ECR Title: Building EOM/AOM Driver	DCC No: E1500135-v1
Date: 2/18/2015
Requester: Daniel Sigg	Impacted Subsystem(s): ISC
Description of Proposed Change(s): Implement the EOM/AOM driver units described in E1400445 on the EOMs driving the two main RF modulation sidebands. This is integration tracker issue 937.
Reason for Change(s): There isn't currently a dedicated EOM driver for the main modulations; we just use fixed outputs of the RF distribution. We removed this item from ISC scope fairly early on in the project, because it wasn't clear that it would be important, at least for early operation, so we dropped it to get everything else done. Now we find that we need a dedicated EOM driver for two reasons: Recent LLO measurements showed that the RF oscillator AM noise was only a factor of a few below the noise floor. The new driver has an AM stabilization servo to deal with this issue. For lock acquisition we need the modulation index to be (2-3x) higher than the design value for final operation; however, with the current setup there is no way to reduce the modulation index after acquisition -- the new driver will allow this.
Estimated Cost: $40k for 9 EOM/AOM drivers, 3 RF AM Measurements units, associated EtherCAT interface and some cabling.
Schedule Impact Estimate: none. The change needs to be implemented by the start of O1.
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: _O1________ 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.): E1400445 and related D1200666, E1200408, T1100472, E1300079, D1100683, E1300688, E1100591
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