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This paper presents the design results of a 100-channel integrated circuit dedicated to various biomedical experiments requiring both electrical stimulation and recording ability. The main design motivation was to develop an architecture that would comprise not only the recording and stimulation, but would also block allowing to meet different experimental requirements. Therefore, both the controllability and programmability were prime concerns, as well as the main chip parameters uniformity. The recording stage allows one to set their parameters independently from channel to channel, i.e., the frequency bandwidth can be controlled in the (0.3 Hz–1 kHz)–(20 Hz–3 kHz) (slow signal path) or (0.3 Hz–1 kHz)–4.7 kHz (fast signal path) range, while the voltage gain can be set individually either to 43.5 dB or 52 dB. Importantly, thanks to in-pixel circuitry, main system parameters may be controlled individually allowing to mitigate the circuitry components spread, i.e., lower corner frequency can be tuned in the 54 dB range with approximately 5% precision, and the upper corner frequency spread is only 4.2%, while the voltage gain spread is only 0.62%. The current stimulator may also be controlled in the broad range (69 dB) with its current setting precision being no worse than 2.6%. The recording channels' input-referred noise is equal to 8.5 µVRMS in the 10 Hz–4.7 kHz bandwidth. The single-pixel occupies 0.16 mm2 and consumes 12 µW (recording part) and 22 µW (stimulation blocks). [ABSTRACT FROM AUTHOR]

A combined X-ray photon correlation spectroscopy and rheology study is carried out to capture the evolution of structure, fast particle-scale dynamics, and moduli (elastic and loss) at early times of gel formation near the fluid–gel boundary of a suspension of nanoparticles. The system is comprised of moderately concentrated suspensions of octadecyl silica in decalin (ϕ = 0.2) undergoing thermoreversible gelation. Near the gel boundary, the rate of gel formation is very sensitive to changes in attraction strength. However, we find that at different attraction strengths, the system goes through identical intermediate states of microscopic and macroscopic behavior, even though the absolute time needed to form a gel varies by orders of magnitude. We identify a single dimensionless time parameter, tw/tg, where tw is the wait time following the quench and tg is the rheologically determined gel time, that captures the similarity in gel formation at a range of attraction strengths. Following a temperature quench below the gel boundary, the system is initially fluidlike and forms diffusive clusters (∼8.5 times the particle diameter). After a lag-time, tL, clusters aggregate to form a network like structure which is characterized by the onset of mechanical rigidity and a rapid growth in microscopic relaxation times. At tg, the Baxter parameter obtained from adhesive hard sphere fits of the structure factor attains a constant value corresponding to the theoretical percolation boundary, thus demonstrating that gelation is percolation driven. [ABSTRACT FROM AUTHOR]

A 64-channel ASIC (SXDR64) aimed to work with both AC and DC coupled detectors (Si, CdTe, GaAs), in a single photon counting mode with an energy window has been developed. Every channel of the ASIC consists of a charge sensitive amplifier, a pole-zero cancellation circuit, a 4th order shaper with programmable gain from 14 \muV/e^- to 50 \muV/e^- and peaking time from 115 ns to 380 ns, a base-line restorer, two independent discriminators, and two 20-bit counters. Control and readout of the chip are done using on-chip LVDS drivers/receivers. The ASIC can work with input leakage currents in the range from -10 nA up to 7 nA. The ENC obtained with an AC-coupled Si detector is 120 e^- for a peaking time Tp=115\ ns and Cdet=1.2\ pF. With a DC-coupled CdTe detector, the ENC is 210 e^-\ rms for a peaking time Tp=380\ ns and Cdet=2\ pF and the leakage current Idleak=0.15\ nA. The implemented trim DACs at the discriminator inputs allows to minimize the effective threshold spread to 8 e^-\ rms (at one sigma level). The ASIC is designed in a CMOS 0.35 \mum technology and its total area is 4800\times 5000\ \mum^2. [ABSTRACT FROM AUTHOR]

