Microscope corrections

Introductions

These corrections need to be computed after the installation of a new microscope, or when the support plate is changed (for example, OPERA-like or SND-like emulsion size).

List of corrections

1. flimgen

2. cormtx (This is a correction of uneven magnification distortion along the field of view)

3. slope (This is a correction of spherical distribution)

4. flatview (Correction allowing to transfer the spherical field of view into a flat one)

5. grainvol (Correction of grain volume/brightness)

Pixel size determination and flimgen

Stretching the image from the camera on two monitor screens, select a point, run it from left to right - record x coordinate, run back - record x coordinate. Repeat at least 3 times, get average value, divide 1 by number of pixels: Nx = 2336

Repeat the procedure for y axis. Divide the average value by the number of pixels: Ny = 1728

Check the results are 0.345 and 0.346

Enter the resulting values in

Modules -> Processor -> img_pixel_size

Make a test scan (flimgen) and convert into clusters

Cormtx

Create two directories: /bot and /top

Launch copied files from previous directory

Select scan parameters x 90 y 70

img_cor_mat_0 and img_cor_mat_1 should be empty in first correction!

Set thickness of bot (top) with a distance of 10-15 μm from base.

Make test scans, convert them into raw.root files

Send them to Y: folder (visibile by nusrv)

Insert Xpix and Ypix in viewdist.rootrc

On Linux server, copy directories to disk Y:

viewdist -f=clust.raw.root

obtain correction map

send the correction map back to LASSO

create folders bot_1 and top_1

Fill these 2 maps in img_cor_mat_0 and img_cor_mat_1. Both the same file, bot if you scan bot, top if you scan top

Repeat the scan and conversion

N.B. When building following maps, remember to build them on top of previous corrections!

Example: (for bot_1 from bot)

viewdist -f=clust.raw.root -add=/home/scanner/sndlhc/cor_gen_MIC5/2.cormtx/bot/correction_matrix.txt

Repeat until map converge. It may complain about EdbViewMatch::CalculateCorr: WARNING: null dxy: ic=43 i=367065 cx,cy: 397.868652 43.176414. This means nothing will be added as correction here. What is the reason?

Obtained files need to be moved to C:\LASSO_x64, renaming them in order to replace already existing files.

Slope

It is only a fast scan

• launch run.bat

• launch scans

• launch OpGrnProc.bat

• launch fit.C:

root -l grains.raw.root fit.C

Flatview and grainvol

They use the same scan:

• copy folders

• Scanning (measure glass, bottom, base and top, check light level, to have gray level about 190)

• OpGrainProc.bat

• run_flatview.bat

• run_grain_vol.bat (from folder 5.grainvol)

• check plots with .C scripts

• copy flatview_0.vfm and flatview_1.vfm in C:\LASSO_x64

• copy grnvol_mtx_0.grv and grnvol_mtx_1.grv in C:\LASSO_x64

gfind

copy fit values in link_corr, link_cor_0, link_cor_1

Note: the last corrections (the 5th, in particular), should be performed with a sampling emulsion film from the OPERA experiment, not one with SND@LHC beam.

Angular offset

This correction cannot be applied before scanning, must be performed a posteriori.

Each microscopes has not an exactly planar stage. Therefore, an angular offset can be observed, depending on the singolar microscope (about 10 mrad in TX and TY).

The proposed solution to correct it is to analyze a plate scanned twice: first normally, second rotated of 180°.