Conceptual drawing of the polarized target for CLAS. The beam enters as indicated by the green arrow, and scattered electrons (as well as other reaction products) can be detected up to an angle of 50 degrees (blue arrow). Sideways windows (indicated at bottom and top) allow additional acceptance around 90 degrees for coincident hadrons. The superconducting Helmholtz coils are indicated in red, and the target refrigerator and cryostat with the light blue wavy lines. The refrigerator contains liquid ⁴He at 1 Kelvin which cools the target cell (indicated in purple) containing radiation-doped NH₃ and ND₃ beads. The target material is dynamically polarized via irradiation with microwaves.

Front view of the polarized target (exit window removed). The central vessel (the so-called "banjo") contains the 1K LHe refrigerant for the target. It is surrounded by the magnet cryostat (hung off 3 centering rods) which in turn is surrounded by the heat shield. The outermost bolt circle belongs to the enclosing vacuum can ("IV"). The 3 stubs visible to the left are alignment targets.

Close-up of the "banjo". One can discern the entrance window into the LHe volume (center), the opening to the refrigerator (above that) and the entry port for the target stick (which is missing in this picture -  pictures of the target stick can be found here). The thin rod to the right is the LHe level meter. Also visible is the microwave guide and horn (entering through the refrigerator hole) used to transmit microwave power (140 GHz) into the target cell for dynamic polarization.

Target stick after extraction from the target. The target stick is filled and must be immersed in liquid nitrogen at all times. One can clearly see the NH3 target cell to the right. The dark spot indicates the area over which the beam was rastered during the preceding run time. Below is a photograph of the exit foil alone, with dimensions given.

Target stick is inserted into the target assembly. The top of the target stick is still visible, with the NMR and sensor cables. The banjo is kept at LHe temperature during insertion, leading to a plume of condensing humidity. Don Crabb is moving the stick in, while Raffaela Devita aids him with a flashlight.

Complete target assembly in Hall B. The front exit window has been removed and the side windows have been blanked off with Al plates. The target hangs off a large support tube attached to the insertion cart (visible in the background, to the left). Also visible is the (white) shielding box for the NMR electronics and the massive pump system for the refrigerator (on top).

Picture of the target ready to move into the CLAS. To the right, one can see the inside of the Region 1 drift chambers and the new lead shielding ("the bullet") for polarized target running.

View from the left side. One can discern the target vessel with the sideways windows (blanketed off for safety while the target is outside CLAS) and the reservoir dewar which fills the superconducting magnet enclosure and the refrigerator with LHe.

Cryogenic control panel for the target. Chris Keith is seen watching pressures and flow rates in the cryogenic system. The mysterious red lights at bottom left belong to the superconducting magnet power supply.

Online NMR signal for a polarized NH₃ sample. The polarization is induced dynamically by irradiating the sample with 140 GHz µwaves in a 5 Tesla magnetic field. The polarization is proportional to the area enclosed by the curve labeled "Signal without baseline and fit". The data were taken with the CLAS polarized target in the EEL building.

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