This is a report of the work carried out on the 4th of February 2019.

• Before begining the exercise I turned all the control systems off. The IM control loop had some gains which I changed to zero. I'll let the person who designed the control filter put them back.
  • Place: VIS_CUST_TYPEB_IM_DAMP_SIX.adl
  • L: 0.020,
  • T: 5,
  • V: 30,
  • R: 1,
  • P: 0,
  • Y: 1.
• Temperature during this exercise: T = 26.2 ºC (25 ºC requested).
• According to my calculation (see spreadsheet attached) the bouyancy corrections for the GAS filters are:
  • BF: -341 µm. (f = 0.461 Hz),
  • F1: -756 µm. (f = 0.270 Hz),
  • F0: -195 µm. (f = 0.5 Hz),
  • Total: -1.29 mm.
  • The minus sign indicates the keystones will sag.
• According to my calculation (see spreadsheet attached) the temperature drift for each filter is
  • BF: -296 µm/ºC, total drift of 355 µm for a temperature decrease of -1.2 ºC.
  • F1: -865 µm/ºC, total: 1,038 µm.
  • F0: -252 µm/ºC, total: 302 µm.
  • The minus sign indicates that when the temperature decreases the GAS filter keystones will raise.
  • Note F1 is more sensitive to temperature (and to the bouyancy) because its relatively low resonant frequency.
• Position of  keysones and their stepper motors at the begining of the exercise were:
  • BF: -73 µm and 0 steps,
  • F1: -95 µm and  0 steps,
  • F0: -1,064 µm and -1,600,000 steps (almost at the lower end of the range).

Bottom filter

The temperature and bouyancy effetcs will act in opposite directions in the current conditions. We expect the temperature to decrease from 26.2 ºC to  25 ºC, thus raising the suspension by 355 µm. Nevertheless, in vacuum the suspension will sag by approximately 341 µm. Therefore, in vacuum and at 25 ºC the BF keystone will end up at -341 µm + 355 µm = 14 µm. This means that as long as we can put the keystone at zero witht he fishing rod, the system will stay in the neighborhood in the final conditions.

I checked the fishing rod range with the LVDT. See the Excel spreadsheet attached. The following applies:

• Tested range of stepper motor (not total range): [ -160,000 , 120,000 ] steps for a total of 280,000 steps.
• LVDT displacement in such a tested range: [ - 476 , 427 ] µm for a total of 903 µm.
• The fishing rod moves the keystone by -3.2 nm/step.
• Note about the tested range:I didn't try to reach the end of range positions to avoid possible jamming of the stepper motor.
• The polarity is such that a negative number of steps produces a positive displacement upwards.
• At the end of the exercise I left the LVDT at 5 µm and the steppermotor at -20,000 steps.
• It might be worth noting that I was able to move the keystone up to 355 µm with 8,500 counts of coil-magnet actuation.

Standard filter F1

The joint effect of the temperature change and the lack of bouyancy in vacuum will bring the keystone to 282 µm if initially at zero: - 756 µm from bouyancy add to + 1,038 µm from temperature change giving 282 µm.

I cheked the fishing rod. See the spreadsheet attached. The following holds:

• Tested range of stepper motor (not total range): [ -110,000 , 100,000 ] steps for a whole range of 210,000 steps.
• LVDT displacement in such a tested range: [ -528 , 253 ] µm for a total of 781 µm.
• The fishing rod moves the keystone by -3.6 nm/step.
• Note about the tested range:I didn't try to reach the end of range positions to avoid possible jamming of the stepper motor.
• The polarity is such that a negative number of steps produces a positive displacement upwards.
• At the end of the exercise I left the LVDT at 0 µm and the stepper motor at -85,000 steps.

Top filter F0

At the begining the plan was to use the top filter to compensate for the bouyancy effect of the whole suspension, a plan that later was cancelled. However, we had already lifted the whole suspension wit the jacks by 1 mm nominal. This means that the F0 keystone won't be in at 0 µm in the final configuration and, therefore, its resonant frequency won't be 0.5 Hz. I have to check the frequency it should have given the new F0 desired postion (-1.1 mm, see entry 7980) and using Hirata-san's measurement when the F1 filter was assembled (entries 5485 and 5487).

What I did was to put the F0 stepper motor at the mid-range position and add 302 grams on the keystone in order to bring the the LVDT readout to -1.1 mm.

I still write here information about the stepper motor range. It is from an old measurement (on 2019-01-24) which has not been properly reported in the klog. In those times I was aiming to compensate the baouyancy effect for the whole chain with F0 and there was not any mass on the keystone and the relationship with the LVDT readout is not expected to hold well straightforwardly. Nevertheless, the motor range still holds.

• Total range of the stepper motor: [ -1,700,000 , 1,500,000 ] steps for a total of 3,200,000 steps.
• LVDT displacement [-990 , 903] µm for a total range of 1.893 mm.
• The fishing rod moves the keystone by 0.6 nm/step.
• The polarity is such that a positive nmber fo steps yields a positive diaplacement (upwards).