Lorentz dissociation of hydrogen ions in a cyclotron

Abstract

Stripping extraction of hydrogen molecular ions has gained interest in the cyclotron industry due to its high extraction efficiency. However, the magnetic field could result in undesired Lorentz dissociation of the hydrogen anion/molecular ions during acceleration. Studies of dissociation under electric fields comparable to that of a Lorentz-transformed magnetic field in a typical cyclotron (a few MV/cm) are sparse. Hence, in order to fill in the missing yet crucial information when designing a cyclotron, this work compiles and summarizes the study of Lorentz dissociation of H-, H+ 2 and H+ 3 for stripping extraction in a cyclotron.

Cyclotrons: Why/how are their dynamics different?

“…This is related to the fact that the H − ions place an upper limit of 0.56 Tesla on the magnetic field, and therefore limit the azimuthal field variation (the 'flutter') to a very low value. More details found in paper by Koay in this issue [29].…”

“…Besides the necessities of extraction (see [29]), for any given design, the energy limit is related to the betatron tune. A difficult feature of cyclotrons is that the radial tune usually varies with radius.…”

A high-intensity superconducting H+ 3 cyclotron for isotope production

“…We concentrate on two types of H + 3 beam loss: electromagnetic dissociation and interactions with residual gas. The electromagnetic dissociation of hydrogen ions is discussed at length in [38]. Here we briefly summarize the points for specific application to the TR150.…”

Intensity limit in compact H- and H+ 2 cyclotrons

“…Higher currents are achievable but at the cost of either more frequent maintenance, or an increase in the injection energy. Lorentz stripping limits such cyclotrons to around 70 MeV [31]. Higher energies with the same advantages of the very large phase acceptance will still only be possible with stripping extraction.…”