Discussion of min/max 4GLS energies 5th March 2007

Magnet designs going 550->600 MeV would be different
RF 550->600 MeV is increased gradient rather than power (check with Peter?)
Cryogenic load would be increased going 500->600 MeV
Collimation depth 550->600 would be increased
Water cooling 550->600 would be increased
CSR emitted power in HACL 550->600 MeV would increase.

Could consider and increase of energy with a decrease of current, to allow greater exploration of undulator output wavelength.

Twin-line variability:
We can straightforwardly change the HACL energy by turning off the XUVFEL.
In the present spreader design the energy ratio is fixed. So
550->600 MeV means 750 MeV->818 MeV on XUVFEL (for same energy ratio), so therefore XUVFEL injector goes 210->228 MV (assume same phases in everything) - the phase might be possible to change (but is complicated!)
The change 540->590 is 9%
The change 210->228 is 8%, so this can be done

So output energy of XUVFEL would now be 818 MeV.

Lower limit is around HACL 450 MeV - no real lower limit identified yet, except perhaps wakes (cavity/resistive and CSR) inducing larger energy spread on the bunch. The VUVFEL may stop working.

Upper limit on cavities is 20 MV/m, which is about 650 MeV. It is agreed to cost items (magnets, collimators, PSUs etc.) at 650 MeV (HACL). Need to work out what this is in XUVFEL line.

It was agreed that no inter-line energy variability is assumed - if operating together, the energy ratio is fixed at 550/750.