This is a frist draft, as discussion base. M. Zolliker, 7 April 2005
Some modifications added by Mark Könnecke, Oct 2005.
The three triple axis instruments at SINQ should get a common instrument software (SICS) with a common syntax.
The idea is to implement and the new syntax on EIGER or RITA-2 first and to upgrade TASP after it is successful.
The command name is DR. The command drive as used at other instruments is available but behaves differently.
Markus Zolliker: this behaviour may confuse the user. My proposition is to rename the original sics drive command and to make dr and drive act similar
Motors are driven as on other SICS instruments. With a single drive command several motors may be driven.
Driving in reciprocal lattice units
> DR QH qh qk ql en
If en (the energy transfer value) is omitted, the energy transfer is assumed as zero (in contrast to TASMAD, where it is the last used value). It is an error to give less than 3 numbers.
WARNING: The new system allows to drive Q out of plane within the limits of the sample goniometers sgu and sgl. If there is some sample device on the table which may not be tilted, restrict the movements of sgu and sgl through software limits.
Markus Zolliker: this behaviour is dangerous, because people will always forget to set software limits. My proposition is to have different names for Q-variables driven in 2 and 3 dimensions. An error should be signaled when driving the 2D Q-variable out of plane
For powders (no more powder mode switch, qm is in Å-1):
> DR QM qm EN en
Driving the energy transfer alone is also possible, (using the last given q values):
> DR EN en
Analyzer and monochromator energies are represented by the virtual motors EI, KI, EF and KF, as in TASMAD.
An error is signaled:
The scan syntax is like on TASMAD.
Arguments of SC:
The presence of 4 argument parts is mandatory, but the order of the parts is not relevant. For every step variable, the corresponding center value must be given. If no step is given for a center variable, a step 0 is used.
Special cases are the variables QH and Q3 , and their corresonding steps DQH and DQ3 which have 3 or 4 values.
> POLSCAN script "scan variables and steps" NP np MN mn
The script contains all what has to be done at one scan point. Its exact syntax is still open.
COcount (arguments: either MN mon or TI time)
FI (FIX)without argument: show which motors are fixed
CLwithout argument: show which motors are fixed
DOalias to exe
LEsummarize q and energy infromation
LZ, LLsummarize zero points and limits informaiton
LMsummarize machine parameters
LSsummarize sample information (the format may change due to the ub matrix system)
LTshow targets and positions
LIthe same as LM, LS, LZ, LT, LE executed one after another
OUTset additional output variables to be printed into the data file and on command history
PR (PRINT)print variable values.
SE (SET)set variable values.
Naturally, all general SICS commands are valid also.
> CELL a b c alpha beta gamma
set unit cell constants. If b or c are omitted, the same value as for a is used, if angles are omitted, they are set to 90 degress. Without arguments, the cell constants are listed.
> addauxref qh qk ql
Define the vectors for the scattering plane.
> REF qh qk ql a3 a4 sgl sgu Ei Ef
Make an entry in the list of peaks. For angles and k-values not given, the current motor positions are used. The peak number and the peak data are returned.
> REF AUX qh qk ql Add an auxiliary reflection to the list of reflections. A4 is calculated from the cell constants, the current ei and ef values are used. A3 is left alone or is calculated to have the right angular difference to the previous reflection. Using auxiliary reflections is a help during setup of the instrument or in powder mode.
ref clear all cell aa bb cc alpha beta gamma addauxref ax ay az addauxref bx by bz makeub 1 2with ax, ay, az being the first plane vector and bx, by, bz being the second plane vector creates a UB matrix which allows to drive Q positions and qm. But be aware that a3, sgu and sgl values are still invalid.
> REF CLEAR peak
Remove a peak.
> REF CLEAR ALL
Remove all peaks.
List all peaks.
> MAKEUB peak1 peak2
Calculate, activate and print out the UB matrix, as well as the peak list with qhkl values calculated back. peak1 is used as the main peak, i.e. driving to the angles given for this peak will correspond to a QHKL which may only differ by a scalar factor of about one, if the cell constants are not correct. peak2 is used only for determining the scattering plane.
It has to be checked that this is fully compatible with the TASMAD specification. In principle, AX,AY,AZ should correspond to peak1 and BX,BY,BZ to peak2.
