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  Starting and Restarting the MGU User Gap Control
Launch
X25 MEDM 		Launch the X25 User Gap Control MEDM as pxuser on the x25-h server from the epx_setup directory as follows:

x25-c_pxuser 1% ssh pxuser@x25-h.nsls.bnl.gov
x25-h_pxuser 1% cd epx_setup
x25-h_pxuser 2% X25

  This brings up the integrated X25 beamline control MEDM as shown below. The gap control window at right displays the CRUE status and the current gap encoder reading. In this example user gap control is disabled and the gap is fully open for a ring fill.

To switch the gap when running at 2.58Gev instead of 2.8Gev
 log in as epics user
ssh epics@x25-h
passwords

In the /tftpboot/epics/x25-v/db directory
there are 3 files

gap_select.db

gap_select2.8gev.db
gap_select2.5gev.db

you have to copy the right file to gap_select.db
prior to rebooting the vme crate close out of cbass etc...
reboot the vme crate...after rebooting the crate, restart cbass
make a wavelength change then move back and realign

**** Don't be too worried about the couts being lower. We are not optimized to ru in this mode.
THERE IS SOMETHING WRONG WITH THE RING!
 Also the equivalent of 1A at 2.8GeV is 1.17A at 2.58GeV.

Launch
Detailed
Gap MEDM
 Click on the 'MGU Control' field (above) to obtain the full User Gap Control MEDM. Its values will agree with those dispalyed on channel 18 of the NSLS TV.
The MEDM's first 6 parameters are readback values from the physical MGU control and the last two are user gap target requests as follows:

Param Definition Values
CRUE Control Room User Enable
 ON / OFF
ERROR MGU physical controller error
 OK / Err
In Progress Gap adjustment reporter In Process / Idle
C-Sum Error Serial line check sum OK / Err
Set Point Physical Gap Set Point 5.6 - 20.0 mm
Avg Encoder Gap Encoder Reading 5.6 - 20.0 mm
Gap Setting User GAP Setting Request 5.6 - 20.0 mm
Set Gap Input of manual gap target 5.6 - 20.0 mm

Note: The 'Gap Setting' is the target that the x25Mgu EPICS record processor transmits to the physical MGU controller. That target will be reached when CRUE is ON and the 'Gap Setting' differs by more than 0.005 mm from the current 'Set Point'. The target remains unchanged during ring fills when operators take over the MGU control (CRUE OFF) and open the gap maximally, and it will automatically be reached again when CRUE is returned to ON. A new 'Gap Setting' is obtained either from an input into the 'Set Gap' field, or more typically it is caluclated by this EPICS record processor when CBASS defines a new wavelength.

Start x25-h
EPICS IOC 		The User Gap Control at X25 is part of the EPICS IOC on x25-h. If this process is not up and running, the value fileds in the x25Mgu MEDM (shown above) are blank and white. The EPICS IOC running on x25-h under linux needs to be restarted by pxuser as follows:

x25-c_pxuser 1% ssh pxuser@x25-h.nsls.bnl.gov
x25-h_pxuser 1% start_mgu

The MEDMs shown above will now repopulate after a short delay. If this is not the case, or if a segmentation fault message appears, repeat the 'start_mgu' command. The window used to 'start_mgu' may be closed using its [x] field. (supplemental info).

Updated 10 July 2006 Security Notice   Webteam   Site Map   Bio   PXRR   NSLS   BNL