Technical Design Report Super Fragment Separator

DRAFT
The expected radiation hardness of CVD diamond is the most important material property initiating
the research and development of diamond detectors. For the tracking of minimum ionizing
particles (mip) in the LHC experiments ATLAS and CMS [25] as well as for a variety of heavy ion
applications with high luminosity beams [26] diamond detectors have been already developed. In
the case of mips no increase in leakage current and unchanged collected charge is obtained for all
kind of particles up to a fluence of about 10 15 particles/cm². However, the heavy ion dose which
starts damaging CVD diamond is still unknown. Currently as a lower limit about 10 13 cm –2 , 12 C
ions (at 1-2 GeV/u) and 131 Xe ions that were even stopped in the detector material have been already
applied without any degradation of these detectors.
According to the fragment distribution as shown in Figure 2.4.104 we would expect an intensity of
10 12 uranium ions per spill on a (10 x 20) mm² area which corresponds to an annual dose of
10 18 /cm 2 /y. Our calculations have shown that the material as such will survive such intensities; the
question to be investigated is now whether a thin detector film can stand such a dose without getting
blind. The beam catcher detector arrays would then have an active area of (40 x 20) cm² build
from the cheapest poly crystalline as grown CVD-D material. They will be freely movable over the
full aperture of the Pre-Separator. A spatial resolution of about 1mm is considered to be ideal for
monitoring the fragment distributions. It has been already demonstrated, that the readout electronics
can be safely placed about 1m away from the detector system without degradation of the
electronic signals. However, a detailed study has to be performed how to build a 600-channel
readout and cabling for these detectors.
2.4.6.2 Diagnostics for slowly extracted beams
We define slow extraction as extraction times that are above 100ms for the Super-FRS. Beam
diagnostics systems will be installed in all intermediate foci PF(0-4), MF(1-12) with a standardized
active area of (40 x 20) cm² whenever possible (at MF11 (90 x 20) cm² will be needed for the LEB).
Two systems will be placed at PF(0, 2, 4) and MF(1-12) to allow an angular measurement. At
intensities above 1 nA in the Pre-Separator, beam induced fluorescence (see section 2.4.6.1) has to
be used. If the energy deposit/mm stays below 100 mW current grids [27] are routinely used to
measure beam profiles. At even lower intensities (< 100 kHz) usually multiwire chambers or gems
[28] with single wire or single pad front-end readout boards will be used to measure beam particles
event-by-event, thus allowing tracking through the separator (see also section 2.4.6.5). This standard
instrumentation is chosen for its moderate system cost. Whenever possible a continuous
recording of the beam positions will be done to allow automatic steering of the beam to the nominal
position.
Additional standard tracking detectors, presently operating at the FRS, are the Time Projection
Chamber (TPC). The high efficiency at 100-200 kHz (see Figure 2.4.84) allow them to be used as
in-beam detectors for experiments using slow-extraction beams, Available drift volumes are (20 x
6,8,10) cm 2 . They are filled with a P10 gas mixture at 1 bar pressure. Using a standard VME
readout (see Figure 2.4.84), reading two x-position and 4 y-position measurements, σx=0.1 and
σy=0.05 mm can be achieved, respectively. Such detectors are ideal for precise momentum-measurements
experiments.
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