POL: Webpages

Links

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

POL Main Status Page

Run Stopped

Point a browser to https://isdaq01:8445/ to access the POL experiment Main Status page (Figure 2). In this example, the run is stopped and the status of the POL Equipments POL_ACQ,VME,INFO,HISTO are coloured green. This indicates that the frontend program (which defines these software Equipments) is running.

If the frontend program is not running, they will be shown as orange. Clicking on these links (POL_ACQ,VME,INFO,HISTO) will show the last event data for those equipments that send the data to the ODB. See also [[vmicbanks.html">Data Banks output by the POL frontend]].

Figure 2 also shows the Alarm System is OFF, and data logging disabled.

Figure 2 Experiment pol main status page when run is stopped

The top line of buttons (Figure 2) i.e. Start/ODB/Messages/Programs etc) are standard MIDAS buttons. The Start button can be used to start the run, the other buttons give access to other pages (e.g. Messages, Programs Alarms etc.). The ODB button allows access to the ODB (online data base) in which all the run parameters are stored.

Note that various "user buttons" have been defined for POL experiment. These buttons appear on the main status page as the second row of buttons below the row of standard Midas buttons. All are Alias or Custom Buttons. The alias buttons are short-cuts to display specific parts of the ODB. Custom buttons switch to a custom page.

• ppg blocks - alias button accesses the blocks that define the ppg cycle
• sis - alias button accesses the SIS3820 MCS ODB parameters
• input - alias button accesses the complete list of ODB input parameters
• output - alias button accesses the ODB output parameters
• ppg_cycle - custom button accesses the POL Custom page

Run in Progress

When a run is in progress, the Main status page appears as in Figure 3. In this case, the #Alarm_System">alarm system is enabled, #Logging_the_data">data logging in enabled, and the Equipment Events column shows that a number of INFO and HISTO events have been sent by the frontend.

Figure 3 Main status page when run is in progress

The ppg_cycle custom button will be most commonly used, since it gives access to the #Pol Custom page.

Display INFO Data Banks

Because the INFO Equipment sends its data banks to the ODB, the contents of these banks can be displayed from the main Status page by clicking on the INFO link, e.g.

Figure 4 Contents of INFO Data Banks
Figure 4: Display of INFO banks from status page

Programs page

The programs page is obtained by clicking on the Programs button on the main status (or custom) page. If the frontend is running, the page will appear as in Figure 5.

Figure 5 Programs page showing frontend is running

Figure 5: Programs page showing frontend running

You can stop the frontend program by clicking the button "Stop pol_fevme". The page will then look like Figure 6. Clicking on "Start pol_fevme" will restart the frontend in its xterm.

Figure 6 Programs page showing frontend is stopped

Figure 6: Programs page showing frontend stopped

Pol Custom page

A custom page for POL has been provided to make it easier for the experimenters to enter the relevent input parameters.

To access the POL Custom page from the #POL Main Status Page, click on the custom button "ppg cycle".

The custom page is shown in Figure 7. This includes graphic representations of one DAC scan, one SuperCycle and one PPG cycle, plus a table of input parameters for the experiment. The values of some of the parameters are shown as labels on the graphic.

The Run Status is also shown (Stopped) and the Frontend status shows that the frontend program

pol_fevme.exe is running. The frontend status graphic can be slow to change colour after the page is reloaded, since it is accessing a watchdog which is rarely updated.

A smaller #Information_Box">information table is also shown.

Buttons are provided to start a run, to access other standard MIDAS pages. Pressing Doc will display this page.

Enter the Input Parameters

The current input parameter values appear on the #Pol Custom Page in the box titled "Input Parameters". To change the input parameter values, click on the hyperlinks and enter the new values. If an illegal value is input, an alert box will appear.

An explanation of each parameter is shown below (#List of Input Parameters").

List of Input Parameters

There are a number of parameters in the ODB that control the experiment. The ones most relevent to the experimenters are listed below. These appear in the Input Parameters box on the custom page.

number of time bins

together with "Dwell time", determines length of PPG cycle

Dwell time (ms)

together with "number of time bins", determines length of PPG cycle

DAC start(Volts)

Voltage at which #DAC_scan should start

DAC increment (Volts)

Voltage to increment DAC each step

Number of DAC increments

Number of increments for DAC scan

DAC sleep time (ms)

Time to delay after changing DAC. Always set to zero. May be removed from the parameter table.

