Other available equipment in the ExpH

Index:

• Energy Reference Filters

• Secondary Slits III (Secondary Source) 

• Sample and Detector Slits

• I₀ monitor

• Dynamic limits

ID01 - Experimental Hutch Reference Energy Filters

For calibrating the X-ray energy 9 reference filters with absorption edges from 5 keV to 39 keV can be inserted into the monochromatic beam (motor att21). These filters are mounted after the multilayer monochromator at the end of the optics hutch (OH1). The filter foils are rotated around the vertical axis by about 45 degrees with respect to the monochromatic beam for observing under 90 degrees the X-ray fluorescence with a PIN diode (counter att2).

For operating the filters type in one of the spec sessions kapin <mne>, kapshow, kapout , e.g.

OPTICS> kapin att2 Cu_7um8
OPTICS> kapshow att2
OPTICS> kapout att2

Dynamical absorbers system

The dynamic range of any of the detectors is much more limited than the intensity of the beam. In order to increase the linear dynamic range of the scintillator counter and other detectors, a system of dynamical absorbers has been installed. The linearity of the detector is especially important when making comparisons of the absolute intensity, as it is often the case when using the anomalous scattering effect. Furthermore, when measuring both Bragg diffraction and diffuse scattering in the same scan, the dynamical range of the interesting signal can be many orders of magnitude.

A special card calculates the detector dead time, and depending of the experimental value and a range of acceptable values set by the user, the system change the absorber to increase or decrease the intensity arriving to the detector. The whole operation is automatic, and the controlling program calculates the corrected intensity in real time. There are absorbers of different materials and thickness, in order to cover the whole range of energies used (2.1 – 35 keV).

The following table helps to choose the appropriate absorber material and thickness. The results are also reported in the following graph.

Cabling Diagram:

Secondary slits III (Secondary Source)

A pair of uncooled slits clean the beam or act as a secondary source to remove any wavefront modulation caused by the upstream optics. They are step motor driven, equipped with limit switches and an incremental encoder. They are pumped with a 220l/s ion pump. The power supply of the pump is in the Electronics Rack 01. Typical pressure 10^-6 mbar.

The motors are controlled with SPEC. Their names are

ss3u (secondary slit up)

ss3d (secondary slit down)

ss3f (secondary slit front)

ss3b (secondary slit back)

ss3vo (secondary slit vertical offset to define the center of the gap)

ss3vg (secondary slit vertical gap to define the aperture).

ss3ho (secondary slit horizontal offset to define the center of the gap)

ss3hg (secondary slit horizontal gap to define the aperture).

I₀ monitor

The beam traverses a thin kapton foil and the diffused radiation is collected by a photodiode. The kapton foil position is controlled by a pneumatic acturator driver (names kap3).

The current is amplified with a Novelec amplifier operated at variable gain from 107 to 109 and it is injected in a voltage/frequency converter. Then the VME counter card communicates to the work station the counting rate which is read as a SPEC counter (Monitor).

Dynamic limits

With the range of possible sample environment and detector combinations at ID1 it is possible that collisions can take place between parts of the diffractometer. To avoid this the control software has been updated to allow limits to be set at the start of each experiment so such a collision cannot take place. It is very important that this is done. Dynamic limits are currently available for the following motor pairs:
- detx/del
- gam/mu
- del/th

They can be activated and changed with 'blmenu'

ID1 - Instrument Menu

01 detx/del limit On (detx>=2000 mm) OR (del>=70 deg)
02 Dld on scans Off
03 Electrometers On
04 Q/Del motor Off
05 Automatic LAMBDA update On
06 gam/mu limit On (gam-mu) >= -0.8477 deg
07 Theta On
08 del/th limit On (del-th) >= -25.9131 deg

Enter number to change, e for extra, or 0 to exit (0)?

The defaults are defined in the setup file of the spec session (see below).

detx/del limit
==============

DETXLIM_VERSION 1.2 PB 2000-10-23

This dynamic limit is used to avoid a crash between the SAXS detector box
and the del-arm of the goniometer. Before detx or del is moved it is checked
whether the target positions fulfill the condition:

(dial(detx)>=DETXLIM) OR (dial(del)>=DETXDELLIM)

If not, the movement is cancelled and the following error message is
shown:

Out of dynamic limits (detx<2000 mm) OR (del<69.9466 deg)

Typical values for DETXLIM and DETXDELLIM are 2000 mm and 70 deg.

