POL

Links

• POL: Hardware and software
• POL: Webpages
• POL: Data format and analysis

Starting the DAQ

ssh pol@midpol
start-all

Then go to https://midpol.triumf.ca to see the DAQ webpages.

Data is written to /data1/pol/data/current.

DAQ machines

• midpol - main daq computer, located on ISAC-1 floor behind the BNMR cage
• lxpol - VME controller in the VME rack near midpol

Main account is pol@midpol.

The POL DAQ System

The DAQ system for the POL experiment uses MIDAS, the standard DAQ system at TRIUMF.

The POL experiment has its own DAQ hardware (i.e. VME crate and DAQ modules). These are controlled and read out by a MIDAS frontend fepol_32bit.exe, which runs on a VMIC VME processor called lxpol.

All the other software runs on the host computer (currently midpol). Both lxpol and midpol run linux.

Running the POL Experiment

Starting the POL Experiment from scratch

• Log on to DAQ host midpol with username pol
• In an terminal, type start-all

More details about start-all is in the scripts section.

Viewing the state of the DAQ programs

Most interaction with the DAQ is done through the web interface at https://midpol.triumf.ca.

However, you can also view the state of the main DAQ program (called the frontend) by typing show-windows in a terminal when logged in as pol@midpol. (If connecting to remotely via ssh, you'll need to enable X11 forwarding to see the window - e.g. ssh -Y pol@midpol).

Configuring settings/parameters

See the documentation about the main status page for settings that users are expected to edit.

Starting a run

Click the "Start" button on the main status page, choose whether to write data to disk or not, then confirm that you want to start the run.

Shutdown the POL DAQ

To shutdown the POL DAQ software completely:

• Log on to DAQ host midpol with username pol
• In an terminal, type kill-all

This will shut down all the clients for the POL experiment, including the web server mhttpd.

Nomenclature

Bin

see #time bin

Cycle

see #PPG Cycle

DAC

The Galil Rio DAC is scanned during the experiment (see #DAC scan).

Dwell Time

The Dwell Time is the same as the Bin Width. This is the time the Scaler collects the data for each #time bin.

DAC Scan (or Sweep)

• Users configure the voltage range and number of increments the DAC should step through. Note that if you specify 10 steps, data will be taken at 11 different voltages. This makes the step size calculation more intuitive (0 to 4V in 10 steps ⇒ 0.4V between data points ⇒ 11 data points as we must include both the lower and upper bounds).
• At begin-of-run, the DAC is set to the value given by DAC Start (V).
• After one #supercycle (i.e. one or more PPG #cycles), the DAC voltage is incremented by the value given by DAC increment (V)
• When the requested number of Number of DAC increments are done, one DAC scan has been completed.
• A number of DAC scans is usually done during each #run.

Galil RIO

DAC/ADC module (see Galil Rio)

Input Parameters

The Input Parameters are parameters whose values are input by the user at the beginning of each run. These parameters control the experiment. The input parameters are available on the POL custom page.

PPG

VME Pulse programmer module (see DAQ Hardware). The PPG outputs a pattern of pulses to control the experiment.

PPG Cycle

• One PPG Cycle is called a cycle.
• A PPG Cycle starts when the PPG receives a "start" signal by
• software or
• a hardware signal sent to the PPG "external trigger" input
• A PPG Cycle ends when its program finishes.
• The length of the PPG cycle*is determined by the input parameters.
  • number of time bins and
  • dwell time (ms)

  *assuming that the input parameters DAC sleep time (ms) and TOF pulse width (ms), which are also part of the PPG cycle, are set to 0 (i.e. the minimum delay (30ns)).

Run

• A run starts when the user starts the DAQ system (by pressing Starton the main status page or Pol custom page)
• A run ends
• when the user stops the DAQ system (by pressing Stop on the main status or custom page) or
• automatically if an error is detected

SIS3820 Scaler/MCS

VME multichannel scaler module (see DAQ Hardware).

Supercycle

• One or more #ppg cycles at the same DAC voltage is called one supercycle
• The number of ppg cycles per supercycle is determined by the input parameter Num PPG cycles per DAC increment
• If the DAC is incremented after each PPG cycle i.e. Num PPG cycles per DAC increment = 1, cycle and supercycle are identical

• The time bin data from each cycle within one supercycle is summed.
• At the end of each supercycle, the scaler data are output (as MIDAS Banks) and the DAC is incremented.

Time Bin

The time during the #scaler is enabled to collect data is divided into a number of time bins, each of length given by the dwell time. Both of these values are input parameters used to program the PPG. The scaler advances to the next time bin when it receives the LNE signal from the PPG (see Hardware).