Calculate and activate a UB which has been calculated from the cell constants alone. This is useful to get a4 when no reflection has yet been found to calculate a proper UB.
>MAKEAUXUB qh qk ql
Calculate a UB matrix from the first reflection and an auxiliary second reflection specified through the miller indices qh , qk, ql. The auxiliary reflection will have the same angles as the first reflection, except a3 and a4 will be adjusted to match the requirements from the crystalls geometry.
Markus Zolliker: there should be a an easy way helping the user to correct the cell constants (for example due to thermal contraction) according to the measured peak.
List the UB matrix, the cell constants and all stored reflections.
This formalism allows to drive out of the scattering plane using the tilt motors of the sample stage. Some cryostats cannot stand this. Therefore driving out of plane can be switched off and on.
> TASUB OUTOFPLANE 1
This command switches out of plane operation on.
> TASUB OUTOFPLANE 0
This command switches out of plane operation off.
> TASUB OUTOFPLANE
lists the current value of the outofplane variable
(Some numbers might not be correct, as this module does not yet work in this form).
We enter cell values > CELL 2.88 2.88 2.88 90 90 90 > MAKEUBFROMCELL MAKEUBFROMCELL builds a UB matrix from the cell only. With this you can drive to 2 0 0 > drive qh 2 0 0 This will get you the correct two-theta == a4. You have to search the peak in a3, sgu and sgl and optimize it. Once we are at the maximum: > REF 2 0 0 Peak QH QK QL A4 A3 SGL SGU 1 2.00 0.00 0.00 65.31 -87.21 1.25 -5.22 > makeauxub 0 4 4 > dr qh 0 4 4 Make an axiliary UB and drive to the theoretical position for 0 4 4 Find the peak 0 4 4 and optimize it. ... Once we are at its maximum: > REF 0 4 4 Peak QH QK QL A4 A3 SGL SGU 1 0.00 4.00 4.00 65.31 -87.21 1.25 -5.22 Show again the peak list: > REF Peak QH QK QL A4 A3 SGL SGU 1 2.00 0.00 0.00 65.31 -87.21 1.25 -5.22 2 0.00 4.00 4.00 99.45 20.39 4.25 -1.22 Calculate the UB matrix, with 2 0 0 as primary peak and 0 4 4 as secondary peak. > MAKEUB 1 2 UB 2.456 0.530 -0.200 -0.530 2.456 -0.090 0.200 0.090 2.456 Peak QH QK QL A4 A3 SGL SGU QH QK QL 1 A 2.00 0.00 0.00 65.31 -87.21 1.25 -5.22 2.03 0.00 0.00 2 B 0.00 4.00 4.00 99.45 20.39 4.25 -1.22 0.02 3.95 4.03 the last 3 columns above show the Q values calculated back from the angles. We drive now to the 2 0 0 peak > DR QH 2 0 0 > PR A4 A3 SGL SGU A4 = 64.218 A3 = -87.515 SGL = 2.258 SGU = -3.217 The value of A4 has changed, because the cell constants do not match the values given for the first peak. The value of A3 has changed by the same reason, and in addition, because the the plane given by 2 0 0 and 0 4 4 is now tilted back into in the scattering plane. For the latter reason SGU and SGL have changed also. > DR QH 3 3 3 > PR A4 A3 SGL SGU A4 = 82.516 A3 = -31.215 SGL = 2.258 SGU = -3.217 note that the values for SGU and SGU have not changed. The will not change as long as we stay in the scattering plane (no drives to Q3) and as long as the UB matrix has not changhed. > REF 3 3 3 Peak QH QK QL A4 A3 SGL SGU 3 3.00 3.00 3.00 82.32 -31.25 2.26 -3.22 > MAKEUB C B UB 2.456 0.530 -0.200 -0.530 2.456 -0.090 0.200 0.090 2.456 Peak QH QK QL A4 A3 SGL SGU QH QK QL 1 2.00 0.00 0.00 65.31 -87.21 1.25 -5.22 2.03 0.00 0.00 2 B 0.00 4.00 4.00 99.45 20.39 4.25 -1.22 0.02 3.95 4.03 3 A 3.00 3.00 3.00 82.32 -31.25 2.26 -3.22 3.00 3.00 3.00 We have calculated a new UB matrix, based on the peak 3 3 3 as primary and the 0 4 4 as secondary peak. The UB matrix has not changed, as we were already exactly at 3 3 3.
