EPICS interface
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[edit] Caveat
Last updated 2 August 2005. This is a work in progress. This section includes a description of a TYPICAL setup in August 2005, and may not reflect current reality. Always check the E-logs for the most recent configuration of the Lecroy 2551 IScalers, Scalers -- what they are, how to view them#IScalers. If in doubt, trace the cables yourself.
[edit] Why you might want to do this
The interface between EPICS and 8pi MIDAS is intended to facilitate beamline setup and beam monitoring, by providing information on the beamline setup and count rates in the 8pi detectors in a way that can be accessed centrally by ISAC operations and the experimenters. It has been recently upgraded to allow ISAC EPICS variables to be included in the data stream.
For example, it would be possible for ISAC operations to simultaneously view SCEPTAR beta-singles count rate and cyclotron current, so that while they are tuning a particularly low-yield product, they would be able to see immediately what effect they are having on delivery to the experimental station. It is now also possible to read in the cyclotron current at a given time, which would be useful for rejecting runs or parts of runs where no useful activity was created and delivered.
[edit] How it works
The Epics client is treated as its own equipment. This version is adapted from a general-purpose MIDAS-EPICS interface. It demands, or attempts to write, data into up to 20 ISAC devices, and measures, or reads back, those same 20 devices. This happens approximately once per second. At specified intervals it writes an Event Type 5 containing the floating-point values demanded in a DMND bank, and the values measured in an MSRD bank.
The channels being accessed and the values being written are controlled through
ODB entries in the /Equipment/Epics/Settings/ tree, http://isdaq08.triumf.ca:8081/Equipment/Epics/Settings?exp=8pi The entries Devices/Epics/Channel names[0...19]
contain the EPICS device (or channel) names to be demanded and measured.
The entries Names[0...19] are set to appropriate labels
for those channels. The Update Threshold Measurement[0...19]
settings do something but I'm not sure what.
The Epics client for the 8pi also has some built-in code that periodically
(once per second) sets the "demand" values 0 to 11 to those in
/Equipment/Iscaler/Variables/ISCL[0...11], i.e., identical to
those in the Scalers -- what they are, how to view them#IScalers.
[edit] Starting the Front-End MIDAS to EPICS client
The Epics client executable is called fe_epics and exists in
/tig/grsmid00_home1/eightpi/online/fe_epics. You will see a green Epics
entry on the status page when it is running properly. Typically you
should run it on grsmid00. To run it:
nice +4 /tig/grsmid00_home1/eightpi/online/fe_epics/fe_epics
NOTES:
- Any time you change channels or names, stop and restart this client.
- This code does NOT run nicely in the background.
- I have not been able to stop it from the Programs listing reliably.
- Chances are you will have to kill it manually.
[edit] Connecting to Epics GUI
The EPICS GUI is handy for viewing the status of beamline, plus it has a
handy "striptooling" feature. To get into it, ssh -X
8pi@isacepics1.
- For striptooling, click on the Utilities button and select Start Strip Tool from the pull-down menu. This brings up a StripTool Controls window. You can then type in any valid EPICS variable in the Plot New Signal field and press Connect, including those mentioned in the "8pi EPICS Once this is done you will get a graphics strip tool that displays traces from the variables you requested. If you lose the Controls window, right click on the graphical traces display and select Controls Dialog from the pulldown.
- For the 8pi beamline, navigate through the various windows and pulldowns, starting with the Vacuum 1 or LE Exp. buttons as appropriate.
If you are having trouble connecting to isacepics1:
- Make sure your
DISPLAYvariable is set properly:echo $DISPLAYfrom a Linux console. Typically it will have a form likeisdaq08.triumf.ca:0.0. Replace isdaq08.triumf.ca with whatever machine you happen to be sitting at. If the DISPLAY variable looks wrong, set it with eitherexport DISPLAY=isdaq08.triumf.ca:0.0orsetenv DISPLAY isdaq08.triumf.ca:0.0 - Delete the
~/.ssh/known_hostsfile and try again.
[edit] EPICS Device Names for the 8pi
The 8pi EPICS virtual devices have the form 8PI:CSCL:VAR1 to
8PI:CSCL:VAR20. Writing to these devices will not actually
affect any real physical devices controlled by the ISAC EPICS server; as far as ISAC is concerned,
it is a purely logical, virtual device.
We can write values to them, and everyone with EPICS access can read
those values.
[edit] Finding ISAC Device Names
Any variable on an EPICS page that is blue is a measured value that can be sent back to the 8pi Epics client for inclusion into the data stream. To determine the EPICS device name, name, middle-click on the value. This will automatically copy the EPICS name into the cut-and-paste buffer. You can then paste it into an entry field, like the StripTool Plot New Signal field, by middle-clicking in the field.
