Guide to Data Taking in Hall A

Bob Michaels,     v3.3,     May 30, 2005

pager: (757)-584-7410,    e-mail:    rom@jlab.org

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

This is information about how to run DAQ and how to configure the trigger in Hall A. See also hallaweb.jlab.org for useful links such as the ROOT/C++ analyzer.

 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 coordinators should know the passwords.  

Where to Run Online Software in Hall A Counting Room

Code	Computer	Public  Account
CODA  (runcontrol)	adaql2	a-onl
ANALYZER	adaql4,5,6,7,8 (not l2)	adaq
trigsetup	adaql1 or 2	atrig
xscaler (two versions)	adaql1	adaq

Computers:   We don't have any SunOS computers anymore. The 'compton' computer belongs to the Compton DAQ and should be avoided. Typically   adaql2 is used for spectrometer DAQ while adaql1 is a backup. adaql1 is sometimes used for Parity and Moller DAQ, adaqep for eP energy measurement DAQ.   adaql3 houses a huge work disk.   adaql3, l4, l5, l6, l7, l8 are for running data analysis using ROOT/C++ analyzer or ESPACE, but any computer where CODA is running should be avoided. Note the large amount of ``work'' disks where you may keep scratch files like hbook. The disks are /adaqlN/workM where N=1,2... and M=1,2,3...etc. Some PCs are also installed in 2nd floor cubicles. Priority for use goes to running experiments.

How to reboot workstations : Hit Ctrl-Alt-F1 to go to console mode, then Ctrl-Alt-Del. (i.e. hold down "ctrl", "alt", and the other button simultaneously)

 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 (dstruct.html)   and FAQ's about deadtime (dtime_faq.html),   plus electronics 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.

Overview of High Resolution Spectrometer (HRS) 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. Thus, the main trigger requires four PMTs.  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 are T2 and T4, which requires 2 out of 3 from among the S1, S2, and another detector (this other detector is S0 on L-arm and Gas-Cherenkov on R-arm for the e94107 experiment. The setup has been different at other times, ask me for details). 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:   During coincidence experiments, the only change between kinematic settings that affect the trigger are delays that change with the momentum and particle ID.   Of course, if you only care about single arm triggers, you may use the default settings.  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

``xscaler'' is the GUI that displays scaler data online. Normally xscaler is running on the hapc5 screen which is above the adaql2 console (in rack CH01A09). If not running, login as adaq, and type "xscaler" and follow the instructions it prints out. There are two versions (old and new), the new version is recommended but that's up to you.

The ``old'' asynchronous readout of scalers are event type 140, which are injected into the datastream asynchronously every few seconds.   A ``new'' readout exists, in which the data are read every synch event (100 events) if DAQ is in buffered mode and every 200 events regardless of mode. This readout also contains helicity and timestamp info necessary for G0 mode. There is also an event type 100 which is the last reading of ring buffers. Details about these new readouts are at www.jlab.org/~rom/scaler_roc10.html and for the G0 helicity scheme see www.jlab.org/~rom/g0helicity.html.

 Scalers are also read and injected into the datastream 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 ~a-onl/scaler.