Performance comparison of streak camera recording systems

This work presents the development of a front-end integrated circuit (IC) targeting the readout of scientific Charge-Coupled Devices (CCDs) for a wide range of applications in the field of X-ray imaging. The reference detector considered is a high-performance 20×480, back-illuminated, n-substrate, fully-depleted CCD developed at the Lawrence Berkeley National Laboratory (LBNL) MicroSystems Lab. The innovation of MARC (Millisecond ASIC for the Readout of CCDs) is to implement a current readout of the CCD, thus overcoming speed limitations of the most common voltage readout source-follower configurations related to the settling of capacitive nodes. By means of the switched-current technique the IC implements a trapezoidal weighting function. The front-end comprises a programmable bias current generator for the CCD output p-MOSFET and the cascade of an integrator and a subtractor stage for the correlated double sampling. MARC also integrates a programmable digital sequencer to drive the switches of the filter. Measurement results show excellent linearity with a maximum error of 0.3 %, an almost ideal weighting function while the simulated ENC is equal to 2.6 hrms+ at an equivalent speed of 200 fps and 9.1 hrms+ at 400 fps. The first prototype of MARC is implemented in a standard CMOS 0.13 µm 1.2 V technology. Design challenges, simulation and preliminary measurement results are presented.

HLS (Hefei Light Source) is an 800MeV electron storage ring in National Synchrotron Radiation Laboratory. To measure electron bunch for Synchrotron Radiation and to understand the machine behavior during the operation, the streak camera system has been built in HLS storage ring on April 2006. The streak camera system mainly consists of the synchrotron light extracting optics setup and OPTOSCOPE the streak camera. The light extracting optics setup consists of the light extracting path and the optics imaging system. The OPTOSCOPE the streak camera consists of a camera main unit with input optics, a remote control unit, a CCD camera readout unit, a power supply unit, a Personal Computer with a frame grabber interface card and ARP-Optoscope software package. The streak camera system operates with synchroscan sweep mode or dual time base sweep mode. Controlling the streak camera and image acquisition is made by the ARP-Optoscope software. At present, the system is used to measure the bunch length and the bunch interval in HLS storage ring. Some typical results of the measurement are given.

<sec>The time-resolved X-ray spectroscopy measurement system based on X-ray streak camera technology is indispensable diagnostic equipment in the study of laser inertial fusion research and high-energy-density physics. However, limited by the effective photocathode length of the X-ray streak tube, the time-resolved spectral measurement system usually used has the shortcomings of narrow spectrum range and poor spectral resolution.</sec><sec>In order to overcome the shortcomings, a novel dual-channel streak tube is developed, which consists of a photocathode, a prefocusing electrode group in temporal direction, an electric quadrupole lens electrode group, a main focusing electrode group in temporal direction, a deflector plate, and a phosphor screen. The photocathode has two slits. When X-rays are incident, two electron beams can be emitted simultaneously. The electric quadrupole lens electrode group is composed of 8 arc electrodes. Two electric quadrupole lenses are formed by the 8 arc electrodes in the spatial direction. Two electron beams emitted from the cathode of the streak tube are first accelerated and prefocused by the prefocusing electrode group in the time direction, and then compressed by the main focusing electrode group in the time direction. In the spatial direction, two electron beams are focused by the two electric quadrupole lenses independently. This novel streak tube structure can focus two electron beams at the same time, thereby increasing the effective photocathode length and maintaining the compact structure of streak tube without increasing the aberration.</sec><sec>The cathode voltage of the designed streak tube is –12 kV, the distance from cathode to grid is 5 mm, and the cathode-grid field strength is 2.4 kV/mm. The cathode is divided into two sections, the spacing between sections is about 13 mm, the length of each section is more than 20 mm, the magnification of the image converter tube is about 1.56 times, the distance between the cathode and the phosphor screen is 300 mm, and the longest size along the cathode direction is 90 mm. The test results of the performance of the streak tube show that the actual effective cathode length of the developed tube reaches 44 mm, the spatial resolution is better than 15 lp/mm, and the deflection sensitivity is better than 40 mm/kV. The effective cathode and spatial resolution of the tube can be increased to 50 mm and 25 lp/mm by further optimizing the structure of the tube and removing the image intensifier with a high sensitivity image recording system, respectively.</sec>

