A cold electron-impact ion source driven by a photo-cathode -- New opportunities for the delivery of radioactive molecular beams?

TL;DR

This paper introduces a novel cold electron-impact ion source driven by a photo-cathode, enabling the potential delivery of radioactive molecular beams for elements difficult to ionize with traditional hot sources.

Contribution

It presents the first measurements of a cold electron-impact ion source using photo-electron emission, offering a new approach for isotope separation and radioactive beam production.

Findings

Successful operation of a cold electron-impact ion source at ambient temperature.

Potential for improved survival of volatile molecules during ionization.

New opportunities for radioactive molecular beam delivery.

Abstract

The thick-target ISOL (Isotope mass Separation OnLine) method provides beams of more than 1000 radionuclides of 74 elements. The method is well established for elements with sufficiently high volatility at ca. 2000 {\deg}C. To extract non-volatile elements the formation of a volatile molecule is required. While successful in some cases (e.g. carbon or boron), most of these elements are not yet available as ISOL beam. A variety of volatile carrier molecules has been proposed for all elements produced in the target material, but their probability of survival during the extraction and ionization process is often limited by the high temperatures required for isotope diffusion in the thick targets and for ion source operation. While cold target concepts have already been proposed, the normal mode of operation of the typically used Versatile Arc Discharge Ion Source (VADIS) with a hot cathode is not well suited. Here, we report about first measurements with an electron-impact ion source operated at ambient temperature using electrons that were liberated via the photo-electric effect from a copper cathode.