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Doing a Pedestal Run
Note: The pulser should be left connected; it is enabled and disabled
by MiniDAQ according to the run type.
If questions arise as to which tables appear in which event, one can
grab events with Staf and print the index tables, which usually have
only a few rows. The event number appears in the first column (?) of
the first row. The sector and location of the readout board (as
defined by its DIP switches) are listed in other columns for each row.
- Verify that the anode-wire high voltage has been reduced
enough to eliminate significant gas gain; other voltages should be at
their normal settings.
- The Run Control GUI on the Run Control desktop shows the EVENT
TYPE; if it's not ``pedestal'' (and both DAQ and SC states are
``idle''), pull the ``OTHER EVENTS'' menu down and ``unconfigure.''
- When DAQ and SC are ``initialized,'' click CONFIG to
bring up a configuration window. (MiniDAW configuration uses
information only from the configuration window; any settings in the
other window are irrelevant for the moment.) Enable the desired
Rosies by clicking the boxes number 1--6, then double click on the
``Pedestal'' event type. Click OK.
- Rosie numbering is not necessarily related to readout board
numbering, although, by convention, it is usually the same.
- When DAQ and SC are ``idle,'' go to the main Run Control
window and set: the run and tape numbers; the comment; enable taping
and netfeeds, if desired. If these pedestals are to be used online
(e.g., for zero suppression), you must have select ``Update
- One can request 1--64 events; 40--64 is typical. It is
possible to take more than 64 events only if one restricts the
pedestal range (using the table browser to adjust the MiniDAQ
configuration parameters); otherwise, MiniDAQ automatically adjusts
the number of events downward to prevent overflows by internal, 16-bit
summing variables. Of course, at least 2 events must be requested to
produce a table of pedestal rms's.
- The requested "number of events" refers to the number of data
events per enabled Rosie; it does not count beginning-of-run
or slow controls events. More significantly, pedestal events are
taken in two cycles whenever two Rosie's on the same i960 processor
are enabled. The first cycle consists of data from the uppermost
enabled Rosie on each i960; the second cycle consists of data from
the bottom Rosie on any i960's with two Rosie's enabled.
Suppose we ask for 64 events from Rosie's 1,2,4,5. The first
event should be the beginning-of-run event; followed by 64 data events
from Rosie's 1,4,5 and another 64 data events from Rosie 2. In the
unlikely event that a readout board misses a trigger, subsequent
tables for that RDO are displaced by one data event. Slow controls
events may also be inserted periodically. Therefore, the number of
events in a run is slightly indeterminate.
- If raw data are needed, 8-bit ADC's are usually adequate,
since the pedestals are supposed to be < 255. Often, one might
request only the result tables: means, shifts, RMS; or no output
tables, if one only wants to initialize the on-line tables for
- After the settings are finalized, click GETSET.
- When DAQ and SC are ``poised,'' click GO.
- If no Run Control logger window is present, open one from the
OPTIONS menu. Verify that events are being logged. If not and
the logger window has been open for awhile, exit from it and open
another one...the logger windows "wear out" for some unknown reason.
- A 64-event run takes 10-15 minutes. Watch the logger window
for empty events, which usually appear after about twice the requested
number of events, given the two possible event cycles. The logger
window event count includes begin-run and slow-controls events.
Written: July, 1996 by Doug Greiner and Wayne Betts
Last modified: August 6, 1998 by R.Bossingham
Roy Bossingham, LBNL