Lower and upper limits and zeros for all motors. L, U and Z are appended as a prefix to the variable names to indicate Lower limit, Upper limit and Zero.
A1 Monochromator angle (Bragg angle in degrees) A2 Scattering angle at mono. (twice Bragg angle in degrees) A3 Sample angle (degs) (A3=0 when (AX,AY,AZ) is along KI) A4 Scattering angle at sample [degrees] A5 Analyzer angle (Bragg angle in deg.) A6 Scattering angle at analyzer (twice A5 in deg.) MCV Mono curvature vertical SRS Sample table second ring ACH Anal curvature horizontal MTL Mono lower translation MTU Mono upper translation STL Sample lower translation STU Sample upper translation ATL Anal lower translation ATU Anal upper translation MGL Mono lower goniometer (Reserved) MGU Mono upper goniometer SGL Sample lower goniometer SGU Sample upper goniometer AGL Anal lower goniometer (Reserved) AGU Anal upper goniometer D1T D1B D1R D1L Diaphragm 1 (top/bottom/right/left) D2T D2B D2R D2L Diaphragm 2 (top/bottom/right/left) D3T D3B D3R D3L Diaphragm 3 (top/bottom/right/left)
EI Incident neutron energy [meV] KI Incident neutron wavevector [Angstroem-1] EF Final neutron energy [meV] KF Final neutron wavevector [Angstroem-1] QH Q in Reciprocal Lattice Units (3 components!) EN Energy transfer; +ve neutron energy loss [meV] QM Length of Q [Angstroem-1]
not yet specified
I assume the UB-stuff is with the intention that one can eventually drive out of the AB-plane using the goniometers? For some experiments - e.g. the incommensurate stuff Oksana, Sabine and I are working on, this would be extremely useful.
This is implemented with the Q3 variable. The only difference to the QH variable is, that it does really move out of the scattering plane, whereas a drive on QH gives an error when a vector outside the scattering plane is given. What remains open, is, how to resolve the redundancy on drives outside the scattering plane. For EN=0, you have 4 angles to drive, but only 3 components of the Q vector. We have to specify, how to resolve this redunant information. One possibility would be, that the vector in the AB-plane, which is perpendicular to the scattering vector, stays in the scattering plane.
"Henrik:" One solution to redundancy problem would be to choose solution that has minimum total tilt - sqrt(Gu^2+Gl^2) would do.
Related to this is a command to tilt the current scattering vector. Normally we always rotate the sample or the cryostat to have the crystallographic axes along the goniometer axes. But this is silly since instead of scanning sgu and sgl independently one can just make a coupled scan that exactly tilts the current scattering vector. Much of the time, this is a small convenience thing, but sometimes, the sample does not have refelctions at perpendicular angles, in which case such a feature would allow more accurate alignment.
Me also, I thought about a virtual motor simulating a goniometer with arbitrary axis. I think about a syntax to implement this.
The other thing we need to think about is how to deal with the multiplexing. For RITA-II its only 7-9 channels, but for EIGER-CAMERA it will be 60 degree continuous scattering and 5 of those. We obviously do not need to sort that out in detail before when CAMREA is closer to ready, but we should make sure that the syntax and underlying code can be generalised to this kind of analyser-detector systems.
I did not specify such things. The aim is, to have the same syntax for all stuff common on the 3 instruments. I have also not specified in detail the polarisation analysis, which is only used on TASP. But if something is found in the syntax, which might give trouble when extended to some instrument specific stuff, then we like to have a feedback.
Bertrand Roessli: thanks Christoph to have sent me the link. The following is just the result of some suggestions that I can think of after discussion with Christof and Markus. Sorry if they are redudant.
-It is written that En is set to zero in case the command 'Sc Qh h k l' does not contain the energy transfer. I think this is quite dangerous if somebody forgets to do it and the instrument drives back automatically to the elastic position.
-It seems there will be no switches in future apparently. Please remember that TASP has polarisation analysis.
-The option with the UB matrix allows scans out of the scattering plane. Some security should be installed to prevent that a typo in a scan or in a job drives the goniometers (and the cryostat that is on it). I am not sure that setting the soft limits is a good option. I like Markus' proposition with the 'sc/dr Q3' command very much.