1. Magnet discussion:
Same magnet used in quark discovery
Warm magnets, dipole bends and quadrupole focuses to reach  the Ceernekov detector

2. Why gun and GaAs both?
Gun for thermionic emission for unpolarized electrons. Few KeV of voltage to accelerate them and then electrons enter LINAC
LBNL has built “steel gun” which accelerates them

3. How to measure 1 part in million?
Pockel cell is used to flip helicity of the photons and that of electron beam. You need 2KeV voltage on pockel cell. At the end of cross section or flux which is 100mV in the Cerenkov detector. Having grounds of accelerator gun and the detector, then you can have mV fluctuations in 2 miles down the tunnel. Demonstrated in Figure 2.

4. Which Feynman diagram?
Z/gamma exchange as electron goes in and electron comes out. Z causes the asymmetry as it interacts with left and right handed electrons differently.

5. Why deuterium than proton?
For elastic: Uud quarks cancel their relative weak charge and it is close to 0 but the coupling is better for neutron so overall deuterium is better. Proton is 10x smaller.
For DIS: It is more or less similar.
Why don’t we use a neutron rich source? We want clean environment. There are few experiments in Jefferson lab which use high A,Z targets to study nuclear densities etc.

6. Figure 3?
Independent check that precession and energy are correctly correlated and nothing is wrong with Pockel cell

7. Results plot: Figure 4