge sensors.

Dilution and adiabatic demagnetization refrigerators based on pulse tube cryocoolers are nowadays used in many low temperature physics experiments, such as atomic force and scanning tunneling microscopy, quantum computing, radiation detectors, and many others. A pulse tube refrigerator greatly simplifies the laboratory activities being a cryogen-free system. The major disadvantage of a pulse tube cooler is the high level of mechanical vibrations at the warm and cold interfaces that could substantially affect the performance of very sensitive cryogenic instruments. In this paper, we describe the performance of a very simple mechanical attenuation system used to eliminate the pulse-tube-induced low frequency noise of the superconducting transition-edge sensors under development for the instruments of the next generation of infra-red and X-ray space observatories.

Study of the Dependency on Magnetic Field and Bias Voltage of an AC-Biased TES Microcalorimeter.

At SRON we are studying the performance of a Goddard Space Flight Center single pixel TES microcalorimeter operated in an AC bias configuration. For x-ray photons at 6 keV the pixel shows an x-ray energy resolution ΔEFWHM =3.7 eV, which is about a factor 2 worse than the energy resolution observed in an identical DC-biased pixel. In order to better understand the reasons for this discrepancy we characterised the detector as a function of temperature, bias working point and applied perpendicular magnetic field. A strong periodic dependency of the detector noise on the TES AC bias voltage is measured. We discuss the results in the framework of the recently observed weak-link behaviour of a TES microcalorimeter.

Two-dimensional polyacrylamide gel electrophoresis map of bull seminal plasma proteins.

A two-dimensional polyacrylamide gel electrophoresis map of bull seminal plasma proteins has been established. About 250 spots were detected after silver staining and polypeptides from 24 spots have been N-terminally sequenced. Major proteins already described in bull seminal plasma, like PDC-109 and aSFP, have been located on the map; proteins not yet reported in male reproductive tracts have been evidenced; for some polypeptides showing a previously unknown N-terminal sequence, structural similarities with proteins described in other organisms have been found. A reference map of seminal plasma proteins could be useful in relating protein pattern changes to physiopathological events influencing the reproductive sphere.

The human side of design: creating a new film library.

The use of continuous quality improvement may keep your film library processes running smoothly, but your staff may still struggle daily with its inadequate design. As the experts who work and live within the design, staff members deserve to play an active role in its improvement. When plans for a construction project that would include a larger film storage area were approved at Tampa General Healthcare, the administrative manager of the film library studied the first generation of blueprints. Encouraged to speak to the designer about her ideas, she presented sketches she had traced over blueprints to relocate the office entrance. Her design suggestions were welcomed. With the film library supervisors now wanting to involve staff members, the administrative manager created a wish list survey asking staff about positive and negative aspects of their work space, and for their suggestions on improving it, if given the chance. They responded with ideas for more soundproofing, better lighting and better storage space. Others recommended better ergonomic design for keyboard height, drawers and even the height of the sliding-glass window in the reception area. These suggestions did not account for the process delays the library experienced, however. Spending time in each of four work areas, the administrative manager found wasted movement, crowding of staff, film and equipment, and inadequate storage. This was the right time for change, she felt, an opportunity that shouldn't slip by. Various plans were created, not only to isolate office workers from noise and traffic, but to include items from the wish list. When it was time for the specifications, staff feedback became critical. The administrative manager consulted with staff members on various shifts and worked with staff ideas and sketches. The time the designer spent visiting the many work areas was critical to finalizing plans. The construction phase came next, after careful planning for carrying out work during the interim, a difficult period. A year later, the administrative manager recommends employee involvement in such projects.

Blood pressure, metabolic variables and adipose tissue distribution in pre- and post-menopausal women.

The study was performed on 289 female patients (aged 20-60) of a family doctor in Castel D'Azzano, a small town near Verona. The following variables were considered: body mass index (BMI), tricepital, subscapular, hypomesogastric, epimesogastric, supra-iliacal and epitrochanteric skinfolds, waist, umbilical and bitrochanteric circumferences, cholesterol, triglycerides, HDL-cholesterol, glycemia, uricemia and blood pressure. A significant worsening with age was observed in the mean values of the variables. This worsening was particularly evident in women over 50. The population was subdivided according to presence or absence of menopause; the two groups were then matched for age. None of the variables showed significant differences. Our results did not confirm any of the many effects that menopause is supposed to have regarding metabolic and blood pressure alterations.

Thallium-induced testicular toxicity in the rat.

Reproductive tract functions were studied in adult male Wistar rats given 10 ppm thallium as thallium sulfate in the drinking water. After 60 days of treatment, spermatozoa isolated from the cauda epididymides and vas deferens showed reduced motility and immature germ cells were found in the tubular lumen. Histological examination of testes in thallium-treated animals revealed disarrangement of the tubular epithelium and ultrastructural changes in the Sertoli cells with cytoplasmic vacuolation and distension of the smooth endoplasmic reticulum. The activity of testicular beta-glucuronidase was significantly reduced whereas acid phosphatase and sorbitol dehydrogenase activities were unchanged. Plasma testosterone levels were within normal limits. No abnormalities in testicular morphology and biochemistry were seen in animals sacrificed at the end of the first month of thallium exposure. These findings indicate that the male reproductive system is a susceptible target site to toxic effects of thallium under chronic exposure. They also suggest a major involvement of Sertoli cells in the mechanism underlying thallium-induced testicular damage.

Artificial insemination by donor results in relation to husband's semen.

A retrospective analysis was undertaken to determine whether there was any difference in conception and abortion rate in an artificial insemination by donor program between couples whose husbands were azoospermic (group A) and couples whose husbands were severely subfertile (group O). The pregnancy rate was significantly higher in group A (64%) than in group O (47%) (p less than 0.05). The abortion rate was significantly lower in group A (10%) than in group O (23%) (p less than 0.05). This study confirms the opinion of other authors [4, 9] that pregnancy may occur despite severely abnormal semen. In fact, the difference in pregnancy and abortion rate between the two groups could be explained by assuming that the average fertility of the women in group O is lower than that in group A.

Semen analysis and in vitro fertilization.

Thirty-seven patients underwent ultrasonographic, clinical, and hormonal monitoring of superovulated cycles in order to time HCG administration in an attempt to schedule the laparoscopy at the optimal time for oocyte recovery. Superovulation was induced by Clomiphene in patients under the age of 35, with both ovaries; Clomiphene and HMG were administered in women over age 35 and/or with only one or half an ovary. Twelve patients were excluded because of poor oestradiol values or LH rise prior to HCG administration. Four patients were excluded at laparoscopy because of inadequate ovarian access (a preliminary laparoscopy was not performed). In 21 patients follicular aspiration was performed: 33 mature, 15 immature, and 5 degenerated oocytes were obtained (1.5 mature oocyte per patient). Thirty eggs were fertilized on a total number of 48 eggs (mature and immature)-fertilization rate of 63%. Twenty-nine embryos cleaved and were transferred to 13 patients at the 4- to 8-cell stage.