Abstract
In order to study the possibilities to produce high currents of pulsed heavy ion beams dedicated to synchrotron injection, two new approaches of ECR devices are now underway. The basic principle consists in maintaining a functioning point of the source with the highest density as possible and a minimum confinement time for the production of a given charge state. It means that for a constant neτi product we try to maximize ne and minimize τi. For this purpose two experiments are in progress at ISN/Grenoblea and IAP/Nizhny Novgorod.b The first one consists of using a minimum |B| magnetic structure with a 1.8 mirror ratio characteristic value with a 28 GHz frequency injection. In this case we explore different functioning points up to 10 kW of UHF power. The second one consists of a simple mirror magnetic system (simple mirror ion source, SMIS) working at 37.5 GHz with a mirror ratio up to 3 (2.5 T) where we study discharges with a peak power up to 100 kW. We will show that, in spite of a very short rising time of the current, we can maintain the production of multicharged ions and that we can observe very high current densities. In the future, the challenge will be the design of an extraction geometry matching theses current levels.
Highlights
The two main parameters that measure the capability of a plasma to produce multicharged ion are the electronic density ne and the confinement time of the ions i especially if we assume that the suitable electronic energy can be achieved in any case due to the efficiency of the ECR heating.The product nei is a rough measurement of the collision rate so it is roughly proportional to theZof the ion in the plasma
The second one consists of a simple mirror magnetic systemsimple mirror ion source, SMISworking at 37.5 GHz with a mirror ratio up to 3 ͑2.5 Twhere we study discharges with a peak power up to 100 kW
The aim of this project consists in multiplying the density by a factor of 3, that seems achievable with a 28 GHz discharge and optimizing the confinement time with a diviaUnder grant CERN/GSI/CEA/IN2P3 K598/PS and EU Contract No HPRI1999-50019. bUnder Grant IAP/IN2P3-2/2001
Summary
The two main parameters that measure the capability of a plasma to produce multicharged ion are the electronic density ne and the confinement time of the ions i especially if we assume that the suitable electronic energy can be achieved in any case due to the efficiency of the ECR heating. The ratio ne /i is roughly proportional to the flux of particles arriving to the wall so the current density of a given charge state. The aim of this project consists in multiplying the density by a factor of 3, that seems achievable with a 28 GHz discharge and optimizing the confinement time with a diviaUnder grant CERN/GSI/CEA/IN2P3 K598/PS and EU Contract No HPRI1999-50019. The current is multiplied by a factor of 10 and theZremains constant so we look for a modification of the charge state distribution as illustrated by Fig. 1 We think that this functioning point could be achieved in a quite simple 28 GHz classical source working with a mirror ratio around 1.5. If we plan to work with high density and low confinement it means that the loss rate of the particles will be very high so that will need of a strong UHF power density in order to maintain the electronic density
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