Dates: September 3 - 14, 2000
Observers: John Monnier and Costas Papaliolios
New Memos Generated from Trip
1. Replacing CCDs
2. Installing Anorad Delay Line Cart
3. Removing Anorad Delay Line Cart
4. Planting and Harvesting Anorad Magnets
5. Anorad Screw Table
Summary of the Engineering Performed
1. Replaced the CCD head and chip in FIXED (ironically), because it was not responding to light. We do not know how much worse/better the sensitivity is compared to the new one, but it works (SM/CP/JDM). Conclusion: Either the first replacement CCD we tried is BAD or the electronic board is bad. We don't know which one.
2. Calibrating Visible Light Piezos around 0 Volts. 0.246 V for 10 HeNe fringes using (visible table) piezo in open loop mode going from -0.006 V to 0.240 volts. If normal incidence, that would be a physical motion of 10*1/4 * 633 nm per 246 mV = 6.4 microns/Volt
3. The "Ozman" light source does not produce visually detectable white
light fringes. Must either replace this bubl with something
else, or use mercury lamp, which required OPD right to within ~2 cm.
4. Autocal white light fringes for S15N15 A delayed:
Optimum solution: for S15N15 A delayed. OFFSET: -1.1cm is optimal using Config file with:
Int. OPD at home, A ... = -104.6
Int. OPD at home, B ... = 203.20
---- these are the numbers in Traub's Jan2000 memo.
These values must be modified now because we have moved the HOME flag, see end of memo
5. If an anorad magnet falls off its mounting plate, it can be re-affixed
with Krazy Glue (but be careful affixing, since magnetic forces
can make the placement tricky).
6. Tried out the first attempt at a refurbished air pad, using deeper
wells around the air ports. The pad vibrated too much, and needs
be to re-worked. We also tested without the stubs: no difference.
7. Potentiometer R3 on the ELTROL card can be used to tune up the feedback with some effect.
8. Re-wired the polarity of one of the Hall sensors and the order of
the motor windings. Replaced 3 bad chips on Harvard Velocity Card
#1. The second pair of ELTROL + Harvard Velocity Cards now work with both the old and new delay line cart.
We used an HC14 chip instead of an F14 chip right after the line receivers -- seems to work fine
9. Pull-down Magnet Measurements for New Table:
Plate thickness: 1 cm
Magnet thickness: 3.5 mm
Length: 5 1/4 inches
We shoud make one with the plate being 1/8 in shorter, and order some magnets (COS wrote down some #s on the current magnets).
10. We need to order anorad SCREWS. Lengths: 1 1/8", 1", and 7/8"
with 8/32 threads. Much time as spent grinding down screws and
popping magnets off plates.
11. We've installed the new delay line table on the track, with the
damping plates in place. We have not been able to test how well
the servo loop performs with the damping plates, but may help with quency vacuum oscillations. The plates clear the tight clearances
in the U-groove fine, it seems.
12. One of the side magnets for the new table may be lifting off its
epoxy. We ended up using one of the (unused) side magnets from
the old table.
13. We've shortened the bar on the old delay line, which should slightly extend the range of motion.
14. We added a new HOME flag, since both carts are on the track now.
New home is 43.8 cm different than the other one.
To correct old Delay.Config files, ADD 87.6 cm to the
line "Int. OPD at home, A beam ..." and "Int. OPD at home, B beam ..."
15. We removed 1/8" metal shims from the pull-down magnets on the old
delay line table and it now moves very smoothly with much
less air flow. We also only installed 2 of the 4 side magnets. In Vacuum, the necessary flow rates are 1.5 and 1.25 (on right-hand
flow meters) to float pad and quench oscillations.
16. We discovered that Test Port (TP) 14 (referenced to TP 1) on the
ELTROL card is a current sensor, revealing how hard the motor
is working. According to the schematics, the conversion is 1 V/Amp. We tried this: when not oscillation and moving at 1 cm/s, the
measurement said ~1 amp. When we upped the air flow (it was oscillating) the current was .3 amps. So we are using 3X the power
with the friction necessary for damping the oscillations.
17. Image quality is still bad in at least one of the telescopes. Suggestion
is to try to improve image quality by visually peering
through alignment telescope and only adjusting the secondary tilt. This should compensate for the tight centration tolerances.