Many questions regarding dynamic materials could be answered by using time-resolved ultra-fast imaging techniques to characterize the physical and chemical behavior of materials in extreme conditions and their evolution on the nanosecond scale. In this work, we perform multi-frame phase-contrast imaging (PCI) of micro-voids in low density polymers under laser-driven shock compression. At the Matter in Extreme Conditions (MEC) Instrument at the Linac Coherent Light Source (LCLS), we used a train of four x-ray free electron laser (XFEL) pulses to probe the evolution of the samples. To visualize the void and shock wave interaction, we deployed the Icarus V2 detector to record up to four XFEL pulses, separated by 1-3 nanoseconds. In this work, we image elastic waves interacting with the micro-voids at a pressure of several GPa. Monitoring how the material’s heterogeneities, like micro-voids, dictate its response to a compressive wave is important for benchmarking the performances of inertial confinement fusion energy materials. For the first time in a single sample, we have combined an ultrafast x-ray framing camera and four XFEL pulse train to create an ultrafast movie of micro-void evolution under laser-driven shock compression. Eventually, we hope this technique will resolve the material density as it evolves dynamically under laser shock compression.
The Icarus camera system, combining a sensor developed by Sandia and readout electronics by LLNL, provides 0.5 Hz bursts of four frames with 3 ns separation. The sensor has 1024×512 25 μm pixels and is 25 μm thick. The system was developed for single line-of-sight measurements at the ns time scale for electrons and X-rays at facilities such as NIF. We report on initial tests of the Icarus system with hard X-rays pulse pairs with nanosecond time spacings at the LCLS, a newly available beam mode. We describe noise, gate profiles, gain, cross-talk, persistence, linearity, and quantum efficiency for the first version of the sensor. We present evidence of the suitability of the system for science measurements at a free electron laser with an X-ray pump X-ray probe experiment. We expect further developments of the technology to allow use of 350 ps bunch separation from the LCLS accelerator and, with a pulsed delay tube like DIXIE, to eventually reach sub-25 ps time-resolved X-ray imaging of processes such as plasma evolution.
The Linac Coherent Light Source (LCLS) poses a number of daunting and often unusual challenges to maintaining X-ray detectors, such as proximity to liquid-sample injectors, complex setups with moving components, intense X-ray and optical laser light, and Electromagnetic Pulse (EMP). The Detector and Sample Environment departments at LCLS are developing an array of engineering, monitoring, and administrative controls solutions to better address these issues. These include injector improvements and monitoring methods, fast online damage recognition algorithms, EMP mapping and protection, actively cooled filters, and more.
KEYWORDS: Prototyping, Sensors, Analog electronics, High dynamic range imaging, Liquid crystal lasers, Photons, Cameras, Signal processing, Image resolution, Free electron lasers
ePix10k is a variant of a novel class of integrating pixel ASICs architectures optimized for the processing of signals in second generation LINAC Coherent Light Source (LCLS) X-Ray cameras. The ASIC is optimized for high dynamic range application requiring high spatial resolution and fast frame rates. ePix ASICs are based on a common platform composed of a random access analog matrix of pixel with global shutter, fast parallel column readout, and dedicated sigma-delta analog to digital converters per column. The ePix10k variant has 100um×100um pixels arranged in a 176×192 matrix, a resolution of 140e- r.m.s. and a signal range of 3.5pC (10k photons at 8keV). In its final version it will be able to sustain a frame rate of 2kHz. A first prototype has been fabricated and characterized. Performance in terms of noise, linearity, uniformity, cross-talk, together with preliminary measurements with bump bonded sensors are reported here.
ePix100 is the first variant of a novel class of integrating pixel ASICs architectures optimized for the processing of signals in second generation LINAC Coherent Light Source (LCLS) X-Ray cameras. ePix100 is optimized for ultra-low noise application requiring high spatial resolution. ePix ASICs are based on a common platform composed of a random access analog matrix of pixel with global shutter, fast parallel column readout, and dedicated sigma-delta analog to digital converters per column. The ePix100 variant has 50μmx50μm pixels arranged in a 352x384 matrix, a resolution of 50e- r.m.s. and a signal range of 35fC (100 photons at 8keV). In its final version it will be able to sustain a frame rate of 1kHz. A first prototype has been fabricated and characterized and the measurement results are reported here.
KEYWORDS: Cameras, Sensors, Liquid crystal lasers, Data acquisition, X-rays, Photons, Free electron lasers, Stanford Linear Collider, Solar concentrators, Imaging systems
The Linear Coherent Light Source (LCLS), a free electron laser operating from 250eV to10keV at 120Hz, is opening windows on new science in biology, chemistry, and solid state, atomic, and plasma physics1,2. The FEL provides coherent x-rays in femtosecond pulses of unprecedented intensity. This allows the study of materials on up to 3 orders of magnitude shorter time scales than previously possible. Many experiments at the LCLS require a detector that can image scattered x-rays on a per-shot basis with high efficiency and excellent spatial resolution over a large solid angle and both good S/N (for single-photon counting) and large dynamic range (required for the new coherent x-ray diffractive imaging technique3). The Cornell-SLAC Pixel Array Detector (CSPAD) has been developed to meet these requirements. SLAC has built, characterized, and installed three full camera systems at the CXI and XPP hutches at LCLS. This paper describes the camera system and its characterization and performance.
KEYWORDS: Sensors, Charge-coupled devices, Near infrared, Electronics, Silicon carbide, CCD image sensors, Space telescopes, Signal detection, Data acquisition, Flexible circuits
Mission concepts for NASA's Wide Field Infrared Survey Telescope (WFIRST)1,2, ESA's Euclid3,4 mission, as well as
next-generation ground-based surveys require large mosaic focal planes sensitive in both visible and near infrared (NIR)
wavelengths. We have developed space-qualified detectors, readout electronics and focal plane design techniques that
can be used to intermingle CCDs and NIR detectors on a single, silicon carbide (SiC) cold plate. This enables optimized,
wideband observing strategies. The CCDs, developed at Lawrence Berkeley National Laboratory, are fully-depleted, pchannel
devices that are backside illuminated and capable of operating at temperatures down to 120K. The NIR
detectors are 1.7 μm and 2.0 μm wavelength cutoff H2RG® HgCdTe, manufactured by Teledyne Imaging Sensors under
contract to LBNL. Both the CCDs and NIR detectors are packaged on 4-side abuttable SiC pedestals with a common
mounting footprint supporting a 44 mm mosaic pitch. Both types of detectors have direct-attached readout electronics
that convert the detector signal directly to serial, digital data streams and allow a flexible, low cost data acquisition
strategy to enable large data rates. A mosaic of these detectors can be operated at a common temperature that achieves
the required dark current and read noise performance necessary for dark energy observations. We report here the
qualification testing and performance verification for a focal plane that accommodates a 4x8 array of CCDs and HgCdTe
detectors.
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