stephenbrooks.orgForumMuon1GeneralLinac900Removable6c2, fully optimized?
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2009-04-18 21:35:20
It looks like we're not making any progress any more.  Is it time to try to optimize a new design? 
2009-04-27 20:52:28
Scratch that!  Looks like it might be moving again! 
Stephen Brooks
2009-04-29 01:29:47
Yes, a bit.  I don't have much time at the moment - conference 2-9 May looming, but I should probably try and update at least the lattice on Muon1 after I get back.
Stephen Brooks
2009-05-19 15:34:36
Seeing as this is now better than our previous 900MeV linac (Linac900Removable12, which made a tiny improvement on Removable6), I've added a thing showing how many percent better than that previous best it is (called the 'baseline' but just for historical reasons).
Stephen Brooks
2009-05-19 15:35:15
Linacwhatever12 got 3.670822% whereas right now ...6c2 has 3.881789%.
2009-05-29 18:27:50
Upto 3.891075% but it has othwerwise virtually stalled over the past ~2wks.

How long does it usually take before they top out? 
2009-06-09 07:58:04
another week with barely any gain, is it time for another tweak?
Stephen Brooks
2009-06-09 14:43:26
It beginning to look like it's not going to have any other sudden increases (been flat for longer than last time).  I'm going to have a look at the top design to see what it suggests to do next.
Stephen Brooks
2009-06-09 15:08:34
The design seems to be pointing towards even longer linacs.  Although this isn't the cheapest option I'm going to extend the range to see what it's up to (has it found a way of increasing the efficiency with more cells even if some are decelerating rather than accelerating - as is the case with the current ..6c2 optimum?)
Stephen Brooks
2009-06-09 15:10:48
New lattices have 6 or 9 "blocks" for optimisation and RF phase ranges changed by 180 degrees (since old optimum went to the 000 or 999 ends of the range often).
Stephen Brooks
2009-06-09 15:11:55
Oh yeah, and the "phase rotation" section has been removed completely as it was being optimised to zero length all the time, the linac appears able to do both jobs in one section.
2009-06-10 08:41:49
I have no idea what you're talking about, lol, except linacs I know what that is. 
Cells??  does that mean a unit within a linac?  blocks??  I know what RF is but phase ranges??  Can't remember what phase rotation is refering to either, is any of this in a FAQ yet?


Btw I'm No1 in the Linac900Ext9d2 list today & No5 in the other , what's with the -%??  some of the beam doubling back?
Stephen Brooks
2009-06-10 17:13:03
A "cell" is just one repeating period, so in the linac a solenoid followed by a drift with an RF cavity in it.  Blocks are things I use in the optimisation so that the chain of say 150 cells is split into 9 segments or blocks within which all the cells are identical.  The RF phase determines at what point in the varying electric field the particles enter the cavity.  Being 180 degrees out of phase with it results in deceleration rather than acceleration for the central particle of the muon bunch.  Phase rotation was a segment that tried to change the energy spread of the particles in a beneficial way without actually doing any net acceleration.

Negative percentages are for early optimisation when not enough of the beam has arrived in the right energy range to be statistically useful.  The range -1% to 0% is where the beam is arriving but at the wrong energy and the closer the energy to the desired range, the less negative the score.  It will go positive at some point soon.
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