The original user's manual was written with the "classical" beam combination table in mind, which was the first application of the NICMOS3 detector.
In November 2000 we had the first observing run with the NICMOS3 camera coupled to the IONIC experiment. First fringes were obtained using two integrated optics components: LEMO (3 outputs, P1, I1, P2) and LETI (4 outputs, P1, I1, I2, P2). See IONIC for information on these exciting new results.
For this first IONIC implementation at IOTA, it was decided to use the FLUOR Observing Software as an interface to the user. Therefore, from the observer's point of view, (almost) everything is as when observing with FLUOR and the NICMOS3 camera.
The FLUOR G3 is still responsible for driving the piezo scanner. However, in this experiment the "IOTA" piezo is used, not the FLUOR one. The "IOTA" piezo has a mechanical stroke of 60 um and is driven by a P.I. 662 amplifier, to which we connect the driving triangle waveform output by the G3. The waveform output by the G3 is in the range -5 to +5 Volt. The P.I. 662 amplifier expects an input in the range 0 to +10 Volt in order to displace the piezo 0 to +60 um. Therefore, an offset of +5 Volt needs to be added to the G3 output, which can be done at the P.I. 662 amplifier by using the OFFSET potentiometer.
New software has been written by Jean-Philippe Berger and myself that: (1) displays detector images and flux information for alignment (qreadio), and (2) samples 3 or 4 pixels in one row and sends the data to the FLUOR G3 (fringeio). Other software improvements are: (a) option to store 16 consecutive image frames to disk, and (b) new sampling functions which permit to sample pixels located in even or odd columns. As before, for the fringe sampling program a configuration file (fringeio.cfg) is used to specify the location of the 3 or 4 target pixels. This configuration file is also used to select readout of 3 (for LEMO) or 4 (for LETI) pixels. In order to minimize the code modifications on the FLUOR side, when using the 3 outputs combiner, the 4th pixel is filled with synthetic data that simulates the fringe complementary to I1. These programs are typically located in a C:\IONIC directory in the NICMOS3 Pentium computer.
As far as the FLUOR Observing Software is concerned, modifications were needed in order to: (1) change the conversion from Volt to microns, from the value appropriate to the FLUOR piezo (18 um/Volt) to the value that corresponds to the "IOTA" piezo (6 um/Volt), and (2) enter new values for the sampling rates, which are different because the number and location of the target pixels are different between FLUOR and IONIC. Guy Perrin implemented those changes in a new version of their Observing Software. As of this writing there is one remaining bug: the duration of the scans is not properly set (is significantly shorter than the scan data aquisition time) so that very frequently a second fringe packet is recorded during the piezo scanner flyback.
The frame rates (inverse of sample times) corresponding to the IONIC pixel locations (and that need to be entered in the FLUOR Observing Software) were measured and are as follows:
|Combiner||Samples/Frame (N Loops)||Reads/Sample (N Reads)||Frame Rate (Hz)|
|LEMO (3 outputs)||4||4||877|
|LETI (4 outputs)||4||4||648|
Note: The above frame rates were measured for the IONIC pixel locations used in the November 2000 run, which were as follows:
LEMO (3 outputs): row = 32, column1 = 26, column2 = 32, column3 = 38.
LETI (4 outputs): row = 32, column1 = 26, column2 = 30, column3 = 34, column4 = 38.
Note: In the November 2000 run, we used the usual code for sampling the pixels which limits
their location to even columns in the case of the LEMO component. The new code which also allows
sampling pixels located on odd columns was written later and tested only with the LETI
component. It is under these conditions that the above frame rates were measured and strictly