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This paper introduces a systematic way to measure most features of the silicon photomultipliers (SiPM). We implement an efficient two-laser procedure to measure the recovery time. Avalanche probability was found to play an important role in explaining the right behavior of the SiPM recovery process. Also, we demonstrate how equivalent circuit parameters measured by optical tests can be used in SPICE modeling to predict details of the time constants relevant to the pulse shape. The SiPM properties measured include breakdown voltage, gain, diode capacitor, quench resistor, quench capacitor, dark count rate, photodetection efficiency, cross-talk and after-pulsing probability, and recovery time. We apply these techniques on the SiPMs from two companies: Hamamatsu and SensL.

The Voxtel VX-798 is a prototype X-ray pixel array detector (PAD) featuring a silicon sensor photodiode array of 48 × 48 pixels, each 130 µm × 130 µm × 520 µm thick, coupled to a CMOS readout application specific integrated circuit (ASIC). The first synchrotron X-ray characterization of this detector is presented, and its ability to selectively count individual X-rays within two independent arrival time windows, a programmable energy range, and localized to a single pixel is demonstrated. During our first trial run at Argonne National Laboratory's Advance Photon Source, the detector achieved a 60 ns gating time and 700 eV full width at half-maximum energy resolution in agreement with design parameters. Each pixel of the PAD holds two independent digital counters, and the discriminator for X-ray energy features both an upper and lower threshold to window the energy of interest discarding unwanted background. This smart-pixel technology allows energy and time resolution to be set and optimized in software. It is found that the detector linearity follows an isolated dead-time model, implying that megahertz count rates should be possible in each pixel. Measurement of the line and point spread functions showed negligible spatial blurring. When combined with the timing structure of the synchrotron storage ring, it is demonstrated that the area detector can perform both picosecond time-resolved X-ray diffraction and fluorescence spectroscopy measurements.

An ultra thin and highly efficient photocathode structure is designed and optimized for the 400 nm optical wavelength regime. The cathode thickness is comparable to the mean free path of the photoelectron allowing design concepts which are built on non-thermalized photoelectrons. Designs for ultra-low emittance and high quantum efficiency are proposed and first test structures are grown and characterized. Additionally, a discussion on the specifics of the transfer and bonding process of ultra-thin cathodes is presented.

The design, manufacture, and test of a two-dimensional pixelated dual-threshold (DT) X-ray photon counting (XPC) detector is described. The DT-XPC detector consists of a 48 × 48-element silicon detector array hybridized to a custom readout integrated circuit (ROIC) using flip-chip bumping and bonding hybridization. The 520-micrometer-thick deep-depleted silicon detector elements are optimized for detection of X-rays in the range of 5 keV to 20 keV. In each 130-μm pitch unit cell, PIN detectors are connected to low-noise pre-amplification and shaping circuits. These circuits convert the charge generated in the photodiode—due to X-ray absorption—into a voltage that is proportional to the energy of the absorbed X-ray photon. The dual-bandwidth pre-amplifier is designed to operate at frequencies of 10 MHz and 100 MHz, allowing X-ray photon counting of X-rays bunched, i.e., 11.4 ns and 153 ns, respectively. The amplified voltage signal is fed to two in-pixel discriminators that determine whether the pulse exceeds one or both of the experiment's user-defined thresholds. The output signal, from both comparators is input to two multipurpose digital counting circuits that can be configured as two separate 15-bit counters, or integrated as a single 30-bit counter. When configured for operation with 15-bit counters, one for each comparator, the device either supports energy-resolving modes of operation or counts only X-rays that fall within a defined energy range. Each counter is individually enabled with a user-programmable gate signal, allowing the XPC to operate in pump/probe mode where external gating signals are used to direct reference counts to one 15-bit counter and signal counts to the other 15-bit counter. To reduce experiment dead time, counters in the pixel are sampled with a 30-bit output latch before readout. This allows the ROIC to operate in integrate-while-read mode.

Presented is a method to build silicon multi-pixel x-ray detectors for use on the Argonne National Laboratory's Advanced Photon Source x-ray synchrotron. These detectors are PIN diodes constructed using heavily doped oxide sources. The construction method chosen helps reduce the background leakage current and allows for a minimum of process steps. We discuss test results of the characterization of the sensors.

We present a progress report on some of the X-ray detector developments on-going at the Argonne National Laboratories Advanced Photon Source. We focus on pixel array detector architecture, and emphasize collaborations, particularly with industries and universities. We discuss our progress establishing a silicon-sensor fabrication facility at Northern Illinois University, our application specific integrated circuit design work, X-ray testing and detector calibration, and readout electronics based on a collection of interchangeable digital circuit boards.

Eddy current NDE has been used for many years to effectively detect defects in conducting materials [1]. However, a major limitation associated with the technique is that imaging techniques are generally qualitative classification schemes which rely on calibration procedures. This is because eddy current phenomena are governed by diffusion, and as such, quantitative inversion/imaging schemes which rely on properties of wave propagation such as diffraction, scattering, and time-of-flight are not applicable. This paper will examine the possibility of using phase shifts associated with time-harmonic eddy current phenomena to solve quantitative inverse problems in the same manner that phase shifts of wave propagation are used.