Bounce back angle from the slit wheel mirror

Now that there is an Al flat mirror in one of the slit wheel positions, we wanted to see at what angle it returns the beam. These photos show the laser bumper where the tip of the red laser fiber lies. A card held over the input beam clearly shows the input beam shining through. What the second photo is *supposed* to show is that the beam returned from the mirror can only be clearly seen by partially obstructing the input beam (there is a bright dot in the middle of the glow from the input beam -- hard to see in this image.) So basically, the mirror returns the beam almost to the point of the laser fiber tip.

preliminary slit mechanism repeatability

The files used here are from a B_12_03_01/. (b208-217)

To look for slit mechanism repeatability, we moved the slit wheel by -12000 steps, then 12000 steps to see if the apparent positions of spectral lines changed after the motion. We only did 10 frames for this test, discarding the first image, in which we brought the slit to 3.6341 V.
by hand turning the mechanism knob.

EXES was looking at the gas cell, targeting 1335 cm^-1 H20 lines.
filter: 7.466um
decker: central arc
V_echelle: 7.9809 V
flip: high medium
lens: OPEN

A sequence of four 3-second images were taken at each iteration. I combined these by doing a linear fit to the pixel values across the frames, and recording the slope into a single 1024^2 array (using [3,6,9,12] seconds as the x-axis for the fit).

 10 x 100 pixel box around a H20 spectral line, used to track changes in the slit wheel position after -12000 step,+12000 step motions.

Figure: jagged line is the sum of a 10x100 pixel box around a water vapor line. Top curve is the smoothed version of this, with a 6-param Gaussian fit. 

Then for this very preliminary test, I focused on just one line, at [128, 516], and summed a 10x100 pixel box of this line to have a 1-d cut. Even though the line was strong, a ~20 adu amplitude sawtooth pattern (probably from 60 Hz noise in the readout) made fitting a Gaussian problematic. I smoothed the 1-d array with a 4pixel boxcar, and then fit a 6 param Gaussian.

The fit centers of the Gaussian (along the y-axis)  
   52.975
   53.021
   52.796
   52.839
   52.767
   52.777
   52.841
   52.876
   52.948
   52.808

For a stddev of 0.09 pix and a maximum difference from the mean of 0.16 pix.

We probably want to know a great deal more about out repeatability than this - longer time baseline, effects of changes in cabin temperature ...

And as far as measuring it, I want to try to correct the 60 hz noise (or whatever it really is) without using the smooth function. But at least the mechanism seems very repeatable over short time baselines.

Instructions to start most recent previous working acq and exesgui combination.

How to switch the basic asriocfg windows driver used to communicate to the eBox.

1. First, make sure the "new" or current driver is unloaded
2. Reboot "gus" the PC.  Hard boot preferable.
3. Load the new driver OR just start acq.

1.  Unload the current driver.  For example:

cd \mikework\nexes\acq\drivers
drvs remove

drvs.bat is a batch file which will load and register a driver with the operating system or if the parameter "remove" is provided it removes the driver.  The sc.exe command of Microsoft Windows XP is used (Microsoft XP reference).

In that directory is the newest driver (at date of this writing) provided by Justin.  asriocfg.sys with the date 8/22/2012, 8:43 AM and size 44,288.  This was unloaded above.





2.  Rebooted the PC.  TURNED OFF AND ON.

3.  Starting the "old" standard acq icon on the desktop starts the program c:\exes\exes.exe.

Since it checks if the service(driver) is available and loads it if it is not available, this works fine. I do not know if this is as permanent as using drvs or not.  I will try to check this.

After the driver was removed, I am not sure what Mark did.  But I believe it is simply to start the "old" acq from the desktop.

I started the gui by going to the directory c:\exes\acq and double-clicking on the exesgui.exe application.

Lens wheel configuration for CD014

Here's the layout of the lens wheel for CD014, looking in from the Dbox wall side. I will update this drawing to include the pot voltages and the position of the UKIRT filter at a later point (I'm keeping the UKIRT filter in vacuum storage until the last minute).