The X-ray Astronomy and Observational Cosmology (XOC) group at Stanford University, in collaboration with the Massachusetts Institute of Technology (MIT) and MIT Lincoln Laboratory (MIT-LL), is developing next generation X-ray detector and readout technologies. Specifically, the XOC group is developing a fast, low noise readout application specific integrated circuit (ASIC) that is intended to be paired with X-ray charge-coupled device (CCD) detectors in development at MIT-LL. This readout ASIC is denoted as the MIT CCD Readout Chip or MCRC. The MCRC prototype is designed in a 350 nm technology node featuring 8 channels. Each channel is composed of two inputs. One is dedicated to read out the proven source follower-based (SF) CCD architecture with two selectable gain settings, an input referred noise of 1.63 e⁻_RMS, an input dynamic range of ±160 mV, channel to channel crosstalk less than -75 dBc, a power consumption of roughly 30 mW/channel, and a bandwidth of approximately 50 MHz, translating to an effective rise time of around 5 ns. Such a response can comfortably support readout speeds for large CCD pixel matrices in excess of 5 Mpixel/s/channel. The chip also features a second input which is an experimental drain-current readout (DR) topology to support Single electron Sensitive Read Out (SiSeRO) CCD stages currently in development at MIT-LL. The MCRC excels in speed while its input noise and bandwidth are on par with commercial discrete offerings, but with smaller power and real-estate footprints. Here we present the latest measurement results for this state-of-the-art prototype readout ASIC.

The LIDAR Thomson scattering technique uses the time of flight of a short laser pulse to spatially resolve measurements of electron temperature (Te) and density (ne) in a plasma. The technique was pioneered at JET and the first profiles were obtained in 1986. The initial system used a 3 J, 0.5 Hz, 300 ps ruby laser and microchannel-plate photomultiplier detectors to make Te and ne profile measurements with ∼10 cm spatial resolution. Since then we have sought to improve both the spatial resolution and frequency of measurement during a JET pulse. It has proved possible to develop a 4 Hz version of the ruby laser and to enhance the rate of cycling of detection and digitizing to match. The main LIDAR system has now been upgraded to 4 Hz and first JET profiles obtained with the new system are presented. For a LIDAR system, the spatial resolution δL along the laser path is given by δL=(c/2)(τ2L+τ2D)1/2, where c is the velocity of light, τL the laser pulse width, and τD the detection system response time. Over a limited spatial extent it is possible to improve spatial resolution by using a streak camera detection system. We have successfully improved the spatial resolution by a factor of 2 by setting up a streak camera detection system in parallel with the main photomultiplier system. The much shorter response time of the streak camera gave ∼5 cm resolution over a 75 cm segment of the ∼2 m plasma diameter. This system was used to examine profile details in the outer part of the JET plasma. Results from this high-resolution LIDAR detection system will be presented. Building on the improved spatial resolution obtained with the streak camera technique, we have now designed and installed a new LIDAR scattering system to diagnose the divertor region of the JET plasma. The laser for the new system is again ruby but uses a different principle to obtain short pulses. We have demonstrated with colleagues from the Troitsk Institute the conversion, using SBS pulse compression, of a standard 25 ns ruby laser into a 300 ps system suitable for LIDAR applications. The main components of the JET Divertor LIDAR system are also described.

The conventional streak camera (CSC) is an optoelectronic instrument that captures the spatial distribution as a function of time of an ultra high-speed luminous phenomenon with picosecond temporal resolution and a typical spatial resolution of several tens of micrometers. This paper presents two tubeless streak camera architectures called MISC (matrix integrated streak camera) and VISC (vector integrated streak camera), which replicate the functionality of a CSC on a single CMOS chip. The MISC structure consists of a lens, which spreads the photon flux on the surface of a specific pixel array-based (Bi)CMOS sensor. The VISC architecture is based on a sensor featuring a single column of photodetectors, where each element is coupled to a front-end and a multi-sampling and storage unit. In this case the optical objective used in front of the sensor focuses the luminous event on the several tens of micrometers wide photosensitive column. For both architectures, the spatial resolution is linked to the size of the photodetector and the temporal resolution is determined by the bandwidths of the photodetectors and the signal conditioning electronics. The capture of a 6 ns full width at half maximum 532 nm laser pulse is reported for two generations of MISC and a first generation of VISC.

