Dionisio Doering

A fast, direct x-ray detection charge-coupled device

A charge-coupled device (CCD) capable of 200 Mpixels/s readout has been designed and fabricated on thick, high-resistivity silicon. The CCDs, up to 600 microm thick, are fully depleted, ensuring good infrared to x-ray detection efficiency, together with a small point spread function. High readout speed, with good analog performance, is obtained by the use of a large number of parallel output ports. A set of companion 16-channel custom readout integrated circuits, capable of 15 bits of dynamic range, is used to read out the CCD. A gate array-controlled back end data acquisition system frames and transfers images, as well as provides the CCD clocks.

Femtosecond Dynamics of the Collinear-to-Spiral Antiferromagnetic Phase Transition in CuO

We report on the ultrafast dynamics of magnetic order in a single crystal of CuO at a temperature of 207 K in response to strong optical excitation using femtosecond resonant x-ray diffraction. In the experiment, a femtosecond laser pulse induces a sudden, nonequilibrium increase in magnetic disorder. After a short delay ranging from 400 fs to 2 ps, we observe changes in the relative intensity of the magnetic ordering diffraction peaks that indicate a shift from a collinear commensurate phase to a spiral incommensurate phase. These results indicate that the ultimate speed for this antiferromagnetic reorientation transition in CuO is limited by the long-wavelength magnetic excitation connecting the two phases.

Development of a compact fast CCD camera and resonant soft x-ray scattering endstation for time-resolved pump-probe experiments

The designs of a compact, fast CCD (cFCCD) camera, together with a resonant soft x-ray scattering endstation, are presented. The cFCCD camera consists of a highly parallel, custom, thick, high-resistivity CCD, readout by a custom 16-channel application specific integrated circuit to reach the maximum readout rate of 200 frames per second. The camera is mounted on a virtual-axis flip stage inside the RSXS chamber. When this flip stage is coupled to a differentially pumped rotary seal, the detector assembly can rotate about 100°/360° in the vertical/horizontal scattering planes. With a six-degrees-of-freedom cryogenic sample goniometer, this endstation has the capability to detect the superlattice reflections from the electronic orderings showing up in the lower hemisphere. The complete system has been tested at the Advanced Light Source, Lawrence Berkeley National Laboratory, and has been used in multiple experiments at the Linac Coherent Light Source, SLAC National Accelerator Laboratory.

Data Acquisition and Trigger System of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

High speed, direct detection 1k Frame-Store CCD sensor for synchrotron radiation

This work presents the development of a high speed, direct detection, 1k Frame Store CCD camera for synchrotron radiation. We review the research and development of this detector from small scale prototypes to a megapixel sensor, highlighting design challenges and solutions, and reporting on the achieved imaging performance. Further, we report on performance improvements obtained by implementing a second-generation fast readout integrated circuit manufactured in 0.25µm CMOS technology, as well as a voltage buffer chip manufactured in high voltage 0.35µm CMOS technology. The camera presented in this paper is high vacuum-compatible to allow for soft X-ray detection.

Implementation and performance of the electronics and computing system of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), a germanium detector system capable of measuring energy and position (within better than 2 mm rms) of gamma-ray interaction points and tracking multiple gamma-ray interactions, has been built. GRETINA is composed of seven detector modules, each with four high purity germanium crystals. Four custom designed electronics support the operation of the detectors: Digitizer/Digital Signal Processing (DSP), Trigger/Timing, Breakout Chassis and the Detector Interface Box. The Digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions within a crystal. The computing system is composed of VME readout CPUs running VxWorks, which communicate with 62 dual-processor farm (each processor with four cores) through a 10 Gb/s Ethernet switch. The CPUs read out the digitizer/DSPs and send the data to the farm. The processors compute the position and track of the interactions of the gamma-ray inside the crystals. The processor farm is capable of processing in real-time the position of 20 000 gamma-ray/s. In this paper we will present the details of the implementation and performance of the electronics and computing system of GRETINA.

A 1MPixel fast CCD sensor for X-ray imaging

This paper describes the performance of a 1MPixel Frame Store CCD sensor for soft X-ray applications at synchrotron light sources. This camera can be operated in frame store mode with a 1Mpixel imaging area running at 200fps, or in full frame mode with a 2M pixels imaging area running at 100fps. The CCD has 192 outputs that are serviced by custom-designed integrated circuits that perform correlated double-sampling signal processing and digitization. The digitized data is acquired by a custom made image acquisition and camera controller board based on the Advanced Telecommunication Computing Architecture system. Results obtained during a test run at the Advanced Light Source are presented demonstrating the X-ray camera performance.

Fast, radiation hard, direct detection CMOS imagers for high resolution Transmission Electron Microscopy

This work presents the development of radiation-hard CMOS monolithic pixel sensors as direct electron detectors for high resolution, fast dynamic imaging in Transmission Electron Microscopy. The R&D path from small scale prototypes to megapixel, reticle size sensors manufactured in 0.35 and 0.18 µm commercial CMOS processes is briefly reviewed. Design challenges and solutions are highlighted, with reporting on the achieved imaging performance and radiation hardness of sensors that can ultimately achieve readout rates as high as 6.4 gigapixels/s. Further, we will report on the latest search for an improved pixel architecture and layout, and introduce the evaluation of a first prototype sensor manufactured in a 65 nm CMOS process.

Use of High Resolution DAQ System to Aid Diagnosis of HD2b, a High Performance

A novel voltage monitoring system to record voltage transients in superconducting magnets is being developed at LBNL . This system has 160 monitoring channels capable of measuring differential voltages of up to 1.5 kV with 100 kHz bandwidth and 500 kS/s digitizing rate. This paper presents analysis results from data taken with a 16 channel prototype system. From that analysis we were able to diagnose a change in the current-temperature margin of the superconducting cable by analysing Flux-Jump data collected after a magnet energy extraction failure during testing of a high field Nb3Sn dipole.

{\rm Nb}_{3}{\rm Sn}

The superconducting magnet group at Lawrence Berkeley National Laboratory has been developing Nb3Sn high-field accelerator magnet technology for the last fifteen years. In order to support the magnet R&D effort, we are developing a diagnostic system that can help identify the causes of performance limiting quenches by recording small flux-changes within the magnet prior to quench-onset. These analysis techniques were applied to the test results from recent Nb3Sn magnets. This paper will examine various types of events and their distinguishing characteristics. The present measurement techniques are discussed along with the design of a new data acquisition system that will substantially improve the quality of the recorded signals.