GUIDE TO DATA TAKING IN HALL A

Bob Michaels,     v2.5,     Oct 4, 2001

pager: (757)-881-7897,    e-mail:    rom@jlab.org

This file :  hallaweb.jlab.org/equipment/daq/guide.html

This is information about how to run DAQ in Hall A, as well as how to configure the trigger and use the ``online'' codes. See also hallaweb.jlab.org for useful links such as ESPACE, the offline code.

 I.  Where   to   Run   Things

Below is a table showing where to run the different codes using the public accounts adaq, atrig, and a-onl.  The run coordinator should know the passwords.  

Where to Run Online Software in Hall A Counting Room

Code	Computer	Public  Account
CODA  (runcontrol)	adaql2	a-onl
ESPACE	adaql1 or adaql3 (not l2)	adaq
trigsetup	adaqlN (N=1,2...) Linux	atrig
dataspy and dhist	adaqs2 or s3	adaq
xscaler	adaqs3	adaq

Computers:   adaqs1 will be the Compton DAQ computer. It should be avoided, e.g. the paths are different. Typically   adaql2 is used for spectrometer DAQ, adaqcp is for Parity DAQ, adaqep for eP energy measurement DAQ, adaqs3 for Moller DAQ.   adaql1 or adaql3 is for running online ESPACE analysis, etc.   adaqh2 is the lone remaining HP-UX which will be removed in the December 2001 break.   The Linux boxes like adaql1, adaql3, etc, are the best places to run ESPACE, but the ones where CODA is running should be avoided. Note the large amount of ``work'' disk on adaql1 and l2 where you may keep scratch files like hbook. The disks are /adaqlN/workM where N=1,2... and M=1,2,3...etc.

How to reboot workstations (rarely necessary): On SunOS its possible to do a quick reboot which can fix some hangups. Login as adaq account and type "reboot". On HP-UX you have to shutdown (cannot reboot). NOTE: If power fails you must do a shutdown before the UPS battery goes bad. Login as adaq and type "shutdown". After several minutes, the screen goes black, wait a bit more, then power off. When power comes back, computer reboots. (Eccentricity of adaqs2: When it comes back from shutdown, there may be sign "ok" where you have to type "boot". Also, don't forget to type "xhost +adaqs2" when you login as adev.) Linux:   Hit Ctrl-Alt-F1 to go to console mode, then Ctrl-Alt-Del, or see Ole's instructions which might be posted near the terminal.

 III.  CODA  

Detailed information about running the spectrometer DAQ in Hall A may be found in hallaweb.jlab.org/equipment/daq/guide2.html  for CODA 2.x setup (read this if nothing else).

Also available are documentation about the raw data structure and frequently asked questions about DAQ deadtime.

IV.  Trigger

The spectrometer trigger was described in some detail in the OPS manual.   Here I give a superficial overview and describe how to download a new setup.   First, here are some simplified instructions to download and check the trigger:

hallaweb.jlab.org/equipment/daq/trigger.html.

Detailed information about the trigger for coincidence experiments:

hallaweb.jlab.org/equipment/daq/trigsetup_coinc.html.

Overview of trigger:  Scintillators make the main trigger in each spectrometer arm, and a coincidence is formed between the spectrometer arms.  The main trigger is formed by requiring that scintillator planes S1 and S2 both fired (and both phototubes in each paddle) in a simple overlap. The trigger requires that S1 and S2 fired.  The coincidence between spectrometers is formed in an overlap AND circuit.  The Right Spectrometer singles triggers are called T1, the Left Spectrometer triggers are called T3, and the coincidence triggers are T5.   Other triggers might be formed which require other detectors. The most important is T2 on R-arm and T4 on L-arm, which are identical, and require 2 out of 3 from among the S1, S2, and S0 detectors (i.e. the "or" of S1 is used, etc). Actually the definition of T2 and T4 has changed 3 times since Jan 2001 (ask me for details); what I described is for e00102.   These "loose" or "majority logic" triggers allows to measure the efficiency of the main trigger. The experiment should always keep about 5 - 10 Hz of these loose triggers.

Downloading the trigger:  For coincidence experiments, it is forseen that the only change between kinematic settings that affect the trigger are delays that track with the momentum.  To change the trigger, login to a linux PC like adaql1 or l2 in the "atrig" account (ask run coordinator for the password) and type from anywhere "trigsetup". This starts a GUI whose usage is obvious.   Further details are at the link above (trigger.html).  

V.  Scalers and Scaler Display

Normally this is already running on adaqs3 (SunOS). If not running, login as adaq, and go to the appropriate directory, which is  (1) ~adaq/$EXPERIMENT/right/scaler for right arm, and (2) ~adaq/$EXPERIMENT/left/scaler for left arm.  ($EXPERIMENT is an environment  variable, like e00102.)  Then  type "xscaler".  Remember to push the button "Start".  For experts:  The configuration of scaler information is controlled in a file scaler.config in the appropriate directory.

More about scalers:  Scalers are read periodically during a run and injected into the data stream as event type 140 and decoded by ESPACE.  They are also read and injected at the end of the run.  A file scaler_history.dat is maintained which is a complete history of scaler readings at the end of the run.  These files should be in ~/scaler for the adev and a-onl accounts.  

VI.  Online   Codes   for   Spectrometer

 There are two codes of interest for doing online diagnostics of raw data, in addition to using ESPACE. They are:  (1) dataspy, and (2) dhist (actually dhist is a shell script).    To run dhist, simply type "dhist" on a SunOS computer like adaqs2 or s3 from the adaq account.   You will see a reminder that you have to go to the proper directory and type "./dhist" there. Just do it.  The dhist script runs "dplot" on online data which it gets off the net in real time, and "dplot" is a code that pops up some HIGZ windows and displays several pages of raw, uncut, data as self-explanatory diagnostics. More details about the dataspy/dataplot codes may be found at

hallaweb.jlab.org/equipment/daq/dplot.html

By default, the online codes obtain data from ET system, hence cannot cause deadtime.   If one uses "espace" to read a the currently written file, one might cause deadtime. One way around this is to start on the present file at the end of a run, or to choose another file. However, below 1 kHz CODA rate, reading the file should cause no deadtime.

The ET system may be implemented for ESPACE. See jlabs1:/home/rom/espace2.8.2/src/r2-8/README_ET for details.