Lateral charge diffusion in back-illuminated CCDs directly affects the point spread function (PSF) and spatial resolution of an imaging device. This can be of particular concern in thick, back-illuminated CCDs. We describe a technique of measuring this diffusion and present PSF measurements for an 800x1100, 15 mu m pixel, 280 mu m thick, back-illuminated, p-channel CCD that can be over-depleted. The PSF is measured over a wavelength range of 450 nm to 650 nm and at substrate bias voltages between 6 V and 80 V.

Instrumentation was developed in 2004 and 2005 to measure the quantum efficiency of the Lawrence Berkeley National Lab (LBNL)total-depletion CCD's, intended for astronomy and space applications. This paper describes the basic instrument. Although it is conventional even to the parts list, there are important innovations. A xenon arc light source was chosen for its high blue/UV and low red/IR output as compared with a tungsten light. Intensity stabilization has been difficult, but sinceonly flux ratios matter this is not critical. Between the light source andan Oriel MS257 monochromator are a shutter and two filter wheels. High-bandpass and low-bandpass filter pairs isolate the 150-nm wide bands appropriate to the wavelength, thus minimizing scattered light and providing order blocking. Light from the auxiliary port enters a 20-inch optical sphere, and the 4-inch output port is at right angles to the input port. An 80 cm drift space produces near-uniform illumination on the CCD. Next to the cold CCD inside the horizontal dewar is a calibrated reference photodiode which is regulated to the PD calibration temperature, 25$^\circ$ C. The ratio ofthe CCD and in-dewar reference PD signals provides the QE measurement. Additional cross-calibration to a PD on the integrating sphere permitslower-intensity exposures.

We describe charge-coupled device (CCD) development activities at the Lawrence Berkeley National Laboratory (LBNL). Back-illuminated CCDs fabricated on 200-300 mu m thick, fully depleted, high-resistivity silicon substrates are produced in partnership with a commercial CCD foundry.The CCDs are fully depleted by the application of a substrate bias voltage. Spatial resolution considerations require operation of thick, fully depleted CCDs at high substrate bias voltages. We have developed CCDs that are compatible with substrate bias voltages of at least 200V. This improves spatial resolution for a given thickness, and allows for full depletion of thicker CCDs than previously considered. We have demonstrated full depletion of 650-675 mu m thick CCDs, with potential applications in direct x-ray detection. In this work we discuss the issues related to high-voltage operation of fully depleted CCDs, as well as experimental results on high-voltage-compatible CCDs.

An overview of CCD development efforts at Lawrence Berkeley National Laboratory is presented. Operation of fully-depleted, back-illuminated CCD's fabricated on high resistivity silicon is described, along with results on the use of such CCD's at ground-based observatories. Radiation damage and point-spread function measurements are described, as well as discussion of CCD fabrication technologies.