We describe our research on the employment of an infrared upconversion screen made of electron trapping material (ETM) in combination with the high sensitivity of the S-20 photocathode responsive to visible radiation to produce a streak camera arrangement capable of viewing and recording infrared incident pulses. The ETM-based upconversion screen converts 800–1600 nm infrared radiation to visible light which is viewed or recorded by the S-20 photocathode. The peak values of the upconversion efficiency are located at 1165 nm for CaS:Eu, Sm and 1060 nm for CaS:Ce, Sm. The present experiment showed time resolution was 12.3 ps for a CaS:Eu, Sm screen and 8.4 ps for a CaS:Ce, Sm screen. The minimum detectability is 4.8×10−9 J/mm2 (minimum detectability of the coupled visible streak camera is 8.3×10−10 J/mm2). Other parameters, such as spatial resolution and dynamic range, have also been measured and analyzed. The results show ETM can be used in the measurement of infrared ultrafast phenomena up to picosecond time domain. In consideration of the limited number of trapped electrons in ETM, the infrared-sensitive streak camera consisting of an ETM-based upconversion screen is suitable to operate in the single shot mode.

Details of the design and development of a bright vacuum ultraviolet Seya–Namioka type spectrometer and streak camera system with reflection-type input optics is presented. The Seya–Namioka spectrometer has a 40 mm by 45 mm holographic grating with a groove density of 600 grooves/mm, linear dispersion of 8 nm/mm, and effective F-number of 4.2. To eliminate loss of light by absorption, the streak camera imaging unit uses Al and MgF2 coated imaging optics with at least 80% reflection from 125–850 nm and has an effective F-number of 4. It is equipped with a synchronized scan unit that can be tuned to 82 MHz and a slow scan speed unit that can measure up to 2-MHz single event. Temporal response of the system at the 20-ns scanning range is evaluated to be around 260 ps.

Two techniques are used to obtain a direct readout of an ultrafast streak camera. The first method uses a linear solid state Reticon diode array and the second technique entails the use of a SEC vidicon camera. Both methods use fiber optics to couple the light from the output of the streak camera to the sensor. In addition, the SEC vidicon is interfaced to a PDP 11/40 graphics computer system for direct data processing. For both systems, data will be presented as to (1) dynamic range, (2) spatial resolution, (3) linearity, (4) signal processing techniques, and (5) problems and modifications of the devices including mechanical mounting procedure for attaching fiber optics directly to the array chip.

A recently developed prototype streak tube designed to produce high gain and resolution by incorporating the streak and readout functions in one envelope thereby minimizing photon-to-charge transformations and eliminating external coupling losses is presented. The tube is based upon a grid-gated Silicon-Intensified-Target Vidicon (SITV) with integral Focus Projection Scan (FPS) TV readout. Demagnifying electron optics (m=0.63) in the image section map the 40-mm-diameter photocathode image unto a 25-mm-diameter silicon target where gains ≥ 103 are achieved with only 10 KV accelerating voltage. This is compared with much lower gains (~ 50) at much higher voltages (~ 30 KV) reported for streak tubes using phosphor screens. Because SIT technology is well established means for electron imaging in vacuum, such fundamental problems as "backside thinning" required for electron imaging unto CCDs do not exist. The high spatial resolution (~ 30 1p/mm), variable scan formats, and high speed electrostatic deflection (250 mm2 areas are routinely rastered with 256 scan lines in 1.6 ms) available from FPS readout add versatility not available in CCD devices. Theoretical gain and spatial resolution for this design (developed jointly by Los Alamos National Laboratory and General Electric Co.) are compared with similar calculations and measured data obtained for RCA 73435 streaks fiber optically coupled to (1) 25-mm-diameter SIT FPS vidicons and (2) 40-mm-diameter MCPTs (proximity-focused microchannel plate image intensifier tubes) fiber optically coupled to 18-mm-diameter Sb2S3 FPS vidicons. Sweep sensitivity, shutter ratio, and record lengths for nanosecond duration (20 to 200 ns) streak applications are discussed.

Summary form only given. The spectral range at which conventional streak camera systems operate is limited by the spectral response of the photocathode used. For most photocathode materials, the sensitivity is limited to wavelengths shorter than 1.5 /spl mu/m. Beyond this wavelength, the quantum efficiency of the photocathode becomes negligible. The temporal profile of mid- and far-infrared light pulses can thus not be measured directly using a conventional streak camera. We constructed an atomic streak camera in which the photocathode used in conventional streak cameras is replaced by a sample of gas phase Rydberg atoms for the conversion from photons to electrons. Due to the low binding energy of the electrons of Rydberg atoms, the IR photon energy is already sufficient to photoionize the atoms and create electrons. The combination of a low ionization threshold with the high photoionization cross section makes a Rydberg atom photocathode very suitable for use in an IR streak camera.

