LBNL has developed an X-ray camera using a custom CCD sensor and custom ADC/readout IC. The first version of CCD sensor used for proof of principle is 480 x 480 pixels. The pixel size is 30x30um. This device is back illuminated, 200 um thick and fully depleted. Its efficiency for X-ray for energies up to about 8 keV is close to 100% and it covers the needs of the Advanced Light Source as a soft X-ray facility. The CCD has 96 outputs that allow the camera to run up to 200 fps. In order to digitize the data from the sensor, we developed a custom ADC/readout ASIC called FCRIC. This chip has 16 inputs and 4 digital outputs. Each output sends the data from 4 inputs serially using LVDS logic. The chip besides digitizing the data in 15 bits range has 3 gain selections that automatically change to accommodate low and high input pulses. It also performs correlated double sampling. These ICs are described in [1]. The first prototype has been used at the ALS and it showed promising results. In order to be able to better fit this camera into new experiments a new camera head was designed. This is called c(compact)FCCD. This new camera uses the same sensor and ADC/readout chip but it fits in a 2.5inch cube. The camera will be used in an experiment on Hutch 2 at LCLS later in 2010.
The forecasts for future light sources needs indicate that faster and bigger (more pixels) sensor will be needed. LBNL is researching new technologies to solve this new requirement. Among several options SOI (Silicon On Insulator) has been studied under Laboratory Directed R&D funds. Some initial good results have been presented. Currently we are working on a X-ray sensor called femtopix. This is a gated chip that performs correlated double sampling. The goal of this chip is to run at 4000fps allowing the study of a femto sliced bunches while avoiding the front end to be swamped by the back ground radiation by gating the input.
The presentation concludes stating the most of the current sensor (not limited to the ones developed at the lab) do not perform image processing in hardware and in real time. They usually send raw data to a storage system. This solution works for the present systems but as we progress into the future where the sensors will run as fast as 100k fps this will not be a reasonable solution because the data through put will too big and the storage systems will also be too big. For this reason research on adding intelligence to these cameras by adding more logic to the pixels and to the readout systems through the use of FPGA is currently taking place at the LBNL. These new sensors and new image processing algorithms will be part of the solution to develop the cameras that will meet the need of the future light sources in our opinion.