Picosecond Ion Pulses from an EN Tandem Created by a Femtosecond Ti:Sapphire Laser

K. D. Carnes, C. L. Cocke, Z. Chang, I. Ben-Itzhak, H. V. Needham, A. Rankin
James R. Macdonald Laboratory, Department of Physics, Kansas State University, Manhattan, KS, USA

The James R. Macdonald Laboratory at Kansas State University is constantly looking for novel ways to combine our traditional accelerator expertise with our ever expanding ultrafast laser capabilities. One such combination is to produce picosecond pulses of stripping gas ions in the high energy accelerating tube of our EN tandem by directing ~100 femtosecond, sub-milliJoule laser pulses up the high energy end of the tandem toward a focusing mirror at the terminal. The scaled time-of-flight spread between ions created by the same laser pulse has been measured at around 70 picoseconds, although the spread between pulses (pulse-to-pulse jitter) is more like a nanosecond. The jitter is caused primarily by the tandem terminal voltage ripple, which can in theory be compensated for with proper feedback electronics. Other broadening effects, such as thermal motion of the gas, size of the laser focus, and space charge, all contribute to the measured width and will be discussed in this talk. SIMION calculations showing the effect of Dowlish titanium spiral inclined field tubes on the pulses will also be presented. We are currently adapting an X-ray streak camera to allow us to better study the time structure of individual ion pulses created by the laser.

This work was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy.

Presented at ISIAC, August 2007 in Crete, Greece.

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