TOF pulse width (ms)

Width of "Start TOF" pulse width. Always set to zero (i.e. minimum width). May be removed from the parameter table.

Number of PPG cycles per #supercycle

Number of PPG cycles for which data is to be summed at each DAC step

Number of scans

run will stop automatically after this number of scans, or enter 0 for free-running

Figure 7 POL Custom page showing the table of input parameters when the run is stopped.

Figure 7: Pol Custom page showing the table of input parameters with the run stopped

Frontend Flags

Several frontend flags (also in the ODB) are shown on the #Pol Custom Page. See Hardware for more information.

discard first bin of every PPG cycle

first bin will contain spurious data collected during the TOF. Always set this to "y" (discard) unless

in test mode.

discard first PPG cycle of every SuperCycle

first PPG cycle is started by software, and will contain spurious data. Always set this to "y" (discard) unless in test mode.

PPG external start

Always set to "y" when running the experiment. The PPG external start signal is supplied at the end of the TOF. This may be set to "n" for testing when an external signal is not available.

Toggle Hot Debug*

set to "n" unless debugging. This causes extra debugging information to be printed by the frontend. It will also slow down the data acquisition slightly.

Toggle Hot Timer*

set to "n" unless debugging. This causes extra timing information to be printed by the frontend. It will also slow down the data acquisition slightly.

*This is a "hot link", which means that it takes effect immediately, instead of only being read at the beginning of run.

Information Table

An extra information table (Table 1) has also been provided on the Custom Page (Figure 7 ) containing parameters that do not need to be changed very often. This includes a link to enable/disable the #Alarm_System.

Table 1: Information Parameter Table

Table 1a: DAC checks enabled	Table 1b: DAC checks disabled
File:Pol info tbl.png	File:Pol info tbl noDACchk.png

Other contents are links to parameters used when stepping the Galil RIO DAC voltage. Unless disabled (Table 1b), a check is done to verify that the DAC voltage has changed each time the DAC has stepped (see algorithm).

These are used to help determine that the DAC voltage has incremented when the increment value is very small. Once determined, they should be left as constants.

Disable DAC check

This should normally be set FALSE. When enabled, a check is done to verify that the DAC voltage has changed after the DAC has stepped.

DAC minimum increment (V)

This is set to a suitable value larger than the "jitter".

DAC jitter (V)

This is set to a suitable value larger than the LSB. It represents the variation you might get when reading the same DAC value several times.

Start a run

Start a run either from the #Pol Custom page (or the #POL_Main_Status_Page">Main Status page) by clicking on the "Start" button. A window as in Figure 8 will then appear. This is the Start Page, and shows the edit-on-start parameters.

Except for testing, the Write data parameter should be checked as shown, so that data is stored on disk. The other parameter controls sending the raw data bank (see ... ) and should not be checked unless debugging.

Figure 8 Run Start window showing edit-on-start parameters

File:Pol start params.png

Logging the data

If data is to be logged, check the "write data" box on the run start page (Figure 8 above). The data will be saved in the directory given by the ODB key /logger/Data dir.

When logging is enabled, the data directory is also shown on the Main Status page Figure 3.

Custom Page with Run in Progress

If the run is started from the Main Status page

the Main Status page will reappear as in Figure 3. Event statistics (e.g. the number of each event type output, the event rates etc.) can be seen on this page.

If the run is started from the POL Custom page

after the screen is reloaded, the Custom Page will appear as Figure 9, with the Input Parameter table replaced by the front-end statistics table which

shows the progress of the run.

Figure 9 Pol Custom page with the run in progress.