Troubleshooting

General advice

1. See if there's an obvious error message on the "Messages" webpage
2. Try restarting the DAQ programs
3. Try power-cycling the VME crate

The run would not start

Check the "Messages" webpage for more information. Reasons for the run not starting include :

• frontend code is not running
• error in frontend parameter values
• hardware not responding properly

The run stopped unexpectedly

Check the "Messages" webpage for more information. Reasons for the run stopping include:

• Run reached number of scans requested (input parameter Stop after N loops is non-zero)
• The frontend code detected a fatal error - see message log and frontend xterm

If the "Messages" webpage shows errors of the form:

Scaler is showing 2948 bins at start of cycle rather than expected 0
Data source Histos isn't ready for the start of the next cycle!

then the scalers are either configured incorrectly, or are not behaving as expected. You will likely need to use the sis3820_interactive_32bit.exe debugging program on lxpol to view the registers on the scaler and ensure they are as expected (especially the LNE prescale setting and whether it's in arm or enable mode). If the scaler settings look okay, there may be a programming error in the DAQ.

Run starts, but scan does not progress

Check the stdout of the frontend program for repeating lines like "Scaler has seen 0/10100 bins".

• If the scaler has seen 0 or -1 bins, check the cabling between the PPG and the scaler, as the PPG probably never started
• If scaler has seen 100 bins (or however many time bins you specified for the "Num time bins" setting) and you're using pulsed beam mode, check the cabling between the RFQ and the PPG
• If the scaler has seen 10099/10100 bins (or one less than the expected number), there is either a programming error in the DAQ or the scaler has been manually configured incorrectly (it is likely configured for "arm" logic rather than "enable" logic). Try restarting the frontend.

Alarm banner is present

This indicates an error that may prevent the run from starting. Fix the problem and clear the alarm.

Frontend code will not run - frontend window disappears immediately

This means that the frontend code has detected an error, and exits. Check for Error Messages. If necessary, start the frontend code in an xterm to get more information, because the window will not disappear on failure.

This error will occur if there is a problem with the VME Crate (e.g. powered down), frontend program not running, Galil Rio DAC/ADC not responding etc.

How to Start frontend code in an xterm

Log onto the VMIC device lxpol, e.g. from an xterm on the host or local computer, and start the frontend code, e.g.

[pol@midpol pol]$ ssh lxpol
[pol@lxpol ~]$ bash
(new daq) [pol@lxpol ~]$ pol_new/packages/pol/bin/fepol_32bit.exe

The frontend will run and go through its initialization procedure.

It may detect an error, e.g.

Connecting to Galil device at IP 192.168.1.100
terminate called after throwing an instance of 'KOsocketException'
Abort

In this case, there is a hardware problem with the Galil Rio DAC and the frontend code is aborted. Check that the Galil Rio DAC is present, powered up and connected to the VMIC via a network connection.

NOTE

If you cannot ssh to lxpol, check that the VME crate is powered up and the network is working.

How to switch the Host Computer

The host computer is the desktop computer that users of the pol experiment log into to run the DAQ. Currently it is midpol. If midpol dies, the experiment can be switched to run on an alternate host that is part of the isdaq00 NIS cluster, e.g. isdaq06. The alternate machine also has access to the /home/pol directory.

• If the current host computer (midpol) is still running, type kill-all and log out.
• Log onto the alternate host computer (isdaq06)
  • Edit the definition of $DAQ_HOST in /home/pol/.bashrc
  • Edit the SHM host file /home/pol/online/.SHM_HOST.TXT
  • Log out and log in again
  • Check environment variable DAQ_HOST is now set to isdaq06
  • Execute start-all and point the webserver to isdaq06:8088

POL DAQ updates

• February 2023 DAQ Host is now midpol
• January 2022 Rewritten using the cycling framework
• April 2016 DAQ Host is now isdaq01
• May 2015 frontend window now created using screen utility
• July 2014 Galil Rio loaded with internal program (by Donald) to average ADC0-3 values. Averaged values are sent to banks CYCL.
• May 2014 DAQ frontend code partially rewritten to reduce dead time.
• April 2014 Galil Rio DAC/ADC replaces GPIB DAC . DAQ host is now isdaq06.
• 2013 GPIB DAC controlled directly from isdaq01 rather than midtis07
• April 2011 VMIC- based system for POL (replaces PPC-based system shared with BNQR expt). Pol's new scaler isthe VME scaler (SIS3820)