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Entry  Thu Mar 7 18:12:03 2013, yuta, Update, Alignment, Input beam drift ~ 0.1 mrad/h in pitch IPangulardrift.png
    Reply  Fri Mar 8 20:51:00 2013, Manasa, Update, Alignment, Input beam drift - investigation **IMPORTANT** 
       Reply  Mon Mar 11 12:29:25 2013, Manasa, Update, Alignment, Input beam drift - weekend trend IPANG_drift.png
          Reply  Tue Mar 12 14:02:22 2013, Jenne, Update, Alignment, Beam drift - mystery partially solved? 
Message ID: 8252     Entry time: Thu Mar 7 18:12:03 2013     Reply to this: 8262
Author: yuta 
Type: Update 
Category: Alignment 
Subject: Input beam drift ~ 0.1 mrad/h in pitch 

[Jenne, Manasa, Yuta]

We temporarily centered the beam on IPANG to see input pointing drift. From eyeball, drift was ~ 0.1 mrad/h in pitch.

What we did:

  1. Aligned TT1/TT2 and aligned input pointing to Yarm.

  2. Tweaked TT2 in pitch to center the beam on the first steering mirror of IPANG path. We still saw Yarm flash in higher order modes at this point. Before tweaking, the beam was hitting at the top edge.

  3. Centered the beam on IPANG QPD.

  4. Moved IPPOS first steering mirror because IPPOS beam was not on the mirror (off in yaw, on mirror edge). Also, IPPOS beam was coming out clipped in yaw.

  5. Centered the beam on IPPOS QPD. We put lens in the path to focus the beam on the QPD.

  6. Left input pointing untouched for 4 hours.

  7. Restored TT2 again. We tried to align Y arm with IPANG available, but it was not possible without touching TRY path and AS was also clipped.

Result:
  Below is the trend of IPANG sum, X, and Y. IPANG Y (IBQPD_Y) drifted by ~0.8 counts in 4 hours. IPANG is not calibrated yet, but Jenne used her eyeball to measure beam position shift on IPANG steering mirror. It shifted by ~2 mm. This means, input pointing drifts ~0.1 mrad/h in pitch.
IPangulardrift.png

Discussion:
  Compared with yaw, pitch drift is quite large considering beam size at ETMY(~5 mm). We can monitor input pointing drift in weekends get longer trend.

Note:
  - IPANG and IPPOS are both changed from the state before pumping.

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