Minutes from Oct. 21 Meeting:

1.  Discussion of Ray Arnold's note (see separate link for this):
	- suggests to use FFTB magnet movers for BPM motion; 100-nm accuracy and mm dynamic range (could be designed to 
		extend this); no backlash and can move very heavy loads.
		position readbacks:  optical encoders and LVDTs;
		need to consider radiation environment for electronics; neutrons after collimation?
	- discussion of 4-magnet chicane scheme; energy measurement primarily from BPM translation measurement at 
		mid-chicane; use outer BPMs before/after chicane for position jitter corrections during calibration cycle.
	- discussion of measurement prescription in 4-magnet scheme
	- following the meeting there was an email correspondence from Alexei Liapine on 4-magnet scheme vs 3-magnet
		(see separate link for this); in general Alexei prefers 4-magnet, though require accurate Bdl for 2 magnets
		rather than 1
2.  Discussion of measurement prescription and Mike Hildreth's note (see separate link for this)
	- discusses initial calibration, routine calibration, and energy measurements with jitter correction; and
		time scales for these
3.  Discussion of optimizing the chicane parameters:  B-field, bend angles, beta-functions, emittance growth,
		drift lengths, BPM resolution needed
	- Marc Ross indicated need to go thru an optimization procedure on these and need to have flexibility for
		machine operation
	- we continued discussion of this optimization at the Nov. 3 IPBI meeting (see separate talk links for this
		for Ray Arnold's talk):  emittance growth demittance/ds~(gamma^5)(eta^2)/R^3/(beta); for energy measurement
		want large eta and small beta, both of which are bad for emittance growth.  Likely want to have different
		magnet designs for middle magnet(s) in chicane than for end magnets:  want lower field, longer magnets where
		eta is large.
	- nominal betas and spotsizes are fairly large (order 100 microns horizontal) at energy spectrometer; 1e-4 energy
		resolution likely to be in range 100nm - 1 micron at this location, hopefully we can design for closer to
		1-micron corresponding to 1e-4 rather than 100nm.
	- Marc pointed out at SLC we got good energy measurements at SLC from 2 measurements with large dispersion with
		pi phase advance between them, so could average and cancel betatron jitter; can we do something similar
		at ILC?
4.  BPM angle sensitivity discussion led by Yury Kolomensky.  Can get systematic position shifts from changes in
		tilt of bunch or BPM rotations.  Need to quantify this better.  We had a further discussion with Steve
		Smith regarding this at the Nov. 3 IPBI meeting.  Steve felt there were several ways to mitigate this
		to be a negligible systematic and didn't think it should be used to justify a 4-magnet chicane over
		a 3-magnet chicane.
5.  Discussion on laser reference system and LICAS (Linear Collider Alignment System).  Mark Ross and Stewart Boogert and 
		Armin Reichold are meeting in early November to discuss this, including possible application for energy
		spectrometer.  Stretched wire system (used at FFTB, LEP energy spectrometer, LHC) is another possibility as
		a reference system.  At ATF a laser reference system is being used with a reference/anchor to the floor.
	
Action items:
1.  need website to assemble documentation, minutes (done, but needs someone to take over and maintain) 
2.  availability of FFTB movers (initial discussions with Tom Markiewicz indicate some should be available;
		need to pursue further)
3.  prepare for KEK ILC meeting:  discussions on energy spectrometer design and beam tests 
4.  next T-474 meeting will be post-KEK ILC meeting 
5.  meeting of Ross and Boogert with Reichold 
6.  prepare document for updated spectrometer schematic and measurement prescription (in progress)