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GSI-ACCELERATORS-02 GSI SCIENTIFIC REPORT 2009
130
Figure 1: Two–dimensional ion beam profiles of Ar 8+ ion
beams at the location of the RFQ entrance for different settings
of the LEBT.
and the instrumentation, the infrastructure and the controls
of the test bench were functional in late 2009.
In order to establish a standard procedure for the production
of 50 Ti beams from highly enriched materials a test series
was started at the EIS to investigate different types of
evaporation ovens.
High Current IS and Penning IS
The PIG source has been used for regular operation of
the accelerator. No specific development was necessary to
satisfy the beam time requirements.
Table 2: Ion beams delivered from the PIG Injector in 2009.
Ion Auxiliary Duration Analyzed intensity
species gas (days) (eµA)
40 Ar +,2+ - 16 150 ... 400
56 Fe 3+ Ar 3 150
58 Ni 2+,3+ Ar 13 10 ... 100
96 Ru 2+ Ar 22 25
136 Xe 3+ - 8 90
197 Au 8+ Ar 12 250
238 U 4+,10+ Ar, Xe 25 10 ... 100
For the planned Li-experiment the PIG source has been
tested with a specific alloy as sputter electrode which
provided good experience in earlier times with an axial
PIG ion source. The used PIG at GSI however has a
radial extraction, which is a substantially different plasma
confinement. At the test bench for the PIG source we
could demonstrate a high fraction of Lithium in the beam,
comparing the ratio of mass 14 N 1+ and mass 7 (N 2+
and Li 1+ ). Whether meta-stable ions are in the beam at
all or what the percentage of meta-stable ions in the beam
is could not determined due to missing diagnostic elements.
The new MUCIS has been set into operation very successfully
for a long period Ar beam time. With this ion
source, designed in 2008 it was possible to increase the
extractable ion current by 10% at even lower arc power,
which indicates a better plasma confinement. Main differences
to the existing version of this source is an enlarged
discharge chamber, a coaxial cathode holder, and an improved
magnetic flux distribution. The higher efficiency of
the ion source results in a longer life time of the filaments.
Table 3: Ion beams delivered from the High Current Injector
in 2009.
Ion Auxiliary Duration analyzed intensity
species gas (days) (emA)
1 H + 3 - 23 0.5
40 Ar + - 24 20
181 Ta 3+ Ar 9 11
238 U 4+ - 36 15
To increase the intensity for very light ions, molecules
can be extracted instead of the desired element in atomic
form. This increases the available extraction voltage,
and as long the particle density within the plasma is
high enough, the extracted current will increase according
Child’s law. At the gas stripper the molecule will brake
apart and all residual electrons will be removed, which
triples the intensity for H and D when 1 H + 3
, respectively
2 D + 3 is extracted from the source.
The high current uranium beam time of September and
October was very successful from the ion source point of
view. The maximum analyzed beam intensity was 20 emA
for 238 U 4+ before entering the rf-accelerator with a repetition
rate of 1 Hz and 1 ms pulse length.
The new ion source service station for radioactive elements
has been taken into operation. Service of ion sources
is now made within a glove box to avoid any contamination
of service personal with radioactive isotopes. Ion source
replacements (Mevva, Varis, PIG) have been done without
any failure.
References
[1] K. Tinschert, R. Lang, J. Mäder, J. Roßbach, P. Spädtke,
A. Yakushev, Proc. 18 th Int. Workshop on ECR Ion Sources,
Chicago, 2008, 92
[2] M. Wengenroth, F. Becker, G. Fehrenbacher, Ch. Pöppe,
K. Tinschert, R. Becker, this report
[3] W. Barth et al., this report
[4] P. Spädtke, R. Lang, J. Mäder, J. Roßbach, K. Tinschert, Proc.
18 th Int. Workshop on ECR Ion Sources, Chicago, 2008, 194
[5] K. Tinschert et al., GSI Report 2008-1, 85