Following a similar prescription as what Keiko's done at LLO (see e.g. LLO aLOG 4030), but now using the new infrastructure, I've installed a few gains,
H1:SUS-PR2_M1_OPTICALIGN_P_GAIN 2.636 [drive cts/urad]
H1:SUS-PR2_M1_OPTICALIGN_Y_GAIN 1.859 [drive cts/urad]
into the new OPTICALIGN bank, which should now be responsible for aligning the optic. With this gain, the offsets
H1:SUS-PR2_M1_OPTICALIGN_P_OFFSET (for Pitch)
H1:SUS-PR2_M1_OPTICALIGN_Y_OFFSET (for Yaw)
are then calibrated into [urad] of optic motion. This gain should be [applicable to / the same for] every HSTS.
I attach some shots of the new screens demonstrating where these gains live (and showing off the new screens).
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How the gain was calculated:
It's along signal chain, but here goes (I use Yaw on an HSTS as an example):
LF +--------+ +------+ +-----------+ +-----------+ +---------+
+->|COILOUTF|->| DAC |->|Coil Driver|->|Coil/Magnet|->|Lever Arm|->+
+-----------------+ +---------------+ +----------+ +--------+ | +[cts/ct]+ +[V/ct]+ +---[A/V]---+ +---[N/A]---+ +---[m]---+ | +-------------+ +------------------+
|OPTICALIGN OFFSET|->|OPTICALIGN GAIN|->|DRIVEALIGN|->|EUL2OSEM|->+ +->|HSTS M1 to M3|-->|Optic Displacement|
+-----[urad]------+ +---[cts/urad]--+ +-[cts/ct]-+ +[cts/ct]+ | +--------+ +------+ +-----------+ +-----------+ +---------+ | +--[rad/N.m]--+ +------[urad]------+
+->|COILOUTF|->| DAC |->|Coil Driver|->|Coil/Magnet|->|Lever Arm|->+
RT +[cts/ct]+ +[V/ct]+ +---[A/V]---+ +---[N/A]---+ +---[m]---+
(see fullsignalchain.png if you browser sucks at ASCII art)
Thankfully, because
- we're only looking for the DC gain of this path,
- the DRIVEALIGN matrix is an identity at this point
- the EUL2OSEM matrix accounts for (divides out) the number of actuators (two in this case) and the lever arm between the OSEM and the center of rotation
- the COILOUTFs are unity at DC
then our calculation only involves this simplified chain:
+-----------------+ +---------------+ +------+ +-----------+ +-----------+ +-------------+ +------------------+
|OPTICALIGN OFFSET|->|OPTICALIGN GAIN|->| DAC |--|Coil Driver|--|Coil/Magnet|->|HSTS M1 to M3|-->|Optic Displacement|
+-----[urad]------+ +---[cts/urad]--+ +[V/ct]+ +---[A/V]---+ +-["N.m"/A]-+ +--[rad/N.m]--+ +------[urad]------+
(see reducedsignalchain.png if you browser sucks at ASCII art)
which means the OPTICALIGN GAIN is:
OPTICALIGN GAIN [cts/urad] = ( DAC [V/ct] * Coil Driver [A/V] * Coil/Magnet [N/A] * HSTS M1 to M3 [rad/N.m] * 1e6 [urad/rad] )^-1
= ( (20/2^18) * 0.011919 * 0.963 * 0.4332 (for Yaw) * 1e6 )^-1
= 1.850 [cts/urad]
The only difference for pitch is that HSTS M1 to M3 [rad/N.m] = 0.6172 (for Pitch). The electronics gains of the signal chain were taken from T1000061 (the contents of which have been experimentally confirmed elsewhere), and the HSTS M1 to M3 coefficients were taken from the production model (e.g. see T1200404).