Required beam condition

As described in the previous section, the momentum and current of beam electron are required to be 1.8 GeV/$c$ and 30$\mu$A, respectively (table 3). Since the E01-011 experiment is the first experiment to use the HKS spectrometer, and the optics nature of Enge spectrometer will be much changed due to tilt, the tuning and calibration of the spectrometer system are essential.

The beam energy spread and stability should be better than 10$^{-4}$ to achieve the energy resolution described in the previous section, therefore the energy lock to Hall C beam line is required. Spot sizes of beam are 60 $\mu$m (rms) and 100 $\mu$m for X and Y, respectively. Detailed beam requirements will be given later (section 7.1).

表 3: The requirements for beam

Purpose	Beam momentum	Beam Current
HKS/Enge calibration	1.8 GeV/$c$	5 $\mu$A
HKS calibration	0.9 GeV/$c$	5 $\mu$A
Physics runs	1.8 GeV/$c$	30 $\mu$A