Development of a Liquid Scintillator and of Data ... - Borexino - Infn

7 The Source Runs in CTF2
7.3 The Source Runs
The sources were inserted into the Inner Vessel from the purification clean room on the top
of the CTF tank. They passed through the scintillator inlet tube. Normally the vessel with
its plumbing is allowed to move freely relative to the water tank. To stabilize it in a certain
position it is counterbalanced by a weight connected over a rope pulley. During the source
operations the plumbing-vessel assembly was held in place with clamps. The top flange (normally
used as attachment point for the rope to the counterbalance weight) was removed and
replaced by a flange with a short ’adapter tube’ attached, that has an inner diameter only few
mm wider than the diameter of the steel rod to which the source was attached. The sources
were inserted through this opening. To prevent air (oxygen and Rn) from getting in contact
with the scintillator, a continuous nitrogen flow in the outward direction was maintained. The
nitrogen was introduced into the plumbing at a tee below the top opening and it exited through
this opening (see fig. 7.3).
Figure 7.3: Setup for the source insertion.
For the positioning of the sources we used a stainless steel rod with a hinge so that positions on
the z-axis as well as positions off-axis could be measured. The rod was divided into 8 sections,
each 1 m long, that could be screwed together while lowering the source into the IV. This was
necessary because of the height limitations imposed by the cleanroom ceiling.
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