Reading MDSplus Data

JETDSP can read data through MDSplus. This can be used for JET data, and also for experimental data from other sites stored in an MDSplus tree. It can also be used to read data from trees stored on your computer.

To read the data you need to know the name of the MDSplus server, and also of the relevant tree and shot of interest. Known signals can be read, or the MDSplus tree can be browsed to find the signal of interest.

To read data via MDSplus, choose the Read Signal option from the File menu of the main window, or from any plot windows which you have created. Select the MDS+ button at the top of the window which is now created, as below.

You must enter the name of the MDSplus server, the shot number and tree name in the relevant fields. To read JET data via MDSplus, you should specify the following fields

• MDS+ server:    mdsplus.jet.efda.org    (this is the default when you first access MDS+ data)
• Shot number:    the JET pulse number you wish to read
• Tree:    enter JET

To read a specific signal enter the appropriate Signal name in the signal field, and press Read. There may be a slight delay when first reading a signal as the program connects to the MDSplus server. You can read in many different signals by entering the relevant signal name and then pressing Read. When you have read all the signals of interest, press Done.

JET data signal names

For JET data the signal name is specified by a ppf or jpf followed by, the dda and datatype for a PPF, or the subsystem and node name for a JPF. Each part of the signal name is delimited by a . so example ppf or jpf signals might be

• ppf.magn.ipla
• ppf.kk3.te20
• jpf.da.c2-ipla

Browsing an MDSplus tree

In is not currently possible to browse the JET data. For all other data, you can browse the tree to find the signal of interest. To do this, enter the MDSPlus server name, tree name and shot number which you wish to browse. Then press the Browse Tree.. button. A window will be created as below, which you can use to browse the MDSplus tree.

In this tree traverser window, the topmost text field shows the current location in the tree. Below this are two lists, the left-hand list indicates all structure nodes (ie branch nodes and sub-trees) from the current tree location. The right-hand list gives all signal type nodes at the current tree location. At present only signal type nodes are listed, and not any other data containing nodes. This is because all signals which can be plotted should be stored as Signal type. Other data-containing node types can be included in the listing, however, if this is requested.

To move to a different branch in the tree, click that branch in the left hand panel and the traverser details will be updated with the details from the new branch node. To return to the previous (parent) branch click the Up a level button. To return to the topmost branch, click the Return to \TOP button.

Use the traverser to find the name of the Signal of interest, select this by clicking on it in the Signals list, as above, and press OK. The selected Signal name should then be entered in the Signal field of the Read a Signal window. Press the Read button in this window to read the signal.