Synchrotron radiation applications of charge coupled device detectors (invited)

Scientific charge coupled devices (CCDs) offer many opportunities for high brightness synchrotron radiation applications where good spatial resolution and fast data acquisition are important. We describe the use of virtual‐phase CCD pixel arrays as two‐dimensional area detectors illustrating the techniques with results from recent x‐ray scattering, imaging, and absorption spectroscopy studies at NSLS, CHESS, SRC, and LURE DCI. The virtual phase architecture allows direct frontside illumination of the CCD detector chips giving advantages in the speed and sensitivity of the detector. Combining developments in x‐ray optics (dispersive geometry), position sensitive area detectors (CCDs), and fast data acquisition, we have been able to perform time‐resolved measurements at the microsecond level. Current developments include faster data transfer rates so that the single bunch timing structure of third generation synchrotron sources can be exploited.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70562/2/RSINAK-63-1-784-1.pd

Real time x‐ray studies of rapidly annealed epitaxial layers

Time‐resolved x‐ray scattering studies of epitaxial overlayers are presented. The results illustrate the usefulness of high‐brightness synchrotron probes for studying the cooperative kinetics of interfaces during rapid thermal processing.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70481/2/RSINAK-63-1-704-1.pd

Assessing the Ability of Simulated Laboratory Scenes to Predict the Image Quality Performance of HDR Captures (and Rendering) of Exterior Scenes Using Mobile Phone Cameras

With the advent of computational photography, most cellphones include High Dynamic Range (HDR) modes or “apps” that capture and render high contrast scenes in-camera using techniques such as multiple exposures and subsequent “addition” of those exposures to render a properly exposed image. The results from different cameras vary. Testing the image quality of different cameras involves field-testing under dynamic lighting conditions that may involve moving objects. Such testing often becomes a cumbersome and time-consuming task. It would be more efficient to conduct such testing in a controlled, laboratory environment. This study investigates the feasibility of such testing. Natural exterior scenes, at day and night, some of which include “motion”, were captured with a range of cellphone cameras using their native HDR modes. The luminance ratios of these scenes were accurately measured using various spectro-radiometers and luminance meters. Artificial scenes, which include characteristics of the natural exterior scenes and have similar luminance ratios, were created in a laboratory environment. These simulated scenes were captured using the same modes as the natural exterior scenes. A subjective image quality evaluation was conducted using some 20 observers to establish an observer preference scale separately for each scene. For each natural exterior scene, the correlation coefficients between its preference scale and the preference scale obtained for each laboratory scene were calculated, and the laboratory scene with the highest correlation was identified. It was determined that while it was difficult to accurately quantify the actual dynamic range of a natural exterior scene, especially at night, we could still simulate the luminance ratios of a wide range of natural exterior HDR scenes, from 266:1 to 15120:1, within a laboratory environment. Preliminary results of the subjective study indicated that reasonably good correlation (0.8 or higher on average) was obtained between the natural exterior and laboratory simulated scenes. However, such correlations were determined to be specific to the type of scene studied. The scope of this study needs to be narrowed. Another consideration, how moving objects in the scene would affect the results, needs further investigation

The performance of "Virtual Phase" CCDs as detectors of minimum-ionizing particles

The Texas Instruments "Virtual Phase" CCD has been the basis of an ambitious design for a precision vertex detector to be used at the Stanford Linear Collider. The performance of this chip shows promise for future use in electron linear colliders. Experimental results are reported in addition to description of the electronic readout and preliminary mechanical design.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26549/1/0000088.pd

Development of an electronic area detector for x-ray synchrotron experiments.

We describe the development and use of a new type of position sensitive x-ray detector for synchrotron radiation applications. The techniques initiated here involve a combination of energy dispersive optics with a high-resolution Charge Coupled Device (CCD). The CCD detector was developed in collaboration with the particle physics group and modified to exploit its potential for high-brightness synchrotron radiation experiments. The new detector has been tested in a number of experiments using the dispersive beamline at the L.U.R.E. synchrotron facility, in Orsay, France. The novel capabilities of the detector system are demonstrated in a detailed study of the anomalous scattering from artificial multilayers of platinum and amorphous carbon. The spectral dependence of the real and imaginary components of the atomic scattering factor of Pt were measured around the $L\\sb{III}$ absorption edge at 11.564 keV. The measured values compare to within 10% with those from a quantum-mechanical calculation. The anomalous scattering factors are used to examine the energy dependence of the reflectivity of the multilayers at glancing angles close to the critical angle for total external reflection. The critical angle for total external reflection was measured to be 6.4mrads compared to a calculated value of 6.6mrads. A new phenomenon not previously remarked upon in the literature was observed. The penetration of the x-ray beam at energies close to an absorption edge is much deeper than one would expect based on a consideration of the evanescent wave. The experimental techniques introduced during these studies have important implications for future synchrotron experiments. In particular, the ability to carry out time-resolved experiments with the CCD is a very exciting possibility for future exploration.Ph.D.Condensed matter physicsUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/162355/1/9001702.pd

Virtual phase CCD x‐ray detectors

A two‐dimensional charge‐coupled device (CCD) detector, based on the Texas Instruments ‘‘virtual phase’’ CCD, has been developed at the University of Michigan for synchrotron radiation applications. A series of performance tests were carried out at the LURE synchrotron facility, and the results show that the detector is ideally suited to measurements in dispersive absorption spectroscopy, high‐resolution diffuse scattering, and small‐angle scattering. The characteristics of the detector also show great promise for time‐resolved experiments.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70354/2/RSINAK-60-7-2280-1.pd

A virtual phase CCD detector for synchrotron radiation applications

A two‐dimensional charge coupled device (CCD) detector, based on the Texas Instruments ‘‘virtual phase’’ CCD, has been developed for synchrotron radiation applications. Simultaneous near‐edge and multilayer scattering experiments have been carried out with the detector on an energy‐dispersive synchrotron beamline. The detector was used in an optical mode where the CCD element is coupled to a phosphor screen by a pair of focusing and demagnifying lenses. We report on the performance of the detector in this mode.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69390/2/RSINAK-60-8-2586-1.pd