To set the detx/del limit use 'blmenu' and than the option 'e'
id1 - Instrument Menu (EXTRA)

01 Set detx/del limit
02 Dld setup
03 Elmeter show
04 set /mu limit
05 Set Theta
06 set del/th limit

Enter option number or 0 to return to main (0)? '1'

Smallest detx position when del is down [mm] (2000)?
Smallest del angle when detector is inside the vessel [deg] (70)?

Type return to leave blmenu

NOTE: Only the limits corresponding to the dial values of detx and gamma
are stored. Therefore, detx and del can be redefined with 'set detx xxx'
or 'set del yyy' without destroying the calibration of the limits.

Now the limits must be written into the setup. Otherwise the old values would
be restored after a restart of the program or after a resetup.

To do that dump the current setting with 'detxlimdump':

The following lines are printed:
detxlimon
detxlim 2000 70
detxlimdial(2000,70)

To make this change permanent paste these lines into the setup file

Open the setup file with 'setup'. Then go with '<return>' to the part
of the file where the limits are defined. Position the cursor at the beginning
of the old lines and delete them by typing two times 'd' for each line that
you want to delete. Afterwards position the cursor at the line where you
want to insert the new limits. Type 'i' for insert and paste the new lines.
To paste the previously copied lines press the middle button of the mouse,
afterwards '<esc>', then ':' and then 'wq' to write and quit. If you think
that you have done an error, do not save the modified file but type 'q!' to
exit without save or type 'e!' to read the file back from disk.

In setup:

...

#
# Delta/Detx limit check
#
jtdo ("ID1detxlim")
p "Setting dynamic Detx/Delta limits to 2000 mm and 70 deg (dial)"
detxlimdial(2000,70)
detxlimon

...

---------

gam/mu limit
============

MULIM_VERSION 1.2 VRB/PB 2001-01-24

The gam/mu limit is used to avoid a crash between the gam-circle (detector)
and the mu-circle (sample). The difference of the DIAL value of gam and mu
must be larger than a limit value. Before mu or gam is moved it is checked
whether the target positions fulfill the condition:

dial(gam) - dial(mu) >= MULIM

If this is not the case the movement is cancelled and a message of the
following type is shown:

Out of dynamic limits (gam - mu) < -0.8477

A typical value for MULIM is 0.5 deg.

Use 'blmenu' 'e' to define the limit:

01 Set detx/del limit
02 Dld setup
03 Elmeter show
04 set /mu limit
05 Set Theta
06 set del/th limit

Enter option number or 0 to return to main (0)? '4'

Minimum difference between gam and mu (gam > mu+difference) (-0.8477)?

NOTE: Only the limit corresponding to the difference of the dial values of
mu and gamma is stored. Therefore, mu and gamma can be redefined with
'set mu xxx' or 'set gam yyy' without destroying the calibration of the
limit.

Dump the new limit with 'mulimdump'
mulimon
mulimdial(0.5)

and paste these lines into setup as it is described above for the detx/del
limit

#
# Mu/Gamma limit check
#
jtdo ("ID1mulim")
p "Setting dynamic Mu/Gamma limit to 0.5 deg (dial)"
mulimdial(0.5)
mulimon

---------

del/th - limit
==============

THETALIM_VERSION 1.4 VRB/PB 2001-01-24

The del/th limit is used to avoid a crash between the detector arm del
and things that are mounted on the theta circle. The difference of the
DIAL value of th and del must be larger than a limit value. Before th or
del is moved it is checked whether the target positions fulfill the
condition:

dial(del) - dial(th) >= THETALIM

If this is not the case the movement is cancelled and a message of the
following type is shown:

Out of dynamic limits (del - theta) < -25.9131 deg

A typical value for THETALIM is -25 deg.

Use 'blmenu' 'e' to define the limit:

01 Set detx/del limit
02 Dld setup
03 Elmeter show
04 set /mu limit
05 Set Theta
06 set del/th limit

Enter option number or 0 to return to main (0)? '6'

Minimum difference between del and th (del > th+difference) (-25.9131)?

Dump the new limit with 'thetalimdump'
thetalimon
thetalimdial(-25.8952)

and paste these lines into setup as it is described above for the
detx/del limit

...

#
# Delta/Theta limit check
#
jtdo ("ID1thlim")
p "Setting dynamic Theta/Delta limit to -25.8952 deg (dial)"
thetalimon
thetalimdial(-25.8952)