CYCLOTRONS 2010 - List of Authors (Mehaudens, M.)

Paper	Title	Page
MOPCP075	Cyclotron Vacuum Model and H⁻ Gas Stripping Losses	200
	V. Nuttens, M. Abs, J.L. Delvaux, Y. Jongen, W.J.G.M. Kleeven, L. Medeiros-Romao, M. Mehaudens, T. Servais, T. Vanderlinden, P. Verbruggen IBA, Louvain-la-Neuve, Belgium
	Many proton cyclotrons take the advantage of stripping for the extraction, by accelerating H⁻ ions. However, before extraction, the negative ion beam can suffer losses from stripping by the residual gas. The higher is the pressure, the higher the losses. Moreover, the stripped beam will be stopped on the inner wall of the cyclotron, inducing an additional degassing and increasing the pressure and hence losses in the cyclotron. For high beam current, degassing can be too large compared to the pumping capacity and the beam transmission can drop down to zero. The pressure inside the cyclotron has therefore a large impact on the current that can be extracted from the cyclotron. A simple model has been set up at IBA to determine the vacuum pressure in the hills and in the valleys of the Cyclone 70 cyclotron. The transmission is then computed by integration of the gas stripping cross-section along the ion orbits in the cyclotron. Pressure and transmission provided by the model are in good agreement with experimental data in the ARRONAX Cyclone 70 cyclotron installed in Nantes.

Paper

Title

Page

Cyclotron Vacuum Model and H⁻ Gas Stripping Losses

200

V. Nuttens, M. Abs, J.L. Delvaux, Y. Jongen, W.J.G.M. Kleeven, L. Medeiros-Romao, M. Mehaudens, T. Servais, T. Vanderlinden, P. Verbruggen
IBA, Louvain-la-Neuve, Belgium

Many proton cyclotrons take the advantage of stripping for the extraction, by accelerating H⁻ ions. However, before extraction, the negative ion beam can suffer losses from stripping by the residual gas. The higher is the pressure, the higher the losses. Moreover, the stripped beam will be stopped on the inner wall of the cyclotron, inducing an additional degassing and increasing the pressure and hence losses in the cyclotron. For high beam current, degassing can be too large compared to the pumping capacity and the beam transmission can drop down to zero. The pressure inside the cyclotron has therefore a large impact on the current that can be extracted from the cyclotron. A simple model has been set up at IBA to determine the vacuum pressure in the hills and in the valleys of the Cyclone 70 cyclotron. The transmission is then computed by integration of the gas stripping cross-section along the ion orbits in the cyclotron. Pressure and transmission provided by the model are in good agreement with experimental data in the ARRONAX Cyclone 70 cyclotron installed in Nantes.