From: sbrooks@bnl.gov 
Sent: 2013 December 26; Thursday 11:59 
To: Vladimir Litvinenko ; Ptitsyn, Vadim ; Trbojevic, Dejan 
Cc: Roser, Thomas ; Ben-Zvi, Ilan ; Aschenauer, Elke ; Stephen Brooks 
Subject: Re: Conditions set by e-beam polarization on FFAG ERL design 

Think I've managed to get this working for a 5+11 split and Vladimir's 
suggested 1.322GeV linac and 12MeV injector.

The trick is that the first ring has TOF variation as its contraint (I got 
54.7ppm or 12cm, larger than we had before, but less than 0.26MW synchrotron 
radiation) and the second ring has synchrotron radiation as the contraint.

The 2nd ring can do:

10588MeV with 5+3 turns and 3.25MW radiation for 50mA.
15876MeV with 5+7 turns and 10.33MW radiation for 50mA.
21164MeV with 5+11 turns and 27.10MW radiation for 50mA, or more 
realistically, 10MW with 18.45mA current.

TOF variation is only 22.3ppm (5cm) in the high-energy ring.  All tunes are 
well-behaved.  Cell geometry was inherited from Vadim's optimal lattices for 
10GeV, I just changed the gradients and quad offsets for the new energy 
ranges.

Note I've used 8,12,16 passes in total that are all factors of 48, allowing 
"perfect" bunch train schemes for h=48 (450MHz RF) with gaps of 6,4,3 
buckets respectively.

More details in a later talk since this has come straight out of the 
optimiser this minute.

    -Stephen



-----Original Message----- 
From: Vladimir Litvinenko
Sent: 2013 December 23; Monday 18:42
To: Ptitsyn, Vadim ; Trbojevic, Dejan ; Brooks, Stephen
Cc: Roser, Thomas ; Ben-Zvi, Ilan ; Aschenauer, Elke
Subject: Conditions set by e-beam polarization on FFAG ERL design


Hi All,

as promised I checked the conditions for polarization in two IRs in ERL with 
two FFAG arcs.

Surprisingly that 15 turns comes naturally for 20 GeV with 1.33 GeV linac 
(11 passes give 15  GeV and 8 passes give 10 GeV).

I found (and resolve) non-trivial problem with injection energy - small 
deviations from exact longitudinal polarization
(polarization remains at 99.99% of maximum possible) allow to inject at 12 
MeV.

Next step is to optimize FFAG for 20 GeV with 15 passes and we how it 
performs at 15 GeV.

Happy Holidays,



Vladimir N. Litvinenko

Professor, Department of Physics and Astronomy, Stony Brook University
Phone: 631-632-8093
e-mail:  vladimir.litvinenko@stonybrook.edu
Director, Center for Accelerator Science and Education, SBU & BNL
(631)-344-2570 Fax: (631)-344-5954






