2.5 Data File Format
The MCA spectra are saved in ascii format. To save a spectra that you've
collected click on the File menu selection
and then select Save As and input the file name in the proper directory. Once
you've done this you can use the Save Next feature to save spectra as numerically sequential files. A
word of caution, though. The MCA display and the scanning routines aren't aware
of what files are actually in the directory.
Once saved the file can be directly displayed in
ascii. The file example_mca.dat (click on the
file name to download) will give you a look at the file format. You'll see the
following information in the header:
VERSION: 3.1
ELEMENTS: 1
DATE:
CHANNELS: 2048
ROIS: 6
REAL_TIME: 300.0000000
LIVE_TIME: 298.6300049
CAL_OFFSET: 1.8733252e+001
CAL_SLOPE: 5.8587302e-002
CAL_QUAD: 0.0000000e+000
TWO_THETA: 5.4373522
ROI_0_LEFT: 632
ROI_0_RIGHT: 672
ROI_0_LABEL: gold 111 &
ROI_1_LEFT: 783
ROI_1_RIGHT: 823
ROI_1_LABEL: gold 200 &
ROI_2_LEFT: 1248
ROI_2_RIGHT: 1288
ROI_2_LABEL: gold 220 &
ROI_3_LEFT: 1522
ROI_3_RIGHT: 1562
ROI_3_LABEL: gold 311 &
ROI_4_LEFT: 1605
ROI_4_RIGHT: 1645
ROI_4_LABEL: gold 222 &
ROI_5_LEFT: 1905
ROI_5_RIGHT: 1945
ROI_5_LABEL: gold 400 &
ENVIRONMENT:
13BMD:OperatorName.VAL="Andrew Campbell, Uchi, Yanbin" (Operator
Name)
ENVIRONMENT:
13BMD:SampleName.VAL="Fe-Ru (15 wt%) T0324" (Sample Name)
ENVIRONMENT:
13BMD:ExperimentComment1.VAL="" (Experiment Comment1)
ENVIRONMENT:
13BMD:ExperimentComment2.VAL="" (Experiment Comment2)
ENVIRONMENT:
13BMD:ExperimentComment3.VAL="" (Experiment Comment3)
ENVIRONMENT:
13BMD:ExperimentComment4.VAL="" (Experiment Comment4)
ENVIRONMENT:
13BMD:ExperimentComment5.VAL="" (Experiment Comment4)
ENVIRONMENT:
13BMD:DMM1Ch1_calc.VAL="34.9353" (Pressure in tons)
ENVIRONMENT:
13BMD:DMM1Ch2_calc.VAL="89.8025" (unused)
ENVIRONMENT:
13BMD:DMM1Ch3_calc.VAL="0.0000" (Ram height in mm)
ENVIRONMENT:
13BMD:DMM1Ch4_calc.VAL="-12.2329" (unused)
ENVIRONMENT:
13BMD:DMM1Ch5_calc.VAL="0.0000" (Thermocouple emf1)
ENVIRONMENT:
13BMD:DMM1Ch6_calc.VAL="-10.8000" (Thermocouple emf2)
ENVIRONMENT:
13BMD:DMM1Ch7_calc.VAL="15.7447" (unused)
ENVIRONMENT:
13BMD:DMM1Ch8_calc.VAL="-1.1527e+147" (unused)
ENVIRONMENT:
13BMD:DMM1Ch9_calc.VAL="900.2378" (Unused)
ENVIRONMENT:
13BMD:DMM1Ch10_calc.VAL="0.0000" (Sample T (C))
ENVIRONMENT: 13BMD:DMM2Ch1_calc.VAL="3.9899"
(Heater Voltage (AC Volt))
ENVIRONMENT:
13BMD:DMM2Ch6_calc.VAL="32.6642" (Heater current (AC amps))
ENVIRONMENT:
13BMD:LVP_furnace_calcs.C="0.122" (Heater resistance (Ohms))
ENVIRONMENT:
13BMD:LVP_furnace_calcs.D="130.328" (Heater power (
ENVIRONMENT:
S:SRcurrentAI.VAL="102.415" (Ring current)
ENVIRONMENT:
13BMD:m1.RBV="-31.580" (Press upstream Y)
ENVIRONMENT:
13BMD:m2.RBV="-31.580" (Press inboard Y)
ENVIRONMENT:
13BMD:m3.RBV="-31.580" (Press downstream Y)
ENVIRONMENT: 13BMD:m4.RBV="-8.572"
(Press upstream X)
ENVIRONMENT:
13BMD:m5.RBV="-8.226" (Press inboard X)
ENVIRONMENT:
13BMD:m6.RBV="-18.463" (Press Z drive)
ENVIRONMENT:
13BMD:m7.RBV="0.000" (Vertical LVP front slit Y position)
ENVIRONMENT:
13BMD:m8.RBV="0.000" (Horizontal LVP front slit X positon)
ENVIRONMENT:
13BMD:m9.RBV="35.508" (Detector X)
ENVIRONMENT:
13BMD:m10.RBV="-7.861" (Detector Z)
ENVIRONMENT:
13BMD:m16.RBV="50.738" (Detector Y)
ENVIRONMENT:
13BMD:m12.RBV="4.575" (Detector Two Theta)
ENVIRONMENT:
13BMD:m13.RBV="-3.235" (Detector Phi)
ENVIRONMENT:
13BMD:m11.RBV="-0.000" (CCD Stage X)
ENVIRONMENT:
13BMD:m14.RBV="172.021" (CCD Stage Y)
ENVIRONMENT:
13BMD:m15.RBV="114.000" (CCD Stage Z)
ENVIRONMENT:
13BMD:m29.RBV="-4.920" (Inboard hutch slit)
ENVIRONMENT:
13BMD:m30.RBV="-1.920" (Outboard hutch slit)
ENVIRONMENT:
13BMD:m31.RBV="3.500" (Top hutch slit)
ENVIRONMENT:
13BMD:m32.RBV="0.500" (Bottom hutch slit)
DATA:
...
Some things are self-explanatory
(date, live_time, real_time, version,...). 'Channels' tells you that in our
current MCA configuration we're saving 2048 channels worth of information.
'ROIS' tells you how many roi's you had defined for this spectra and farther
down in the header you'll see a listing of what channel numbers (0-2047) had
been defined as the left and right edges of that ROI (ROI_0_LEFT, ROI_0_RIGHT,
ROI_1_LEFT, etc.). Two vitally important bits of information if you want to
plot this spectrum in a spreadsheet are the 'CAL_OFFSET' and 'CAL_SLOPE'.
CAL_OFFSET tells you what the energy of the first channel number (Channel 0) is
in KeV. In this example its value is 18.733252 KeV. This offset may sound terribly big, but it is
done intentionally – sometimes you need to play with with the MCA electronics
to have just enough coverage for all the peaks you are interested within the available
2048 channels. For examples of the IOC
and Amplifier settings, click here. The CAL_SLOPE then gives you the energy of
each subsequent channel in KeV, in this example 0.00928 KeV. If you look at the
data in the file you'll then see a single column of 2048 numbers. This is the
raw data saved in each channel (0-2047). To plot it in you'll need to make a
line graph where the first X value is 0.5413 and each subsequent value
increases by 0.00928. You'll probably also want to change you're Y scaling to be
logarithmic rather than linear.
You may also see some vital bits
of information saved in the file. Particularly ring current, experiment
comments, heater current, voltage, power, and motor positions. In order for this data to be saved in the
spectrum file you have to make sure that the file "catch1d.env" is in
your data directory and that it’s got the right settings. This is an ascii file
that the MCA routine looks for. An
example of the catch1d.env file is here.