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