Achromatically filtered diamond photoconductive detectors for high power soft x-ray flux measurements

Abstract

A 1 mn-t square diamond photoconductive detector (PCD) has been installed on the LLNL Nova laser system, for use as a broad band soft x-ray power diagnostic. The PCD is installed behind an array of pinholes, which cast multiple, overlapping images of the source onto the diamond. This allows reduction of the x-ray intensity, to avoid saturation problems, while avoiding the spectral dependency of thin film filters. The diode current is read out on a 5 GHz bandwidth scope. The system is calibrated by comparison to an absolutely calibrated array of filtered vacuum x-ray photodiodes (XRD's) ("dante"). The time response of the PCD and its bias electronics have been characterized using the 5th harmonic (210 run) of a short pulse (< 1 ps) Ti:sapphire laser. The data show a fast rise, limited by the 5 GHz scope bandwidth, and a slower fall off, characterized by an RC time of order 200 ps. Abstract A 1 mm square diamond photoconductive detector (PCD) has been installed on the LLNL Nova laser system, for use as a broad band soft x-ray power diagnostic. The PCD is installed behind an array of pinholes, which cast multiple, overlapping images of the source onto the diamond. This allows reduction of the x-ray intensity, to avoid saturation problems, while avoiding the spectral dependency of thin film filters. The diode current is read out on a 5 GHz bandwidth scope. The system is calibrated by comparison to an absolutely calibrated array of filtered vacuum x-ray photodiodes (XRD's) ("dante"). The time response of the PCD and its bias electronics have been characterized using the 5th harmonic (210 nm) of a short pulse (< 1 ps) Ti:sapphire laser. The data show a fast rise, limited by the 5 GHz scope bandwidth, and a slower fall off, characterized by an RC time of order 200 ps.

Analytic models of high-temperature hohlraums

“…10 and 19 are equivalent; however, Eq. 19 gives T,(t) as a function of f~, fW, T~, and TW, quantities that can be directly measured as a function of time in a hohlraum experiment [83,[87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][105][106].…”

Shock propagation, preheat, and x-ray burnthrough in indirect-drive inertial confinement fusion ablator materials

“…19 These x-ray diagnostics were used to confirm the time-, spatially, and spectrally dependent x-ray emission from the hohlraum walls and from the x-ray driven side of the ablator samples. The Dante diagnostic measures hohlraum x-ray reemission flux with an array of ten K-and L-edge filtered photocathode detectors with grazing incidence mirrors on some the low energy channels.…”

Diagnostics development plan for ZR.

“…9), with one LOS pipe section extending to 26 m. The LOS 5/6 diagnostics package is designed to provide the primary x-ray energy, power, and spectral measurements of the z-pinch itself. Five port locations exist and are typically used to field instruments including a bolometer array [67], an x-ray diode (XRD) array [68], a photoconducting detector (PCD) array [69][70][71], a transmission grating spectrometer (TGS) [43] (Fig. 10), and a total energy and power (TEP) diagnostic [72] or a calorimeter [73].…”

“…Diamond photoconducting detectors (PCDs) [69][70][71] are primary x-ray flux diagnostics on Z that feature fast, stable, flat response out to about 6 keV with a rugged, readily cleanable surface and very limited sensitivity to bremsstrahlung radiation. Initial attempts to calibrate the PCDs with NSLS and dc Henke x-ray sources resulted in unacceptably large error bars because of the variation of detector response across the surface and the spatial nonuniformity of the calibration sources.…”