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NAME hecus - Hecus ASA-32 MCA
INTRODUCTION
The ASA-32 is the ISA acquisition card for the Hecus SAX/SWAX
X-ray system. The system has two detectors for obtaining both
small- and wide-angle data with the position-sensitive detectors.
The system can be operated in a pure small-angle (SAX) mode or a
multiplexed small/wide angle (SWAX) mode, where the time slots
assigned to each detector are independently adjustable from 0.01
to 2 seconds. The ASA-32 card can return both position and
energy data for each of the two detectors.
FUNCTIONS
Since the MCA has two detectors and both energy and position
data arrays are available for each, the usual numbering scheme in
spec for selecting MCA devices has been
extended. To access other than the default detector (detector 1,
the SAX detector) or the default data (energy), the
mca_sget() and mca_spar() functions
must be used rather than mca_get() and
mca_par().
Normally, the first argument of mca_sget() and
mca_spar() selects which MCA device, when more than
one are configured. The ASA-32 is treated as one MCA device, but
the first argument usage is extended. Instead of a simple
number, the first argument can be passed as a string that
contains first the number of the selected MCA, then a colon, then
a number that selects the detector and/or the type of data. The
lowest order hex digit of that second number is zero for detector
one or one for detector two. The next hex digit is zero or one
to code for energy or position, respectively. Decimal values are
valid, too. For example,
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mca_sget("0:0x10", data)
or
mca_sget("0:16", data)
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reads the position array for detector one, while
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mca_sget("0:0x11", data)
or
mca_sget("0:17", data)
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reads the position data for detector two. The command
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reads the energy data for detector one, as does
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With respect to parameters that can apply to either detector, a
command such as
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mca_spar("0:0x1", "energy_lower")
or
mca_spar("0:1", "energy_lower")
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would return the parameter value for detector two.
The parameters where a detector designation makes a
difference are:
"preset", but only in energy- or position-
stop mode,
"mplex_time",
"energy_lower" and
"energy_upper",
"ADC_counts", "energy_counts",
"position_counts" and "trigger_counts".
The standard MCA commands supported by spec
are described in the
mca help file. Of the standard
functions, the ASA-32 MCA supports mca_get() but not
mca_put(). The standard mca_par()
options "info", "chans",
"max_chans", "max_channels",
"disable", "auto_run",
"soft_preset", "auto_clear",
"native_type", "preset",
"run", "halt", and
"clear", are supported by the ASA-32 MCA.
For options that apply to the "selected detector",
detector 1 (the SAX detector) is selected by default, and the
mca_spar() first argument can be used to select
detector 2, as explained above.
mca_par("preset") Returns the preset
value for the current stop mode and the selected detector. The
preset time parameter is returned in real-time and live-time stop
modes. The preset count parameter is returned in energy and
position stop modes.
mca_par("preset", value)
Sets the preset value for the current stop mode. For real-
time and live-time stop modes, sets the number of seconds for
acquisition. For energy and position stop modes, sets the total
counts for the selected detector at which to stop acquisition.
mca_par("mode") Returns either of the
strings "sax" or "swax" to indicate
whether the device is in pure SAX mode, or multiplexed SWAX mode.
mca_par("mode", value)
Sets the acquisition mode to SAX or SWAX respectively for the
arguments "sax" and "swax".
mca_par("mplex_time") Returns the time in
seconds devoted to the selected detector in the multiplexed SWAX
mode.
mca_par("mplex_time",
value) Sets the selected detector
multiplex time to the specified value, which can be from 0 to 2
seconds, in increments of 0.01 second.
mca_par("stop_mode") Returns one of the
strings "realtime", "livetime",
"energy" or "position" to indicate the
current stop mode. Acquisition halts when the specified
acquisition value reaches the preset value.
mca_par("stop_mode",
value) Sets the stop mode
according to the argument, which can be "realtime",
"livetime", "energy" or
"position".
mca_par("energy_lower") Returns the lower
energy limit for the selected detector.
mca_par("energy_lower",
value) Sets the lower energy limit for
the selected detector to value. The valid
range is from 0 to 4095. The default value is 2048.
mca_par("energy_upper") Returns the upper
energy limit for the selected detector.
mca_par("energy_upper",
value) Sets the upper energy limit
for the selected detector to value. The
valid range is from 0 to 4095. The default value is 3072.
mca_par("high_voltage") Reports the
status of the high-voltage supply. A positive return value
indicates the supply is on.
mca_par("high_voltage",
value) Turns the high-voltage
supply on if value is nonzero. Turns the
high-voltage supply off if value is zero.
mca_par("ratemeter") Returns either of
the strings "trigger" or "position" to
indicate the mode of the rate-meter output.
mca_par("ratemeter",
value) Sets the mode of the rate-
meter output according to the argument which can be
"trigger" or "position".
mca_par("ADC_counts") Returns the total
counts converted by the analog-to-digital converter.
mca_par("energy_counts") Returns the
total counts collected into the energy array.
mca_par("position_counts") Returns the
total counts collected into the position array.
mca_par("trigger_counts") Returns the
number of counts seen by the input trigger.
mca_par("elapsed_time") Returns the
elapsed time of acquisition.
mca_par("dump") Displays current device
settings for high-voltage status, ratemeter, position resolution
and energy resolution.
mca_par("reset") Resets the board,
forcing a reload of the firmware. Currently nonfunctional.
mca_par("min_delay") Returns the value
for the parameter that is the minimum time between two pulses
from the detector to be counted as separate pulses.
mca_par("min_delay",
value) Sets the above parameter to
value. Note, this parameter is a constant
for the detector and should not need to be changed. The default
value, appropriate for the PSD-50M, is zero.
mca_par("time_correction") Returns the
value for the detector dead-time parameter.
mca_par("time_correction",
value) Set the above parameter to
value. Note, this parameter is a constant
for the detector and should not need to be changed. The default
value, appropriate for the PSD-50M, is 0x573.
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Last Formatted May 12, 2012
Last Updated 12/18/04
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