What is EPR optics?
In principle the photodiode can be put anywhere close to the cell since a small amount of light is enough for the measurement. That is what we did during tests in target lab. However, during the real runs down in the hall, the photodiode will be damaged by radiation in a few hours if it is positioned close to the cell. During E94010 and E95001 in 1998, EPR was only performed during maintainance day, when people can access to the hall and put photodiode on top of the oven. For E99117 and E97103, we construct an optics system which can focus the fluorence light and lead it to seven meters away from the target pivot, where there is enough space to put shielding for the photodiode. The EPR optics for E99117/E97103 consists (1) two lenses and two mirrors inside the target enclosure, which focus the fluorence light and lead it out of the target, and (2) nine lenses, related supports and light tubes which lead fluorence to photodiode, and protect people from the light (lasers). The difficult
