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 modesand testing

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• 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

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

•External triggering•Programmable delay between

trigger edge and capturing

•Data flow:

•.raw

•.cal

•.h5

Improvementspimp my 4D…

• SW: Acquisition steps splitted

Capture .raw 28 HzProcess .cal 9 HzReduce .h5 1.2 Hz

Faster capturingIndependent sessions:Sampling -- Processing

1

Improvements

•Data transfer to HD unreliableRamDisk 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.

2

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 verifiedUsing a sinchronized PZTRepeatability better than 0.5ms

3

Improvements

•Trigger interface converterFrom BCU39 to 4D

BCU39

Optic Fiber, 40MHz bus(25 ns pulses)

Interface

4DNo delay, 200 us pulses

0-5V TTL TTL & Opto-coupled(TTL used)

4

Sampling sessions

BCU39Interface

4D

AdSec

AOWS

WFS

PhaseCamFastlink1

TX

Trigger

Shapes

Sampling

Start of Frame

Timeline

Time

BCU39

AdSec

4D

Start of frame 12ms Start of frame

0 20 40 ms

Slopes to AdSec Slopes to AdSec

Received commands

Commands applied

Oversampling period (5 ms)

Trigger Trigger

8 ms Image acquisition 8 ms Image acquisition

A!

A!B!

!• A!: the image is captured

Before the mode application

The transient is not seen!

We command a trefoil and 4 zero-shapesas starting point reference

Starting trefoil +mode -mode +mode

Trigger Command

Trigger Command

Sampling procedure

0. connect & set-up» Connect HW

» Set the shell

» Configure BCU & 4D

1. Create a set of shapes (IF, MirModes, KL)2. Start 4D acquisition (no action on trigger)

3. Enable the shapes sending» Commands to AdSec

» Pulses to 4D interface

30 min

2 sec

2sec

1

Sampling procedure

0. Commands applied by AdSec» +zeroes+starting trefoil…

» Oversampling

1. Modes commands template: [1,-1,1]

2. Images are captured

3. ‘Move’ from RamDisk to HD

4. Download of command history from SDRAM

50sec

40sec

5 min

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

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

Analisys of electrical data

30min

20min1 min

2