Spectrally selective X-ray imaging provides improved material and tissue discrimination in comparison with the state-of-the-art dual energy technologies that are commonly used in medical, industrial, and security applications. Cadmium telluride (CdTe)- and cadmium zinc telluride (CdZnTe)-based line scanners and small size two-dimensional X-ray sensors are emerging to the market, but the need for large-scale panels is axiomatic. In this study, a seamless CdTe tile was developed that enables the implementation of large-sized, energy selective X-ray detector panels. The developed tile consists of a $64\times64$ pixel array (with $150~\mu \text{m}$ pitch) with a necessary substrate, ASIC, and CdTe crystal. The performance of the constructed seamless tile was characterized by focusing on spectral resolution and stability. In addition, a simple pixel trimming method that automates the equalization of each energy selective pixel was developed and analyzed. The obtained results suggest that the proposed concept of seamless (tileable) detector structures is a feasible approach to scale up panel sizes. The seamless tile shows comparable spectral resolution and stability performance with commercial CdTe sensors. The effect of tile to tile variation, the realization of a large-scale panel, as well as the charge sharing performance were left out of the scope and are to be studied in the next phase. [ABSTRACT FROM AUTHOR]

The VIPIC1 readout integrated circuit was designed for X-ray Photon Correlation Spectroscopy experiments that are typically performed using mono-energetic (8 keV) X-rays at a synchrotron radiation facility. The device is a pixel detector with sparsification and parallel readout from the groups, yielding high timing resolution. Recent improvements in bonding alignment of wafers resulted in deliveries of 3D bonded wafers. The stacks, bonded with both the Cu-Cu thermo-compression method and the Cu DBI bonding method, yielded operational devices that have been tested. Chips (with a pixel pitch of 80~\mu\m) were also bonded to silicon pixelated sensors (with a pixel pitch of 100~\mu\m) and the assemblies were exposed to X-ray sources for the first time. The paper focuses on the test results, including the calibrated noise (ENC) and the conversion gain. The noise measured corresponded to 39~\e^ - and 70~\e^ - , respectively for the readout channels that were not connected and connected to the sensor diodes. The conversion gain varied from 43 to 52~\mu\V/e^ - as a function of the bias current in the front-end block. Essentially all the pixels on a small prototype were operational. [ABSTRACT FROM PUBLISHER]

The Vertically Integrated Photon Imaging Chip (VIPIC) project explores opportunities of the three-dimensional integration for imaging of X-rays. The design details of the VIPIC1 chip are presented and are followed by results of testing of the chip. The VIPIC1 chip was designed in a 130 nm process, in which through silicon vias are embedded right after the front-end-of-line processing. The integration of tiers is achieved by the Cu-Cu thermo-compression or Cu-based oxide-oxide bonding. The VIPIC1 readout integrated circuit was designed for high timing resolution, pixel based, X-ray Photon Correlation Spectroscopy experiments typically using 8 keV X-rays at a synchrotron radiation facility. The design was done for bonding a Silicon pixel detector, however other materials can be serviced as long as the positive polarity of charge currents is respected. [ABSTRACT FROM PUBLISHER]

The dynamics of concentrated suspensions of the eye-lens protein alpha crystallin have been measured using x-ray photon correlation spectroscopy. Measurements were made at wave vectors corresponding to the first peak in the hard-sphere structure factor and volume fractions close to the critical volume fraction for the glass transition. Langevin dynamics simulations were also performed in parallel to the experiments. The intermediate scattering function f(q,τ) could be fit using a stretched exponential decay for both experiments and numerical simulations. The measured relaxation times show good agreement with simulations for polydisperse hard-sphere colloids. [ABSTRACT FROM AUTHOR]

We have examined the formation and dissolution of gels composed of intermediate volume-fraction nanoparticles with temperature-dependent short-range attractions using small-angle x-ray scattering, x-ray photon correlation spectroscopy, and rheology to obtain nanoscale and macroscale sensitivity to structure and dynamics. Gel formation after temperature quenches to the vicinity of the rheologically determined gel temperature, Tgel, was characterized via the slowdown of dynamics and changes in microstructure observed in the intensity autocorrelation functions and structure factor, respectively, as a function of quench depth (ΔT=Tquench-Tgel), wave vector, and formation time tf. We find the wave-vector-dependent dynamics, microstructure, and rheology at a particular ΔT and tf map to those at other ΔTs and tfs via an effective scaling temperature, Ts. A single Ts applies to a broad range of ΔT and tf but does depend on the particle size. The rate of formation implied by the scaling is a far stronger function of ΔT than expected from the attraction strength between colloids. We interpret this strong temperature dependence in terms of cooperative bonding required to form stable gels via energetically favored, local structures. [ABSTRACT FROM AUTHOR]