There is concern about running with a large Wien angle. The anticipated Wien angle for G0 in mid-March is about 90 degrees. All 3 halls will be running. Question: What can be done? Answer: Nothing, here’s why? Forget for a moment about Hall’s A & B. Hall C needs 687 MeV at one pass, or 37 + 325 + 325. Precession between source & Hall C turns out to be about 89 degrees. What about “linac trick”, i.e., ~37 + (325 + D) + (325 - D) ? Precession between source & Hall C is then 89 deg + (0.43 deg/MeV ∙ D [MeV]) So, roughly it’s about 1.5 degree per percent linac energy change…..or, about nothing.

Next, question… Will G0 forward be a guiding light for G0 backward? Well, probably not…Wien was -13 degrees & we had the “high bunch charge injector”. Have we run physics with Wien at 90 degrees previously? Well, yes, when we have delivered vertical polarization (Wien=90 + Solenoids=90) Usual goal => change solenoid spin (∫B∙dL), constant solenoid focussing (∫ B2∙dL). So, when have we done that? March 22, 2004 (Archiver => “Yikes”, Allsave 4239 @+85 & 4240 @-94) July 15, 2004 (Archiver => “Yikes”, Wien = +91) August 29, 2005 (Archiver => OK, Wien = +90)

August 29, 2005 3 Halls Wien=+90.24 deg A=40 uA B=12 nA C=10-20 uA