Polarization pyrometry: an improvement to multi-wavelength optical pyrometry.

We describe a new method that improves upon temperature measurement by optical pyrometry. The main uncertainty in the traditional pyrometry technique is the surface emissivity, which is generally unknown and hard to measure. A common approach to deal with this problem is to measure the thermal emission at multiple wavelengths - an approach called multi-wavelength pyrometry. However, this technique can still result in a level of uncertainty in the surface temperature that is unsatisfactory for scientific applications, such as a measurement of equation of state of warm dense matter. In contrast to the conventional multi-wavelength technique, in the polarization pyrometry approach described herein, p- and s-polarization components of thermal radiation at multiple-angles are used to deduce the temperature. This paper describes the concept and the results of an initial proof-of-principle static experiment with an electrically heated tungsten ribbon. It was found that in the same experiment, the accuracy of the polarization pyrometry measurement was substantially greater than that achieved using conventional multi-wavelength pyrometry.

Diagnostics for ion beam driven high energy density physics experiments.

Intense beams of heavy ions are capable of heating volumetric samples of matter to high energy density. Experiments are performed on the resulting warm dense matter (WDM) at the NDCX-I ion beam accelerator. The 0.3 MeV, 30 mA K(+) beam from NDCX-I heats foil targets by combined longitudinal and transverse neutralized drift compression of the ion beam. Both the compressed and uncompressed parts of the NDCX-I beam heat targets. The exotic state of matter (WDM) in these experiments requires specialized diagnostic techniques. We have developed a target chamber and fielded target diagnostics including a fast multichannel optical pyrometer, optical streak camera, laser Doppler-shift interferometer (Velocity Interferometer System for Any Reflector), beam transmission diagnostics, and high-speed gated cameras. We also present plans and opportunities for diagnostic development and a new target chamber for NDCX-II.

Heavy-ion-induced electronic desorption of gas from metals.

During heavy-ion operation in several particle accelerators worldwide, dynamic pressure rises of orders of magnitude were triggered by lost beam ions that bombarded the vacuum chamber walls. This ion-induced molecular desorption, observed at CERN, GSI, and BNL, can seriously limit the ion beam lifetime and intensity of the accelerator. From dedicated test stand experiments we have discovered that heavy-ion-induced gas desorption scales with the electronic energy loss (dE_{e}/dx) of the ions slowing down in matter; but it varies only little with the ion impact angle, unlike electronic sputtering.

Drift compression of an intense neutralized ion beam.

Longitudinal compression of a velocity-tailored, intense neutralized beam at 300 keV, 25 mA has been demonstrated. The compression takes place in a 1-2 m drift section filled with plasma to provide space-charge neutralization. An induction cell produces a head-to-tail velocity ramp that longitudinally compresses the neutralized beam, enhancing the beam peak current by a factor of 50 and producing a pulse duration of about 3 ns. This measurement has been confirmed independently with two different diagnostic systems.