Technical Design Report Super Fragment Separator

DRAFT
extracted beams. Its use for the Super-FRS is limited to intensities up to about 10 10-11 particles/spill
to avoid damaging of the detector.
Figure 2.4.86: Layout of the SEETRAM counter. It consists of titanium foils (#1) with 10 µm thickness
sandwiched between two aluminium foils of 14 µm thickness each (#2 and #3). Each foil has a diameter of
11.5 cm. They are mounted perpendicular to the beam axis. The outer foils are connected to a voltage of
+80 V. They and their supporting aluminium rings form the detector housing. The middle foil is supported by
two Teflon rings and is insulated against other parts of the detector. The foils are curved in order to reduce
the sensitivity to mechanical vibration of the beam line. Secondary electrons emitted from the middle foil are
collected by the two outer foils. The created current in the middle foil is measured by a current digitizer
(CD1010 developed at GSI).
In order to calibrate the current measurement up to now the calibration proceeds via two steps: first
a scintillator detector is used in counting mode; second an ionization chamber takes over in order to
calibrate the SEETRAM detector. For the Super-FRS we will benefit from the high counting rates
that can be taken by a diamond detector (10 x 10 cm², PC-CVC-DD (AG)) and thus be able to leave
out the ionization chamber. Thus we will be able to reduce the setup and calibration phase for the
experiments. The diamond detector here can also be used at reduced rates of 10 9...10 /spill – as has
been done already for the SIS18 – to analyze the spill structure after slow extraction from the
different SIS rings.
(ii) For the entrance of the main separator a SEETRAM counter and a diamond detector are
planned to be used for the luminosity measurements. The diamond counter can be used (as shown
in section 2.4.6.5) also as start counter for a time-of-flight measurement. The expected spot size is
here about (2 x 3) mm² as given by the magnification (Mx = 2, My = 1.5) of the Pre-Separator optics.
With rates up to 10 9 /s uranium ions, this is just at the limit of what can be counted using a
PC-CVD-DD. One may consider using single crystal material here. The recent available
SC-CVD-D material is presently investigated by NoRHDia [34]. The charge collection efficiency
of SC-CVD-D detectors amount to almost 100 %, and the signal amplitudes are uniform over the
detector area, which is not the case for PC-CVC-DD. However, due to much lower concentration
of traps the detectors behave as fast drift chambers. Therefore, the count rate capability is lower
and only 50 MHz are manageable. Instead of single particle counting one should investigate the
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