Background: Tim clearly demonstrated narrow bandwidth with >2.5mj FEL can be achieved with the
stacker and also shows the energy spread shape at SAB with stacker is similar to (slightly better than)
single arm – see tim’s slides. But JimT keep saying current large bandwidth is caused by the stacker.
With the continuing arguments, I would go back same conditions for injector as last year. However I
have to remind you: stacker improves the emittance for sure - removing stacker eliminates the option
although we do not surely know the stacker impacts the bandwidth; and also we may not draw any solid
conclusion whether the stacker impacts bandwidth or not no matter what consequence without stacker.
Nevertheless, the planned md is still worthy to do, which simplifies injector setup, eliminates one
possible source for the problem and also we can map out the bandwidth/intensity on the cathode.
MD Plans (~8.5hrs) (Zhou, Ding, Maxwell):
1. Record FEE spectrum and xtcav with current settings (tweak some parameters like BC1 current,
L1X amp,, BC2 Ipeak) (0.5hrs)
2. Switch to laser2 (w/ single arm); establish FEL (hard, >2.5mj) by tuning injector, BC1 Ipeak, L1X
amp, BC2 Ipeak, taper, matching. (4 hrs)
a. FEL diagnostic: FEE spectrometer
b. LTU WS246 correlated energy spread
c. Xtcav?
3. Map FEL bandwidth/intensity on the cathode; then choose a spot with good FEL
bandwidth/intensity (2hrs)
a. FEL spectrometer
b. LTU WS246 total energy spread
4. After choosing best spot, move s-p arms delay line to 1.8ps, tune FEL with adjustment of BC1
Ipeak, L1X amp, BC2 Ipeak, taper, matching (2hrs)