TVO, TJ, Hang, Danny
TJ, TVO and I had a discussion yesterday on how to better center the Hartmann beam on the ITM. We noted that we did not currently have an idea of how the HWS ITMX and HWS ITMY upper periscope picomotors are calibrated so we decided that moving those mirrors in a random (but well noted) direction, then running an ITM ring heater test should provide enough information for a decent calibration. Before we left the site we moved both HWSY and HWSX upper periscope mirrors on the corner table 100 counts to the left and 100 counts down from the previous position in alog 43288 . Hang ran the ITMX and ITMY ring heaters after for 12 minutes at 2 watts (4 watts total for each ITM) last night. Attached to this post are the contour/gradient plots as well as the prism and spherical power trend data.
It's important to note that in these tables we use the following: Distance of the Hartmann beam from ITM center = abs((Max change in prism)/(Max change in spherical power))
8-8-2018 ring heater measurement* (12 minute, 2 watts)
| Max change in spherical power (µ diopters) | Max change in prism x (µ rad) | Max change in prism y (µ rad) | Distance from ITM center in x (cm) | Distance from ITM center in y (cm) | |
| ITMX | -30 | -.125 | 1.5 | .4 | 5 |
| ITMY | -20 | .65 | .75 | 3.3 | 3.75 |
8-7-2018 ring heater measurement (1 hour, 3 watts)
| Max change in spherical power (µ diopters) | Max change in prism x (µ rad) | Max change in prism y (µ rad) | Distance from ITM center in x (cm) | Distance from ITM center in y (cm) | |
| ITMX | -175 | 10 | 2.5 | 5.7 | 1.4 |
| ITMY | -175 | 3.5 | 3.5 | 2 | 2 |
We estimate how many cms the upper periscopes move per count in each direction:
| horizontal direction | vertical direction | |
| HWS ITMX | .053 cm/count (or 19 count/cm) | .036 cm/count (or 28 count/cm) |
| HWS ITMY | .013 cm/count (or 77 count/cm) | .0175 cm/count (or 57 count/cm) |
*Note: there is a small particulate that can be seen on ITMX HWS we think that it is a bit of dust one of the on table optics. Also, there is probably clipping on the iris right before the CCD. Both of these things could be messing us up. Attempts at removing the particulate and future measurements are coming very soon.
Seems like overall we made things worse. Will probably move things back 100+ counts up and 100+ counts right to push the beam in the correct direction.
TJ, Danny
Update: We moved HWS ITMY upper periscope mirror up 214 counts and right 254 counts and because there is a bit of uncertainty with the HWS ITMX upper periscope mirror we decided to move it up 150 counts and right 150 counts. While we were out at the table we also took some time to remove dust from a few of the mirrors along the ITMX HWS path in hopes that spot would go away.
Another ring heater test coming tonight.
Gifs of the 8-8-2018 measurement
GIfs of the 8-7-2018 measurement
