These plots are results of a rate study for our luminosity monitors. Starting at the left, the first plot is of the ep-elastic, moller and photon shower electron rates at the luminosity monitor position. The second plot is of the electron shower rate with and without multiple scattering in the target. The third is a plot of the ep and moller electron rates at the luminosity monitor position, without the physics processes turned on (DRAY=BREM=LOSS=MULS=0).
Figure 1
Here is a picture of the the second test luminosity monitor and housing, the test luminosity monitors in the beamline, and the amplifier box in the shielding.
Figure 2
Here is a picture of the photodiode we used in our test (right) and one that we didn't use at all (left). It appears that the photodiode was in fact radiation damaged during our test. It has a distinct orange-brown discoloration.
Figure 3
These are pictures of the luminosity monitor housings before we tried to open them, after being in the beamline at Jefferson Lab for several months. The effects of the radiation damage are obvious. The delrin is discolored from its usual black color to a white. It is also cracked throughout the end that was in the highest dose rate area.
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This grouping shows the VPD housing as we "undressed" the VPD. As you can see in the second picture, there were big cracks, especially around the screws. The endcap fell apart - it literally crumbled - so we were lucky to be able to get it off at all. Even the inside of the endcap was damaged, as you can see in picture 5, although it didn't turn white as it had on the outside.
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This grouping shows the radiation damage to the various components of the housing. The LED plastic is severely yellowed. Picture 1 shows a comparison to the undamaged LEDs on the right. The quartz seems visibly undamaged (Picture 2). The VPD itself is also extremely yellowed; it is shown compared to an undamaged one on the right in Pictures 3 and 4.
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