ECR Title: Adding auto-alignment for ALS	DCC No: E1400071-v1
Date: 2/19/2014
Requester: Daniel Sigg	Impacted Subsystem(s): ISC
Description of Proposed Change(s): Add back the wavefront sensors for ALS. This change would include placing 2 WFS heads on each ISCTEX/Y table and installing the necessary hardware to acquire the new channels. The change mostly follows the original OAT design. For each detector this change requires 4 iLIGO style WFS heads tuned to 24.5 MHz, 4x feedthrough panels D1100434-v5, 4 ISC whitening chassis, D1002559, 4 WFS I/Q demodulators, D0902796, 2 legacy WFS interface chassis, D1100749, 2 ASC demod. Concentrators, D1100696, and 2 demod. patch panels, D1100905. It requires associated cabling and software changes, both in the real-time and slow controls systems. Existing ADC and DAQ channels are used, as well as existing binario IO channels for whitening switching. New Beckhoff modules are required to read the demodulator RF readbacks.
Reason for Change(s): Due to the high transmission of the 532 nm ETM coatings the sensitivity to alignment fluctuations and pointing errors is greatly enhanced. This is made worse by the change of cavity geometry between OATS/HIFO-Y and the current Advanced LIGO configuration which results in 3x higher cavity beam motion for the same misalignment.
Estimated Cost: whitening chassis, demodulator chassis, legacy WFS interface chassis, bias supply, slow controls ADCs:
Schedule Impact Estimate: 2-4 weeks of integration time.
Nature of Change (check all that apply): Safety Correct Hardware Correct Documentation	Improve Hardware Improve/Clarify Documentation Change Interface Change Requirement
Importance: Desirable for ease of use, maintenance, safety Desirable for improved performance, reliability Essential for performance, reliability Essential for function Essential for safety	Urgency: No urgency Desirable by date/event: ____________ Essential by date/event: _HIFO-X_____ Immediately (ASAP)
Impacted Hardware (select all that apply): Repair/Modify. List part & SNs: ______________________ Scrap & Replace. List part & SNs:_____________________ Installed units? List IFO, part & SNs: _________________ Future units to be built	Impacted Documentation (list all dwgs, design reports, test reports, specifications, etc.): D1201448, D1100607, D1001423, E1300151, D1101126, D1201495, T1100472, D1100434, E1100591, E1300079, D1100683, E1200376
Disposition of the proposed change(s): The disposition of this proposed engineering change request is to be completed by Systems Engineering and indicated in the “Notes and Changes” metadata field in the DCC entry for this ECR. The typical dispositions are as follows: Additional Information Required: in which case the additional information requested is defined. The ECR requester then re-submits the ECR with the new information using the same DCC number for the ECR but with the next version number. Rejected: in which case the reason(s) for the rejection are to be given Approved Approved with Caveat(s): in which case the caveat(s) are listed TRB: the ECR is referred to an ad-hoc Technical Review Board for further evaluation and recommendation. It is the System Engineer’s (or designee’s) responsibility to organize the TRB. The System Engineer (or designee) then makes a technical decision based on the TRB’s recommendation. Links to the TRB’s documentation (charge, memos, final report, etc.) are to be added to the “Related Documents” field for this ECR. CCB: a change request for approval of additional funds or schedule impact is to be submitted to the Configuration Control Board. Links to the CCB’s documentation (CR, etc.) are to be added to the “Related Documents” field for this ECR. Concurrence by Project Management: Acknowledgement/acceptance/approval of the disposition is to be indicated by the electronic “signature” feature in the DCC entry for this ECR, by one the following personnel: Systems Scientist Systems Engineer Deputy Systems Engineer