File:Pol custom running.png

Parameters Table

The values shown in the Parameters Table are described below:

Table 2: Parameters Table

Parameters
Per PPG Cycle		Per Supercycle
Bins	True number of bins per PPG Cycle. This will be the #number of time bins requested + 1 if parameter #discard first bin of every PPG cycle is true). This is the number of bins you would see looking at PPG output MSC Next on the oscilloscope.	Cycles	True number of PPGcycles per supercycle.This will be the (#number of cycles per supercycle requested + 1) if parameter #discard first cycle of every SuperCycle is true) This is the number of bins you would see looking at PPG output MSC Next on the oscilloscope over a SuperCycle.	Totbins	True total number of bins in one SuperCycle This will be the number requested + any bins discarded
Discard	This will be 1 if parameter discard first bin of every PPG cycle is true, otherwise 0	Discard	This will be 1 if parameter discard first bin of every SuperCycle is true, otherwise 0	Discard	The number of bins discarded or 0 if none have been discarded.
Bins	The number of bins requested by the user, and also the number of data bins in the histograms.	Cycles	The number of cycles/supercycle requested by the user.	Totbins	The number of bins in one SuperCycle requested by the user.

Frontend Statistics Table

The contents of the frontend statistics table are described below. The statistics table is not updated very often. The statistics data are sent to the ODB at the end of each supercycle, but the custom page is updated every 5s or so. Some of these counters are used to check the frontend is running correctly (this is more for debugging).

Table 3: Statistics Table

Counter	Explanation
Cycle	counts #cycles. It will count up in units of Cycles/Supercycle
SCycle	counts supercycles.
DAC Scans	counts the number of complete #DAC_scan"s
DAC Inc	shows the current increment number within the DAC scan. Varies from 1 to #number of DAC increments
DAC Set(V)	shows the current setting of the DAC in volts
Buffrd	the number of data words still buffered in the SIS3820 - usually 0 for small (<4K) events where buffer can be read in one operation.
LNE/cyc	#True number of time bins (i.e. LNE events) read out from the SIS3820 scaler per PPG cycle. Should be the same as counter Nbins.
LNEfromSIS	LNE count read out from SIS3820 acquisition count register (i.e. number of input LNE pulses device has received from PPG output).
LNEpreset	LNE preset value set in the SIS3820 preset register. Should be the same as #True Total Number of bins/supercycle.
Nbins	True number of time bins per cycle.
Sum per SuperCycle	Sum of all the time bins for each Input Channel of the scaler over 1 SuperCycle

Note

in normal operation, the counters

• LNE/cyc and Nbins will both be equal to #True number of bins/cycle
• LNEfromSIS and LNEpreset will both be equal to #True total number of bins/SuperCycle.

Stop the run

To stop the run, press Stop. You will see a "transition in progress" state while the run is stopping.

Pressing Stop will stop the run mid-cycle. To stop the run at the end of the present DAC scan, use StopAtEndScan on the Custom page.

Run stops automatically

The run will stop automatically if

• a fatal error is detected

or

• if the input parameter num DAC scans before run stops is > 0, and that number of scans has been reached

Alarm System

MIDAS provides an alarm system which can be used to indicate various problems to the user.

Note

the alarm system should always be enabled unless testing.

Enabling/disabling the alarm system can be done using the Information Table on the #Pol Custom page (Table 4a), or by pressing Alarm on either the Custom or main status page.

If the alarm system is disabled, the alarm system line on the Information Table on the custom page (Table 4b) will turn red.

Table 4 Information table on custom page (run stopped)

Table 4a: ... with alarm enabled	Table 4b: ... with alarm disabled
info table with alarm enabled	information table with alarms disabled"

Figure 10 shows an alarm status banner on the main status page. A similar banner will appear on the Custom page.

Figure 10 Main status page showing alarm banner

status page with alarm banner

The alarm banner will disappear if Alarm Reset is pressed. However, it will reappear after a short time if the alarm condition is not fixed.

Error/Information Messages

MIDAS has a sophisticated messaging scheme, whereby messages from the various clients are collected together in the message buffer. This can be easily viewed by pressing Messages at the top of the #POL Main Status Page or #Pol Custom page.

The most recent error/information message is displayed at the bottom of the Main Status page and the POL Custom Page.

Additional messages from the frontend code can be viewed in the #The Frontend window for the POL experiment.