This page is designed to show you how to make basic modifications to the M13 beamline (changing momentum, manipulating slits, etc) using the EPICS interface. There is some help available once you get the EPICS interface running, but this should also help you get started.
(Please remember to make a note in the elog when you change things.)
Call the control room at 7333 and ask them to restart the M13 EPICS processor. If the response seems to indicate they don't know what we're talking about (not all operators have done this or know about it), give them the following instructions:
"Go into the computer room, and follow the rebooting instructions posted by rack 2B-2C (which has 3 monitors in it), closest to NE wall."
Glen Marshall got this suggestion from John Kaminsky, one of the operators. He said that it is easy to do but if he hadn't done it before, he wouldn't necessarily know where to look for the instructions.
More information is available from Sing Lee.
From an xterm, log onto the central control system (ccs) Sun EPICS control computer (ccssunp1) by typing
ssh -l twist ccssunp1and then supply the usual password. After logging in, type at the prompt
m13 &This gives you the Status and Controls page. Click on the box at the bottom labelled "Next/Prev" to get a diagrammatic representation of M13, along with BL1A current and T1 informational displays.
To adjust a device (magnet, slit, etc.) click (that is, with the left mouse button) on the black rectangle containing the name for the particular device. A control box opens. Depending on the type of device, it may contain switches for on or off (e.g., magnets) which can be clicked, a slider box for adjustments (magnets), or a box to enter a value directly. The slider box interface is particularly baffling. You can use it as a slider, but it may be more effective to click on the slider, then right-click-and-hold, then drag and release to select a function. "Increment" and "Decrement" will do just that, by a value which is larger or smaller depending on whether you may have previously selected "Coarse", "Medium", or "Fine". These select the amount by which the DAC is changed, for a magnet type of device. Or, you can enter a number after clicking on "Setup", and then select "Custom" to to make "Increment" or "Decrement" change by the number you entered.
Whenever you use an adjustment box, you have to place the cursor over the box, click on it, then enter the number you want (deleting the previous digits as necessary), and then press "Enter" on the keyboard. For a slit, nothing happens at this stage, until you click on "Move". It should then move to approximately the desired position.
See the M13 schematic below for where all the slits and jaws are. Each side of a slit can be controlled independently, using adjustment boxes for both position and width, while a jaw moves in a symmetric way only and has only a width box.
Choose the value for the position or width as described previously (click the entry box, delete/type the number, and press Enter), and click "Move". It should move such that the readback value (in blue) is somewhere near what you want. If it isn't close enough, try overshooting by a millimeter or so. Also, double check the position after adjusting the width (or vice versa) for a slit; changing one can change the other. Try to make the value within 1 millimeter of what you really want. For example, if you want a width of 20 mm and a position of 0 mm, try to get the width between 19 and 21 mm, and the position between -1 and 1 mm.
The absorber wheels consist of two wheels immediately downstream of the F1 slits. Each wheel has four positions, for a total of sixteen combinations which are numbered from 0 to 15. The "0" position has no absorber, while all others have either some thickness(es) of CH_2 and/or some vertical collimation (see list).
Tunes can be saved and restored. Bring up the save and restore page by clicking the box at the bottom of the Status and Controls page. Beam line settings are stored in a device "snap" (.snap) file, according to information in a device "request" (.req) file. The request file determines what you want to have saved in the snap file. There are also corresponding beam request and snap files. To see what they might be doing, look at a set of the files from the ccssunp1 session, in the subdirectory of the twist account called twist_save.
When saving, beware: files of the same name will be overwritten without prompting. You can select standard names or names with a timestamp (which should be unique). Or, you can select an existing file name or type in your own name. The program will enforce some naming conventions (names beginning m13dev_ and m13beam_). Click on "Accept names", check if they are what you want, then click on "Save".
Restoring is similar, but name selection is easier since the files have to exist. Choose one, click on "Accept", then click on "Restore". Check that you got what you wanted.