CRYSIS    -    CRYogenic Stockholm Ion Source


CRYSIS is an ion source of EBIS-type (Electron Beam Ion Source) and is the injector to CRYRING. One important feature of an EBIS is that it can produce highly intense electron beams with high current densities. By colliding with the atoms the electron beam ionizes the gas. An ionization process is when an electron initially bound to the atom is removed. When the desired charge state is reached the ion beam is transported through the beam line system to the storage ring or to some other experiment. This type of ion source is designed specially for production of ions with very high charge states.
 


 

An EBIS source consists of an electron gun producing an electron beam which is compressed and confined by the magnetic field of the solenoid. CRYSIS uses a superconducting solenoid in order to produce the high magnetic field necessary to achieve high electron beam densities. The cryostat is cooled to -269 °C by liquid helium and is configured to provide the extremely high vacuum inside the source necessary to prevent recombination of highly charged ions.

There are two ways of inject gas into the EBIS. For simple gases like Ar or Ne a gas inlet is used. The gas is injected more or less directly into the electron beam. The other way to inject gas is to use the external ion source named INIS. It is typically used for metallic ions, where the gas inlet can't be used. In this case an ion beam is injected through the electron collector and into the EBIS. Here they are trapped in a potential well, created radially by the electron space charge and axially by a system of tube electrodes around the beam. During the injection from INIS the potential distribution is such that it allows the injected ions to overcome the potential barrier and be caught in the potential well. When the trap is full, the potential distribution is changed and the ions are trapped. The charge state increases gradually by successive ionization as the ions collide with energetic electrons.

After a selected ionization time the potential distribution is changed and the ions are extracted through the electron collector again. The well defined ionization time in this type of ion source leads to a narrow charge state distribution. The attainable charge state is limited by the electron beam energy which must be greater than the ionization energy for the last electron. CRYSIS is designed for 50 keV electron energy which is sufficient for the production of bare nuclei of all elements up to xenon.

CRYSIS characteristics:

 
nominal values max values units
electron gun perveance 0.47 - µA/V²´³
electron beam current 350  1300 mA
electron beam energy 20  27.5 keV
trap length 1.2  - m
magnetic field 1.5 5 T
electron beam current density 150 250 A/cm²
ion energy 3.5 50 keV × q
charge per pulse 1-2 4 nC
ion pulse length 0.05-100 - µs
containment time 20-2000 - ms



For more information about the CRYSIS ion source, contact Leif Liljeby email: liljeby@msi.se


webmaster@msi.se
2003-03-28