PSI Scientific Report 2007
User facilities – Tandem accelerator 87
The PSI/ETH Laboratory of Ion Beam Physics
Hans-Arno Synal, Vasily Alfimov, George Bonani, Marcus Christl, Max Döbeli, Irka Hajdas, Peter Kubik, Marc Mallepell, Arnold Müller, Matthias Ruff, Martin Suter, Martin Stocker, Emanuel von Wartburg, Lukas Wacker, Research Department Particles and Matter, PSI and Institute of Particle Physics, ETH Zurich; Susan Ivy-Ochs, Institute of Particle Physics, ETH Zurich and Geography Institute, University of Zürich
In 2007 the PSI/ETH-Laboratory of Ion Beam Physics had four accelerators operating. The 6 MV EN Tandem was online for more than 2,774 hours. The 600 kV Tandy AMS system was used for experimental AMS work and routine operations with 129I, Pu, Pa. Routine handling of 14C samples has begun with the 200 kV MICADAS AMS System. In addition, the gas feed operation has been extended. The new 200 kV BioMICADAS system was completed in October 2007. This system is under specification tests and it is planned to ship it to Vitalea Science, our partner for biomedical AMS, in 2008.
Approximately 5,700 AMS samples were analyzed at the laboratory of ion beam physics in 2007. About 65 % of them, 10
Be, 26Al, 36Cl and 55 % of the 14C samples, were measured
with the 6 MV Tandem based AMS system. The remaining 35% were analysed with our smaller systems Tandy and MICADAS. Here, about 45 % of the
14
C samples and all
129
I, Pu and Pa
14
were analysed. A significant fraction of the C analyses were made with very small samples of less 50 μg carbon using the MICADAS system. This became possible by routinely using our gas ion source. In 2007, we had to exchange the charging belt of the EN Tandem accelerator. Consequently, an increased portion of beam time had to be spent on conditioning and machine testing. The new belt has now been running for six
Figure 1: The new BioMICADAS system.
months and we can expect to have stable operation conditions again for the next three years. The Material Science (MS)
operational for Heavy Ion Rutherford Backscattering (HIRBS).
program has used about 20 per cent of the total EN accelera-
With this detector, a significantly enhanced mass resolution
tor time. A new annular gas ionisation detector became
over conventional best practice RBS experiments has been achieved.
EN Tandem Accelerator Operation Hours AMS
2005
2006
2007
The dedicated biomedical AMS system BioMICADAS was
Be-10
738
978
617
completed in October 2007. The new ion source in particular
C-14
804
700
703
has shown excellent performance and design specifications
Al-26
33
126
56
have been exceeded.
Cl-36
265
472
287
Using the HE-spectrometer magnet of the BioMICADAS system
Heavier Elements
126
MS Materials Science
438
422
447
SSIMS
42
159
94
for test experiments at the Tandy AMS system, we were able to demonstrate that background events can be significantly reduced. For
10
Be it became possible to reach a detection
limit of few times 10-15, a value which had before only been
Maintenance Conditioning/Tests
428
259
444
reached with large AMS systems. Based on these results the
Total
2748
3116
2774
design of an improved spectrometer for the Tandy AMS system
Table 1: Beam time statistics 2005-2007 EN Tandem.
has begun.