This time we wanted to have the 38 mm KRS5 lens focus the grating onto the detector at its new position (0.125" closer to the grating).
The nominal EFL for the 38mm KRS5 lens is 38mm -- however, it is a 8mm thick meniscus lens and i wasn't sure where the EFL is referenced. So I carefully measured the back FL at optical wavelengths (0.63um, n=2.57) in the lab. I got an average of 31.1 mm. The EFL would have been closer to something like 31.1+4 =35.1mm. At 10.6um (n=2.37), then the EFL is 40.2mm, and the BFL=36.2 mm.

To focus the grating 1000mm away, the back of the lens should be 37.9 mm from the detector.

The distance from the new detector position to the lens barrel is 27.2, so the back of the 38mm KRS5 lens was placed at 10.7 mm into the lens wheel (or 13.8 into the lens barrel).

For the ZnSe lens, I picked a closer distance to the detector of 31.9 mm from the back of the lens.

Note: Drawing updated to actual CD014 configuration on 5/13/2013.

Mounting the square UKIRT 20um filter

Here's some pictures of the holder for the UKIRT 20um filter, which will be installed in the lens wheel for CD014. The black rings are made from delrin, adapted from the stock rings with threaded outer diameter. I milled out the inside of one ring to hold the filter. The white rings are 0.01" teflon sheets with 0.875" holes punched out. The filter is 0.06" thick; the delrin slot is 0.0815" deep. One teflon ring fits into the slot. The other has the same ID, but will be sandwiched between the two delrin pieces. (so the total material in the slot is just 0.06"+0.01" --> i.e. no compression on the filter).
 

CD 14 tasks: V 1.0

UPDATED: 11/30/12 (ver 1.1)

Changed some blocker notes.  changed lens wheel notes.

UPDATED: 11/2/12 (ver 1.0)

I've added a bit more to the list:
Filled in filter slots, filled in decker slots, added imaging tests, added fast framerate tests, added generic data taking tests.

Configuration:

1. Tilted focal plane at detector.  
2. Incorporate directional/size indicator at cold stop.
3. Lens Wheel (note: order isn’t important, but having these components is required)
1. Mirror (will always have mirror and make it position 1)
2. open
3. 1.5” diameter ZnSe lens (note distance of lens edge relative to detector side of lens mounting barrel - would like it to be about half as much as KRS5 lens)
4. 1.5” diameter KRS5 lens (note distance of lens edge relative to detector side of lens mounting barrel - use numbers for IR focus from blog post in May 2012)
5. 1.5” diameter ZnSe blocker 
6. UKIRT filter
4. Slit wheel should have mirror in place (only 1 open position)
5. Decker Wheel filters (note: order isn’t important, but having these components is required)
1. BBP_8000_11000 + BaF2 Blocker - NEW
2. BBP_4700_5615 (no blocker) - New
3. BBP5030_5720 (filter list suggests blocker is not needed. No blocker is mentioned for CD13.  If blocker is present, should be CaF2)  CD13: decker wheel 3
4. BBP5500_6000 (filter list suggests blocker needed, but no blocker is mentioned for CD13.  If blocker is present, should be CaF2) CD13: decker wheel 4
6. Filter Wheel (note: order isn’t important, but having these components is required) 
1. Open CD13: Slot 3
2. 18a (add KBr blocker) CD13: slot 1
3. Soifer Filter - Move from Decker wheel CD13: decker wheel 1
4. 6.2 + MgF2 blocker - New
5. BP14100_850 CD13: slot 12
6. N04679-4 + CaF2 blocker.  Note that this could be N04769-4 (dyslexia) For throughput testing, this need LONG integrations or the blackbody heated up. CD13 slot 2
7. N10247-9 + BaF2 blocker - New
8. OCLI Q + BaF2 blocker - New
9. OCLI R + BaF2 blocker CD13: slot 9
10. BP6000_250 + CaF2 blocker - New
11. BP6600_320 + CaF2 blocker - New
12. N04582-8 + CaF2 blocker - New

Tasks:  As much as possible, use Mike's GUI and ND sampling schemes with any number of S's thrown in to make the integration time as desired.   

