758
M. Dohlus et al.
elements has been an ongoing effort at JINR, GSI, and RIKEN, in particular, but
other laboratories such as JYFL, Jyväskylä, have recently entered; others such as
SPIRAL2 plan to do so. In this article it is not possible to mention the complete
list of facilities. An overview of nuclear physics facilities, including the heavy ion
accelerators that exist worldwide, is given in the IUPAP Report 41 [157]. Indeed,
there has been something of a renaissance in low- and medium-energy heavy ion
accelerators in recent years.
The history of heavy ion accelerators, which began with the Berkeley cyclotrons
in the 1950s, is described by E. Wilson in Chap. 1.
11.5.2.2 Special Issues of Heavy Ion Accelerators and Storage Rings
Some specific issues must be considered when designing accelerators and storage
rings for heavy ions. These issues are not relevant for proton or light ion machines.
Ion sources are needed which can generate highly charged, intense ion beams
of accelerator-compatible beam quality for the full spectrum of elements, with
their varying physical and chemical properties. During the acceleration of partially
ionized, highly charged heavy ions, charge-changing processes occur, whether by
accident or design. Knowledge of the equilibrium ion beam charge after it passes
targets (strippers), and of the yield in the desired charge state after stripping, is
important when designing and optimising an accelerator layout. The high specific
energy loss and irradiation effects are much more important issues for heavy ions
than for light ones. Knowledge of charge-changing cross sections is important when
estimating beam transmission in synchrotrons and beam lifetimes in storage rings
for given vacuum conditions, as well as recombination processes during electron
cooling. In synchrotrons and storage rings, heavy-ion-induced gas desorption
processes are crucial with respect to intensity limits and lifetimes of ion beams.
The reference atom for the design of the large in-flight driver accelerators to be
described later is 238 U. Therefore, the explanation of aspects specific to heavy ions
will mainly be confined to that element.
11.5.2.2.1 Ion Sources
The first ion sources used for multiply charged ions in accelerators were been
Penning ion sources. In the 1950s, the cold-cathode Penning type was developed
at Berkeley for ion beam production [158]. Later, the hot-cathode Penning ion
source, which provided higher ion-beam currents for medium-charged ions, was
the favourite choice both for linear and cyclotron heavy ion accelerators up to the
mid-1980s [159]. It was now possible to deliver beams of up to several 100 μA for
U 10+ [160]. However, the source lifetime was limited by erosion of the discharge
electrodes. In addition, in view of the fact that beams from metallic elements were
produced by using the sputtering technique, the lifetime of sputter electrodes was a
limiting factor, too, along with rather high material consumption. This was a serious
M. Dohlus et al.
elements has been an ongoing effort at JINR, GSI, and RIKEN, in particular, but
other laboratories such as JYFL, Jyväskylä, have recently entered; others such as
SPIRAL2 plan to do so. In this article it is not possible to mention the complete
list of facilities. An overview of nuclear physics facilities, including the heavy ion
accelerators that exist worldwide, is given in the IUPAP Report 41 [157]. Indeed,
there has been something of a renaissance in low- and medium-energy heavy ion
accelerators in recent years.
The history of heavy ion accelerators, which began with the Berkeley cyclotrons
in the 1950s, is described by E. Wilson in Chap. 1.
11.5.2.2 Special Issues of Heavy Ion Accelerators and Storage Rings
Some specific issues must be considered when designing accelerators and storage
rings for heavy ions. These issues are not relevant for proton or light ion machines.
Ion sources are needed which can generate highly charged, intense ion beams
of accelerator-compatible beam quality for the full spectrum of elements, with
their varying physical and chemical properties. During the acceleration of partially
ionized, highly charged heavy ions, charge-changing processes occur, whether by
accident or design. Knowledge of the equilibrium ion beam charge after it passes
targets (strippers), and of the yield in the desired charge state after stripping, is
important when designing and optimising an accelerator layout. The high specific
energy loss and irradiation effects are much more important issues for heavy ions
than for light ones. Knowledge of charge-changing cross sections is important when
estimating beam transmission in synchrotrons and beam lifetimes in storage rings
for given vacuum conditions, as well as recombination processes during electron
cooling. In synchrotrons and storage rings, heavy-ion-induced gas desorption
processes are crucial with respect to intensity limits and lifetimes of ion beams.
The reference atom for the design of the large in-flight driver accelerators to be
described later is 238 U. Therefore, the explanation of aspects specific to heavy ions
will mainly be confined to that element.
11.5.2.2.1 Ion Sources
The first ion sources used for multiply charged ions in accelerators were been
Penning ion sources. In the 1950s, the cold-cathode Penning type was developed
at Berkeley for ion beam production [158]. Later, the hot-cathode Penning ion
source, which provided higher ion-beam currents for medium-charged ions, was
the favourite choice both for linear and cyclotron heavy ion accelerators up to the
mid-1980s [159]. It was now possible to deliver beams of up to several 100 μA for
U 10+ [160]. However, the source lifetime was limited by erosion of the discharge
electrodes. In addition, in view of the fact that beams from metallic elements were
produced by using the sputtering technique, the lifetime of sputter electrodes was a
limiting factor, too, along with rather high material consumption. This was a serious