1/10/01 HVS

	This note is to give you all a run-down on the status of some
magnet changes made for some of the X/Y Correctors at sector one
girder 8. The changes were made to allow pulse-by-pulse steering of
the launch at the end of sector one into the NLTR, SLTR, and straight
ahead.

	AMW Jim Craft has done most of the "Engineering Modifications"
which include a new (fast) driver chassis for the effected units, 
new CAMAC (PAU rather than DAC/SAM) for the effected units, and some 
wiring modifications upstairs to hook the effected magnet loads to the
new driver chassis. We tried to retain provision to go back to DC 
operation if problems arise. 

	The physical magnets which we choose to pulse are XCORs 821/841,
and YCORs 811/831. These are all relatively high beta magnets (i.e.
"strong" magnets) for electrons, weak for positrons.

	The database for the new intallation is unusual, but not too
hard to figure out. If (when) you go to look at the LI01 XCORs or YCORs
you will (should) notice something different. XCORs 821/841 and YCORs
811/831 are now offline. The database for those units is directed to 
hardware which is disconnected. There are some new database magnet units.
Basically;

	XCOR LI01 821  gets replaced by   XCOR LI01 8210 and
                                          XCOR LI01 8211 and
                                          XCOR LI01 8212 and
					  XCOR LI01 8213.

 	and similarly for XCOR LI01 841
                          YCOR LI01 811
                          YCOR LI01 831.

	There are new touchpanels (one for the pulsed horizontal magnets, 
one for the pulsed vertical magnets) which you will find when you go poking 
around the LI01 corrector touchpanels. These touchpanels also have the 
PAU handles for dealing with the timing. Currently 8XX1 channels are 
programmed to happen on TS1, and the 8XX2 channels to happen on TS4.
That programming will change once we start pulsing the DRIP. 

	So that's the good news.

	The bad news is that there are some "issues". I list them in order
of importance:

Issue 1:There is some crosstalk between channels. (By "channels" I mean the
	different pulse levels which happoen at different times for an
	individual magnet). The amount of crosstalk (the fraction by which
	changing channel A effects channel B 8mS later) is small for small
	differences in channel output. At maximum difference (i.e. largest
	pulsed excursions) the fraction is about 10%. This can cause channel 
	A to go out of tolerance if channel B level is changed. Please don't
	write superfluous CATERs about this. I doubt that we can fix it.
	We'll have to deal with any inconvenience (hopefully small).  

Issue 2:In order to get the fast (~8 mS) changes to be of any useful
	amplitude, it was necessary to re-wire the magnet coils from 
	series to parallel (series wiring was too much inductance for
	the +/-30 volt driver to ramp in 8mS) which makes the field per
	unit current half what we had before. Presently we get only
	+/-0.027 kGm from these magnets. History buffer indicates this
	should be OK. 

Issue 3:Due to a subtle control system software feature which I didn't 
	recognize until late in the game, using PAU pipeline mode 2 (which
	means set PAU output 2 fiducials prior to beam time...this is 
	necessary) precludes use of PAU channel zero. This means the 8XX0 
	magnet units won't be available. We'll only get three PAU channels
	(8XX1,8XX2, and 8XX3) per physical magnet. This should also be OK.

Issue 4:There are a number of multiknob files which use these physical 
	magnets: X/X' , Y/Y', e+ and e- for steering launch into the 
	NLTR and SLTR. I asked Hanif to modify the files to use the new
	magnet units, but once we start pulsing, that will be the wrong
	thing to do. I suggest everyone refrain from using these knobs. 
	Just do it by hand.

Issue 5:Because of Issue #1 above, magnet calibration is tricky. I was 
	able to calibrate, but there is a special trick. If you want to 
	calibrate successfully, you need to calibrate all channels of an
	individual physical magnet together. "ACCESS" software is handy
	for this.

	I hope everyone gets a chance to play with these magnets. It is
clear to me that pulsed steering in this location is necessary for 
successful interlacing of Damping Ring and Straightahead beams. I hope 
this tool proves to be useful for you.

							Howard