Technical concepts for the operation of a Cameca 7f-Auto as ion source for the HZDR Super-SIMS

Super-SIMS - also called Accelerator-SIMS - is an ultrasensitive analytical method (Döbeli et al., 2013; Renno et al., 2013). A Super-SIMS-Set-up is now under installation at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) by connecting a conventional SIMS-source (Cameca 7f-Auto) to a 6 MV tandem accelerator (Akhmadaliev et al., 2013). The operation of a classical SIMS demands strong structural and building technological efforts [Cameca, 2012]. The requirements for the 6 MV tandem accelerator at the HZDR are of the same complexity.

Requirements # Cameca 7f-Auto # 6 MV tandem accelerator
vibrations # very strict # -
temperature | fluctuation # 19°C < T < 23°C|< 1°C•h-1 # max. 25°C
relative humidity | fluctuation # 30% < RH < 75% | < 10%•h-1 # 30%< RH < 75%
spurious magnetic field # < 3•10-7 Tesla # < 10-4 Tesla
vacuum # 10-9 mbar # 10-6 mbar
cooling | fluctuation # 17°C – 19°C | < 1°C•h-1 # 20°C – 25°C
nitrogen # N4.8 # N4.8
compressed air # dry | 5 – 7 bar | 35 – 50 L•min-1 # dry | 5 – 7 bar
uninterruptible power supply # 10 min # only for PC
radiation safety # - # very strict

The original specifications to optimally run both machines are in many cases incompatible. An additional challenge originates from the fact that a pre-acceleration voltage of 30 kV to inject negative secondary ions into the accelerator is needed. To guarantee the compliance with all specifications and safety regulations a specific concept for the housing of the Cameca 7f-Auto following a house-in-house-principle was developed. This concept guarantees the following operational options:

• independent operation of the 6 MV tandem accelerator
• independent operation of the Cameca 7f-Auto
• combined operation as a Super-SIMS by remote control
• operation of the Super-SIMS by remote control from outside the HZDR in the framework of the planned Helmholtz-SIMS network SIGMA

The most critical issue is the complete separation of all electric circuits in- and outside the SIMS housing by an insulating transformer, demanding the supply of electricity, gases, cooling, the intranet broadband network as well as all HVACR (heating, ventilation, air conditioning and refrigeration) without the use of electrically conductive materials. The strong vibrations in the accelerator hall are asking for further precautions. To follow all laboratory specifications for the Cameca instrument, the SIMS will be fixed on a cuboid made of natural gabbro (weight 6.4 t, size: 1.4 m x 1.8 m x 0.86 m) and all peripheral instruments on a frame vibrationally decoupled from the cuboid. This construction ensures the isolation of the SIMS and guarantees the compliance with all high-voltage safety regulations.
References
Döbeli et al., 2013, this meeting.
Renno et al., 2013, this meeting.
Akhmadaliev S., Heller R., Hanf D., Rugel G., Merchel S. (2013) The new 6 MV AMS-facility DREAMS at Dresden. Nucl. Instr. Meth. Phys. Res. B, 294, 5-10.
CAMECA (2012) IMS 7F Auto Installation & Delivery Conditions