Difference between revisions of "HV HowTo for Experts"

Revision as of 11:46, 9 January 2014

High Voltage in Hall A

First of all, please be aware of the simple instructions for users:

https://hallaweb.jlab.org/wiki/index.php?title=HowTo_for_Users

Overview of Architecture

The HV crates sit in the hall, e.g. on the detector stacks. A set of cards with 12 channels of negative or positive HV are inserted into the crates. A custom "serial board" (built by Javier Gomez and Jack Segal) talks to the cards. This "serial board" replaces an old, obsolete motherboard. A Perl "Shim" server (written by Brad Sawatzky) runs on a PC nearby the HV crate. The "Shim" server uses (via the Perl "Expect" module) a low-level C code written by Javier to interact with the HV crate. On the User end, a Java GUI (written by Roman Pomatsalyuk) displays the HV information and provides User control. This Java GUI talks to the Shim server. Alternatively, the Java GUI can talk to the motherboard via a Portserver. The latter alternative is being phased out, but still exists in two places at the moment: the beamline HV and one of the HV crates in the test lab DVCS setup, as I write this (Jan 2014).

All the elements in this chain must be working in order to have control and readback of HV.

Existing Crates

Here is a list of HV crates in Hall A and the Test Lab as of Jan 2014

Location                Portserver, or PC for Shim            Config on ~/slowc     How to start on adev

Left HRS (1 crate)      Intel PC: intelha3                       LEFT               cd ~adev/slowc ; ./hvs LEFT

Right HRS (top crate)    laptop: ahut1                           RIGHT 
 
Right HRS (bottom crate)  Intel PC: halladaq8                    RIGHT              cd ~adev/slowc ; ./hvs RIGHT  
                                                                                    (this starts both R-HRS crates)

Beamline                portserver hatsv4: 2003                  BEAMLINE           cd ~adev/slowc ; ./hvs BEAMLINE

Test Lab                portserver and PC                        DVCS               cd ~/slowc ; ./hvs DVCS
                                                                                    (see the README file)

Where the Servers are

The Intel PCs share the following which becomes their root partition /root/diskless/i386/Centos5.8/root/shim/LecroyHV_shim and the low-level C code is in ./LecroyHV_FE

Software that runs on the Intel PCs must, however, run from their local disk because output is not permitted on the root partition.

A cron script ensures that the server is running [root@intelha3 ~]# crontab -l

1. Start the shim server for HV

2,10,20,30,40,50 * * * * /shim/scripts/prepHV

On the "ahut" laptops, it's a bit different. See /home/ahut/shim/LecroyHV_shim. As above, a cron script (prepHV) runs under root.

On the DVCS computer in the test lab, you have to start everything by hand. Go to ~/slowc and see the README file.

What can go wrong ?

Short answer: lots (too much)

Common troublshooting items are listed here (search for troubleshooting)

https://hallaweb.jlab.org/wiki/index.php?title=HV_HowTo_for_Users

Below is a list of other problems I've seen and their solution.

1. Power-cycling a HV crate has been known to help.

2. Cannot login to intelPC as root. Probably because you don't have /root, in which case the solution is to "cd /root ; ./mount_diskless" on adaql1 as root. (It looks like /root/diskless disappears when you reboot adaql1 !)

3. No connection to server. Try rebooting the PC.

4. If you try to run the Shim software by hand you might see "Can't connect to mainframe" and the Shim script dies !

This is a good one. On the IntelPCs, the /shim directory where the software exists is not writeable. You must run from /root/shim, or else the software cannot write its log file and will die very mysteriously ! But this should not affect ordinary users since the Shim software is running automatically.

Another possibility is that the mainframe really cannot be connected to. First thing to try is to run, by hand, ./shim/LecroyHV_shim/LecroyHV_FE/i2lchv_linux* depending on if you're connected to S0 or S2. If that runs ok, the HV crate is on and is talking. If not, then check your cabling and power status.