Runs

A run is a measurement using the data acquisition system.
LINUX commands can always be typed after the dollar ($) prompt. In order to begin the set up of a buffer run (or series of runs), initiate a work terminal in the proper directory (make a directory if necessary) :

[bt4@bt4 bt4]$ cd [user directory]
Once in the appropriate user-defined directory, initiate the "prepare" program:

[bt4@bt4 user directory]$ prepare &
The & option allows the working terminal to remain active and not be blocked by the program being executed.

After the ICP Prepare window appears, choose the option under the pull down menu .
A screen terminal similar to the picture below will appear:

A buffer can be edited by entering the following parameters in the ICP Prepare window:

Comments:

Enter here a five-character file name followed by a general description of experimental conditions. A file name containing more than 5 characters will be truncated.

Energy:

Enter the starting energy (E Start) of scan. Remember that at 20"-20" collimation the incident energy is the starting energy plus 1.2 meV.

E Step (x dE):

Enter the step size (in fraction of energy resolution) from the pull down menu.

NPTS:

Enter the number of points to be collected. Each time a number is entered here, the [Enter] key must be pressed. ICP "prepare" automatically calculates the final energy from the number of points entered.

Temp/H:

In icp, if the temperature flag is set to T+, this feature allows for the control and monitoring of the temperature set point ( Be sure to connect the temperature control cable to the LakeShore temperature controler. The temperature will be controlled using the parameters:

Temp Parameter	Function
T0	Starting Temperature
Inc-T	Temperature increment
Wait	Wait time (min.)
Err	maximum (Tset - Tactual) allowed
Hld0	Time hold (1st pt)
Hld	Time hold per pt

Monitor:

Enter the number of monitor counts tobe reached at each energy point if preparing a SAMPLE run or the time in seconds for each energy point if preparing a FAST BCKGRND run (see pg 6). The total count for each point measured is the number entered in Monitor times the prefactor. Do not forget to set the proper M-typ option.

Prefac:

If the prefactor is set to 3 or higher, a statistical check of the data will be performed for each prefactor. Data outside the acceptable statistical range will be remeasured guarantying points with good statistics are recorded.

M-typ:

Measurement flag. When set to "Neutron" (normal instrument operational mode), data is collected with respect to total monitor counts. If set to " Time", data is collected with respect to total time per point (in secs). The "Time" setting is used when measuring fast background.

After all of the necessary parameters are entered, do not forget to update the buffer by either pressing the [F9] key or by clicking on [Update] button located at the bottom left side of the window.

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ICP Control

Note that only one instance of icp is allowed to control the instrument. Any other instance of icp allows only limited control. At the Linux prompt, start the instrument control program by typing:

[bt4@bt4 user directory]$ icp

BT-4 Instrument Control Program Version 20.3 Aug 2004 Station number: 4 Status Flags TR+ W- S+ T- H- P- F: 3 4 5 *

The "Status Flag" line indicates the default commands and flags. The (+)/(-) flags indicate on/off respectively.

TR+	Motors #2 and #9 are coupled (NORMAL INSTRUMENT OPERATING MODE). Thus TR- uncouples these motors.
W-	Do not write file log (if flag set to +, a log file named after the current date will be generated
S+	This flag tells you whether the statistics check is enabled or not. If flag set to S+ and the prefactor ≥3, the program will check the intensity data for statistical consistency.
T-	Temperature control. If set to T+ and a temperature controller is connected, the sample temperature will be monitored and controlled during scans.
H-	Magnetic field control. If set to H+ and a magnet controller is connected, you are able to change and/or monitor field during scans.
P-	Denotes polarized (P+) or unpolarized (P-) beam. Not used on FANS
F:	F: is followed by a list of the motors that are currently "fixed" on the instrument. Typically motors 3, 4, 5, and 6 are fixed for FANS operation A fixed motor will not be moved by a buffer execution. It may, however, be moved with a drive command. The command PFIX will print out a list of the fixed motor(s) at any time.

While the computer is executing a previous command, the * prompt will not appear on the screen. Wait for the * prompt before inputting another command.

Checking a Buffer Run

A specific buffer run created as described above can be verified by using the command:
drtn
The command drtn [were n is a buffer number] will generate a list of energies and angles in the range defined in prepare. This is a good way to verify if the motor limits for a run specified in "prepare" will not be exceeded before a run is actually executed. Nevertheless, a buffer will be executed if just rtn is typed.

Programming and Running a Sequence

Using commands (in bold) such as below to define a sequence of runs or to drive a specific motor;

dem=[Ei]	Drives the instrument (i.e. motors #1, 2 ,7, 8, and 9) to the incident energy specified. Remember that Ei= Etransfer + 1.2 meV.
rs=[sequence]	Define a sequence.
rs=12([sequence])	Define a sequence to run a total of 12 times. one may execute a sequence consisting of three runs of the same buffer with commands separated by a semicolon. rs=rt1; rt1; rt1 is equivalent to rs=3(rt1)
prs	Verify what sequence is currently defined
rs=del	Delete a sequence.
rs	Run a defined sequence

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Instrument scientists

Craig M. Brown		(301) 975 5134
Terry Udovic		(301) 975 6241
Juscelino Lećo		(301) 975 8867

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Go to the NCNR home page.
Go to the NCNR Sample Environments page.
Go to the NCNR Cold Neutron Instruments page.
Go to the NCNR Thermal Neutron Instruments page.

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Last modified 04-May-2004 by website owner: NCNR (attn: )