[Yokozawa, YamaT]

Abstract

We installed Coil Driver Switcher for the TM stage of ETMX.
Now we can reach LOCK_ACQUISITION state and excite the TM stage only via HPCD.
For switching LPCD, model update is required (maybe on the next maintenance day?).
 

Details

Installation of Coil Driver Switcher board
As an operation test of the Coil Driver Switcher was completed in klog#32943, we installed it for ETMX_TM. The Coil Driver Switcher hasn't been assembled to a formal chassis yet, S-number is not assigned for the chassis. A S-number of the used circuit board is S2516468. After preparing front/rear panels and a formal chassis, it should be replaced for a proper management of S-number for installed circuits. From the view point of gain adjustment, coil balance, and calibration, it may be better to keep using the same board until finishing O4c. S2516468 was installed rear side at U42 of EXV2 rack as shown in Fig.1. Output port of this board is connected to the feedthrough at the EXV chamber (a cable which had been connected to the output port of TM HPCD was moved to the output port of this board).

Connection with Coil Driver chassis
Two DB9 inputs of this board are connected with the output ports of TM HPCD and TM LPCD for CRYp. HPCD (S2315283) has been used in the past and wasn't changed in this work. LPCD for CRYp (S1604776) which had been installed for the IM blade damp and hasn't been used until today was reused for this purpose (see Fig.2). So there is no new installation of the coil driver chassis.

BIO cables
BIO cables were stolen from ones for BFV coil driver chassis for this purpose (see also Fig.3). Though we cannot enable the de-whitening filters for BFV now, it should be no impact for the daily operation because we haven't used de-whitening filters for the tower stages. k1iopex1 has now 5 BIO cards and one more BIO card may be able to be installed. If we will try it and will return stolen BIO cables to BFV, we probably need a whole day as a maintenance time.

Operation check
After the installation, we requested LOCK_ACQUISITION for VIS_ETMX guardian and it works well. Because there is no DAC output for TM stages in this state, I ensured that HPCD path is now enabled by using awg excitation. Figure 4 shows the TM Oplev signals with excitations from a HPCD path of the TM stage. For switching to a LPCD path and checking the injection via LPCD, we need to modify the real-time model. It will be done in next(?) maintenance day. Anyway, IFO lock with HPCD is probably now available.

Note
[1] DC power for the switcher board is derived from LPCD chassis. So we need to turn on LPCD before HPCD. On the contrary we need to turn off HPCD before LPCD. (see also Fig.5).
[2] A cable between the feedthrough and the coil driver output of IM blade damp is still left in EXV2 rack as shown in Fig. 6. If we don't need IM blade damp for future, they should be uninstalled.
[3] 'open' and 'close' of BIO are assigned for using HPCD and using LPCD, respectively in the current connection. In the case of Z-switch of OMC, 400Ohm (BIO 'close') has many peaks compared with 100Ohm (BIO 'open'). Though we haven't been sure the actual reason yet, BIO 'close' may induces undesirable noise due to additional connection to GND. If we will face many peaks when we swtich to LPCD, it may be better to try swapping the BIO assignement as 'open' for LPCD and 'close' for HPCD.