^{a)}

^{a)}Contributed paper, published as part of the Proceedings of the 17th Topical Conference on High-Temperature Plasma Diagnostics, Albuquerque, New Mexico, May 2008.

^{1}, Kirk A. Flippo

^{1}and Sandrine A. Gaillard

^{1,c)}

### Abstract

Radiochromic film (RCF) is increasingly being used as a detector for protonbeams from short-pulse laser-matter interaction experiments using the RCF imaging spectroscope technique. The community has traditionally used inexpensive flatbed scanners to digitize and analyze the data, as opposed to more expensive and time-consuming microdensitometers (MicroDs). Often, the RCF densities in some regions exceed an optical density (OD) of 3. Flatbed scanners are generally limited to a maximum OD of . Because of the high exposure density, flatbed scanners may yield data that are not reliable due to light scatter and light diffusion from areas of low density to areas of high density. This happens even when the OD is slightly above 1. We will demonstrate the limitations of using flatbed scanners for this type of radiographic media and characterize them compared to measurements made using a MicroD. A technique for cross characterizing both systems using a diffuse densitometer with a NIST wedge will also be presented.

This work was performed at Los Alamos National Laboratory under the auspices of the U. S. Department of Energy under Contract No. DE-AC52-06NA25396. K.A.F. was supported under LANL Grant No. LDRD-DR 20040064. S.A.G. was supported by DOE-NNSA/UNR under Grant No. DE-FC52-01NV14050.

I. INTRODUCTION

II. METHODOLOGY

III. RESULTS

IV. CONCLUSIONS

### Key Topics

- Image scanners
- 36.0
- Light scattering
- 7.0
- Calibration
- 4.0
- Image sensors
- 4.0
- Optical properties
- 4.0

## Figures

False color example of small-size high-dose structures seen in the beams from ion acceleration experiments. The legend shows OD ranging from OD 0 to OD 5.12 demonstrating data in the image in excess of 5 OD. This image was scanned using a MicroD.

False color example of small-size high-dose structures seen in the beams from ion acceleration experiments. The legend shows OD ranging from OD 0 to OD 5.12 demonstrating data in the image in excess of 5 OD. This image was scanned using a MicroD.

Plot showing counts vs OD for flatbed scanners and MicroD. Scanners graphed are the Epson Expression 1680 at 500 dpi and the Epson V750 at 500 dpi. Note that the curve for the Epson V750 at 6400 dpi is almost identical to that of the same scanner at 500 dpi.

Plot showing counts vs OD for flatbed scanners and MicroD. Scanners graphed are the Epson Expression 1680 at 500 dpi and the Epson V750 at 500 dpi. Note that the curve for the Epson V750 at 6400 dpi is almost identical to that of the same scanner at 500 dpi.

(a) Comparison of two flatbed scanners at a resolution of 500 dpi, Epson V750, Epson Expression 1680, and the Epson V750 at a higher resolution of 6400 dpi. Each curve corresponds to a different nominal value (0.1, 0.2, 0.3, 0.6, 0.9, 2, 3, and 4) of the WNDF’s OD. The horizontal axis represents the diameter in millimeter of the small WNDF disks. The vertical axis represents the ratio / (number of counts obtained when scanning a large piece of WNDF). Note that varies from to . (b) Expanded view of (a) about the low OD data (0.1, 0.2, 0.3, 0.6, and 0.9), for the Epson V750 at 500 dpi, the Epson Expression 1680 at 500 dpi, and the Epson V750 at 6400 dpi. Note that the ratio now only varies from to . (c) Scans preformed on the MicroD. Each curve corresponds to a different nominal value (0.1, 0.2, 0.3, 0.6, 0.9, 2, 3, and 4) of the WNDF’s OD. The horizontal axis represents the diameter in mm of the small WNDF disk. The vertical axis represents the ratio / (number of counts obtained when scanning a large piece of WNDF). Note that the ratio varies from to for the entire range of ODs.

(a) Comparison of two flatbed scanners at a resolution of 500 dpi, Epson V750, Epson Expression 1680, and the Epson V750 at a higher resolution of 6400 dpi. Each curve corresponds to a different nominal value (0.1, 0.2, 0.3, 0.6, 0.9, 2, 3, and 4) of the WNDF’s OD. The horizontal axis represents the diameter in millimeter of the small WNDF disks. The vertical axis represents the ratio / (number of counts obtained when scanning a large piece of WNDF). Note that varies from to . (b) Expanded view of (a) about the low OD data (0.1, 0.2, 0.3, 0.6, and 0.9), for the Epson V750 at 500 dpi, the Epson Expression 1680 at 500 dpi, and the Epson V750 at 6400 dpi. Note that the ratio now only varies from to . (c) Scans preformed on the MicroD. Each curve corresponds to a different nominal value (0.1, 0.2, 0.3, 0.6, 0.9, 2, 3, and 4) of the WNDF’s OD. The horizontal axis represents the diameter in mm of the small WNDF disk. The vertical axis represents the ratio / (number of counts obtained when scanning a large piece of WNDF). Note that the ratio varies from to for the entire range of ODs.

A typical calibration of the best flatbed scanner, Epson V750 at 6400 dpi, to known ODs from the WNDFs. A fit to the data has been added. (a) “Maximum OD of 4” shows the calibration curve fitted to all the ODs’ nominal values (0.1, 0.2, 0.3, 0.6, 0.9, 2, 3, and 4). (b) “Maximum OD of 3” shows the calibration curve fitted to all of the ODs’ nominal values without the OD of 4 (0.1, 0.2, 0.3, 0.6, 0.9, 2, and 3). (c) “Maximum OD of 2” shows the calibration curve fitted to the ODs’ nominal values (0.1, 0.2, 0.3, 0.6, 0.9, and 2). (d) “Maximum OD of 1” shows the calibration curve fitted to the ODs’ nominal values (0.1, 0.2, 0.3, 0.6, and 0.9).

A typical calibration of the best flatbed scanner, Epson V750 at 6400 dpi, to known ODs from the WNDFs. A fit to the data has been added. (a) “Maximum OD of 4” shows the calibration curve fitted to all the ODs’ nominal values (0.1, 0.2, 0.3, 0.6, 0.9, 2, 3, and 4). (b) “Maximum OD of 3” shows the calibration curve fitted to all of the ODs’ nominal values without the OD of 4 (0.1, 0.2, 0.3, 0.6, 0.9, 2, and 3). (c) “Maximum OD of 2” shows the calibration curve fitted to the ODs’ nominal values (0.1, 0.2, 0.3, 0.6, 0.9, and 2). (d) “Maximum OD of 1” shows the calibration curve fitted to the ODs’ nominal values (0.1, 0.2, 0.3, 0.6, and 0.9).

For the best flatbed scanner case, the Epson V750 at 6400 dpi, and for each diameter of the WNDF disks (1.5, 2.5, 3, 4, 5, 5.5, 6, and 8 mm), the percent error is plotted as a function of , which is the OD measured by the DD. corresponds to the fit to the OD of the neutral density filter obtained for (a) from Fig. 4(a), for (b) from Fig. 4(b), for (c) from Fig. 4(c), and for (d) from Fig. 4(d).

For the best flatbed scanner case, the Epson V750 at 6400 dpi, and for each diameter of the WNDF disks (1.5, 2.5, 3, 4, 5, 5.5, 6, and 8 mm), the percent error is plotted as a function of , which is the OD measured by the DD. corresponds to the fit to the OD of the neutral density filter obtained for (a) from Fig. 4(a), for (b) from Fig. 4(b), for (c) from Fig. 4(c), and for (d) from Fig. 4(d).

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