The resolution of streak camera systems strongly depends on the slew rate of the deflecting element, being proportional to the amplitude and the frequency of the deflector. An attractive approach to reach femto and even sub-femto second resolution are THz driven electron streak cameras, which have been only recently proposed. Here, the ultra fast streaking field is generated by exciting a suitable resonant THz antenna, e.g. a split ring resonator with an intense THz pulse [1]. With today’s THz sources streak field amplitudes in excess of 1 GV/m are within reach. Here, we present the concept for a proof of principle system. The THz pulse will be generated by rectifying the pulse from an existing 800 nm laser system in a suitable crystal as LiNbO3 [2]. For the source of the electron beam to be streaked, we plan to use an RF photo gun yielding a relativistic 6.5 MeV beam. We describe the setup of the system and present simulations of the beam dynamics.

Several scientific programs at Lawrence Livermore National Laboratory (LLNL) require instrumentation that can capture optical signals with high fidelity. Typically, they require high temporal resolution, high spatial resolution, and high dynamic range. The instrument of choice for most of these multichannel, data-recording applications is the optical streak camera. We have evaluated three optical streak camera systems under similar conditions: (1) the EG&G model L-CA-15 streak camera, designed and built under U.S. Department of Energy (DOE) contract, with a streak tube designed for a time response of a few picoseconds; (2) an in-house (LLNL) design, with an ITT F4157 streak tube that operates in the extraction mode; and (3) a Thomson-CSF model TSN 506 streak camera, with an ITT F4157 streak tube that also operates in the extraction mode. All three systems were found to be capable of time response better than 40 ps FWHM, a dynamic range of greater than 100, and spatial resolution greater than 5 line pairs per millimeter (lp/mm). The experimental setup and plots of results are presented and discussed.

A high-speed imaging device based on a streak camera has been demonstrated, which provides multiple images from non-repeatable transient events of time scale >= 1 ns. It can be employed for pulsed laser beam diagnostics, measuring laser beam spatial and temporal structure on a single-pulse basis. The system currently has angular resolution of 16 X 16 pixels, with a time resolution of 250 ps. The laser beam width is sized to fill the input optic, and the image is dissected by a square array of optical fibers. At the other end of the fiber optic image converter, the 256 fibers form a line array, which is input to the slit of a streak camera. The streak camera sweeps the input line across the output phosphor screen so that position is directly proportional to time. The resulting 2-D image (fiber position vs. time) at the phosphor is read by an intensified (SIT) vidicon TV tube, and the image is digitized and stored. A computer subsequently decodes the image, unscrambling the linear pixels into an angle-angle image at each time. We are left with a series of snapshots, each one depicting the laser beam spatial profile (intensity cross-section) at succeeding moments in time. The system can currently record several hundred images over a span of 25 to 400 ns. This detector can study lasers of pulse width >= 1 ns and with a visible wavelength (200 - 900 nm). Candidate lasers include doubled Nd:YAG, excimer, ruby, nitrogen, metal vapor, and Ti:Sapphire. The system could also be simply configured as an 8 X 8 element wavefront sensor to record the cross-sectional distribution of phase, as well as amplitude. Finally, suggestions for system improvement are detailed, and the ultimate limitations of the method in terms of spatial and temporal resolution are discussed.

Small-animal PET has become a rapidly growing approach to problems in human health, from addiction to cancer to drug development. However, the best presently available PET technology (/spl sim/2 mm resolution) still has significant limitations in spatial resolution and sensitivity which are particularly problematic for applications attempting to take advantage of powerful transgenic mouse models. Most currently proposed approaches to improving resolution face a number of technical obstacles which force trade-offs in performance. A novel design which circumvents many of these compromises is a miniaturized and modernized "Anger" or "gamma" camera, with a principle similar to well-known detectors for SPECT, in which a continuous scintillator crystal is used and position is determined from light-sharing among groups of photodetectors. Critical improvements over the traditional Anger design include a more appropriate scintillator for PET (LSO), a thinner crystal for higher spatial resolution, and large-area avalanche photodiode (APD) technology as the photodetector which allows layering of the detector to improve sensitivity, among other benefits. The feasibility of the approach has been studied in terms of spatial and energy resolution, sensitivity, and cost, with promising results. A prototype is complete and preliminary measurements have been performed.