There are a couple zeroth order tests relating to the detector and how the data taking software behave

1. see if the array behaves at 0.5 second frametime, which we would like to make our default.  If it doesn't behave at 0.5 second frametime, adjust frametime by 0.1 second intervals to see at what frametime we get good behavior.  Defining good behavior may be hard, but perhaps "repeatable" is more important than absolute performance. We want there to be no (or <1%???) echos from pixels with strong emission.
2. Verify some basic readout patterns and timing.  Assuming framerate is 0.5 seconds, every integration (time between Destructive reads "Ds") will be integer multiple of 0.5 seconds.  For all integrations of two or more frametimes, we will use a combination of a non-destructive read and a destructive read for the integration (ND).  The exact integration time will be achieved by including spins (S's) where we clock through the array, but do not reset or convert.  
1. Verify that doing something like 20 D's takes 10 seconds (0.5second frametime).  Ideally, this would result in a single FITS file with naxis3 = 20.  
2. Verify that doing 20 ND's takes 20 seconds (0.5 second frametime).  Ideally this would result in single FITS file with naxis3 = 40.  Every second frame from FITS file (corresponds to the D's) should have twice the signal of the other frames.
3. Verify that we can do integrations of arbitrary length up to 30 seconds and that timing and fluxes seem accurate.  For 0.5 second frametime, 30 seconds would be "N, 58 S's, D"

Optical tests to be done are:

1. Focus in Med mode at 13.7 microns
1. Investigate whether image size depends on location on detector.  With tilting, we expect ~2500 micron difference in path length from one end of detector to the other (Based on my memory that we’re getting 6 degree tilt with a 25 mm detector -> 25000*cos(6 deg) = 2526).  Orientation should be such that adjusting echelle grating to move a spot from one side of the detector to the other results in different path lengths.
2. Adjust echelle mirror to bring gas cell pinhole spots in center of array to best focus.
3. Assuming it is measurable, determine how many turns of echelle mirror required to go from best focus at one edge of detector to best focus at the other edge.  Assuming the number in 1.1 for path length difference across the full array (2500 microns), and the 80 turns/inch pitch of the mirror screws (317.5 microns per turn), and a 2:1 change in movement at the focal plane compared to movement at the mirror, we would expect 2500/317.5/2 = 4 turns.
4. Return to best focus at center of array.
5. Measure line profile at center of array using slits 1-6 (not flux slit).
2. Focus in High res mode at 13.7 microns
1. Minimize spot size in high res mode at center of array by adjusting echelon mirror while keeping echelle mirror fixed.  Hope is that we go through focus.
2. See if possible to reduce spot size by moving echelon and echelle mirrors in opposite directions.  Hope is that we go through best focus.
3. Map spot size around best focus with +-2 turn grid on both mirrors.  
4. Measure line profile at center of detector at best focus through slits 1-6 (not flux slit).
5. If echelle mirror is at different position from med mode best focus, than measure med mode resolving power at current mirror position.
3. For those filters that have not been tested, map filter transmissions looking at continuum source with short slit.  Adjust integration time so that good signal where light comes through well, but does not drive response >1% non-linear. We will be looking for grating positions that show 1% leaks.
4. Map 18a filter with ZnSe blocker in beam and with KBr blocker in beam
5. Investigate alignment of fore-optics ellipsoid compared to entrance window. 
6. Test imaging photon rate through N04679-4 filter and through N10247-9.
7. Image cold stop in pupil mode.  Use both KRS5 and ZnSe lenses.  Experiment with how moving optics impacts pupil image.  Restrict aperture at slit plane to sharpen image and cut down photon flux.  Try N04679-4 and N10247-9 filters
8. Mount to TAAS 
1. In pupil mode with restricted aperture at slit plane, use small chopped hot plate (SCHP) to map EXES beam.  Determine size of cold stop compared to size of SCHP and location of EXES beam center.  If EXES beam is good relative to entrance window (Item 5 above), then try “walking” beam via shimming at flange to SCHP position matching SOFIA.
2. Investigate alignment compared to large chopped hot plate in pupil mode.   Goal is to see image of LCHP at cold stop.  
3. Switch to FCLS and imaging mode.  Try imaging spot.  See if can get a spectrum of it.  Move FCLS so it matches slit location (don’t move slit around).