Target Stick for the EG1 polarized Target

The following figures are from the target stick designed and constructed by the INFN group of Genova.

Figure 1.

Hall B polarized target stick as realized by the INFN group of Genova. An aluminum structure [1] supports four different cells (1.5 cm diameter ,1 cm length, 0.02 cm thickness ). The first two containers starting from the top [2] will house the polarizable material for the proton (NH3) and deuteron (ND3) target while a carbon target (third cell) and an empty one (fourth cell) will be exploited for background measurement.

Figure2.

View of the cells located on the target stick. The four PCTFE cylindrical container are fixed on the aluminum structure and closed on the back by an aluminum foil (11 micron thickness). The second cell [1], filled with plastic beads for a test measurement, shows the final configuration where a thin (45 micron) Kapton foil closes the containers. The coils for the NMR polarization measurement are positioned outside the container and connected to the external NMR circuit by coaxial cables [2]. A resistor for the annealing [3] (heating of the material to 70-80 K to cancel the effects of radiation damage) is located between the first and second cell, while the target temperature during this process will be controlled through thermocouples positioned inside the cells [4]. The metal tube on the right of the stick [5] contains the helium level gauge to monitor the liquid helium level.

Figure 3.

View of the upper flange of the target stick. Hermetic feed-through for the temperature [1] and helium level [2] gauges and the SMA [3] connector for the NMR cables are positioned on the flange. A stepping motor acting on the central rod [4] is controlled from the outside to allow the up and down movement necessary to place the different target container on the beam axis.