If and kl measurements with 4d interferometer
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IF and KL measurements with 4D interferometer. Runa Briguglio, OAA. Rationale. New experimental set-up (4D+BCU39), that permits the reduction of convection and vibration noise. Acquisition of Influence Functions. Determination of KL modes and testing. Table of contents.

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IF and KL measurements with 4D interferometer

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If and kl measurements with 4d interferometer

IF and KL measurementswith 4D interferometer

Runa Briguglio, OAA


Rationale

Rationale

New experimental set-up (4D+BCU39),

that permits the reduction of convection

and vibration noise.

Acquisition of Influence Functions

Determination of KL modes

and testing


Table of contents

Table of contents

  • 4D interferometer

    • Dinamic interferometry

    • High sensitivity

    • High speed external trigger

  • Improvements and tests

    • RamDisk

    • Software modifications

    • Trigger interface

  • Measurements

    • Exp. Set-up and connections

    • Acquisition procedure

    • IF: Zonal & Modal

    • KL


  • 4d interferometer

    4D interferometer

    • Simultaneous phase shifting

      • No moving parts

      • No delay between frames

      • Single CCD for 0°,90°,180°,270° phases

    • High sensitivity

      • High density of fringes is detectable

      • Great help for alignment and first flattening

  • External trigger


  • Burst acquisition few points

    Burst acquisition:few points

    • Continous images sampling, 0.14Hz<F<28.5Hz

    • Data flow:

    • .raw

    • .cal

    • .h5

    • External triggering

    • Programmable delay between trigger edge and capturing


    Improvements pimp my 4d

    1

    Improvementspimp my 4D…

    • SW: Acquisition steps splitted

    Capture  .raw28 Hz

    Process  .cal 9 Hz

    Reduce  .h5 1.2 Hz

    Independent sessions:

    Sampling -- Processing

    Faster capturing


    Improvements

    2

    Improvements

    • Data transfer to HD unreliable

      • RamDisk installed

      • Storage: 1600 frames, 0% faults

    …Depending on

    Frequency and n° of frames…

    No faults found at f<15Hz

    Ok for IF acquisition, at max freq.


    Improvements1

    3

    Improvements

    • Testing:

    • GUI  scripting conflict

      • GUI commands reset the trigger settings

  • Ext trigger > Fmax is processed

    • ! Rising edges are detected after 1/28Hz

  • Internal delay verified

    • Using a sinchronized PZT

    • Repeatability better than 0.5ms


  • Improvements2

    4

    Improvements

    • Trigger interface converter

      • From BCU39 to 4D

    Interface

    BCU39

    4D

    No delay, 200 us pulses

    0-5V TTL

    Optic Fiber, 40MHz bus

    (25 ns pulses)

    TTL & Opto-coupled

    (TTL used)


    Sampling sessions

    Sampling sessions

    Shapes

    AOWS

    WFS

    AdSec

    PhaseCam

    Fastlink1

    BCU39

    Start of Frame

    Interface

    TX

    4D

    Trigger

    Sampling


    Timeline

    Timeline

    Time

    BCU39

    AdSec

    4D

    0 20 40 ms

    A!

    Start of frame 12ms Start of frame

    Slopes to AdSec Slopes to AdSec

    Received commands

    Commands applied

    Oversampling period (5 ms)

    B!

    A!

    Trigger Trigger

    8 ms Image acquisition 8 ms Image acquisition


    If and kl measurements with 4d interferometer

    !

    • A!: the image is captured

      Before the mode application

      The transient is not seen!

    We command a trefoil and 4 zero-shapes

    as starting point reference


    If and kl measurements with 4d interferometer

    Starting trefoil +mode -mode +mode


    If and kl measurements with 4d interferometer

    TriggerCommand

    TriggerCommand


    Sampling procedure

    1

    Sampling procedure

    0. connect & set-up

    • Connect HW

    • Set the shell

    • Configure BCU & 4D

  • Create a set of shapes (IF, MirModes, KL)

  • Start 4D acquisition (no action on trigger)

  • Enable the shapes sending

    • Commands to AdSec

    • Pulses to 4D interface

  • 30 min

    2 sec

    2sec

    noise measurements


    Sampling procedure1

    2

    Sampling procedure

    50sec

    40sec

    5 min

    0. Commands applied by AdSec

    • +zeroes+starting trefoil…

    • Oversampling

  • Modes commands template: [1,-1,1]

  • Images are captured

  • ‘Move’ from RamDisk to HD

  • Download of command history from SDRAM

  • Images ‘production’ (process+reduction:.dat .h5)

    Data analisys w/template: [1,-1,1]

    Analisys of electrical data

    30min

    20min

    1 min


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