Superharps

Superharps are used to measure the beam size or profile at the specific locations alone the beam line where beam quality can be characterized. At each such location, there is a standard pair of superharps with known separation distance (1.817 meters), sandwiched a BPM in the middle. For example, at location C07, Superharp C07A is at upstream of the BPMC07 and Superharp C07B is at downstream of the BPMC07 with equal distance.

The four important locations are: (1) C07 (entrance of the arc), (2) C12 (middle of the arc), C17 (exit of the arc), and (4) H00 (2.5 meter before target).

For a normal archromatic tune (as most of the experiments use), the size of the beam at C07 and C17 should be around 100$\mu$m in both x and y directions. At the middle point of the arc, the momentum dispersion is maximized about 3-4 cm%, depending on the required beam energy. This means that the size of beam in x direction should be $< 300 \mu{\rm m}$, corresponding to an energy spread $< 10^{-4}$, while the size in y direction be around $100 \mu{\rm m}$. Harp scan at the location of H00 will verify the beam size on target. Beam size at H00 can be specified to MCC based on the need of the experiment. MCC will tune the multipole magnets to meet the requirement. Around $100 \mu{\rm m}$ (FWHM) has been achieved in the past.

The centers of the beam profiles extracted from scanning the pair of superharps at the specfic location can provide the beam incident angles at that location.

The superharps cannot be used continuously. Harp scan should be done to verify the beam tune. The frequency of such scan depend on the need of experiments.