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| QC PLOTS |
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CURRENT |
HISTORY |
| Grating stability |
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| QC1 database (advanced users):
browse
| plot |
Click on CURRENT to see the current trending (Health Check).
Click on HISTORY to see the historical evolution of the trending. |
A set of frames is measured daily to monitor
the stability of the gratings and of the fiber system. These frames carry the DPR
TYPE SIMLAMP,TAL (TAL = thorium-argon lamp) and are created by the arclamp of the
simultaneous calibration unit. The arc lamp is used to illuminate the simultaneous
calibration fibres. The signal is correlated both in X (cross-disperion) and Y (dispersion)
against a reference frame. There is a set of five such health check measurements,
one for each slit system (Medusa1 and 2, IFU1 and 2, Argus).
The data are also used to monitor the arclamp
efficiency.
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SIMLAMP,TAL frame (closeup).
There are five simultaneous calibration fibres, illuminated by the
arclamp. |
The gratings are observed to have both thermal and non-thermal motions.
To control the thermal motions, the temperature sensor TEMP53 is used, located on
top of the grating table. It delivers a value into the header of each raw frame.
QC1 parameters
| parameter |
QC1 database: table, name |
procedure |
| temperature from sensor TEMP53, in degree Celsius |
giraffe_simlamp..ins_temp53_val |
written into raw file fits header; sensor is close to grating |
| TEMP54 |
giraffe_simlamp..ins_temp54_val |
similar value, with the sensor close to the grating table; in most cases, this
value deviates by a few tenth of a degree at most |
| delta_T |
giraffe_simlamp..delta_temp |
difference between these two values |
Trending
As a reference evalue, the temperature TEMP53 is plotted in box 1 and
repeated in box 4 of the trending
plot.
| top Grating
motions in X and Y |
Each of the Health Check data is correlated in X and Y to a reference frame. The set
of reference
frames is arbitrarily taken from date 2003-07-24. The difference (X_new - X_ref)
is plotted vs. time. The same is done for the Y (dispersion) direction.
QC1 parameters
| parameter |
QC1 database: table, name |
procedure |
| mean_xdiff (gratings HR and LR) (left panel, plots 2 and 3) |
giraffe_simlamps..mean_xdiff |
difference in X between new frame and reference, HR and LR gratings |
| mean_ydiff (gratings HR and LR) (middle panel, plot 5 and 6) |
giraffe_simlamps..mean_ydiff |
difference in Y between new frame and reference, HR and LR gratings |
Trending
Boxes 2 and 3 of the trending
plot display the X motions of the HR and LR grating (selected is the Medusa1 frame),
boxes 5 and 6 the Y motions. Box 4 repeats the temperature record from
box 1 for comparison.
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Stability trending plot, panel 1 .
On top there is the trending of the temperature (in degree Celsius), and below
are the plots for the shift in X direction, both for the HR and the LR grating.
The temperature sensor selected is TEMP53 ('surface table temperature top').
A similar column is plotted for the Y shifts (panel 2).
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| top Correlation
of shifts with temperature |
The third panel shows the shifts in X and Y versus temperature TEMP53.
For both directions, there is essentially the same anti-correlation with temperature.
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Correlation plot. Boxes 7 and 8 show the shift of the grating in X direction, in pixels, versus the temperature
drifts (TEMP53 as above). X-axis: grating shifts in X; Y-axis: TEMP53 in degrees
Celsius.
Boxes 9 and 10 display the same for the Y shifts.
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Note that the Giraffe gratings occasionally show sudden non-thermal
shifts. These are detected in the trending plot as corresponding shift of the correlation
pattern in X direction.
History
| date |
event |
| 2007-11-14 |
earthquake; non-thermal jump of HR grating in X (+1) and Y
(+2) pixels |
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