On modern mice, the wheel is your middle button; push it down. If you are on a two-button system, like most older PCs and some laptops, X servers can be configured to emulate the middle button by simultaneously pressing both buttons. Check the help menus on your X server for "middle button" to see how this is done.
Some other handy variables you might want to be able to Striptool:
- Ion guage near 8pi target chamber:
ILE1A:IG9:RDVAC - Main separator magnet measured field:
IMS:MB2:RDMETER - Main separator magnet measured current:
IMS:MB2:RDCUR - Shack temperature:
ILE1A:TC1:RDVOL
[edit] Common Non-ISAC Device Names
Some handy Non-ISAC device names:
- Beam Line 2A Current:
CCS2ISAC:BL2ACURRENT
Ultimately, Jane Richards is the person to contact if you want to inquire about non-ISAC variables that might be available to ISAC EPICS for striptooling. If you come across any other good varfiables let Greg know and he'll (try to) add them to this list.
[edit] A typical configuration
Some typical settings are demonstrated in the follwing extract from an
odbedit session:
[local:8pi:S]/> ls -l "/equipment/epics/Settings/Devices/Epics/Channel name"
Key name Type #Val Size Last Opn Mode Value
---------------------------------------------------------------------------
Channel name STRING 20 32 3h 0 RWD
[0] 8PI:CSCL:VAR1
[1] 8PI:CSCL:VAR2
[2] 8PI:CSCL:VAR3
[3] 8PI:CSCL:VAR4
[4] 8PI:CSCL:VAR5
[5] 8PI:CSCL:VAR6
[6] 8PI:CSCL:VAR7
[7] 8PI:CSCL:VAR8
[8] 8PI:CSCL:VAR9
[9] 8PI:CSCL:VAR10
[10] 8PI:CSCL:VAR11
[11] 8PI:CSCL:VAR12
[12] CCS2ISAC:BL2ACURRENT
[13] IMS:MB2:RDMETER
[14] IMS:MB2:RDCUR
[15] ILE1A:IG9:RDVAC
[16] 8PI:CSCL:VAR17
[17] 8PI:CSCL:VAR18
[18] 8PI:CSCL:VAR19
[19] 8PI:CSCL:VAR20
[local:8pi:S]/> ls -l "/equipment/epics/Settings/Names"
Key name Type #Val Size Last Opn Mode Value
---------------------------------------------------------------------------
Names STRING 20 32 3h 1 RWD
[0] Ge Array Raw
[1] Ge Accepted
[2] Plastic Array Raw
[3] Plastic 01 Raw
[4] Plastic 18 Raw
[5] Plastic Accepted
[6] SiLi Array Raw
[7] SiLi Accepted
[8] BaFF Array Raw
[9] BaFF Accepted
[10] Ge-Plastic Rate
[11] Gamma-Gamma
[12] BL2A Current
[13] Magnet Field
[14] Magnet Current
[15] Target Chamber Vacuum
[16] Unused
[17] Unused
[18] Unused
[19] Unused
[local:8pi:S]/> ls -l /equipment/epics/Variables/Measured[12]
Key name Type #Val Size Last Opn Mode Value
---------------------------------------------------------------------------
Measured[12] FLOAT 20 4 1s 0 RWD
[12] 32.9
This arrangement gives the physical meaning of the
Scalers -- what they are, how to view them#IScalers 0 to 11, and sends them to the
virutal devices 8PI:CSCL:VAR1 to VAR12. These
can be read in the ISAC operations control room and possibly used to help
tune beam. The cyclotron current
CCS2ISAC:BL2ACURRENT is also read back as the 12th (from
zero) device; in this screen dump it is measured to be 32.9 microamps.
As noted the demand and measured data are both dumped to event type 5:
8pi@isdaq08:/home/8pi> mdump -i 5 -1.9.4 -- Enter <!> to Exit ------- Midas Dump --- ------------------------ Event# 1 ------------------------ Evid:0005- Mask:0000- Serial:3595- Time:0x42eff51b- Dsize:184/0xb8 #banks:2 - Bank list:-DMNDMSRD- Bank:DMND Length: 80(I*1)/20(I*4)/20(Type) Type:Real*4 (FMT machine dependent) 1-> 2.059e+03 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 9-> 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 17-> 0.000e+00 0.000e+00 0.000e+00 8.900e+01 Bank:MSRD Length: 80(I*1)/20(I*4)/20(Type) Type:Real*4 (FMT machine dependent) 1-> 2.059e+03 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 0.000e+00 9-> 0.000e+00 0.000e+00 0.000e+00 0.000e+00 3.290e+01 -2.772e+03 1.302e+02 8.956e-07 17-> 0.000e+00 0.000e+00 0.000e+00 8.900e+01
The 13th (or 12th, counting from zero) element of MSRD corresponds
to measured device 12, CCS2ISAC:BL2ACURRENT, and happens to
be reading 32.9 μA.
